JP6884982B2 - A method for manufacturing a negative electrode material for a non-aqueous secondary battery, and a non-aqueous secondary battery using a negative electrode material for a non-aqueous secondary battery. - Google Patents

Description

The present invention relates to a method for producing a negative electrode material for a non-aqueous secondary battery and a non-aqueous secondary battery using the negative electrode material for a non-aqueous secondary battery.

In recent years, with the miniaturization of electronic devices, the demand for high-capacity secondary batteries has been increasing. In particular, lithium-ion secondary batteries having a higher energy density and excellent high-current charge / discharge characteristics than nickel-cadmium batteries and nickel-hydrogen batteries have been attracting attention. Conventionally, increasing the capacity of lithium-ion secondary batteries has been widely studied, but in recent years, there has been an increasing demand for higher performance of lithium-ion secondary batteries, and further increasing the capacity and input / output. , It is required to achieve a long life.

It is known that a carbon material such as graphite is used as an active material for a negative electrode in a lithium ion secondary battery. Above all, when graphite having a high degree of graphitization is used as an active material for a negative electrode for a lithium ion secondary battery, a capacity close to the theoretical capacity of graphite occlusion of 372 mAh / g can be obtained, and further, cost and durability can be obtained. It is known that it is preferable as an active material for a negative electrode because of its excellent properties. On the other hand, when the density of the active material layer containing the negative electrode material is increased in order to increase the capacity, the material is destroyed and deformed, resulting in an increase in the charge / discharge irreversible capacity during the initial cycle, a decrease in the large current charge / discharge characteristics, and a decrease in the cycle characteristics. There was a problem such as a decrease.

In order to solve the above problems, for example, Patent Document 1 discloses a technique for producing spherical natural graphite by subjecting scaly natural graphite to mechanical energy treatment.
Further, Patent Document 2 discloses a method of obtaining spheroidized graphite particles having a smooth particle surface by adding a resin binder to the raw material graphite particles and performing a spherical treatment.

Japanese Patent No. 3534391 Japanese Unexamined Patent Publication No. 2014-114197

However, according to the study by the present inventors, the method for producing spherical graphite disclosed in Patent Document 1 is insufficient in the processing efficiency of sphericalization, and in order to obtain spherical graphite having a high tap density A long processing time was required. Further, in the method disclosed in Patent Document 1, fine powder and coarse powder are generated at the same time as those having a target particle size range. Therefore, in order to obtain graphite having a higher degree of spheroidization, fine powder or classification treatment is performed to obtain fine powder or coarse powder. Since a process for excluding coarse powder may be required, there is a concern that the product yield may decrease.
Similarly, in the method for producing spherical graphite disclosed in Patent Document 2, the adhesive force between the graphite particles due to the addition of the resin binder was small, and the treatment efficiency for sphericalization was insufficient. On the other hand, a technique of adding a resin binder solution dissolved in a toluene solvent to form a sphere is also disclosed as an example, but since the flash point of the solvent is low, the temperature rises above the flash point due to the temperature rise during the sphere treatment. Further improvement is needed due to the risk of explosion and fire during manufacturing.

The present invention has been made in view of the background art, and the subject thereof is to provide a method for producing a spherical carbon material, which is simpler and has higher processing efficiency than a conventional method for producing a spherical carbon material, and as a result. The purpose is to provide a high-performance non-aqueous secondary battery.

As a result of diligent studies to solve the above problems, the present inventors have included an organic compound having a relative permittivity of 9.0 or more and no branched chain in the molecular structure when the carbon material is sphericalized. We have found that a non-aqueous secondary battery negative electrode material having a high tap density can be obtained in a short time by using a granulating agent, and have completed the present invention.
The reason why the carbon material according to the present invention exerts the above effect is considered as follows.

When the granulation treatment is performed in the presence of a granulator containing an organic compound having a relative permittivity of 9.0 or more and no branched chain in the molecular structure, graphites are bonded to each other to efficiently form the graphite. Can be grained. An organic compound having a relative permittivity of 9.0 or more means that the molecule has a large polarity, and indicates that the molecule has a polar group in which electrons are polarized and easily react. When graphites collide with each other and are pulverized in the spheroidizing treatment, the C = C bond and CC bond of the graphite are broken and radicals are generated on the graphite surface. When the spheroidization treatment is carried out in the atmosphere, the generated radicals and oxygen in the atmosphere are combined, and -OH group (hydroxyl group), -C = O group (carbonyl group), -C = O (-C = O (-) on the graphite surface. Functional groups such as OH) (carboxyl group) are generated. The functional groups formed on the surface of the graphite repel each other and act in a direction of inhibiting the bond between the graphites, and graphite particles that cannot be bonded are generated as fine powder or coarse powder. On the other hand, when the spheroidization treatment is performed in the presence of the organic compound having a specific dielectric constant of 9.0 or more in the present invention, the polar groups in the organic compound molecule react with the radicals generated on the graphite surface and chemically. It can be bonded, and the graphite particles tend to be strongly bonded to each other via the organic compound. This promotes the spheroidization of the graphite particles. Even in an organic compound having a specific dielectric constant of 9.0 or more, if a branched chain is present in the molecule, the branched chain inhibits the approach of the polar group in the organic compound to the graphite surface radical, and the radical becomes a radical. Since the organic compound tends to be less likely to be bonded, the effect of promoting spheroidization becomes insufficient. Further, an organic compound having a relative permittivity of less than 9.0 means that the polarity of the molecule is small, and indicates that the molecule has no or few polar groups. When there is no polar group in the organic compound, the radical on the surface of the graphite does not react with the organic compound and only physically adsorbs the organic compound. Therefore, the bond between the graphite particles is weak and the effect of promoting spheroidization is not sufficient. Even when there are few polar groups in the organic compound, the amount of radicals on the graphite surface reacting with the organic compound to chemically bond is small, and the amount physically adsorbed is large, so that the bonds between the graphite particles are formed. It is weak and the effect of promoting spheroidization does not work sufficiently.

That is, the gist of the present invention is the production of a negative electrode material for a non-aqueous secondary battery having a granulation step of applying at least one of mechanical energy of impact, compression, friction, and shearing force to make the raw material carbon material spherical. The method is a production method characterized in that the granulation step is performed in the presence of a granulator containing an organic compound having a relative permittivity of 9.0 or more and no branched chain in the molecular structure. ..
In addition, other gist lies in the non-aqueous secondary battery using the negative electrode material for the non-aqueous secondary battery obtained by the above manufacturing method.

According to the method for producing spheroidal graphite used for the negative electrode material for a non-aqueous secondary battery of the present invention, spherical graphite particles having a high tap density can be obtained in a short time, and the negative electrode activity for a non-aqueous secondary battery can be obtained. By using it as a substance, it is possible to provide a non-aqueous secondary battery having a high capacity and good low temperature input / output characteristics.

Hereinafter, the contents of the present invention will be described in detail. The description of the constituent requirements of the invention described below is an example (representative example) of the embodiment of the present invention, and the present invention is not specified in these forms unless the gist thereof is exceeded.

The present invention is a method for producing a negative electrode material for a non-aqueous secondary battery, which comprises a granulation step of applying at least one of impact, compression, friction, and shearing force to make a raw material carbon material spherical. The negative electrode for a non-aqueous secondary battery is characterized in that the granulation step is performed in the presence of a granulator containing an organic compound having a relative permittivity of 9.0 or more and no branched chain in the molecular structure. It is a method of manufacturing a material.
If the granulation step is provided, another step may be further provided if necessary. Another step may be carried out independently, or a plurality of steps may be carried out at the same time. One embodiment includes the following first to sixth steps.

(1st step) Step of adjusting the particle size of the raw material carbon material (2nd step) Step of mixing the raw material carbon material and the granulator (3rd step) Step of granulating the raw material carbon material (4th step) Step of removing granules (5th step) Step of purifying the granulated carbon material (5'step) Step of increasing the crystallinity of the granulated carbon material (6th step) Further raw material for the granulated carbon material Steps for Adhering Carbon Substances with Lower Crystalline than Carbon Materials These steps will be described below.

(First Step) Step of Adjusting the Particle Size of Raw Material Carbon Material The raw material carbon material used in the present invention is not particularly limited, and the above-mentioned artificial graphite or natural graphite can be used. Above all, it is preferable to use natural graphite because of its high crystallinity and high capacity.
Examples of the natural graphite include scaly, scaly, lumpy or plate-shaped natural graphite, and among them, scaly graphite is preferable.

The average particle size (volume-based median diameter: d50) of the raw material carbon material such as scaly graphite, which is the raw material of spherical graphite, obtained in the first step is preferably 1 μm or more, more preferably 2 μm or more, still more preferable. Is 3 μm or more, preferably 80 μm or less, more preferably 50 μm or less, still more preferably 35 μm or less, very preferably 20 μm or less, and particularly preferably 10 μm or less. The average particle size can be measured by the method described later.

When the average particle size is within the above range, it is possible to prevent an increase in irreversible capacity and a decrease in cycle characteristics. In addition, the intraparticle void structure of spherical graphite can be precisely controlled. Therefore, the electrolytic solution can be efficiently distributed to the voids in the particles, and the Li ion insertion / desorption sites in the particles can be efficiently used, so that the low temperature output characteristics and the cycle characteristics are improved. Tend to do. Further, since the circularity of the spherical graphite can be adjusted to be high, the electrolytic solution can be smoothly moved in the interparticle voids without increasing the bending degree of Li ion diffusion, and the rapid charge / discharge characteristics are improved.
When the average particle size is within the above range, the fine powder generated during the granulation process adheres to the base material to be granulated graphite (hereinafter referred to as granulated carbon material) or inside the base material. It is possible to granulate while wrapping, and it is possible to obtain a granulated carbon material having a high degree of spheroidization and a small amount of fine particles.

Examples of the method for adjusting the average particle size (d50) of the raw material carbon material within the above range include a method of pulverizing and / or classifying (natural) graphite particles.
The apparatus used for crushing is not particularly limited, and examples of the coarse crusher include a shear mill, a jaw crusher, an impact crusher, a cone crusher, and the like, and examples of the intermediate crusher include a roll crusher and a hammer mill. Examples of the fine crusher include a mechanical crusher, an air flow crusher, a swirling flow crusher, and the like. Specific examples thereof include ball mills, vibration mills, pin mills, stirring mills, jet mills, cyclone mills, and turbo mills. In particular, when obtaining graphite particles of 10 μm or less, it is preferable to use an air flow type crusher or a swirling flow type crusher.
The apparatus used for the classification process is not particularly limited, but for example, in the case of dry sieving, a rotary sieving, a swaying sieving, a oscillating sieving, a oscillating sieving, etc. can be used. In this case, a gravity classifier, an inertial force classifier, or a centrifugal force classifier (classifier, cyclone, etc.) can be used, and in the case of wet sieving, a mechanical wet classifier, a hydraulic classifier, etc. A sedimentation classifier, a centrifugal wet classifier, or the like can be used.

Further, it is preferable that the raw material carbon material obtained in the first step satisfies the following physical properties.
The ash content contained in the raw material carbon material is preferably 1% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.1% by mass or less, based on the total mass of the raw material carbon material. Further, the lower limit of the ash content is preferably 1 ppm or more.
When the ash content is within the above range, when a non-aqueous secondary battery is used, the deterioration of battery performance due to the reaction between the carbon material and the electrolytic solution during charging and discharging can be suppressed to a negligible extent. In addition, since the production of carbon material does not require a large amount of time, energy and equipment for pollution prevention, the cost increase can be suppressed.

The aspect ratio of the raw material carbon material is preferably 3 or more, more preferably 5 or more, still more preferably 7 or more, and particularly preferably 10 or more. Further, it is preferably 1000 or less, more preferably 500 or less, still more preferably 100 or less, and particularly preferably 50 or less. The aspect ratio is measured by the method described later. When the aspect ratio is within the above range, it is difficult to form large particles having a particle size of about 100 μm, while the contact area is appropriate when pressure is applied from one direction, so that a strong granulated carbon material can be easily obtained. Become. If the aspect ratio is too large, large particles with a particle size of about 100 μm tend to be formed, and particles that are too small do not form a strong granulated material because the contact area is small when pressure is applied from one direction. There is a tendency, and even if the particles are granulated, the specific surface area tends to be more than ^{30 m 2 / g, reflecting the small specific surface area of the scaly graphite.}

_{The plane spacing (d 002} ) and crystallite size (Lc) of the 002 planes of the raw material carbon material by the X-ray wide-angle diffraction method _{are usually 3.37 Å or less (d 002} ) and 900 Å or more (Lc). It is preferable that (d ₀₀₂ ) is 3.36 Å or less and (Lc) is 950 Å or more. The interplanar spacing (d ₀₀₂ ) and crystallinity size (Lc) are values indicating the crystallinity of the carbon material bulk, and the _{smaller the interplanar spacing (d 002} ) value of the 002 plane, the larger the crystallinity size. The larger (Lc) is, the higher the crystallinity of the carbon material is, and the amount of lithium entering the graphite layers approaches the theoretical value, so that the capacity increases. If the crystallinity is low, excellent battery characteristics (high capacity and low irreversible capacity) when highly crystalline graphite is used for the electrode will not be exhibited. It is particularly preferable that the above ranges are combined for the interplanar spacing (d _{002) and the crystallite size (Lc).}
X-ray diffraction is measured by the following method. The material is a mixture of carbon powder and X-ray standard high-purity silicon powder, which is about 15% by mass of the total amount, and the CuKα ray monochromated with a graphite monochromator is used as the radiation source. Measure the line diffraction curve. Then, the interplanar spacing (d ₀₀₂ ) and the crystallite size (Lc) are determined using the Gakushin method.

The packed structure of the raw material carbon material depends on the size and shape of the particles, the degree of interaction between the particles, etc., but in this specification, tap density is applied as one of the indexes for quantitatively discussing the packed structure. It is also possible to do. In the study by the present inventors, it has been confirmed that in lead particles having substantially the same true density and average particle size, the tap density is higher as the shape is spherical and the particle surface is smoother. That is, in order to increase the tap density, it is important to make the shape of the particles rounded to make them spherical, and to maintain smoothness by removing hangnail and defects on the particle surface. When the particle shape approaches a spherical shape and the particle surface is smooth, the filling property of the powder is greatly improved. The tap density of the raw material carbon material is preferably 0.1 g / cm ³ or more, more preferably 0.15 g / cm ³ or more, still more preferably 0.2 g / cm ³ or more, and particularly preferably 0. .3 g / cm ³ or more. The tap density is measured by the method described later in the examples.

The argon ion laser Raman spectrum of the raw material carbon material is used as an index showing the properties of the surface of the particles. Raman R value is the peak intensity ratio in the vicinity of 1360 cm ^-1 to the peak intensity near 1580 cm ^-1 in the argon ion laser Raman spectrum of the raw carbon material is preferably 0.05 to 0.9, more preferably 0 It is 0.05 or more and 0.7 or less, and more preferably 0.05 or more and 0.5 or less. The Raman R value is an index showing the crystallinity near the surface of the carbon particles (from the particle surface to about 100 Å), and the smaller the Raman R value, the higher the crystallinity or the undisturbed crystal state. The Raman spectrum is measured by the method shown below. Specifically, the particles to be measured are naturally dropped into the measurement cell of the Raman spectrometer to fill the sample, and while irradiating the measurement cell with an argon ion laser beam, the measurement cell is placed in a plane perpendicular to the laser beam. Measure while rotating. The wavelength of the argon ion laser light is 514.5 nm.

The X-ray wide-angle diffraction method of the raw material carbon material is used as an index showing the crystallinity of the entire particles. The scaly graphite preferably has a ratio of 3R / 2H to a strength of 3R (101) on the 101st surface based on the rhombohedral crystal structure by the X-ray wide-angle diffraction method and a strength of 2H (101) on the 101st surface based on the hexagonal crystal structure. .1 or more, more preferably 0.15 or more, still more preferably 0.2 or more. The rhombohedral crystal structure is a crystal form in which the accumulation of graphite network structures is repeated every three layers. The hexagonal crystal structure is a crystal form in which the accumulation of graphite network structures is repeated every two layers. In the case of scaly graphite showing a crystal morphology having a large proportion of the rhombohedral crystal structure 3R, the acceptability of Li ions is higher than that of graphite having a small proportion of the rhombohedral crystal structure 3R.

The specific surface area of the raw material carbon material by the BET method is preferably 0.3 m ² / g or more, more preferably 0.5 m ² / g or more, ^{still more preferably 1 m 2} / g or more, and particularly preferably 2 m ² / g or more. Most preferably, it is 5 m ² / g or more, preferably 30 m ² / g or less, more preferably 20 m ² / g or less, and further preferably 15 m ² / g or less. The specific surface area by the BET method is measured by the method of Examples described later. When the specific surface area of the raw material carbon material is within the above range, the acceptability of Li ions becomes good, and it is possible to prevent a decrease in battery capacity due to an increase in irreversible capacity. If the specific surface area of scaly graphite is too small, the acceptability of Li ions deteriorates, and if it is too large, it tends to be impossible to prevent a decrease in battery capacity due to an increase in irreversible capacity.

(Second Step) Step of Mixing Raw Material Carbon Material and Granulation Agent The present invention uses a granulation agent containing an organic compound having a relative permittivity of 9.0 or more and no branched chain in its molecular structure.
By using the above-mentioned granulating agent, the adhesive force between the raw material carbon materials is increased in the subsequent step of granulating the raw material carbon material in the third step, and the raw material carbon material can be adhered more firmly. Become.
This step may be carried out as a single step or may be carried out in combination with the subsequent third step.

(Organic compound with relative permittivity of 9.0 or more and no branched chain in molecular structure)
The granulator used in the present invention contains an organic compound having a relative permittivity of 9.0 or more and no branched chain in its molecular structure.
A high relative permittivity indicates that the molecule has high polarity and has a polar group that easily reacts in the molecule. When the carbon materials collide with each other, the radicals generated on the surface of the carbon particles react with the polar groups in the organic compound to form a chemical bond. Therefore, the graphite particles are strongly bonded to each other via the organic compound to form granules. The effect of, and thus the spheroidizing effect, is promoted.

The relative permittivity of the organic compound contained in the granulator is 9 or more, preferably 12 or more, more preferably 14 or more, still more preferably 15 or more, and usually 90 or less, preferably 60 or less, more preferably 40 or less. , More preferably 30 or less. If the specific dielectric constant of the organic compound is too low, there are no or few polar groups in the molecule of the organic compound, so that there is no or few chemical bonds between the radicals on the carbon surface and the organic compound, and the bonds between the carbon particles are sufficient. Is not strong, and the effect of promoting granulation and spheroidization may not be sufficiently exhibited.

The relative permittivity of the organic compound can be measured by the following method.
(measuring device)
Body: Agilent 4284A PRECISION LCR METER
Jig: Agilent 16452A LIQUID TEST FIXTURE
(Measurement condition)
Measurement frequency: 100KHz
Measurement temperature: 25.3 ± 2 ° C
Measured humidity: 48 ± 5%
Electrode spacing: 0.3 mm
Measured voltage: 1V
(Measurement principle)
The relative permittivity is calculated from the capacitance value of the capacitor formed by the electrode and the organic compound material provided between them from the following equation.
εr = (t × Cp) / (Axε ₀ )
εr: Relative permittivity of organic compounds
ε ₀ : Permittivity of vacuum = 8.854 × ^10-12 (F / m)
Cp: Capacitance (F)
A: Electrode area (m ² )
t: Electrode spacing: (m)

Further, the organic compound contained in the granulating agent in the present invention does not have a branched chain in its molecular structure. Since the molecular structure does not have a branched chain, steric hindrance does not occur, so that the polar groups in the molecule do not prevent the polar groups from approaching the distance to react with the radicals on the graphite surface, and the organic compound and the radicals on the graphite surface are not prevented from approaching. Reacts to easily form chemical bonds, and graphite particles are strongly bonded to each other via the organic compound, and the granulation effect and thus the spheroidization effect are promoted.
Further, the preferable properties of the organic compound contained in the granulating agent of the present invention will be described below.

-Viscosity The viscosity of the organic compound contained in the granulator of the present invention at 20 to 25 ° C. is preferably 1 cP or more and 10000 cP or less, more preferably 5 cP or more and 1000 cP or less, and further preferably 10 cP or more and 600 cP or less. It is preferable, and it is particularly preferable that it is 20 cP or more and 300 cP or less. When the viscosity is within the above range, it is possible to prevent the adhered particles from being detached due to an impact force such as a collision with a blade or a casing when granulating the raw material carbon material.

For the viscosity, use a commercially available viscometer (Brookfield DV-II cone plate type).
A predetermined amount of a measurement target (here, a granulator) is placed in a cup, and the temperature is adjusted to a predetermined temperature for measurement. When the shear stress at a shear rate of 100 s ^-1 is 0.1 Pa or more, ^{the value measured at a shear rate of 100 s -1} is measured, and when the shear stress at a shear rate of 100 s ^-1 is less than 0.1 Pa ^{, the value is measured at 1000 s -1} . The value measured at a shear rate at which the shear stress is 0.1 Pa or more when the shear stress is less than 0.1 Pa at a shear rate of 1000 s- ^{1 is defined as the viscosity in the present specification.} The shear stress can be 0.1 Pa or more by making the spindle to be used a shape suitable for a low-viscosity fluid.

-Carbon number The carbon number of the organic compound contained in the granulator of the present invention is usually 2 or more, preferably 3 or more, more preferably 4 or more, and usually 15 or less, preferably 13 or less, more preferably 10 or less. More preferably, it is 8 or less.
Within the above range, the polar groups of the organic compound work effectively, and the effect of promoting spheroidization tends to be higher. If the number of carbon atoms is smaller than the above range, the amount of organic compounds may decrease due to evaporation or the like during the granulation treatment, and the spheroidization promoting effect may be reduced. When the number of carbon atoms is larger than the above range, the relative amount of polar groups in the organic compound is reduced, and the spheroidizing promoting effect may be reduced.

-Density The density of the organic compound contained in the granulator of the present invention is usually 0.90 g / cm ³ or more, preferably 0.95 g / cm ³ or more, more preferably 1.0 g / cm ³ or more, still more preferably 1. and a .05g / cm ³ or more, usually 1.5 g / cm ³ or less, preferably 1.3 g / cm ³ or less, more preferably 1.25 g / cm ³ or less, more preferably 1.20 g / cm ³ or less is there.
Within the above range, the amount of polar groups contained in the organic compound is appropriate, and the effect of promoting spheroidization tends to be higher. Since the polar groups are appropriately associated with each other by hydrogen bonds or the like, the specific gravity tends to increase. The fact that the density of the organic compound is smaller than the above range indicates that the amount of polar groups is small or absent, and the spheroidization promoting effect tends to be small. On the other hand, if the density is higher than the above range, it is possible that the association of polar groups in the organic compound is strong, and the association of polar groups in the granulation treatment may be difficult to dissociate. The amount of reaction with radicals on the surface may decrease, and the effect of promoting spheroidization may decrease.
The density of the organic compound can be measured by the method described in Examples.

-Boiling point The boiling point of the organic compound contained in the granulator of the present invention is usually 150 ° C. or higher, preferably 200 ° C. or higher, more preferably 230 ° C. or higher, still more preferably 250 ° C. or higher, and the upper limit is not particularly limited.
If it is less than the above range, the organic compound may evaporate during the granulation treatment, the amount of the organic compound may decrease, and the spheroidization promoting effect may be reduced, which is not desirable. Within the above range, the evaporation of the organic compound during the granulation treatment is small enough not to affect the promotion of the spheroidization effect, or the evaporation does not occur, and the spheroidization promotion effect of the organic compound tends to be sufficiently exhibited. Become.
The boiling point of the organic compound can be measured by the method described in Examples.

-Polar group The organic compound contained in the granulating agent of the present invention is not particularly limited as long as it has a specific dielectric constant of 9.0 or more and no branched chain in the molecular structure, but the polar group includes a carboxyl group (polar group). -COOH), hydroxyl group (-OH), carbonyl group (-C = O), alkoxide group (-OCH ₃ , -OCH ₂ CH ₃ , -OCH _2- )), amino group (-NH ₂ ), nitrile group It preferably has (-CN), halogen (-F, -Cl, -Br, -I), etc., among which carboxyl group (-COOH), hydroxyl group (-OH), amino group (-NH ₂ ) and the like. However, it is more preferable because the terminal atoms are easily dissociated and the reaction with the radical generated on the surface of the graphite is easy.
The organic compound having the above characteristics may be used alone or in combination of two or more, and may be used by being dissolved in another organic solvent not contained in the organic compound, water or the like. The content of the organic compound having the above characteristics in the granulating agent is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, and 100% by mass or less.

Further, when the granulating agent used in the present invention contains another organic solvent, at least one of them does not have a flash point, or when it has a flash point, the flash point is 5 ° C. or higher, preferably 50 ° C. or higher. More preferably, it is 90 ° C. or higher, and particularly preferably 150 ° C. or higher. As a result, it is possible to prevent the risk of ignition, fire, and explosion of the organic compound induced by impact or heat generation when granulating the raw material carbon material in the subsequent third step, so that the production is stable and efficient. Can be carried out.

As a method of mixing the raw material carbon material and the granulating agent, for example, a method of mixing the raw material carbon material and the granulating agent using a mixer or a kneader, or a method of dissolving the organic compound in a low-viscosity dilution solvent (organic solvent). Examples thereof include a method of removing the diluting solvent (organic solvent) after mixing the granulator and the raw material carbon material. Further, when the raw material carbon material is granulated in the subsequent third step, the granulating agent and the raw material carbon material are put into the granulation apparatus, and the raw material carbon material and the granulating agent are mixed and granulated. There is also a method of performing the process at the same time.

The amount of the granulating agent added is preferably 0.1 part by mass or more, more preferably 1 part by mass or more, still more preferably 3 parts by mass or more, still more preferably 6 parts by mass or more with respect to 100 parts by mass of the raw material carbon material. More preferably, it is 10 parts by mass or more, preferably 1000 parts by mass or less, more preferably 100 parts by mass or less, further preferably 80 parts by mass or less, particularly preferably 50 parts by mass or less, and most preferably 20 parts by mass or less. Is. If it is within the above range, problems such as a decrease in the degree of spheroidization due to a decrease in the adhesive force between particles and a decrease in productivity due to the adhesion of the raw material carbon material to the apparatus are less likely to occur.

(Third step) A step of granulating the raw material carbon material (a step of spheroidizing the raw material carbon material)
The carbon material is preferably one that has been subjected to a spheroidizing treatment (hereinafter, also referred to as granulation) by applying mechanical actions such as impact compression, friction, and shearing force to the raw material carbon material. Further, the spherical graphite is preferably composed of a plurality of scaly graphite or scaly graphite, and ground graphite fine powder, and particularly preferably composed of a plurality of scaly graphite.
The production method of the present invention includes a granulation step of granulating a raw material carbon material by applying at least one of mechanical energy of impact, compression, friction, and shearing force.
As an apparatus used in this step, for example, an apparatus can be used in which mechanical actions such as compression, friction, and shearing force including the interaction of raw material carbon materials are repeatedly applied mainly to an impact force.

Specifically, it has a rotor with a large number of blades installed inside the casing, and by rotating the rotor at high speed, it is a machine that impacts, compresses, frictions, shears, etc. with respect to the raw material carbon material introduced inside. A device that gives a specific action and performs surface treatment is preferable. Further, it is preferable that the material has a mechanism for repeatedly giving a mechanical action by circulating the raw material carbon material.
Examples of such a device include a hybridization system (manufactured by Nara Machinery Co., Ltd.), a cryptron, a cryptron orb (manufactured by EarthTechnica Co., Ltd.), a CF mill (manufactured by Ube Industries, Ltd.), a mechanofusion system, a novirta, and a faculty (manufactured by Ube Industries, Ltd.). Examples include Hosokawa Micron Co., Ltd.), Theta Composer (manufactured by Tokuju Kosakusho Co., Ltd.), COMPOSI (manufactured by Nippon Coke Industries Co., Ltd.), and the like. Of these, a hybridization system manufactured by Nara Machinery Co., Ltd. is preferable.

When processing using the above device, for example, the peripheral speed of the rotating blade is preferably 30 m / sec or more, more preferably 50 m / sec or more, still more preferably 60 m / sec or more, particularly preferably 70 m / sec or more, most preferably. It is preferably 80 m / sec or more, and preferably 150 m / sec or less. When it is within the above range, it is preferable that the fine powder can be more efficiently sphericalized and at the same time adhered to the base material and encapsulated by the base material.
Further, the treatment of giving a mechanical action to the raw material carbon material can be performed by simply passing the raw material carbon material through, but it is preferable to treat the raw material carbon material by circulating or retaining it in the apparatus for 30 seconds or more. The treatment is carried out by circulating or staying in the apparatus for more preferably 1 minute or longer, further preferably 3 minutes or longer, and particularly preferably 5 minutes or longer.

The internal volume of the casing of the device is not particularly limited, but is usually 1 L or more, preferably 10 L or more, usually 3000 L or less, and preferably 1000 L or less.
If it is within the above range, the processing capacity can be increased, the power for rotating the rotor is also appropriate, and efficient processing can be performed, which is preferable. If the internal volume of the casing is smaller than the above range, the amount of raw materials to be charged is small, so that the processing capacity is inferior, which is not preferable. On the other hand, if it is larger than the above range, a large amount of raw material is charged in the casing, so that a large amount of power tends to be required to rotate the rotor. Further, although it is possible to reduce the amount of raw materials to be charged even when the internal volume of the casing is larger than the above-mentioned defeat range, the equipment tends to have an internal volume larger than necessary with respect to the amount of raw materials to be charged, resulting in inefficiency.

The length of the blade of the device is not particularly limited, but is usually 10 mm or more, preferably 30 mm or more, usually 1000 mm or less, and preferably 800 mm or less.
If it is within the above range, the raw material efficiently collides with the blade, so that the granulation effect spheroidizing effect is high and the processing capacity is high, which is preferable. When the length of the blade is shorter than the above range, the area of the blade that collides with the raw material is small, so that it tends to take a long time to form a granulated sphere. If the length of the blade is larger than the above range, a large amount of power tends to be required to rotate the rotor.

Further, in the step of granulating the raw material carbon material, the raw material carbon material may be granulated in the presence of other substances, and the other substances include, for example, a metal that can be alloyed with lithium or an oxide or scale thereof. Examples include graphite, scaly graphite, ground graphite fine powder, amorphous carbon, and raw coke. By granulating together with a substance other than the raw material carbon material, it is possible to manufacture a negative electrode material for a non-aqueous secondary battery having various types of particle structures.

Further, the raw material carbon material, the granulating agent, and the other substances may be all charged into the apparatus, may be separately charged sequentially, or may be continuously charged. Further, the raw material carbon material, the granulating agent, and the other substances may be charged into the apparatus at the same time, may be mixed and charged, or may be charged separately. The raw material carbon material, the granulating agent and the above-mentioned other substances may be mixed at the same time, the above-mentioned other substances may be added to the mixture of the raw material carbon material and the granulating agent, or the other substances may be formed. The raw material carbon material may be added to the mixture of granules. It can be added and mixed separately at an appropriate timing according to the particle design.

In the spheroidizing treatment of the carbon material, it is more preferable to perform the spheroidizing treatment while adhering the fine powder generated during the spheroidizing treatment to the base material and / or encapsulating the spheroidized particles. By adhering the fine powder generated during the spheroidizing treatment to the base material and / or performing the spheroidizing treatment while encapsulating the spheroidized particles, the void structure in the particles can be further densified. For this reason, the electrolytic solution effectively and efficiently spreads to the voids in the particles, and the Li ion insertion / desorption sites in the particles cannot be efficiently used, so that the electrolytic solution tends to exhibit good low-temperature output characteristics and cycle characteristics. Further, the fine powder adhering to the base material is not limited to that generated during the spheroidizing treatment, and may be adjusted so as to contain the fine powder at the same time when adjusting the particle size of the scaly graphite, or is separately added and mixed at an appropriate timing. You may.

In order to attach the fine powder to the base material and enclose it in the spherical particles, the adhesive force between the scaly graphite particles and the scaly graphite particles, between the scaly graphite particles and the fine powder particles, and between the fine powder particles and the fine powder particles is strengthened. Is preferable. Specific examples of the adhesive force between particles include van der Waals force and electrostatic attraction force not via interparticle inclusions, physical and / or chemical cross-linking force via interparticle inclusions, and the like.

The van der Waals force becomes "self-weight <adhesive force" as the average particle size (d50) becomes smaller at the boundary of 100 μm. Therefore, the smaller the average particle size (d50) of the scaly graphite (raw material carbon material), which is the raw material of the spherical graphite, the greater the interparticle adhesion, and the fine powder adheres to the base material and is contained in the spherical particles. It is easy to be in a state and is preferable. The average particle size (d50) of the scaly graphite is preferably 1 μm or more, more preferably 2 μm or more, still more preferably 3 μm or more, preferably 80 μm or less, more preferably 50 μm or less, still more preferably 35 μm or less, and very preferably. It is 20 μm or less, particularly preferably 10 μm or less.

The electrostatic attraction is derived from charging due to particle friction or the like, and the drier the particles, the easier it is to be charged, and the adhesive force between particles tends to increase. Therefore, for example, the adhesive force between particles can be enhanced by reducing the amount of water contained in the graphite before the spheroidization treatment.

The spheroidizing treatment is preferably carried out in a low humidity atmosphere so that the scaly graphite during the treatment does not absorb moisture, and the oxidative reaction on the surface of the scaly graphite proceeds due to the energy of the mechanical treatment during the treatment and is acidic. It is preferable to perform the spheroidizing treatment in an inert atmosphere for the purpose of preventing the introduction of functional groups.
Physical and / or chemical cross-linking forces via interparticle inclusions include physical and / or chemical cross-linking forces via liquid inclusions, solid inclusions. Examples of the chemical cross-linking force include a cross-linking force when a covalent bond, an ionic bond, a hydrogen bond, or the like is formed between particles and interparticle inclusions due to a chemical reaction, sintering, mechanochemical effect, or the like. ..

<Physical properties of granulated carbon material (spherical graphite) before removal of granulator>
The preferable physical properties of the granulated carbon material (spherical graphite) granulated by the third step will be described.

-Volume-based average particle size (average particle size d50)
The volume-based average particle size (also referred to as "average particle size d50" or "median diameter") of the granulated carbon material (spherical graphite) before removal of the granulator is preferably 1 μm or more, more preferably 3 μm or more. It is more preferably 5 μm or more, particularly preferably 8 μm or more, and particularly preferably 9.5 μm or more. The average particle size d50 is preferably 50 μm or less, more preferably 40 μm or less, still more preferably 35 μm or less, particularly preferably 31 μm or less, and particularly preferably 30 μm or less. Within the above range, when used as a negative electrode material for non-aqueous secondary batteries, an increase in irreversible capacity of non-aqueous electrified secondary batteries can be suppressed, and productivity such as streaks in slurry application is not impaired. There is a tendency.
If the average particle size d50 is too small, the irreversible capacity of the non-aqueous secondary battery tends to increase and the initial battery capacity tends to be lost. It may cause generation, deterioration of high current density charge / discharge characteristics, and deterioration of low temperature output characteristics.

Further, in the present specification, the average particle size d50 is defined as a commercially available laser diffraction / scattering particle size distribution measuring device (for example, LA-920 manufactured by HORIBA) in which 0.01 g of a carbon material is suspended in 10 mL of isopropanol and used as a measurement sample. It is defined that the measurement sample is irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute and then measured as a volume-based median diameter with the measuring device.

・ Average particle size d10
The particle size (d10) corresponding to the cumulative 10% from the small particle side of the particle size measured on the volume basis of the granulated carbon material (spherical graphite) before removing the granulator is preferably 30 μm or less, more preferably 2
It is 0 μm or less, more preferably 17 μm or less, preferably 1 μm or more, more preferably 3 μm or more, still more preferably 5 μm or more.

When d10 is within the above range, when used as a negative electrode material for a non-aqueous secondary battery, the tendency of particle aggregation does not become too strong, causing process inconvenience such as an increase in slurry viscosity, and an electrode in a non-aqueous secondary battery. It is possible to avoid a decrease in strength and a decrease in initial charge / discharge efficiency. In addition, there is a tendency to avoid deterioration of high current density charge / discharge characteristics and low temperature output characteristics.
d10 is defined as a value in which the frequency% of the particles is 10% in total from the small particle size in the particle size distribution obtained in the measurement of the average particle size d50.

-Average particle size d90
The particle size (d90) corresponding to the cumulative 90% from the small particle side of the particle size measured on the volume basis of the granulated carbon material (spherical graphite) before removal of the granulator is preferably 100 μm or less, more preferably 70 μm. Below, it is more preferably 60 μm or less, still more preferably 50 μm or less, particularly preferably 40 μm or less, most preferably 35 μm or less, preferably 10 μm or more, still more preferably 12 μm or more, still more preferably 15 μm or more.

When d90 is within the above range, when used as a negative electrode material for a non-aqueous secondary battery, it is possible to avoid a decrease in electrode strength and a decrease in initial charge / discharge efficiency in the non-aqueous secondary battery, and a streak at the time of application of the slurry. There is a tendency to avoid the occurrence of process inconveniences such as pulling, deterioration of high current density charge / discharge characteristics, and deterioration of low temperature output characteristics.
d90 is defined as a value obtained by integrating the particle size% from the particle size having a small frequency% to 90% in the particle size distribution obtained in the measurement of the average particle size d50.

・ D90 / d10
The d90 / d10 of the granulated carbon material (spherical graphite) before removing the granulator is usually 1 or more, more preferably 1.5 or more, further preferably 1.7 or more, particularly preferably 2 or more, and usually 10 Below, it is preferably 7 or less, more preferably 6 or less, still more preferably 5 or less. When d90 / d10 is within the above range, when used as a negative electrode material for a non-aqueous secondary battery, the filling property of the negative electrode material for a non-aqueous secondary battery is improved by allowing small particles to enter the voids between large particles. As a result, the interparticle pores, which are relatively large pores, can be made smaller and the volume can be reduced, so that the mode diameter in the pore distribution obtained by the mercury intrusion method for powder can be reduced. As a result, it tends to exhibit high capacity, excellent charge / discharge load characteristics, and input / output characteristics.
d90 / d10 is defined as a value obtained by dividing d90 measured by the above method by d10.

Tap density granulating removed prior to granulation carbon material tap density of (spherical graphite) is usually 0.7 g / cm ³ or higher, preferably 0.75 g / cm ³ or more, more preferably 0.8 g / cm ³ or more, more preferably 0.85 g / cm ³ or higher, preferably 0.88 g / cm ³ or more so especially, particularly preferably 0.90 g / cm ³ or more, more particularly preferably 0.91 g / cm ³ or more, and most preferably Is 0.92 g / cm ³ or more, preferably 1.3 g / cm ³ or less, more preferably 1.2 g / cm ³ or less, and further preferably 1.1 g / cm ³ or less.

When the tap density is within the above range, when used as a negative electrode material for a non-aqueous secondary battery, productivity such as streaks during fabrication of an electrode plate becomes good, and high-speed charge / discharge characteristics are excellent. Further, since the carbon density in the particles does not easily increase, the rollability is good, and it tends to be easy to form a high-density negative electrode sheet.
For the tap density, a powder density measuring device is used to attach a cylinder having a diameter of 5 cm and a height of 5 cm to the upper part of a cylindrical tap cell having a ^{diameter of 5 cm and a volume capacity of 100 cm 3, and the measurement sample is dropped through a sieve having a mesh size of 300 μm.} After filling the upper cylinder and tapping with a stroke length of 20 mm 500 times, the upper cylinder is removed, and the powder on the upper part of the cell is scraped off with a spatula on the upper surface of the cell, and the volume inside the cell and the sample inside the cell at that time are removed. It is defined as the density obtained from the mass of.

The granulated carbon material (spherical graphite) before removing the granulating agent is used as it is, or the fourth step described below is carried out, or after the fourth step is carried out, the fifth and subsequent steps are carried out as necessary, or next. It is used as a negative electrode material for non-aqueous secondary batteries by carrying out the fifth step described above, or by carrying out the sixth and subsequent steps as necessary after carrying out the fifth step, or by carrying out the sixth and subsequent steps as necessary. be able to.

(Fourth Step) Step of Removing Granulation Agent In one embodiment of the present invention, there may be a step of removing the granulation agent. Examples of the method for removing the granulating agent include a method of cleaning with a solvent and a method of volatilizing / decomposing and removing the granulating agent by heat treatment.
The heat treatment temperature is preferably 60 ° C. or higher, more preferably 100 ° C. or higher, still more preferably 200 ° C. or higher, still more preferably 300 ° C. or higher, particularly preferably 400 ° C. or higher, most preferably 500 ° C. or higher, and preferably 1500 ° C. ° C. or lower, more preferably 1000 ° C. or lower, still more preferably 800 ° C. or lower. When the heat treatment temperature is within the above range, the granulator can be sufficiently volatilized, decomposed and removed, and the productivity can be improved.

The heat treatment time is preferably 0.1 to 48 hours, more preferably 0.2 to 40 hours, still more preferably 0.4 to 30 hours, and particularly preferably 0.5 to 24 hours. When the heat treatment time is within the above range, the granulating agent can be sufficiently volatilized, decomposed and removed, and the productivity can be improved.

The heat treatment atmosphere may be an active atmosphere such as an air atmosphere or an inert atmosphere such as a nitrogen atmosphere or an argon atmosphere. The heat treatment is not particularly limited when the heat treatment is performed at 200 ° C to 300 ° C, but the heat treatment is performed at 300 ° C or higher. From the viewpoint of preventing the oxidation of the graphite surface, an inert atmosphere such as a nitrogen atmosphere or an argon atmosphere is preferable.

<Physical properties of granulated carbon material (spherical graphite) after removal of granulator>
The preferable physical properties of the granulated carbon material (spherical graphite) from which the granulating agent has been removed by the fourth step will be described.

-Volume-based average particle size (average particle size d50)
The volume-based average particle size (also referred to as "average particle size d50" or "median diameter") of the granulated carbon material (spherical graphite) after removing the granulator is preferably 1 μm or more, more preferably 3 μm or more. It is more preferably 5 μm or more, particularly preferably 8 μm or more, and particularly preferably 9.5 μm or more. The average particle size d50 is preferably 50 μm or less, more preferably 40 μm or less, still more preferably 35 μm or less, particularly preferably 31 μm or less, and particularly preferably 30 μm or less. Within the above range, when used as a negative electrode material for non-aqueous secondary batteries, an increase in irreversible capacity of non-aqueous electrified secondary batteries can be suppressed, and productivity such as streaks in slurry application is not impaired. There is a tendency.
If the average particle size d50 is too small, the irreversible capacity of the non-aqueous secondary battery tends to increase and the initial battery capacity tends to be lost. It may cause generation, deterioration of high current density charge / discharge characteristics, and deterioration of low temperature output characteristics.

・ Average particle size d10
The particle size (d10) corresponding to the cumulative 10% from the small particle side of the particle size measured on the volume basis of the granulated carbon material (spherical graphite) after removing the granulating agent is preferably 30 μm or less, more preferably 20 μm. Below, it is more preferably 17 μm or less, preferably 1 μm or more, more preferably 3 μm or more, still more preferably 5 μm or more.

When d10 is within the above range, when used as a negative electrode material for a non-aqueous secondary battery, the tendency of particle aggregation does not become too strong, causing process inconvenience such as an increase in slurry viscosity, and electrode strength in a non-aqueous secondary battery. And the decrease in initial charge / discharge efficiency can be avoided. In addition, there is a tendency to avoid deterioration of high current density charge / discharge characteristics and low temperature output characteristics.

-Average particle size d90
The particle size (d90) corresponding to the cumulative 90% from the small particle side of the particle size measured on the volume basis of the granulated carbon material (spherical graphite) after removing the granulating agent is preferably 100 μm or less, more preferably 70 μm. Below, it is more preferably 60 μm or less, still more preferably 50 μm or less, particularly preferably 40 μm or less, most preferably 35 μm or less, preferably 10 μm or more, still more preferably 12 μm or more, still more preferably 15 μm or more.

When d90 is within the above range, when used as a negative electrode material for a non-aqueous secondary battery, it is possible to avoid a decrease in electrode strength and a decrease in initial charge / discharge efficiency in the non-aqueous secondary battery, and a streak at the time of application of the slurry. There is a tendency to avoid the occurrence of process inconveniences such as pulling, deterioration of high current density charge / discharge characteristics, and deterioration of low temperature output characteristics.

・ D90 / d10
The d90 / d10 of the granulated carbon material (spherical graphite) after removing the granulator is usually 1 or more, more preferably 1.5 or more, further preferably 1.7 or more, particularly preferably 2 or more, and usually 10 Below, it is preferably 7 or less, more preferably 6 or less, still more preferably 5 or less. When d90 / d10 is within the above range, when used as a negative electrode material for a non-aqueous secondary battery, the filling property of the negative electrode material for a non-aqueous secondary battery is improved by allowing small particles to enter the voids between large particles. As a result, the interparticle pores, which are relatively large pores, can be made smaller and the volume can be reduced, so that the mode diameter in the pore distribution obtained by the mercury intrusion method for powder can be reduced. As a result, it tends to exhibit high capacity, excellent charge / discharge load characteristics, and input / output characteristics.

Tap density granulating granulating carbon material after removal tap density of (spherical graphite) is usually 0.7 g / cm ³ or higher, preferably 0.75 g / cm ³ or more, more preferably 0.8 g / cm ³ or more, more preferably 0.85 g / cm ³ or higher, preferably 0.88 g / cm ³ or more so especially, particularly preferably 0.90 g / cm ³ or more, more particularly preferably 0.91 g / cm ³ or more, and most preferably Is 0.92 g / cm ³ or more, preferably 1.3 g / cm ³ or less, more preferably 1.2 g / cm ³ or less, and further preferably 1.1 g / cm ³ or less.

When the tap density is within the above range, when used as a negative electrode material for a non-aqueous secondary battery, productivity such as streaks during fabrication of an electrode plate becomes good, and high-speed charge / discharge characteristics are excellent. Further, since the carbon density in the particles does not easily increase, the rollability is good, and it tends to be easy to form a high-density negative electrode sheet.

-Bulk density The bulk density of the granulated carbon material (spherical graphite) after removing the granulator is preferably 0.3 g / cm ³ or more, more preferably 0.35 g / cm ³ or more, still more preferably 0.4 g / cm. cm ³ or more, particularly preferably 0.45 g / cm ³ or more, more preferably 1.3 g / cm ³ or less, more preferably 1.2 g / cm ³ or less, particularly preferably 1.1 g / cm ³ or less, Most preferably, it is 1 g / cm ³ or less.
When the bulk density is within the above range, when it is used as a negative electrode material for a non-aqueous secondary battery, streaks and the like during fabrication of an electrode plate are suppressed, productivity is improved, and high-speed charge / discharge characteristics are excellent. Further, since it has appropriate pores, the electrolytic solution can move smoothly, and tends to exhibit good charge / discharge load characteristics and low temperature input / output characteristics.
The bulk density is determined by using a powder density measuring device to drop a negative electrode material for a non-aqueous secondary battery into a cylindrical tap cell having a diameter of 5 cm and a volume capacity of 100 cm ^{3 through a sieve having an opening of 300 μm to fill the cell.} It is defined as the density obtained from the volume and the mass of the sample.

・ BET specific surface area (SA)
The specific surface area (SA) of the granulated carbon material (spherical graphite) measured by the BET method after removing the granulator is preferably 5 m ² / g or more, more preferably 10 m ² / g or more, still more preferably 15 m ^2. / G or more, particularly preferably 18 m ² / g or more. Further, it is preferably 40 m ² / g or less, more preferably 30 m ² / g or less, and further preferably 28 m ² / g or less.
When the specific surface area is within the above range, when used as a negative electrode material for a non-aqueous secondary battery, it is possible to secure a sufficient portion for Li to enter and exit, so that it is excellent in high-speed charge / discharge characteristics and output characteristics, and is suitable for an electrolytic solution of an active material. Since the activity can be suppressed appropriately, the initial irreversible capacity does not increase, and there is a tendency that a high capacity battery can be manufactured.
Further, when a negative electrode is formed by using a carbon material, an increase in reactivity with the electrolytic solution can be suppressed and gas generation can be suppressed, so that a preferable non-aqueous secondary battery can be provided.

For the BET specific surface area, a surface area meter (for example, Shimadzu Corporation's specific surface area measuring device "Gemini 2360") was used to preliminarily dry the carbon material sample at 100 ° C. for 3 hours under nitrogen flow, and then liquid nitrogen. It is defined as a value measured by the nitrogen adsorption BET 6-point method by the gas flow method using a nitrogen helium mixed gas that has been cooled to a temperature and accurately adjusted so that the value of the relative pressure of nitrogen with respect to atmospheric pressure is 0.3.
The granulated carbon material (spherical graphite) after removing the granulating agent is used as it is, or the fifth step described below is carried out, or after the fifth step is carried out, the sixth and subsequent steps are carried out as necessary, or the first step is carried out. By carrying out the sixth and subsequent steps as necessary, it can be used as a negative electrode material for non-aqueous secondary batteries.

(Fifth Step) Step of Purifying Granulated Carbon Material In the present invention, there may be a step of purifying the granulated carbon material. As a method for purifying the granulated carbon material, there is a method of performing an acid treatment containing nitric acid and hydrochloric acid, and a metal or metal in graphite without introducing a sulfate which can be a highly active sulfur source into the system. It is preferable because impurities such as compounds and inorganic compounds can be removed.
For the above acid treatment, an acid containing nitric acid or hydrochloric acid may be used, and other acids such as bromic acid, hydrofluoric acid, boric acid or iodic acid, or citric acid, formic acid, acetic acid and shu An acid in which an organic acid such as an acid, trichloroacetic acid or trifluoroacetic acid is appropriately mixed can also be used. Concentrated hydrofluoric acid, concentrated nitric acid and concentrated hydrochloric acid are preferable, and concentrated nitric acid and concentrated hydrochloric acid are more preferable. In the present invention, graphite may be treated with sulfuric acid, but it is used in an amount and concentration that does not impair the effects and physical characteristics of the present invention.

When a plurality of acids are used, for example, a combination of hydrofluoric acid, nitric acid, and hydrochloric acid is preferable because the above impurities can be efficiently removed. When the types of acids are combined as described above, the mixing ratio of the mixed acids is usually 10% by mass or more, preferably 20% by mass or more, and more preferably 25% by mass or more. The upper limit is a value that is a mixture of all equal amounts (represented by 100% by mass / type of acid).

The mixing ratio (mass ratio) of graphite and acid in the acid treatment is usually 100:10 or more, preferably 100:20 or more, more preferably 100:30 or more, still more preferably 100: 4.
It is 0 or more, and 100: 1000 or less, preferably 100: 500 or less, and more preferably 100: 300 or less. If it is too small, the impurities tend to be unable to be removed efficiently. On the other hand, if it is too large, the amount of graphite that can be washed at one time is reduced, which leads to a decrease in productivity and an increase in cost, which is not preferable.

The acid treatment is performed by immersing graphite in an acidic solution as described above. The immersion time is usually 0.5 to 48 hours, preferably 1 to 40 hours, more preferably 2 to 30 hours, still more preferably 3 to 24 hours. If it is too long, it tends to cause a decrease in productivity and an increase in cost, and if it is too short, it tends to be difficult to sufficiently remove the above impurities.
The immersion temperature is usually 25 ° C. or higher, preferably 40 ° C. or higher, more preferably 50 ° C. or higher, still more preferably 60 ° C. or higher. When an aqueous acid is used, the theoretical upper limit is 100 ° C., which is the boiling point of water. If this temperature is too low, the impurities tend to be insufficiently removed.

It is preferable to carry out further water washing for the purpose of removing the acid content remaining by the acid washing and raising the pH from weakly acidic to the neutral range. For example, if the pH of the graphite (treated graphite) washed with the acid is usually 3 or more, preferably 3.5 or more, more preferably 4 or more, still more preferably 4.5 or more, it is washed with water. This can be omitted, and if it is not within the above range, it is preferable to wash with water if necessary. It is preferable to use ion-exchanged water or distilled water as the cleaning water from the viewpoint of improving cleaning efficiency and preventing impurities from being mixed. The specific resistance, which is an index of the amount of ions in water, is usually 0.1 MΩ · cm or more, preferably 1 MΩ · cm or more, more preferably 10 MΩ · cm or more. The theoretical upper limit at 25 ° C. is 18.24 MΩ · cm. When this value is small, it indicates that the amount of ions in water increases, and there is a tendency for impurities to be mixed and the cleaning efficiency to decrease.

The time for washing with water, that is, stirring the treated graphite and water is usually 0.5 to 48 hours, preferably 1 to 40 hours, more preferably 2 to 30 hours, still more preferably 3 to 24 hours. is there. If it is too long, the production efficiency tends to decrease, and if it is too short, residual impurities and acids tend to increase.
The mixing ratio of the treated graphite and water is usually 100:10 or more, preferably 100:30 or more, more preferably 100:50 or more, still more preferably 100: 100 or more, and 100: 1000 or less. It is preferably 100: 700 or less, more preferably 100: 500 or less, and even more preferably 100: 400 or less. If it is too large, the production efficiency tends to decrease, and if it is too small, residual impurities and acids tend to increase.

The stirring temperature is usually 25 ° C. or higher, preferably 40 ° C. or higher, more preferably 50 ° C. or higher, still more preferably 60 ° C. or higher. The upper limit is 100 ° C., which is the boiling point of water. If it is too low, residual impurities and acid content tend to increase.
When the water cleaning process is performed in a batch system, it is preferable to repeat the stirring-filtration process in pure water a plurality of times for cleaning from the viewpoint of removing impurities and acids. The above treatment may be repeated so that the pH of the above-mentioned treated graphite is within the above range. Usually, it is once or more, preferably twice or more, and more preferably three times or more.

By performing the treatment as described above, the wastewater hydrogen ion concentration of the obtained graphite is usually 200 ppm or less, preferably 100 ppm or less, more preferably 50 ppm or less, further preferably 30 ppm or less, and usually 1 ppm or more, preferably 2 ppm. As mentioned above, it is more preferably 3 ppm or more, still more preferably 4 ppm or more. If the hydrogen ion concentration is too high, the acid content tends to remain and the pH tends to decrease, and if it is too low, the treatment takes time and tends to lead to a decrease in productivity.

(Fifth step) Step of heat-treating the granulated carbon material In the present invention, a step of heat-treating may be provided in order to adjust the unstable carbon amount and crystallinity of the granulated carbon material. When the above-mentioned granulation treatment is performed, the anxious low carbon amount on the surface of the carbon material particles may increase too much, and the anxious low carbon amount can be appropriately reduced by performing the heat treatment.
The temperature conditions during the heat treatment are not particularly limited, but are usually 300 ° C. or higher, preferably 500 ° C., more preferably 700 ° C., particularly preferably 800 ° C. or higher, and usually 2000 ° C., depending on the desired degree of crystallinity. The temperature is in the range of ° C. or lower, preferably 1500 ° C. or lower, particularly preferably 1200 ° C. or lower. Under the above temperature conditions, the crystallinity of the surface of the carbon material particles can be appropriately increased.

Further, when the granulated carbon material contains a carbon material having low crystallinity, it is possible to increase the crystallinity by graphitizing the carbon material having low crystallinity in this step for the purpose of increasing the discharge capacity. The temperature conditions during the heat treatment are not particularly limited, but are usually 600 ° C. or higher, preferably 900 ° C., more preferably 1600 ° C., particularly preferably 2500 ° C. or higher, and usually 3200 ° C., depending on the desired degree of crystallinity. The temperature is in the range of ° C. or lower, preferably 3100 ° C. or lower. Under the above temperature conditions, the crystallinity of the surface of the carbon material particles can be enhanced.
Further, the crystals on the surface of the carbon material particles may be disturbed, and the disorder is particularly remarkable when the above-mentioned granulation treatment is performed. Therefore, the crystals on the surface of the carbon material particles disturbed by the heat treatment are performed. Can be repaired.

When the heat treatment is performed, the holding time for keeping the temperature condition in the above range is not particularly limited, but is usually longer than 10 seconds and 72 hours or less.
The heat treatment is performed in an atmosphere of an inert gas such as nitrogen gas or in a non-oxidizing atmosphere of a gas generated from the raw material graphite. The apparatus used for the heat treatment is not particularly limited, and for example, a shuttle furnace, a tunnel furnace, an electric furnace, a reed hammer furnace, a rotary kiln, a direct energization furnace, an Achison furnace, a resistance heating furnace, an induction heating furnace and the like can be used.

(Sixth Step) A step of adhering a carbonaceous material having a lower crystallinity than the raw material carbon material to the granulated carbon material In the production method of the present invention, the granulated carbon material has a carbonaceous material having a lower crystallinity than the raw material carbon material. It may have a step of adhering (B). That is, the composite carbon material can be composited with the carbonaceous substance (B) for the purpose of suppressing side reactions with the electrolytic solution and improving the rapid charge / discharge property. According to this step, it is possible to obtain a carbon material capable of suppressing side reactions with the electrolytic solution and improving the rapid charge / discharge property.
Composite graphite obtained by impregnating a granulated carbon material with a carbon material having a lower crystallinity than the raw material carbon material may be referred to as a "carbon material composite carbon material", a "multilayered carbon material" or a "composite carbon material".

-Content of carbonaceous material (B) in composite carbon material The content of carbonaceous material (B) in the composite carbon material is usually 0.01% by mass or more, preferably 0.1% by mass, based on the granulated carbon material. By mass% or more, more preferably 0.5% or more, still more preferably 1% by mass or more, particularly preferably 2% by mass or more, most preferably 3% by mass or more, and the content is usually 30% by mass or less. It is preferably 20% by mass or less, more preferably 15% by mass or less, still more preferably 10% by mass or less, and particularly preferably 7% by mass or less.

If the content of the carbonaceous material (B) in the composite carbon material is too large, the carbon material (A) will be damaged when rolling is performed at a pressure sufficient to achieve a high capacity in a non-aqueous secondary battery. When given, material destruction tends to occur, leading to an increase in charge / discharge irreversible capacity during the initial cycle and a decrease in initial efficiency. On the other hand, if the content is too small, it tends to be difficult to obtain the effect of coating.
Further, the content of the carbonaceous material (B) in the composite carbon material can be calculated from the sample mass before and after firing the material as shown in the following formula. At this time, it is calculated assuming that there is no change in mass of the granulated carbon material before and after firing.

Content (mass%) of carbonaceous material (B) = [(w2-w1) / w1] × 100
(W1 is the mass of the granulated carbon material (kg), and w2 is the mass of the composite carbon material (kg))
The amount of carbonaceous material (B) in the composite carbon material is the amount of carbon added when the granulated carbon material and the carbonaceous material (B) precursor are combined when the carbonaceous material (B) is compounded by the mixing method. It can be controlled by the amount of the pledge (B) precursor, the residual carbon content of the carbonaceous (B) precursor, and the like. For example, JIS
When the residual carbon content of the carbonaceous substance (B) precursor determined by the method described in K2270 is p%, a carbonaceous substance (B) precursor that is 100 / p times the desired amount of the carbonaceous substance (B) is added. It will be. Further, when the carbonaceous substance (B) is compounded by the vapor phase method, it can be controlled by the temperature, pressure, time and the like of the carbonaceous substance (B) precursor flow.

X-ray parameter of carbonaceous material (B) The d value (interlayer distance) of the lattice plane (002 plane) obtained by X-ray diffraction by the Gakushin method of carbonaceous material (B) is usually 0.3445 nm or less, preferably 0. .335 nm or more and less than 0.340 nm. Here, the d value is more preferably 0.339 nm or less, still more preferably 0.337 nm or less. When the d ₀₀₂ value is within the above range, the amount of lithium entering the graphite layers increases, so that a high charge / discharge capacity is exhibited.

The crystallite size (Lc) of the carbonaceous substance (B) determined by X-ray diffraction by the Gakushin method is preferably in the range of 1.5 nm or more, more preferably 3.0 nm or more. Within the above range, the amount of lithium entering the graphite layers increases, so that a high charge / discharge capacity is exhibited. The lower limit of Lc is the theoretical value of graphite.
The X-ray parameters of the carbonaceous substance (B) can be analyzed by, for example, heating and calcining only the carbonaceous substance (B) precursor to obtain the carbonaceous substance (B).

-Composite with granulated carbon material In order to contain the carbonaceous material (B) on the surface of the granulated carbon material, for example, the granulated carbon material is mixed with the precursor of the carbonaceous material (B) or the carbonaceous material (B). Is vapor-deposited. Particularly preferably, a treatment in which an organic compound which is a precursor of a carbonaceous substance (B) is uniformly coated with a granulated carbon material and heated in a non-oxidizing atmosphere (referred to as a mixing method in the present invention). Alternatively, a treatment (referred to as a vapor phase method in the present invention) in which a vapor phase coating raw material compound which is a precursor of a carbon substance (B) is uniformly deposited on a granulated carbon material in an inert gas atmosphere can be mentioned. Hereinafter, the mixing method and the gas phase method will be described.

(Mixing method)
In the mixing method, the granulated carbon material is mixed with the organic compound which is the precursor of the carbonaceous substance (B) so as to be uniformly covered, and heated in a non-oxidizing atmosphere.

<Types of organic compounds that are precursors of carbonaceous substances (B)>
Organic compounds that are precursors of carbonaceous substances (B) include various soft to hard coal tar pitches, carbon-based heavy oils such as coal tar and coal liquefaction oil, and petroleum such as crude oil at atmospheric pressure or vacuum distillation residual oil. Various kinds of heavy oils such as heavy oils and decomposition heavy oils, which are by-products of ethylene production by naphtha decomposition, can be used.
Further, as one embodiment of the present invention, the affinity with a granulating agent having an aniline point of 80 ° C. or lower is good, and an organic compound serving as a carbonaceous material precursor can be uniformly adhered to the surface of the granulated graphite. Therefore, it is preferable to use a petroleum-based raw material oil or a carbon-based raw material oil, and it is particularly preferable to use a carbon-based raw material oil.

Examples of the resin-derived organic compound include thermosetting resins such as phenol resins, polyacrylic nitriles and polyimides, thermoplastic resins such as polyvinyl chloride, polyvinylidene chloride and polyvinyl alcohol, and celluloses, starches and polysaccharides. Natural polymers can be mentioned.

Examples of coal-based raw material oils include coal tar pitch produced from coal as a raw material, impregnation pitch, molding pitch, coal-based heavy oil such as coal liquefied oil, and refined coal tar pitch obtained by removing insoluble components in coal tar pitch. Can be used. Coal-based raw material oil contains a large amount of flat aromatic hydrocarbons such as dibenzocoronene and pentacene in which a large number of benzene rings are bonded. When the temperature of the fragrant hydrocarbon having a flat plate structure increased and the fluidity increased in the firing step, the surfaces of the aromatic hydrocarbon having the flat plate structure easily overlapped with each other, and the flat plate structures overlapped due to the polycondensation reaction by heat. Since it proceeds in a state, the van der Waals force acting between the surfaces of the hydrocarbons polymerized by polycondensation becomes stronger, and the distance between the surfaces of the polymerized hydrocarbons tends to decrease, resulting in crystallization. The degree of progress is high.

Examples of the petroleum-based raw material oil include distillation residual oil of heavy oil, cracked naphtha residual oil, and catalytically cracked heavy oil. Further, heat treatment pitches such as ethylene tar pitch, FCC decant oil, and Ashland pitch obtained by heat-treating the cracked heavy oil can be mentioned. The petroleum-based raw material oil also contains flat-plate aromatic hydrocarbons to which a large number of benzene rings are bonded, but also contains a large number of linear paraffin-based hydrocarbons, and further, a large number of benzene rings are bonded. It is known that many flat aromatic hydrocarbons have side chains such as methyl groups, and that many of them contain a part of the benzene ring replaced with a cyclohexane ring. Has been done. Therefore, when the temperature rises in the firing step and the fluidity increases and the surfaces of the aromatic hydrocarbons having a flat plate structure try to overlap each other, the overlap is hindered by the large amount of the linear paraffin on the surfaces. There is a tendency. Further, flat aromatic hydrocarbons having a side chain such as a methyl group tend to interfere with the overlap of the flat aromatic hydrocarbons. In addition, the cycloxane ring also tends to inhibit the overlap of aromatic hydrocarbons, but the cycloxane ring is decomposed by heat to form a side chain such as a methyl group, and further tends to inhibit the overlap. From these facts, the coal-based raw material oil tends to have a higher degree of crystallization progress than the petroleum-based raw material oil, and is therefore preferable as an organic compound serving as a carbonaceous substance precursor used in the present invention.

Specifically, petroleum-based heavy oil generated during petroleum refining and coal-based raw material oil using coal tar generated during the production of iron-making coke as a starting material are preferable, and when distilling coal tar. A soft pitch of 0 ° C. or higher, preferably 30 to 100 ° C., which is extracted from the bottom of the tower, or a pitch called a medium pitch is more preferable. Further, as the organic compound serving as the carbonaceous substance precursor of the present invention, a petroleum-based raw material oil, a resin-derived organic compound, or another solvent may be added to these coal-based raw material oils.

In addition, since these coal-based raw material oils usually contain light oil components, it is preferable to carry out a distillation operation to extract useful components and increase productivity, and to purify and use them.

The residual carbon content of the organic compound as the precursor of the carbonaceous substance (B) is usually 1% or more, preferably 10% or more, more preferably 20% or more, still more preferably 30% or more, and particularly preferably 45% or more. It is usually 99% or less, preferably 90% or less, more preferably 70% or less, still more preferably 60% or less. The residual coal ratio can be measured by a method conforming to JIS 2270, for example. When the residual coal ratio is within the above range, it can be uniformly diffused and permeated into the surface of the granulated carbon material and the inside of the micropores, and the input / output characteristics tend to be improved.

Further, the carbonaceous substance (B) precursor can be diluted by adding a solvent or the like, if necessary. By adding a solvent or the like, it becomes possible to reduce the viscosity of the carbonaceous material (B) precursor, and the carbonaceous material (B) precursor tends to diffuse and permeate more uniformly on the surface of the granulated carbon material and inside the micropores. There is.

The method of mixing the organic compound serving as the carbonaceous substance (B) precursor with the granulated carbon material is not particularly limited, and for example, various kinds of the granulated carbon material and the organic compound serving as the carbonaceous substance (B) precursor can be used. Examples thereof include a method of obtaining a mixture in which an organic compound is attached to a granulated carbon material by mixing using a commercially available mixer, kneader or the like.

Raw materials such as a granulated carbon material, an organic compound as an organic compound as a precursor of a carbonaceous substance (B), and a solvent added as needed are mixed under heating as necessary. As a result, the granulated carbon material is in a state in which an organic compound serving as a liquid carbonaceous substance (B) precursor is attached. In this case, all the raw materials may be charged into the mixer to mix and raise the temperature at the same time, or components other than the organic compound serving as the precursor of the carbonaceous substance (B) may be charged into the mixer, preheated in a stirred state, and mixed. An organic compound which becomes a carbonaceous material precursor which has been melted by normal temperature or preheating after the temperature has risen to the temperature may be added. When the granulated graphite particles come into contact with the organic compound that becomes the carbonaceous substance precursor, the organic compound that becomes the carbonaceous substance (B) precursor cools and becomes highly viscous to prevent the coating form from becoming non-uniform. In order to obtain the carbonaceous material (B), a component other than the organic compound as a precursor is charged into the mixer and preheated in a stirred state. After the temperature rises to the mixing temperature, the carbonaceous material is preheated to the mixing temperature and becomes a molten state. (B) It is more preferable to add an organic compound as a precursor.

The heating temperature is usually equal to or higher than the softening point of the organic compound that is the precursor of the carbonaceous substance (B), preferably a temperature 10 ° C. or higher higher than the softening point, more preferably a temperature 20 ° C. or higher higher than the softening point, and further preferably 30. The temperature is higher than ° C., particularly preferably 50 ° C. or higher, and is usually 450 ° C. or lower, preferably 250 ° C. or lower. If the heating temperature is too low, the viscosity of the organic compound that becomes the precursor of the carbonaceous substance (B) becomes high, which may make mixing difficult and the coating form may become non-uniform. If the heating temperature is too high, the carbonaceous substance (B) Due to the volatilization and polycondensation of the organic compound as a precursor, the viscosity of the mixed system becomes high, which makes mixing difficult and may result in non-uniform coating morphology.

The mixer is preferably a model having a stirring blade, and for example, a commercially available mixer such as a ribbon mixer, an MC processor, a proshare mixer, or a KRC kneader can be used. The mixing time is usually 1 minute or more, preferably 2 minutes or more, more preferably 5 minutes or more, and usually 300 minutes or less, preferably 120 minutes or less, more preferably 80 minutes or less. If the mixing time is too short, the coating form may become non-uniform, and if it is too long, the productivity tends to decrease and the cost tends to increase.

The heating temperature (calcination temperature) varies depending on the carbonaceous material (B) precursor used for preparing the mixture, but is usually heated to 800 ° C. or higher, preferably 900 ° C. or higher, more preferably 950 ° C. or higher to be sufficiently amorphous. Quality Carbonized or graphitized. The upper limit of the heating temperature is the temperature at which the carbide of the carbonaceous material (B) precursor does not reach the crystal structure equivalent to the crystal structure of the scaly graphite which is the carbon material (A) in the mixture, and is usually at most 3500. ℃. The upper limit of the heating temperature is preferably 3000 ° C., preferably 2000 ° C., more preferably 1500 ° C.

The atmosphere during the heat treatment is performed under the flow of an inert gas such as nitrogen or argon or in a non-oxidizing atmosphere in which the gaps are filled with granular carbon materials such as breathe and packing coke in order to prevent oxidation. Equipment used for heat treatment includes reaction tanks such as shuttle furnaces, tunnel furnaces, reed hammer furnaces, rotary kilns, and autoclaves, cokers (heat treatment tanks manufactured by coke), electric furnaces and gas furnaces, and Achison furnaces for electrode materials. The temperature rise rate, cooling rate, heat treatment time, etc. can be arbitrarily set within the permissible range of the equipment to be used.

(Phase method)
Examples of the vapor phase method include treatments such as a CVD (Chemical Vapor Deposition) method in which a vapor phase coating raw material compound, which is a precursor of a carbonaceous substance (B), is uniformly deposited on the surface of a granulated carbon material in an inert gas atmosphere. Be done.
As a specific example of the gas phase coating raw material compound which is a precursor of the carbonaceous material (B), a gaseous compound which can be decomposed by heat, plasma or the like to form a carbonaceous material (B) film on the surface of the carbonaceous material (A) is used. Can be used. Examples of the gaseous compound include unsaturated aliphatic hydrocarbons such as ethylene, acetylene and propylene, saturated aliphatic hydrocarbons such as methane, ethane and propane, and aromatic hydrocarbons such as benzene, toluene and naphthalene. These compounds may be used alone or as a mixed gas of two or more kinds. The temperature, pressure, time, etc. for performing the CVD treatment can be appropriately selected according to the type of coating raw material used and the desired amount of coated carbonaceous material (B).

(Other processes)
The composite carbon material of the present invention can be obtained by subjecting the above-mentioned mixing method or vapor phase method to crushing and / or crushing treatment, classification treatment, etc., if necessary.
The shape is arbitrary, but the average particle size is usually 2 to 50 μm, preferably 5 to 35 μm, and particularly 8 to 30 μm. Crush and / or crush and / or classify as necessary so as to be within the above particle size range.
In addition, as long as the effect of this embodiment is not impaired, other steps may be added or control conditions not described above may be added.

<Physical characteristics of composite carbon material (multi-layer structure carbon material)>
The preferable physical properties of the composite carbon material produced by the sixth step will be described.

-Volume-based average particle size (average particle size d50)
The volume-based average particle size (also referred to as "average particle size d50" or "median diameter") of the composite carbon material is preferably 1 μm or more, more preferably 3 μm or more, still more preferably 5 μm or more, and particularly preferably 8 μm. As mentioned above, it is particularly preferably 9.5 μm or more. The average particle size d50 is preferably 50 μm or less, more preferably 40 μm or less, still more preferably 35 μm or less, particularly preferably 31 μm or less, and particularly preferably 30 μm or less. Within the above range, an increase in irreversible volume can be suppressed, and productivity such as streaks in slurry application tends not to be impaired.
If the average particle size d50 is too small, the irreversible capacity of the non-aqueous secondary battery obtained by using the composite carbon material tends to increase and the initial battery capacity tends to be lost. On the other hand, if the average particle size d50 is too large, the slurry is applied. In some cases, process inconveniences such as streaks may occur, high current density charge / discharge characteristics may be deteriorated, and low temperature output characteristics may be deteriorated.

・ Average particle size d10
The particle size (d10) corresponding to the cumulative 10% from the small particle side of the particle size measured on the volume basis of the composite carbon material is preferably 30 μm or less, more preferably 20 μm or less, still more preferably 17 μm or less, preferably 1 μm or more. , More preferably 3 μm or more, still more preferably 5 μm or more.
When d10 is within the above range, the tendency of particle aggregation does not become too strong, and it is possible to avoid the occurrence of process inconvenience such as an increase in slurry viscosity, a decrease in electrode strength in a non-aqueous secondary battery, and a decrease in initial charge / discharge efficiency. In addition, there is a tendency to avoid deterioration of high current density charge / discharge characteristics and low temperature output characteristics.

-Average particle size d90
The particle size (d90) corresponding to the cumulative 90% from the small particle side of the particle size measured on the volume basis of the composite carbon material is preferably 100 μm or less, more preferably 70 μm or less, still more preferably 60 μm or less, still more preferably. It is 50 μm or less, particularly preferably 40 μm or less, most preferably 35 μm or less, preferably 10 μm or more, more preferably 12 μm or more, still more preferably 15 μm or more.
When d90 is within the above range, it is possible to avoid a decrease in electrode strength and a decrease in initial charge / discharge efficiency in a non-aqueous secondary battery, causing process inconvenience such as streaking during slurry application, and high current density charge / discharge characteristics. There is a tendency that the decrease in low temperature output characteristics can be avoided.

・ D90 / d10
The d90 / d10 of the composite carbon material is usually 2 or more, more preferably 1 or more, further preferably 1.5 or more, particularly preferably 2.2 or more, and usually 10 or less, preferably 7 or less, more preferably 6 or less. , More preferably 5 or less. When d90 / d10 is within the above range, the filling property of the negative electrode material for a non-aqueous secondary battery is improved by allowing small particles to enter the voids between large particles, and the interparticle pores, which are relatively large pores, are improved. Since the volume can be reduced and the volume can be reduced, the mode diameter in the pore distribution obtained by the mercury press-fitting method for the powder can be reduced. As a result, it tends to exhibit high capacity, excellent charge / discharge load characteristics, and input / output characteristics.

-Tap density The tap density of the composite carbon material is usually 0.7 g / cm ³ or more, preferably 0.75 g / cm ³ or more, more preferably 0.8 g / cm ³ or more, still more preferably 0.83 g / cm ³ or more. , Especially preferably 0.85 g / cm ³ or more, particularly preferably 0.88 g / cm ³ or more, more particularly preferably 0.9 g / cm ³ or more, and most preferably 0.95 g / cm ³ or more. is a 1.3 g / cm ³ or less, more preferably 1.2 g / cm ³ or less, further preferably 1.1 g / cm ³ or less.
When the tap density is within the above range, the productivity such as streaks during the production of the electrode plate becomes good, and the high-speed charge / discharge characteristics are excellent. Further, since the carbon density in the particles does not easily increase, the rollability is good, and it tends to be easy to form a high-density negative electrode sheet.

-Bulk density The bulk density of the composite carbon material is preferably 0.3 g / cm ³ or more, more preferably 0.35 g /.
cm ³ or more, more preferably 0.4 g / cm ³ or more, particularly preferably 0.45 g / cm ³ or more, more preferably 1.3 g / cm ³ or less, more preferably 1.2 g / cm ³ or less, It is particularly preferably 1.1 g / cm ³ or less, and most preferably 1 g / cm ³ or less.
When the bulk density is within the above range, streaks and the like during the production of the electrode plate are suppressed, the productivity is improved, and the high-speed charge / discharge characteristics are excellent. Further, since it has appropriate pores, the electrolytic solution can move smoothly, and tends to exhibit good charge / discharge load characteristics and low temperature input / output characteristics.

・ BET specific surface area (SA)
The specific surface area (SA) of the composite carbon material measured by the BET method is preferably 1 m ² / g or more, more preferably 3 m ² / g or more, still more preferably 4 m ² / g or more, and particularly preferably 5 m ² / g or more. Is. Further, it is preferably 30 m ² / g or less, more preferably 28 m ² / g or less, and further preferably 25 m ² / g or less.

When the specific surface area is within the above range, it is possible to secure a sufficient portion for Li to enter and exit, so that the output characteristics of high-speed charge / discharge characteristics are excellent, and the activity of the active material with respect to the electrolytic solution can be appropriately suppressed. Does not increase, and there is a tendency that high-capacity batteries can be manufactured.
Further, when a negative electrode is formed by using a carbon material, an increase in reactivity with the electrolytic solution can be suppressed and gas generation can be suppressed, so that a preferable non-aqueous secondary battery can be provided.

The composite carbon material can be used as a negative electrode material for a non-aqueous secondary battery as it is or by carrying out other steps as necessary.
The carbon material produced by the production method according to the embodiment of the present invention can stably produce carbon materials having various types of particle structures. Typical particle structures include a carbon material produced by folding scaly graphite having a large or medium average particle size as a raw material carbon material, and granulating (folding) scaly graphite having a small average particle size. Examples include the carbon material to be manufactured and the carbon material obtained by impregnating natural graphite with artificial graphite.

As an example of the stable production of carbon materials having various types of particle structures, the yield (carbon material weight / total solid raw material weight) expressed by the carbon material weight ratio to the total solid raw material weight is usually 60%. The above is preferably 80% or more, and more preferably 95% or more.

<Negative electrode material for non-aqueous secondary batteries>
Any material may contain the negative electrode material for a non-aqueous secondary battery in the present invention, the granulated carbon material obtained by the above-mentioned production method, and / or the composite carbon material.
Further, for the purpose of improving the orientation of the electrode plate, the permeability of the electrolytic solution, the conductive path, etc., and improving the cycle characteristics, the swelling of the electrode plate, etc., a carbon material different from the granulated carbon material or the composite carbon material is used. It can be mixed (hereinafter, a carbon material different from the granulated carbon material or the composite carbon material may be referred to as an "added carbon material", and the granulated carbon material or the composite carbon material may be mixed with the above. A carbon material obtained by mixing a granulated carbon material or a carbon material different from the composite carbon material is sometimes referred to as a "mixed carbon material").

As the added carbon material, for example, a material selected from natural graphite, artificial graphite, coated graphite in which the carbon material is coated with a carbonaceous material, amorphous carbon, and a carbon material containing metal particles or a metal compound can be used. .. Further, the composite carbon material may be mixed. These materials may be used alone or in combination of two or more in any combination and composition.

As the natural graphite, for example, a highly purified carbon material or a spherical natural graphite can be used. Purification is usually performed by treating with an acid such as hydrochloric acid, sulfuric acid, nitric acid, or phosphoric acid, or by combining a plurality of acid treatment steps to remove ash, metals, etc. contained in low-purity natural graphite. It means an operation of dissolving and removing, and usually, a water washing treatment or the like is performed after the acid treatment step to remove the acid content used in the high purification treatment step. Further, ash, metals and the like may be evaporated and removed by treating at a high temperature of 2000 ° C. or higher instead of the acid treatment step. Further, ash, metals and the like may be removed by treating with a halogen gas atmosphere such as chlorine gas at the time of high temperature heat treatment. Furthermore, these methods may be used in any combination.

The volume-based average particle size of natural graphite (also simply referred to as the average particle size) is usually 5 μm or more, preferably 8 μm or more, more preferably 10 μm or more, particularly preferably 12 μm or more, and usually 60 μm or less, preferably 40 μm or less. , Especially preferably in the range of 30 μm or less. When the average particle size is in this range, high-speed charge / discharge characteristics and productivity are good, which is preferable.
The BET specific surface area of natural graphite is usually in the range of 1 m ² / g or more, preferably 2 m ² / g or more, and usually 30 m ² / g or less, preferably 15 m ² / g or less. When the specific surface area is in this range, high-speed charge / discharge characteristics and productivity are good, which is preferable.

The tap density of natural graphite is usually 0.6 g / cm ³ or more, preferably 0.7 g / c.
m ³ or more, more preferably 0.8 g / cm ³ or more, still more preferably 0.85 g / cm ³ or more, and usually 1.3 g / cm ³ or less, preferably 1.2 g / cm ³ or less, more preferably. 1
.. The range is 1 g / cm ^{3 or less.} Within this range, high-speed charge / discharge characteristics and productivity are good, which is preferable.

Examples of artificial graphite include particles obtained by graphitizing carbon material. For example, single graphite precursor particles are calcined in the form of powder, graphitized particles, or a plurality of graphite precursor particles are molded and calcined. Granulated particles that have been graphitized and crushed can be used.
The volume-based average particle size of the artificial graphite is usually in the range of 5 μm or more, preferably 10 μm or more, and usually 60 μm or less, preferably 40 μm, and more preferably 30 μm or less. Within this range, swelling of the electrode plate is suppressed and productivity is improved, which is preferable.
BET specific surface area of the artificial graphite is usually 0.5 m ² / g or more, preferably 1.0 m ² / g or more and usually 8m ² / g or less, preferably 6 m ² / g or less, more preferably 4m ² / It is in the range of g or less. Within this range, swelling of the electrode plate is suppressed and productivity is improved, which is preferable.

The tap density of artificial graphite is usually 0.6 g / cm ³ or more, preferably 0.7 g / c.
m ³ or more, more preferably 0.8 g / cm ³ or more, still more preferably 0.85 g / cm ³ or more, and usually 1.5 g / cm ³ or less, preferably 1.4 g / cm ³ or less, more preferably. The range is 1.3 g / cm ^{3 or less.} Within this range, swelling of the electrode plate is suppressed and productivity is improved, which is preferable.

Examples of the coated graphite in which the carbon material is coated with a carbonaceous material include particles obtained by coating, calcining and / or graphitizing an organic compound which is a precursor of the above-mentioned carbonaceous material on natural graphite or artificial graphite, or natural graphite or artificial graphite. Particles coated with a carbonaceous material by CVD can be used.
The volume-based average particle size of the coated graphite is usually 5 μm or more, preferably 8 μm or more, more preferably 10 μm or more, particularly preferably 12 μm or more, and usually 60 μm or less, preferably 40 μm or less, particularly preferably 30 μm or less. is there. When the average particle size is in this range, high-speed charge / discharge characteristics and productivity are good, which is preferable.

The BET specific surface area of the coated graphite is usually 1 m ² / g or more, preferably 2 m ² / g or more, more preferably 2.5 m ² / g or more, and usually 20 m ² / g or less, preferably 10 m ² / g or less. More preferably, it is in the range of 8 m ² / g or less, and particularly preferably in ^{the range of 5 m 2} / g or less. When the specific surface area is in this range, high-speed charge / discharge characteristics and productivity are good, which is preferable.
The tap density of the coated graphite is usually 0.6 g / cm ³ or more, 0.7 g / cm ³ or more, more preferably 0.8 g / cm ³ or more, and even more preferably 0.85 g / cm ³ or more. Further, usually 1.3 g / cm ³ or less, 1.2 g / cm ³ or less is preferable, and 1.1 g / cm ³ or less is more preferable. When the tap density is in this range, high-speed charge / discharge characteristics and productivity are good, which is preferable.

As the amorphous carbon, for example, particles obtained by calcining bulk mesophase or particles obtained by insolubilizing an easily graphitizing organic compound and calcining can be used.
The volume-based average particle size of amorphous carbon is usually in the range of 5 μm or more, preferably 12 μm or more, and usually 60 μm or less, preferably 40 μm or less. Within this range, high-speed charge / discharge characteristics and productivity are good, which is preferable.

BET specific surface area of the amorphous carbon is usually 1 m ² / g or more, preferably 2m ² / g or more, more preferably 2.5 m ² / g or more and usually 8m ² / g or less, preferably 6 m ² / g or less
More preferably, it is in ^{the range of 4 m 2} / g or less. When the specific surface area is in this range, high-speed charge / discharge characteristics and productivity are good, which is preferable.
The tap density of amorphous carbon is usually 0.6 g / cm ³ or more, 0.7 g / cm ³ or more, more preferably 0.8 g / cm ³ or more, and further preferably 0.85 g / cm ³ or more. preferable. And usually 1.3 g / cm ³ or less, preferably 1.2 g / cm ³ or less, 1.1 g / cm ³
The following is more preferable. When the tap density is in this range, high-speed charge / discharge characteristics and productivity are good, which is preferable.

Carbon materials containing metal particles and metal compounds include, for example, Fe, Co, Sb, Bi, Pb, Ni, Ag, Si, Sn, Al, Zr, Cr, P, S, V, Mn, Nb, Mo, Examples thereof include a metal selected from the group consisting of Cu, Zn, Ge, In, Ti and the like, or a material obtained by combining a metal thereof with graphite. As the metal or a compound thereof that can be used, an alloy composed of two or more kinds of metals may be used, and the metal particles may be alloy particles formed by two or more kinds of metal elements. Among these, a metal selected from the group consisting of Si, Sn, As, Sb, Al, Zn and W or a compound thereof is preferable, and Si and SiOx are particularly preferable. This general formula SiOx is _{obtained by using silicon dioxide (SiO 2} ) and metallic Si (Si) as raw materials, and the value of x is usually 0 <x <2, preferably 0.2 or more and 1.8. Below, it is more preferably 0.4 or more and 1.6 or less, and further preferably 0.6 or more and 1.4 or less. Within this range, it is possible to reduce the irreversible capacity due to the combination of Li and oxygen at the same time as having a high capacity.

From the viewpoint of cycle life, the volume-based average particle size of the metal particles is usually 0.005 μm or more, preferably 0.01 μm or more, more preferably 0.02 μm or more, still more preferably 0.03 μm or more, and usually 10 μm or less. It is preferably 9 μm or less, more preferably 8 μm or less. When the average particle size is in this range, the volume expansion due to charge / discharge is reduced, and good cycle characteristics can be obtained while maintaining the charge / discharge capacity.

The BET specific surface area of metal particles is usually 0.5 m ² / g or more and 120 m ² / g or less, 1 m ² / g.
It is preferably 100 m ² / g or less. When the specific surface area is within the above range, the charge / discharge efficiency and discharge capacity of the battery are high, lithium is taken in and out quickly in high-speed charge / discharge, and the rate characteristics are excellent, which is preferable.
The apparatus used for mixing the granulated carbon material or the composite carbon material with the added carbon material is not particularly limited, but for example, in the case of a rotary mixer: a cylindrical mixer, a twin cylindrical mixer, etc. For double conical mixers, cubic mixers, stag beetle mixers, fixed mixers: spiral mixers, ribbon mixers, Muller mixers, Helical Flit mixers, Pu
A gmil type mixer, a fluidization type mixer and the like can be used.

<Negative electrode for non-aqueous secondary batteries>
The negative electrode for a non-aqueous secondary battery of the present invention (hereinafter, also appropriately referred to as an “electrode sheet”) includes a current collector and a negative electrode active material layer formed on the current collector, and the active material layer is at least. It is characterized by containing the negative electrode material for a non-aqueous secondary battery. More preferably, it contains a binder.

As the binder, one having an olefinically unsaturated bond in the molecule is used. The type is not particularly limited, and specific examples thereof include styrene-butadiene rubber, styrene / isoprene / styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, and ethylene / propylene / diene copolymer. By using a binder having such an olefinically unsaturated bond, the swelling property of the active material layer with respect to the electrolytic solution can be reduced. Of these, styrene-butadiene rubber is preferable because of its availability.

By using a binder having such an olefinically unsaturated bond in combination with the above-mentioned active material, the strength of the negative electrode plate can be increased. When the strength of the negative electrode is high, deterioration of the negative electrode due to charging and discharging is suppressed, and the cycle life can be extended. Further, in the negative electrode according to the present invention, since the adhesive strength between the active material layer and the current collector is high, even if the binder content in the active material layer is reduced, when the negative electrode is wound to manufacture a battery. It is presumed that the problem of the active material layer peeling off from the current collector does not occur.

As the binder having an olefinically unsaturated bond in the molecule, it is desirable that the binder has a large molecular weight or a large proportion of unsaturated bonds. Specifically, in the case of a binder having a large molecular weight, the weight average molecular weight is preferably in the range of 10,000 or more, more preferably 50,000 or more, preferably 1 million or less, and more preferably 300,000 or less. Is desirable. In the case of a binder having a large proportion of unsaturated bonds, the number of moles of olefinically unsaturated bonds per gram of all binders is preferably 2.5 × ^10-7 mol or more, more preferably 8 × 10 ^{−. It} is preferably in the range of 7 mol or more, preferably 1 × ^10-6 mol or less, and more preferably 5 × ^10-6 mol or less. The binder may satisfy at least one of these molecular weight regulations and unsaturated bond ratio regulations, but it is more preferable that both regulations are satisfied at the same time. When the molecular weight of the binder having an olefinically unsaturated bond is within the above range, the mechanical strength and flexibility are excellent.

The binder having an olefinically unsaturated bond has a degree of unsaturation of preferably 15% or more, more preferably 20% or more, further preferably 40% or more, and preferably 90% or less, more preferably 80. % Or less. The degree of unsaturation represents the ratio (%) of double bonds to the repeating unit of the polymer.
In the present invention, a binder having no olefinically unsaturated bond can also be used in combination with the above-mentioned binder having an olefinically unsaturated bond as long as the effect of the present invention is not lost. The mixing ratio of the binder having no olefinically unsaturated bond to the binder having an olefinically unsaturated bond is preferably in the range of 150% by mass or less, more preferably 120% by mass or less.

The coatability can be improved by using a binder having no olefinically unsaturated bond in combination, but if the amount used in combination is too large, the strength of the active material layer decreases.
Examples of binders that do not have olefinic unsaturated bonds include thickening polysaccharides such as methyl cellulose, carboxymethyl cellulose, starch, caraginan, purulan, guar gum, and zansan gum (xanthan gum), and polyethers such as polyethylene oxide and polypropylene oxide. Vinyl alcohols such as polyvinyl alcohol and polyvinyl butyral, polyacids such as polyacrylic acid and polymethacrylic acid, metal salts of these polymers, fluoropolymers such as polyvinylidene fluoride, alcan polymers such as polyethylene and polypropylene, and theirs. Examples include copolymers.

When the negative electrode material for a non-aqueous secondary battery is used in combination with the above-mentioned binder having an olefinically unsaturated bond, the ratio of the binder used for the active material layer can be reduced as compared with the conventional one. Specifically, it may be a mixture of a negative electrode material for a non-aqueous secondary battery and a binder (in some cases, a binder having an unsaturated bond as described above and a binder having no unsaturated bond). The mass ratio with (.) Is preferably 90/10 or more, more preferably 95/5 or more, preferably 99.9 / 0.1 or less, and more preferably 99.5 / in each dry mass ratio. It is in the range of 0.5 or less. When the ratio of the binder is within the above range, the decrease in capacity and the increase in resistance can be suppressed, and the strength of the electrode plate is also excellent.

The negative electrode of the present invention is formed by dispersing the above-mentioned negative electrode material for a non-aqueous secondary battery and a binder in a dispersion medium to form a slurry, which is applied to a current collector. As the dispersion medium, an organic solvent such as alcohol or water can be used. If desired, a conductive agent may be added to this slurry. Examples of the conductive agent include carbon black such as acetylene black, ketjen black and furnace black, Cu and Ni having an average particle size of 1 μm or less, and fine powder made of an alloy thereof. The amount of the conductive agent added is preferably about 10% by mass or less with respect to the negative electrode material for a non-aqueous secondary battery.

As the current collector to which the slurry is applied, a conventionally known current collector can be used. Specific examples thereof include metal thin films such as rolled copper foil, electrolytic copper foil, and stainless steel foil. The thickness of the current collector is preferably 4 μm or more, more preferably 6 μm or more, preferably 30 μm or less, and more preferably 20 μm or less.
After applying the slurry on the current collector, the temperature is preferably 60 ° C. or higher, more preferably 80 ° C. or higher, and preferably 200 ° C. or lower, more preferably 195 ° C. or lower, under dry air or an inert atmosphere. It dries and forms an active layer.

The thickness of the active material layer obtained by applying and drying the slurry is preferably 5 μm or more, more preferably 20 μm or more, further preferably 30 μm or more, preferably 200 μm or less, more preferably 100 μm or less, still more preferably. It is 75 μm or less. When the thickness of the active material layer is within the above range, it is excellent in practicality as a negative electrode in consideration of the particle size of the active material, and a sufficient Li storage / release function for a high-density current value can be obtained. ..

The density of the carbon material in the active material layer varies depending on the application, but in applications where capacity is important, it is preferably 1.55 g / cm ³ or more, more preferably 1.6 g / cm ³ or more, still more preferably 1.65 g / cm. It is cm ³ or more, particularly preferably 1.7 g / cm ³ or more. Further, it is preferably 1.9 g / cm ³ or less. When the density is within the above range, the capacity of the battery per unit volume can be sufficiently secured, and the rate characteristics are less likely to deteriorate.

When the negative electrode for a non-aqueous secondary battery is produced using the negative electrode material for a non-aqueous secondary battery described above, the method and selection of other materials are not particularly limited. Further, even when a lithium ion secondary battery is manufactured using this negative electrode, the selection of members necessary for the battery configuration such as the positive electrode and the electrolytic solution constituting the lithium ion secondary battery is not particularly limited. Hereinafter, the details of the negative electrode for a lithium ion secondary battery and the lithium ion secondary battery using the negative electrode material for a non-aqueous secondary battery will be illustrated, but the materials that can be used, the manufacturing method, and the like are limited to the following specific examples. It's not something.

<Non-water secondary battery>
The basic configuration of the non-aqueous secondary battery of the present invention, particularly a lithium ion secondary battery, is the same as that of a conventionally known lithium ion secondary battery, and usually has a positive electrode and a negative electrode capable of occluding and releasing lithium ions, and an electrolyte. To be equipped. As the negative electrode, the negative electrode of the present invention described above is used.
The positive electrode is formed by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector.

Examples of the positive electrode active material include metal chalcogen compounds that can occlude and release alkali metal cations such as lithium ions during charging and discharging. Metallic chalcogen compounds include transition metal oxides such as vanadium oxide, molybdenum oxide, manganese oxide, chromium oxide, titanium oxide, and tungsten oxide, vanadium sulfide, and molybdenum sulfide. things, sulfides of titanium, transition metal sulfides such as _CuS, NIPS 3, FEPS phosphorus transition metals, such as ₃ - sulfur _compounds, VSe 2, selenium compounds of transition metals such as NbSe _{3, Fe 0.25} V _0. Examples thereof include composite oxides of transition metals such as ₇₅ S ₂ and Na _0.1 CrS _2, and composite sulfides of transition metals such as _{LiCo S 2} and LiNi S _2.

Among _{these, V 2 O 5, V 5} O 13, VO 2, Cr 2 O 5, MnO 2, TiO 2, MoV 2 O 8, LiCoO 2, LiNiO 2, LiMn 2 O 4, TiS 2, V 2 S ₅ , Cr _0.25 V _0.75 S ₂ , Cr _0.5 V _0.5 S _2, etc. are preferable, and LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ and some of these transition metals are particularly preferable. Is a lithium transition metal composite oxide in which is replaced with another metal. These positive electrode active materials may be used alone or in combination of two or more.

As the binder for binding the positive electrode active material, a known binder can be arbitrarily selected and used. Examples include inorganic compounds such as silicate and water glass, and resins having no unsaturated bond such as Teflon (registered trademark) and polyvinylidene fluoride. Of these, a resin having no unsaturated bond is preferable. If a resin having an unsaturated bond is used as the resin for binding the positive electrode active material, it may be decomposed during the oxidation reaction. The weight average molecular weight of these resins is usually in the range of 10,000 or more, preferably 100,000 or more, and usually 3 million or less, preferably 1 million or less.

A conductive material may be contained in the positive electrode active material layer in order to improve the conductivity of the electrode. The conductive agent is not particularly limited as long as it can be mixed with an active material in an appropriate amount to impart conductivity, but usually, carbon powder such as acetylene black, carbon black, and graphite, various metal fibers, powder, and foil are used. And so on.
The positive electrode plate is formed by slurrying a positive electrode active material or a binder with a solvent, applying it on a current collector, and drying it in the same manner as in the production of the negative electrode as described above. Aluminum, nickel, stainless steel (SUS) and the like are used as the current collector of the positive electrode, but the current collector is not limited in any way.

As the electrolyte, a non-aqueous electrolyte solution in which a lithium salt is dissolved in a non-aqueous solvent, or a gel-like, rubber-like, or solid sheet-like electrolyte obtained by dissolving this non-aqueous electrolyte solution in an organic polymer compound or the like is used.
The non-aqueous solvent used for the non-aqueous electrolyte solution is not particularly limited, and can be appropriately selected and used from known non-aqueous solvents that have been conventionally proposed as solvents for the non-aqueous electrolyte solution. For example, chain carbonates such as diethyl carbonate, dimethyl carbonate and ethyl methyl carbonate; cyclic carbonates such as ethylene carbonate, propylene carbonate and butylene carbonate; chain ethers such as 1,2-dimethoxyethane; tetrahydrofuran, 2-methyl. Cyclic ethers such as tetrahydrofuran, sulfolane and 1,3-dioxolane; chain esters such as methyl formate, methyl acetate and methyl propionate; cyclic esters such as γ-butyrolactone and γ-valerolactone.

Any one of these non-aqueous solvents may be used alone, or two or more thereof may be mixed and used. In the case of a mixed solvent, a combination of a mixed solvent containing a cyclic carbonate and a chain carbonate is preferable, and when the cyclic carbonate is a mixed solvent of ethylene carbonate and propylene carbonate, high ionic conductivity can be exhibited even at a low temperature, and low-temperature charging is performed. It is particularly preferable in that the non-characteristics are improved. Among them, propylene carbonate is preferably in the range of 2% by mass or more and 80% by mass or less, more preferably in the range of 5% by mass or more and 70% by mass or less, and further preferably in the range of 10% by mass or more and 60% by mass or less with respect to the whole non-aqueous solvent. preferable. If the proportion of propylene carbonate is lower than the above, the ionic conductivity at low temperature decreases, and if the proportion of propylene carbonate is higher than the above, propylene carbonate solvated with lithium ions moves between the graphite phases when a graphite-based electrode is used. The co-insertion causes delamination deterioration of the graphite-based negative electrode active material, and there is a problem that a sufficient capacity cannot be obtained.

The lithium salt used in the non-aqueous electrolyte solution is not particularly limited, and can be appropriately selected and used from known lithium salts known to be usable for this purpose. For example, halides such as LiCl, LiBr, perhalonates _{such as LiClO 4 , LiBrO 4} , LiClO ₄ , inorganic lithium salts such as inorganic fluoride salts such as LiPF ₆ , LiBF ₄ , LiAsF _{6 , LiCF 3} SO ₃ , Examples thereof include _{perfluoroalcan sulfonates such as LiC 4} F ₉ SO _3, and fluorine-containing organic lithium salts such as perfluoroalcan sulfonic acid imide salts such as Li trifluorosulphonimide ((CF ₃ SO ₂ ) _{2 NLi).} Of these, LiClO ₄ , LiPF ₆ , and LiBF ₄ are preferable.

The lithium salt may be used alone or in combination of two or more. The concentration of the lithium salt in the non-aqueous electrolyte solution is usually in the range of 0.5 mol / L or more and 2.0 mol / L or less.
Further, when the above-mentioned non-aqueous electrolyte solution contains an organic polymer compound and is used in the form of a gel, rubber, or solid sheet, specific examples of the organic polymer compound include polyethylene oxide and polypropylene oxide. Polyether-based polymer compound; Crosslinked polymer of polyether-based polymer compound; Vinyl alcohol-based polymer compound such as polyvinyl alcohol and polyvinyl butyral; Insoluble material of vinyl alcohol-based polymer compound; Polyepicrolhydrin; Polyphosphazene; Poly Siloxane; Vinyl-based polymer compounds such as polyvinylpyrrolidone, polyvinylidene carbonate, polyacrylonitrile; poly (ω-methoxyoligooxyethylene methacrylate), poly (ω-methoxyoligooxyethylene methacrylate-co-methylmethacrylate), poly (hexafluoro) Examples thereof include polymer copolymers such as propylene-vinylidene fluoride).

The above-mentioned non-aqueous electrolyte solution may further contain a film-forming agent. Specific examples of the film-forming agent include carbonate compounds such as vinylene carbonate, vinylethyl carbonate and methylphenyl carbonate, alkene sulfides such as ethylene sulfide and propylene sulfide; and sulton compounds such as 1,3-propane sulton and 1,4-butane sulton. ; Examples include acid anhydrides such as maleic anhydride and succinic anhydride. Further, an overcharge inhibitor such as diphenyl ether or cyclohexylbenzene may be added. When the above additive is used, its content is usually 10% by mass or less, particularly preferably 8% by mass or less, further 5% by mass or less, and particularly preferably 2% by mass or less. If the content of the additive is too large, it may adversely affect other battery characteristics such as an increase in initial irreversible capacity, a decrease in low temperature characteristics, and a decrease in rate characteristics.

Further, as the electrolyte, a polymer solid electrolyte which is a conductor of an alkali metal cation such as lithium ion can also be used. Examples of the polymer solid electrolyte include those in which a lithium salt is dissolved in the above-mentioned polyether polymer compound, and a polymer in which the terminal hydroxyl group of the polyether is replaced with an alkoxide.
Usually, a porous separator such as a porous membrane or a non-woven fabric is interposed between the positive electrode and the negative electrode in order to prevent a short circuit between the electrodes. In this case, the non-aqueous electrolyte solution is used by impregnating the porous separator. As the material of the separator, polyolefins such as polyethylene and polypropylene, polyether sulfone and the like are used, and polyolefins are preferable.

The form of the non-aqueous secondary battery of the present invention is not particularly limited. Examples include a cylinder type in which the sheet electrode and the separator are spirally formed, a cylinder type having an inside-out structure in which the pellet electrode and the separator are combined, a coin type in which the pellet electrode and the separator are laminated, and the like. Further, by storing the batteries of these forms in an arbitrary outer case, they can be used in any shape such as a coin type, a cylindrical type, and a square type.

The procedure for assembling the non-aqueous secondary battery of the present invention is not particularly limited and may be assembled by an appropriate procedure according to the structure of the battery. For example, a negative electrode is placed on an outer case and an electrolytic solution is placed on the negative electrode. A separator can be provided, and a positive electrode can be placed so as to face the negative electrode and crimped together with a gasket and a sealing plate to form a battery.

Next, specific embodiments of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these examples.
In the examples, the physical characteristics of graphite and the granulating agent were measured by the following methods.

<Bulk density>
Using a powder density measuring instrument, the composite carbon material of the present invention was dropped into a cylindrical tap cell having a diameter of 5 cm and a volume capacity of 100 cm ^{3 through a sieve having a mesh size of 300 μm, and the volume and sample when the cell was fully filled.} The density obtained from the mass was defined as the bulk density.

<Tap density>
Using a powder density measuring device, attach a cylinder with a diameter of 5 cm and a height of 5 cm to the upper part of a cylindrical tap cell with a diameter of 5 cm and a volume capacity of 100 cm ³ , drop the measurement sample through a sieve with a mesh size of 300 μm, and fill the cell and the upper cylinder. After that, after tapping with a stroke length of 20 mm 500 times, the upper cylinder was removed, and the powder on the upper part of the cell was scraped off with a spatula on the upper surface of the cell, and it was obtained from the volume inside the cell and the mass of the sample inside the cell at that time. Defined as density.

<D50, d90, d10, d90 / d10>
0.01 g of carbon material was suspended in 10 mL of a 0.2 mass% aqueous solution of polyoxyethylene sorbitan monolaurate (for example, Tween 20 (registered trademark)) as a surfactant, and this was used as a measurement sample. Introduced into a commercially available laser diffraction / scattering particle size distribution measuring device (for example, LA-920 manufactured by HORIBA), the measurement sample was irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute, and then the volume-based d50, d90 and d10 were measured, and d90 / d10 was calculated.

<BET specific surface area (SA)>
Using a surface meter (Shimadzu Seisakusho's specific surface area measuring device "Gemini 2360"), the carbon material sample was preliminarily dried under nitrogen flow at 100 ° C. for 3 hours, cooled to liquid nitrogen temperature, and then cooled to atmospheric pressure. Using a nitrogen helium mixed gas accurately adjusted so that the value of the relative pressure of nitrogen relative to the gas was 0.3, the measurement was performed by the nitrogen adsorption BET 6-point method by the gas flow method.

<Relative permittivity of granulators>
It was done according to the following.
(measuring device)
Body: Agilent 4284A PRECISION LCR METER
Jig: Agilent 16452A LIQUID TEST FIXTURE
(Measurement condition)
Measurement frequency: 100KHz
Measurement temperature: 25.3 ± 2 ° C
Measured humidity: 48 ± 5%
Electrode spacing: 0.3 mm
Measured voltage: 1V
(Measurement principle)
The relative permittivity was calculated from the capacitance value of the electrode and the capacitor formed by the organic compound material provided between them from the following equation.
εr = (t × Cp) / (Axε ₀ )
εr: Relative permittivity of organic compounds
ε ₀ : Permittivity of vacuum = 8.854 × ^10-12 (F / m)
Cp: Capacitance (F)
A: Electrode area (m ² )
t: Electrode spacing: (m)

<Density of granulator>
(Measurement method)
Set the container containing the granulating agent in a constant temperature bath, set the granulating agent to 20 ° C, and use the density floating to read the scale of the floating neck by the upper edge regulation (read the top edge of the meniscus). , Granulator density.

<Viscosity of granulator>
(measuring device)
Brookfield DV-II Cone Plate Type (Measurement Conditions)
Sample cup: CPE-44PY
Cone: CPE41
Sample amount: 2 ml
Measurement temperature: Temperature shown in the example table (viscosity value)
The viscosity of the shear rate of 100 sec ^-1 was read and used as the viscosity of this example.

<Boiling point of granulator>
It was measured by the distillation method.
In the examples, the battery characteristics were measured by the following method.

<Preparation of electrode sheet>
Using the graphite particles of Examples or Comparative Examples, a electrode plate having an active material layer having an active material layer density of 1.60 ± 0.03 g / cm ^{3 was prepared.} Specifically, 50.00 ± 0.02 g of the negative electrode material, 50.00 ± 0.02 g of a 1 mass% carboxymethyl cellulose sodium salt aqueous solution (0.500 g in terms of solid content), and styrene having a weight average molecular weight of 270,000. -Aqueous dispersion of butadiene rubber (1.00 ± 0.05 g (0.5 g in terms of solid content) was stirred with a hybrid mixer manufactured by Keyence for 5 minutes and defoamed for 30 seconds to obtain a slurry.

This slurry is 10c wide using a small die coater manufactured by ITOCHU Machining so that the negative electrode material adheres to a copper foil having a thickness of 10 μm, which is a current collector, at 12.00 ± 0.3 mg / cm ^2.
It was applied to m and rolled pressed using a roller having a diameter of 20 cm ^{to adjust the density of the active material layer to 1.60 ± 0.03 g / cm 3} to obtain an electrode sheet.

<Method of manufacturing non-aqueous electrolyte secondary battery (laminated battery)>
The electrode sheet produced by the above method was cut into a size of 4 cm × 3 cm to form a negative electrode, a positive electrode made of NMC was cut out in the same area, and a separator (made of a porous polyethylene film) was placed between the negative electrode and the positive electrode to combine them. Laminated battery by injecting 250 μl of an electrolytic solution in which _{LiPF 6} is dissolved at 1.2 mol / L in a mixed solvent of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate (volume ratio = 3: 3: 4). Was produced.

<Low temperature output characteristics>
Using the laminated non-aqueous electrolyte secondary battery produced by the above method for producing a non-aqueous electrolyte secondary battery, the low temperature output characteristics were measured by the following measurement method.
For a non-aqueous electrolyte secondary battery that has not undergone a charge / discharge cycle, the voltage range is 4.1V to 3.0V and the current value is 0.2C at 25 ° C. The current value is 1C, the same applies hereinafter) for 3 cycles, the voltage range is 4.2V to 3.0V, and the current value is 0.2C (when charging, constant voltage charging is performed at 4.2V for another 2.5 hours). Implementation) Initial charging and discharging were performed for 2 cycles.
Further, after charging to 50% SOC at a current value of 0.2C, the current values of 1 / 8C, 1 / 4C, 1 / 2C, 1.5C, and 2C are used for 2 seconds in a low temperature environment of -30 ° C. Discharge with a constant current, measure the drop in battery voltage after 2 seconds in discharging under each condition, and calculate the current value I that can be passed in 2 seconds when the upper limit charging voltage is set to 3V from those measured values. Then, the value calculated by the formula of 3 × I (W) was used as the low temperature output characteristic of each battery.

<Discharge capacity and cycle characteristics>
Using the laminated non-aqueous electrolyte secondary battery produced by the above method for producing a non-aqueous electrolyte secondary battery, the discharge capacity and cycle characteristics were measured by the following measurement methods.
For a non-aqueous electrolyte secondary battery that has not undergone a charge / discharge cycle, the voltage range is 4.1V to 3.0V and the current value is 0.2C at 25 ° C. The current value is 1C, the same applies hereinafter) for 3 cycles, the voltage range is 4.2V to 3.0V, and the current value is 0.2C (when charging, constant voltage charging is performed at 4.2V for another 2.5 hours). Implementation) Initial charging and discharging were performed for 2 cycles. The discharge capacity at this time was taken as the discharge capacity of this battery.
Next, in an atmosphere of 60 ° C., charging and discharging are performed for 500 cycles with a voltage range of 4.2V to 3.0V and a current value of 2C (constant voltage charging is performed at 4.2V for an additional 2.5 hours during charging). The ratio of the discharge capacity at the 500th cycle to the discharge capacity at the 1st cycle was expressed in% and used as the cycle maintenance rate.

(Example 1)
-Spheroidization processing Equipment 1 is charged with 20 kg of graphite A, 2.4 kg of an organic compound A having a relative permittivity of 20.4 at 100 kHz and no branched chain structure in the molecule as a granulator, and a peripheral speed of 80 m / sec. And 60 min processing was performed.
The tap density of the obtained treated graphite (granulated carbon material before removing the granulator) is 0.961 g / cm.
It was ^3.
-Removal of granulator The graphite (granulated carbon material before removal of the granulator) was subsequently heat-treated at 700 ° C. in an inert gas to remove the granulator.
Table 1 shows the treatment conditions and the properties of the obtained treated graphite (granulated carbon material before and after removal of the granulating agent).
Table 2 shows the properties of the raw material graphite used, Table 3 shows the properties of the granulator, and Table 4 shows the specifications of the equipment used.

(Comparative Example 1)
The same procedure as in Example 1 was carried out except that the organic compound B having a relative permittivity of 2.2 at 100 kHz and no branched chain structure in the molecule was used as the granulating agent.
The tap density of the obtained treated graphite (granulated carbon material before removing the granulator) is 0.912 g / cm.
^{At 3} , the value was lower than that of Example 1. Table 1 shows the treatment conditions and the properties of the obtained treated graphite (granulated carbon material before and after removal of the granulating agent).

(Comparative Example 2)
After the granulator was added, the treatment was carried out in the same manner as in Comparative Example 1 except that the treatment at a peripheral speed of 80 m / sec was set to 120 min.
The tap density of the obtained treated graphite (granulated carbon material before removing the granulator) is 0.949 g / cm.
^In No. 3, the value was as high as in Example 1, but required twice the processing time as in Example 1. Table 1 shows the treatment conditions and the properties of the obtained treated graphite (granulated carbon material before and after removal of the granulating agent).

(Example 2)
The same procedure as in Example 1 was carried out except that the organic compound C having a relative permittivity at 100 kHz and no branched structure in the molecule was used as the granulating agent.
The tap density of the obtained treated graphite (granulated carbon material before removing the granulator) is 0.978 g / cm.
^{At 3} , the value was as high as in Example 1. Table 1 shows the treatment conditions and the properties of the obtained treated graphite (granulated carbon material before and after removal of the granulating agent).

(Comparative Example 3)
The same procedure as in Example 1 was carried out except that the organic compound D having a relative permittivity of 13.6 at 100 kHz and having a branched chain structure in the molecule was used as the granulating agent.
The tap density of the obtained treated graphite (granulated carbon material before removing the granulator) is 0.809 g / cm.
It was a low value of ^3. Table 1 shows the treatment conditions and the properties of the obtained treated graphite (granulated carbon material before and after removal of the granulating agent).

(Example 3)
-Spheroidization processing 2.25 kg of graphite A was added to the equipment 2, and 0.27 kg of an organic compound A having a relative permittivity of 20.4 at 100 kHz and no branched chain structure was charged into the molecule as a granulator, and the peripheral speed was 80 m. The process was performed for 20 minutes at / sec.
The tap density of the obtained treated graphite (granulated carbon material before removal of the granulator) is 0.990 g / cm ³
It was a high value.
-Removal of granulating agent Subsequently, the obtained graphite (granulated carbon material before removal of the granulating agent) was heat-treated at 700 ° C. in an inert gas to remove the granulating agent.
Table 1 shows the treatment conditions and the properties of the obtained treated graphite (granulated carbon material before and after removal of the granulating agent).

(Example 4)
The same procedure as in Example 3 was carried out except that the organic compound E having a relative permittivity at 100 kHz and no branched chain structure in the molecule was used as the granulating agent.
The tap density of the obtained treated graphite (granulated carbon material before removing the granulator) is 0.975 g / cm.
It was a high value at ^3. Table 1 shows the treatment conditions and the properties of the obtained treated graphite (granulated carbon material before and after removal of the granulating agent).

(Comparative Example 4)
The same procedure as in Example 3 was carried out except that the organic compound F having a relative permittivity of 8.0 at 100 kHz and no branched chain structure in the molecule was used as the granulating agent.
The tap density of the obtained treated graphite (granulated carbon material before removing the granulator) is 0.894 g / cm.
^{At 3} , the value was lower than that of Example 3. Table 1 shows the treatment conditions and the properties of the obtained treated graphite (granulated carbon material before and after removal of the granulating agent).

(Example 5)
The same procedure as in Example 3 was carried out except that the amount of the granulating agent was 0.25 kg.
The tap density of the obtained treated graphite (granulated carbon material before removing the granulator) is 0.929 g / cm.
It was a high value at ^3. Table 1 shows the treatment conditions and the properties of the obtained treated graphite (granulated carbon material before and after removal of the granulating agent).

(Example 6)
The treated graphite (before removal of the granulating agent) obtained in Example 1 and Mitsubishi Chemical's coal tar pitch were mixed to obtain a graphite coal tar pitch mixture.
This graphite pitch mixture was calcined at 1300 ° C. in an inert atmosphere and then crushed by a pulverizer to obtain a multi-layered carbon material.
The amount of carbonaceous material derived from coal tar pitch with respect to graphite of the obtained multi-layered carbon material was 8%. Table 6 shows the properties of the multi-layered carbon material.
Next, using this multi-layered carbon material, a negative electrode for a non-aqueous secondary battery was produced by the above-mentioned method, and further, a non-aqueous secondary battery was produced by the above-mentioned method, and the battery was evaluated.
As a result, the low temperature output of the battery showed a high value of 92 mW. The battery characteristics are shown in Table-6.

(Example 7)
The treated graphite (before removal of the granulator) obtained in Example 3 and 14 parts by weight of coal tar manufactured by Mitsubishi Chemical Corporation were mixed to obtain a graphite coal tar mixture.
This graphite pitch mixture was calcined at 1300 ° C. in an inert atmosphere and then crushed by a pulverizer to obtain a multi-layered carbon material.
The amount of coal tar-derived carbonaceous material with respect to graphite of the obtained multi-layered carbon material was 5%. Table 6 shows the properties of the multi-layered carbon material.
Next, using this multi-layered carbon material, a battery was manufactured and a battery was evaluated in the same manner as in Example 6.
As a result, the low temperature output of the battery showed a high value of 93 mW. The battery characteristics are shown in Table-6.

(Comparative Example 5)
The same procedure as in Example 6 was carried out except that commercially available graphite was used as the graphite. The properties of the graphite used are shown in Table-5. The amount of coal tar-derived carbonaceous material with respect to graphite of the obtained multi-layered carbon material was 5%. The properties of the multi-layered carbon material are shown in Table-6.
Next, using this multi-layered carbon material, a battery was manufactured and a battery was evaluated in the same manner as in Example 6.
As a result, the low temperature output of the battery was as low as 73 mW. The battery characteristics are shown in Table-7.

Claims (6)

A method for producing a negative electrode material for a non-aqueous secondary battery, which comprises a granulation step of applying a mechanical energy of at least one of impact, compression, friction, and shearing force to make a raw material carbon material spherical.
In the granulation step, the relative permittivity is 9.0 or more and 60 or less.
20 ° C. or higher, with respect to 100 parts by weight of raw carbon material granulating agent containing no organic compounds having branched chains and the molecular structure viscosity of less 300cP than 10cP at 25 ° C. or less 0. A method for producing a negative electrode material for a non-aqueous secondary battery, which is carried out in the presence of 1 part by mass or more and 20 parts by mass or less. The method for producing a negative electrode material for a non-aqueous secondary battery according to claim 1, wherein an organic compound having a relative permittivity of 14.0 or more is used. The method for producing a negative electrode material for a non-aqueous secondary battery according to claim 1 or 2, wherein the density of the organic compound is 0.90 g / cm ³ or more and 1.30 g / cm ^{3 or less.} Any 1 of claims 1 to 3, characterized in that the boiling point of the organic compound is 150 ° C. or higher.
The method for manufacturing a negative electrode material for a non-aqueous secondary battery according to the section. The method for producing a negative electrode material for a non-aqueous secondary battery according to any one of claims 1 to 4, wherein the organic compound has 2 or more and 15 or less carbon atoms. The organic compound has a polar group capable of reacting with radicals.
The method for producing a negative electrode material for a non-aqueous secondary battery according to any one of claims 1 to 5.