JP6546582B2 - Method for producing lithium metal composite oxide having layered crystal structure - Google Patents

Description

  The present invention relates to a method for producing a lithium metal composite oxide having a layered crystal structure, which can be used as a positive electrode active material of a lithium battery.

  Lithium batteries, among them lithium secondary batteries, have features such as high energy density and long life, so they can be used in home appliances such as video cameras and portable electronic devices such as laptop computers and mobile phones. It is used as a power source. Recently, the lithium secondary battery is also applied to a large battery mounted on an electric vehicle (EV) or a hybrid electric vehicle (HEV).

  The lithium secondary battery is a secondary battery having a structure in which lithium is dissolved out as ions from the positive electrode during charge, moves to the negative electrode and is absorbed, and lithium ions are returned from the negative electrode to the positive electrode during discharge. It is known to be attributable to the potential of the positive electrode material.

As a positive electrode active material of a lithium secondary battery, in addition to lithium manganese oxide (LiMn ₂ O ₄ ) having a spinel structure, lithium metal composite oxides such as LiCoO ₂ , LiNiO ₂ and LiMnO ₂ having a layered crystal structure are known. It is done. For example, LiCoO ₂ has a layered crystal structure in which a lithium atomic layer and a cobalt atomic layer are alternately stacked via an oxygen atomic layer, has a large charge / discharge capacity, and is excellent in the diffusivity of lithium ion storage and storage. Therefore, many of lithium secondary batteries currently marketed are lithium metal composite oxides having a layered crystal structure such as LiCoO ₂ .

A lithium metal composite oxide having a layered crystal structure such as LiCoO ₂ or LiNiO ₂ is represented by the general formula LiMO ₂ (M: transition metal). The crystal structure of the lithium metal complex oxide having such a layered crystal structure belongs to the space group R-3m ("-" is usually attached to the upper part of "3" to indicate turning. The same applies hereinafter), The Li ion, Me ion and oxide ion occupy 3a site, 3b site and 6c site, respectively. And it is known that a layer (Li layer) composed of Li ions and a layer (Me layer) composed of Me ions exhibit a layered crystal structure alternately stacked via an O layer composed of oxide ions.

  With regard to a method for producing a lithium metal composite oxide having a layered crystal structure, for example, in Patent Document 1, an alkaline solution is added to a mixed aqueous solution of manganese and nickel to coprecipitate manganese and nickel, and then lithium hydroxide is added, A process for obtaining a lithium metal composite oxide by firing is disclosed.

  Further, in Patent Document 2, raw materials containing a lithium salt compound, a manganese salt compound, a nickel salt compound and a cobalt salt compound are mixed, mixed and stirred in water to prepare a slurry, and the slurry is pulverized and obtained. There is disclosed a method of producing a lithium metal composite oxide having a layer structure by granulating and drying a pulverized slurry using a thermal spray drier or the like, followed by firing and crushing.

By the way, since the positive electrode active material has a lower electric conductivity than a general conductor, an element having a higher electric conductivity so as to further increase the electric conductivity between the current collector and the positive electrode active material or between the active materials. It has been proposed to modify the positive electrode active material by
For example, Patent Document 3 proposes a method of improving cycle characteristics and reducing internal resistance by modifying a lithium composite oxide with a compound such as Co.
Further, in Patent Document 4, after mixing raw materials of lithium composite oxide, Al, Mg, Sn, having a predetermined thickness on the surface of composite oxide particles manufactured through steps of firing, crushing, heat treatment and classification. It is disclosed that the internal resistance can be lowered and a high output can be obtained by using, as a positive electrode active material, a surface-modified metal compound film containing at least one of Ti, Zn, and Zr. .

JP-A-8-171910 JP, 2013-232400, A Japanese Patent Application Laid-Open No. 2002-151083 JP 2005-310744 A

When a lithium metal composite oxide having a layered crystal structure is used as a positive electrode active material of a lithium secondary battery, it is used at a charge voltage of 4.3 V or less based on metallic lithium under high temperature, or charge / discharge exceeding 4.3 V If this is done, the surface of the lithium metal composite oxide changes due to the reaction with the electrolytic solution, and the battery has a problem that the life characteristics of the battery deteriorate.
As an example of the means for solving such problems, it is conceivable to coat the particle surface of the lithium metal complex oxide with an oxide. However, covering the particle surface of the lithium metal composite oxide with an oxide causes a new problem that the output characteristics of the battery are degraded.
Thus, in the case of lithium metal composite oxide having a layered crystal structure, it was not easy to make the life characteristics and the output characteristics compatible.

  Therefore, the present invention relates to a method for producing a lithium metal composite oxide having a layered crystal structure, which suppresses reaction with an electrolytic solution to enhance the life characteristics of the battery when used as a positive electrode active material of a lithium secondary battery. It is an object of the present invention to provide a new method for producing a lithium metal composite oxide which can be made as well as the output characteristics can be made equal or higher.

  The present invention provides a surface treatment step of surface treating a lithium metal composite oxide powder using a surface treating agent containing at least one of aluminum, titanium and zirconium, and a lithium metal composite oxide after the surface treatment. It is a manufacturing method of lithium metal complex oxide which has a layered crystal structure provided with the heat treatment process which heat-treats powder, and, in the above-mentioned heat treatment process, lithium metal complex oxide powder after surface treatment is carried out in oxygen content atmosphere. A method for producing a lithium metal composite oxide having a layered crystal structure is proposed, characterized in that heat treatment is performed so as to be maintained at 700 to 950 ° C.

  According to the method for producing a lithium metal complex oxide proposed by the present invention, a surface layer containing at least one of aluminum, titanium and zirconium can be formed on the surface of lithium metal complex oxide particles. Thereby, when the said lithium metal complex oxide particle is used as a positive electrode active material of a lithium secondary battery, while being able to suppress reaction with electrolyte solution and improving a lifetime characteristic, an output characteristic is equal or more than that Can be Therefore, the obtained lithium metal composite oxide is particularly excellent as a positive electrode active material of a battery mounted on a vehicle, particularly, a battery mounted on an electric vehicle (EV: Electric Vehicle) or a hybrid electric vehicle (HEV: Hybrid Electric Vehicle). It becomes a thing.

It is a figure for demonstrating the structure of the cell for electrochemical evaluation produced by the battery characteristic evaluation of the Example.

  Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiment.

<Manufacturing method>
A method for producing a lithium metal composite oxide (hereinafter referred to as “the present lithium metal composite oxide”) according to an example of the present embodiment (referred to as “the present production method”) contains at least one of aluminum, titanium and zirconium. Surface treatment step of surface-treating lithium metal complex oxide powder (referred to as "base lithium metal complex oxide powder") using a surface treatment agent, and heat treatment of lithium metal complex oxide powder after the surface treatment A method of producing a lithium metal composite oxide having a layered crystal structure, comprising the heat treatment step of

  The present manufacturing method only needs to include the surface treatment step and the heat treatment step, and may further include other steps. For example, a crushing step may be inserted after the heat treatment step, or a crushing step or a classification step may be inserted before the surface treatment step. Also, other steps may be added.

<This lithium metal complex oxide>
The present lithium metal complex oxide, which is a product of the present manufacturing method, is not particularly limited in composition as long as it is a lithium metal complex oxide having a layered crystal structure. That is, the present lithium metal composite oxide may be a lithium metal composite oxide having a layered crystal structure in which a lithium atomic layer and a metal atomic layer are alternately stacked via an oxygen atomic layer.

If it is a lithium metal complex oxide having a layered crystal structure, it has common problems, and the effects of surface treatment and heat treatment are the same, so there is no need to limit the composition.
However, since it is easy to understand in this section that the present manufacturing method is described based on a more specific example, in-vehicle batteries, in particular, electric vehicles (EV: Electric Vehicle) and hybrid electric vehicles (HEV: Hybrid Electric Vehicle) The following lithium metal composite oxide which is preferable as a positive electrode active material of a lithium secondary battery to be mounted on will be described as an example.

As an example of the present lithium metal composite oxide represented by the general formula (1): and lithium metal composite oxide having a layered crystal structure represented by _{Li 1 + x M 1-x} O 2.

  “1 + x” in the above formula (1) is more preferably 1.00 to 1.07, particularly 1.01 to 1.07, and more preferably 1.02 to 1.06.

In the above formula (1), “M” is Mn, Co, Ni, and a transition element existing between the elements of Group 3 to Group 11 of the periodic table and the third period of the periodic table. It may be any one or more of the typical elements.
Here, as a transition element existing between the group 3 element of the periodic table and the group 11 element and typical elements up to the third period of the periodic table, for example, Al, V, Fe, Ti, Mg, Cr And Ga, In, Cu, Zn, Nb, Zr, Mo, W, Ta, Re and the like.
“M” is, for example, one of Mn, Co, Ni, Al, V, Fe, Ti, Mg, Cr, Ga, In, Cu, Zn, Nb, Zr, Mo, W, Ta and Re. It is sufficient if it is the above. Therefore, “M” may be composed of, for example, only the three elements of Mn, Co and Ni, or the three elements may contain one or more of the other elements or may have other configurations. .

When “M” in the above-mentioned formula (1) contains three elements of Mn, Co and Ni, the content molar ratio of Mn, Co and Ni is Mn: Co: Ni = 0.10 to 0.45: It is preferable that it is 0.05-0.40: 0.30-0.75, and Mn: Co: Ni = 0.10-0.40: 0.05-0.40: 0.30-0. More preferably, it is 75.
In addition, in said General Formula (1) (2), although the atomic ratio of the amount of oxygen is described as "2" for convenience, you may have some non-stoichiometry.

  The present lithium metal composite oxide may contain S as an impurity at 0.33 wt% or less and other elements at 0.17 wt% or less. This amount is considered to have little influence on the characteristics of the present lithium metal complex oxide.

<Raw material>
As a lithium compound which is a raw material, for example, lithium hydroxide (including LiOH and LiOH.H ₂ O), lithium carbonate (Li ₂ CO ₃ ), lithium nitrate (LiNO ₃ ), lithium oxide (Li ₂ O), other fatty acids Lithium and lithium halide etc. can be mentioned.
The type of manganese compound is not particularly limited. For example, manganese carbonate, manganese nitrate, manganese chloride, manganese dioxide, manganese (iii) oxide, trimanganese tetraoxide and the like can be used, among which manganese carbonate and manganese dioxide are preferable. Among them, electrolytic manganese dioxide obtained by an electrolytic method is particularly preferable.
The type of nickel salt compound is also not particularly limited, and, for example, nickel carbonate, nickel nitrate, nickel chloride, nickel oxyhydroxide, nickel hydroxide, nickel oxide, etc. can be used, among which nickel carbonate, nickel hydroxide, nickel oxide preferable.
The type of cobalt compound is also not particularly limited, and, for example, basic cobalt carbonate, cobalt nitrate, cobalt chloride, cobalt oxyhydroxide, cobalt hydroxide, cobalt oxide and the like can be used. Among them, basic cobalt carbonate and cobalt hydroxide , Cobalt oxide and cobalt oxyhydroxide are preferable.
The type of aluminum compound is also not particularly limited. For example, aluminum carbonate, aluminum nitrate, aluminum chloride, aluminum oxyhydroxide, aluminum hydroxide, aluminum oxide, etc. can be used, and among them, aluminum carbonate, aluminum hydroxide, aluminum oxide is preferable. .

  In addition, hydroxide salts, carbonates, nitrates and the like of the M element in the above formula (1) can be used as a raw material.

<Mother lithium metal complex oxide powder>
In the present production method, the host lithium metal complex oxide powder is obtained by mixing the raw materials, granulating and drying as required, and calcining, heat treating as necessary, and crushing as necessary. Can. The obtained lithium metal composite oxide powder can also be obtained by performing a predetermined treatment.

The matrix lithium metal composite oxide powder preferably has a water content of 50 to 1000 ppm measured at 110 to 300 ° C. by the Karl Fischer method. If the said water content is 50 ppm or more, reaction with a coupling agent can be heightened especially among surface treatment agents, and the surface treatment effect can be heightened. On the other hand, if the water content is 1000 ppm or less, it is preferable in that the battery characteristics can be made equal or more.
From this point of view, the water content of the host lithium metal composite oxide powder is preferably 50 to 1000 ppm, and more preferably 50 ppm or more or 700 ppm or less, more preferably 50 ppm or more or 500 ppm or less, and further 400 ppm or less. preferable.
The water content measured at 110 to 300 ° C by the Karl Fischer method is measured in an apparatus set at 110 ° C in a nitrogen atmosphere using a Karl Fischer moisture meter (eg CA-100 manufactured by Mitsubishi Chemical Corporation) The amount of water released when a sample (sample) is heated for 45 minutes and then heated to 300 ° C. and heated at 300 ° C. for 45 minutes.
The water content measured at 110 to 300 ° C. by the Karl Fischer method is considered to be mainly water chemically bonded to the inside of the host lithium metal composite oxide powder particles.

  Drying, dehumidification, humidity control, etc. can be mentioned as a means to adjust the moisture content of host lithium metal complex oxide powder in the said range. However, it is not limited to such a method.

(Mixing process)
It is preferable to mix the raw materials for obtaining the matrix lithium metal composite oxide powder by adding a liquid medium such as water and a dispersant and wet mixing to form a slurry. And when adopting the spray-drying method mentioned later, it is preferable to grind | pulverize the obtained slurry of the above-mentioned with a wet crusher. However, dry grinding may be performed.

  In the mixing step, at least a nickel compound and optionally a nickel compound and an aluminum compound are pulverized and classified before mixing the raw materials in order to enhance the homogeneity in mixing the raw materials by removing coarse powders of the nickel raw materials. The maximum particle size (Dmax) of the nickel compound is preferably adjusted to 10 μm or less, preferably 5 μm or less, and more preferably 4 μm or less.

(Granulation)
After mixing the raw materials, it is preferable to granulate as required.
The granulation method may be wet or dry as long as various raw materials are dispersed in the granulated particles without separation, and extrusion granulation method, rolling granulation method, fluid granulation method, mixing granulation method, spraying A dry granulation method, a pressure molding granulation method, or a flake granulation method using a roll or the like may be used.
However, in the case of wet granulation, it is necessary to sufficiently dry before firing. In this case, the drying method may be a known drying method such as a spray heat drying method, a hot air drying method, a vacuum drying method, a freeze drying method, and the like, among which the spray heat drying method is preferable.
Spray thermal drying is preferably carried out using a thermal spray dryer (spray dryer) (herein referred to as "spray dry").
However, it is also possible to produce a co-precipitate which is subjected to calcination, for example by the so-called co-precipitation method (herein referred to as "co-precipitation method"). In the coprecipitation method, coprecipitation can be obtained by dissolving the raw material in a solution and then adjusting the conditions such as pH for precipitation.

  In the spray drying method, the powder strength is relatively low, and voids tend to be generated between particles. Therefore, in the case of employing the spray drying method, the crushing strength is higher in the crushing step after the firing step to be described later than in the conventional crushing method, for example, the crushing method using a coarse crusher with a rotation speed of about 1000 rpm. It is preferred to employ a high grinding method.

(Firing process)
In the firing step for obtaining the host lithium metal composite oxide powder, it is preferable to perform a temporary firing at 500 to 840 ° C., and then a main firing at 700 to 1000 ° C., if necessary. It is also possible to carry out main baking at 700 to 1000 ° C. without carrying out the temporary baking.
By pre-baking, a gas (for example, CO ₂ ) generated from components contained in the raw material can be extracted. Therefore, for example, when carbonates such as lithium carbonate (Li ₂ CO ₃ ), manganese carbonate, nickel carbonate, basic cobalt carbonate and the like are used as a raw material, it is preferable to perform calcination.
And in this baking, the crystallinity of particle | grains can be raised or it can adjust to a desired particle size by baking at high temperature rather than temporary baking.

The pre-baking is performed in an atmosphere, in an atmosphere of oxygen gas, in an atmosphere in which the partial pressure of oxygen is adjusted, in an atmosphere containing carbon dioxide gas, or in another atmosphere in a firing furnace. This means the temperature when a thermocouple is brought into contact with the fired product in the firing furnace), among which 600 ° C. or more or 840 ° C. or less, among them 650 ° C. or more or 750 ° C. or less for 0.5 hour to 30 hours It is preferable to bake so as to
The type of firing furnace is not particularly limited. For example, it can bake using a rotary kiln, a stationary furnace, and other baking furnaces.

This firing is performed in an atmosphere, in an atmosphere of oxygen gas, in an atmosphere in which the partial pressure of oxygen is adjusted, in an atmosphere containing carbon dioxide gas, or in another atmosphere in a firing furnace. This means the temperature when a thermocouple is brought into contact with the fired product in the furnace), preferably 750 ° C. or more or 950 ° C. or less, more preferably 800 ° C. or more or 950 ° C. or less, further preferably 850 ° C. or more. Alternatively, firing is preferably performed so as to be held at 910 ° C. or less for 0.5 hours to 30 hours. Under the present circumstances, it is preferable to select the calcination conditions which can consider that the baking products containing a several metal element are single phase of lithium metal complex oxide of the target composition.
The type of firing furnace is not particularly limited. For example, it can bake using a rotary kiln, a stationary furnace, and other baking furnaces.

  However, when the main firing is performed without temporary firing, the temperature is 700 ° C. to 1000 ° C., particularly 750 ° C. or more and 950 ° C. or less, particularly 800 ° C. or more and 950 ° C. or less, and further 850 ° C. or more and 0 ° C. or less. It is preferable to bake so as to hold for 5 hours to 30 hours.

(Heat treatment)
Heat treatment after firing is preferably performed when it is necessary to adjust the crystal structure. As the heat treatment atmosphere at that time, it is preferable to perform the heat treatment under the conditions of an oxidizing atmosphere such as an atmosphere, an oxygen gas atmosphere, an atmosphere in which the oxygen partial pressure is adjusted, and the like.

(Crushing)
Crushing after firing or heat treatment is preferably carried out using a high-speed rotary crusher or the like. Crushing by means of a high-speed rotary crusher makes it possible to crush parts where the particles are agglomerated or weak in sintering, and to suppress distortion of the particles. However, the invention is not limited to the high-speed rotary crusher.

A pin mill can be mentioned as an example of a high speed rotary crusher. A pin mill is known as a disc rotary crusher, and is a crusher of a type in which powder is drawn from a raw material supply port by applying a negative pressure to the inside by rotating a pin-equipped rotary disk. Therefore, the fine particles are easy to ride on the air flow because they are light in weight, and pass through the clearance in the pin mill, while coarse particles are surely crushed. Therefore, if it is crushed by a pin mill, it is possible to reliably solve the aggregation between particles and the weakly sintered portion, and to suppress the occurrence of strain in the particles.
The rotational speed of the high-speed rotary crusher is preferably 4,000 rpm or more, particularly 5,000 to 12,000 rpm, and more preferably 7,000 to 10,000 rpm.

  Since classification after firing has the technical significance of foreign matter removal as well as particle size distribution adjustment of agglomerated powder, it is preferable to select and classify a sieve with a mesh with a preferred size.

(Surface treatment process)
In the surface treatment step, a surface treatment agent containing at least one of aluminum, titanium and zirconium may be brought into contact with the host lithium metal composite oxide powder obtained as described above.
For example, organometallic compounds containing at least one of aluminum, titanium and zirconium, such as titanium coupling agent or aluminum coupling agent or zirconium coupling agent or titanium / aluminum coupling agent or titanium / zirconium coupling agent or aluminum A surface treatment agent such as a zirconium coupling agent or a titanium / aluminum / zirconium coupling agent is dispersed in an organic solvent to form a dispersion, and the dispersion and the host lithium metal complex oxide powder obtained as described above And a method of performing surface treatment by bringing

  The surface treatment agent may be a compound having an organic functional group and a hydrolyzable group in the molecule, and among them, one having phosphorus (P) in the side chain is preferable. The coupling agent having phosphorus (P) in the side chain is particularly excellent in the binding property with the binder because the compatibility with the binder is better.

  In the surface treatment step, a surface treatment agent equivalent to 0.1 to 20 parts by mass is preferably brought into contact with 100 parts by mass of the lithium metal composite oxide powder, and in particular 0.5 parts by mass or more or 10 parts by mass or less Among them, it is more preferable to contact the lithium metal complex oxide powder with a surface treatment agent in an amount of 1 part by mass or more and 5 parts by mass or less and further 1 part by mass or more and 3 parts by mass or less.

  More specifically, for example, the ratio of the total number of moles of aluminum, titanium and zirconium in the surface treatment agent to the number of moles of the lithium metal composite oxide powder {(M / lithium metal composite oxide powder) × 100 ( M: Al, Ti, Zr) to be 0.005 to 4%, and in particular 0.04% or more or 2% or less, in particular 0.08% or more or 1% or less In particular, it is preferable to contact the lithium metal composite oxide powder with the surface treatment agent so that the content is particularly 0.08% or more or 0.6% or less.

Further, the ratio of the total number of moles of aluminum, titanium and zirconium in the surface treatment agent to the number of moles of nickel in the lithium metal composite oxide powder {(M / Ni) × 100 (M: Al, Ti, Zr) } So as to be 0.01% to 13%, particularly 0.05% or more or 7% or less, in particular 0.1% or more or 3.5% or less, particularly 0 It is preferable to contact the lithium metal complex oxide powder and the surface treatment agent so as to be at least 1% or at most 2%.
When the content of Ni is high, the lifetime deterioration at a relatively high voltage becomes relatively large, so it is preferable to adjust the total amount of aluminum, titanium and zirconium in the surface treatment agent in a ratio to the amount of Ni contained.

  With respect to the amount of dispersion in which the surface treatment agent is dispersed in an organic solvent, it is 0.2 to 20 parts by mass, and more preferably 1 part by mass or more, or 15 parts by mass or less with respect to 100 parts by mass of lithium metal complex oxide powder. Among them, it is preferable to contact the lithium metal composite oxide powder with a dispersion of 2 parts by mass or more and 10 parts by mass or less, and further more preferably 2 parts by mass or more and 7 parts by mass or less.

In the case of a lithium metal complex oxide having a layered crystal structure, lithium in the layered crystal structure is eluted when the amount of the organic solvent to be contacted is large, so the amount of surface treating agent or surface treating agent is dispersed in the organic solvent It is preferred to limit the amount of dispersion applied as described above.
Further, by contacting the lithium metal composite oxide powder with a dispersion in which a small amount of the surface treatment agent or the surface treatment agent is dispersed in the organic solvent as described above, the surface treatment agent is a lithium metal composite while being mixed with the air or oxygen. It can be brought into contact with the oxide powder. Thus, oxygen can be left on the particle surface, which can be presumed to contribute to the supply of oxygen consumed in the oxidation reaction of the organic substance at the time of the subsequent heat treatment.
At this time, the surface treatment agent or the dispersion in which the surface treatment agent is dispersed in the organic solvent is not contacted and mixed with the lithium metal composite oxide powder at one time, but is contacted in several times. It is preferable to repeat the mixing process.
In the contact method at this time, that is, the method of contacting the lithium metal composite oxide powder with the dispersion in which the surface treatment agent is dispersed in an organic solvent, for example, the dispersion is sprayed onto the lithium metal composite oxide powder A method, a method of dropping, or a method of spraying can be mentioned.

  Moreover, the kind of mixer used for surface treatment is not specifically limited. Mixing can be performed using a mixing / kneading mixer, a container rotary mixer, and the like, for example, a planetary mixer, a Henschel mixer, a Nauta mixer, a cutter mill, and other mixers.

  When surface treatment is performed using the surface treatment agent as described above, it is preferable to perform heat treatment in the next step after drying by heating to, for example, 40 to 120 ° C. to evaporate the organic solvent.

(Heat treatment process)
In the heat treatment step, the lithium metal composite oxide powder after the surface treatment is heated to a temperature of 700 to 950 ° C. (at the temperature when a thermocouple is brought into contact with the fired product in the furnace) under an atmosphere of oxygen concentration 20 to 100%. That is, it is preferable to perform heat treatment so as to hold the product temperature) for a predetermined time.
By such heat treatment, the organic solvent can be volatilized, side chains of the surface treatment agent can be decomposed, and aluminum or titanium or zirconium in the surface treatment agent can be diffused from the surface in a deeper direction. Thus, the life characteristics can be improved, and the output characteristics can be made equal or higher.

  From the viewpoint of further enhancing the effects of such heat treatment, the treatment atmosphere in the heat treatment step is preferably an oxygen-containing atmosphere. Among them, an oxygen-containing atmosphere having an oxygen concentration of 20 to 100% is preferable, among which 30% or more or 100% or less, among them 50% or more or 100% or less, further 70% or more or 100% or less Among them, an oxygen-containing atmosphere of 80% or more or 100% or less is more preferable.

  Moreover, it is preferable that the processing temperature in a heat treatment process is 700-950 degreeC (: The temperature at the time of making the baked product in a baking furnace contact a thermocouple.). When the heat treatment temperature is 700 ° C. or higher, the bond between the lithium metal composite oxide and the surface layer to be formed can be further strengthened, and the output characteristics can be enhanced. On the other hand, if the heat treatment temperature is 950 ° C. or lower, it is possible to suppress the release of oxygen from the lithium metal composite oxide and maintain the cycle characteristics. From this point of view, the heat treatment temperature is preferably 700 to 950 ° C., and may be higher than 800 ° C., more preferably 750 ° C. or more and 900 ° C. or less, and still more preferably 750 ° C. or more and 850 ° C. or less.

Furthermore, the treatment time in the heat treatment step is preferably 0.5 to 20 hours, depending on the treatment temperature, and is preferably 1 hour or more and 10 hours or less, and more preferably 3 hours or more and 10 hours or less. Is more preferred.
The type of furnace is not particularly limited. For example, it can bake using a rotary kiln, a stationary furnace, and other baking furnaces.

After the heat treatment step, the lithium metal composite oxide powder may be crushed at a crushing strength such that the rate of change in specific surface area (SSA) before and after crushing is 100 to 250%.
Changes in the specific surface area (SSA) before and after crushing from the viewpoint that it is better to carry out crushing after heat treatment so that the new surface under the surface treatment layer is not exposed too much so as to retain the effect of surface treatment. The rate is preferably 100 to 200%, and more preferably 100% or more or 175% or less, among them 100% or more or 150% or less, and among them 100% or more or 125% or less. preferable.

  As a preferable example of such a crushing method, using a crusher (for example, a pin mill) crushed by a pin attached to a crushing plate rotating at a high speed in a relative direction, the rotation speed is 4000 rpm to 10000 rpm, and more preferably 4000 rpm or more or 9000 rpm Among them, a method of pulverizing at 4,000 rpm or more or 8,000 rpm or less can be mentioned.

(Classification)
Since classification after crushing has the technical significance of foreign particle removal as well as particle size distribution adjustment of agglomerated powder, it is preferable to select and classify a sieve with a mesh with a preferred size.

<Characteristics and application>
As a common feature that the present lithium metal complex oxide obtained by the present production method can have, an Al element, Ti, or the like on the entire surface or part of the surface of the lithium metal complex oxide particles observed by TEM. elements and containing at least lithium metal composite oxide particles kind exists of Zr elements, the specific surface area (SSA) is 0.2 to 3 ² / g, among others 0.2 m ² / g or more or ^2m 2 / g hereinafter, 0.2 m ² / g or more or 1.0 m ² / g or less among them, mention may be made of points even not greater than 0.2 m ² / g or 0.8 m ² / g among them.
When the lithium metal composite oxide of the present invention is used as a positive electrode active material of a lithium secondary battery by the presence of at least one of Al element, Ti element and Zr element in the surface layer of the particles, It is possible to suppress the reaction, improve the life characteristics, and make the output characteristics equal or more.
Therefore, the present lithium metal composite oxide is suitable for use as a positive electrode active material of a lithium secondary battery, and in particular, an on-vehicle battery, in particular an electric vehicle (EV: Electric Vehicle) or a hybrid electric vehicle (HEV: Hybrid) It is particularly excellent as a positive electrode active material of a battery mounted on an electric vehicle.

For example, the lithium metal composite oxide powder, a conductive material made of carbon black and the like, and a binder made of Teflon (Teflon is a registered trademark of DUPONT in the US) binder and the like are mixed to form a positive electrode. Can be manufactured. Then, such a positive electrode mixture is used for the positive electrode, for example, a material capable of inserting and extracting lithium such as lithium or carbon is used for the negative electrode, and lithium such as lithium hexafluorophosphate (LiPF ₆ ) is used for the non-aqueous electrolyte. A lithium secondary battery can be configured using a salt dissolved in a mixed solvent such as ethylene carbonate-dimethyl carbonate. However, it does not mean to limit the battery to such a configuration.

  A lithium battery provided with the present lithium metal composite oxide as a positive electrode active material exhibits excellent life characteristics (cycle characteristics) when it is repeatedly used in charge and discharge, and in particular, it can be used as an electric vehicle (EV: Electric Vehicle) or It is particularly excellent in applications of a positive electrode active material of a lithium battery used as a power source for driving a motor mounted on a hybrid electric vehicle (HEV: Hybrid Electric Vehicle).

The "hybrid vehicle" is a vehicle using two power sources of an electric motor and an internal combustion engine in combination.
The term "lithium battery" is intended to encompass all batteries containing lithium or lithium ion in the battery, such as lithium primary batteries, lithium secondary batteries, lithium ion secondary batteries, and lithium polymer batteries.

<Explanation of the phrase>
In the present specification, when expressing as “X to Y” (X and Y are arbitrary numbers), “preferably greater than X” or “preferably Y” with the meaning of “X or more and Y or less” unless otherwise stated. Also includes the meaning of "smaller".
Also, when expressed as “X or more” (X is an arbitrary number) or “Y or less” (Y is an arbitrary number), “greater than X is preferable” or “preferably less than Y” It also includes the intention.

  Next, the present invention will be further described based on examples and comparative examples. However, the present invention is not limited to the examples shown below.

Example 1
Lithium carbonate having an average particle diameter (D50) of 7 μm, electrolytic manganese dioxide having an average particle diameter (D50) of 23 μm and a specific surface area of 40 m ² / g, nickel hydroxide having an average particle diameter (D50) of 22 μm, D50) Cobalt oxyhydroxide of 14 μm and aluminum hydroxide of average particle diameter (D50) 1.4 μm, in a molar ratio of Li: Mn: Ni: Co: Al = 1.05: 0.27: 0.46 It weighed so that it might become: 0.21: 0.01.

An aqueous solution of polycarboxylic acid ammonium salt (SN Disperse 5468 manufactured by San Nopco Co., Ltd.) was added as a dispersant to ion exchange water. The amount of dispersant added was 6 wt% relative to nickel hydroxide and aluminum hydroxide.
Nickel hydroxide and aluminum hydroxide were added to the above-mentioned ion exchange water and mixed and stirred to prepare a slurry having a solid content concentration of 40 wt%. The slurry was wet-ground for 60 minutes at 1300 rpm using a wet crusher (SC220 / 70A-VB-ZZ manufactured by Nippon Coke), and the average particle size (D50) was 0.56 μm and the maximum particle size (Dmax) was 1. A ground slurry of 9 μm was obtained.
Subsequently, electrolytic manganese dioxide, cobalt oxyhydroxide and lithium carbonate, and ion-exchanged water, which have been weighed, are added to the above-mentioned pulverized slurry containing nickel hydroxide and aluminum hydroxide to adjust the slurry to a solid content concentration of 60 wt% did. At that time, a dispersant was added so as to be 6 wt% relative to the solid content in the slurry.
The slurry was wet milled at 1300 rpm for 50 minutes using the same wet mill as above to obtain a mixed mill slurry having an average particle size (D50) of 0.45 μm and a maximum particle size (Dmax) of 1.6 μm. The
The obtained mixed and ground slurry was granulated and dried using a thermal spray dryer (spray dryer, OC-16 manufactured by Ohkawara Kakohki Co., Ltd.). At this time, granulation drying was performed using a two-fluid nozzle for spraying, adjusting the temperature so that the spraying pressure was 0.6 MPa, the slurry supply amount was 14 kg / hr, and the outlet temperature of the drying tower was 100 to 110 ° C. .
The obtained granulated powder was calcined at 700 ° C. for 5 hours in the atmosphere using a stationary electric furnace for 5 hours, and then calcined at 910 ° C. in the atmosphere for 20 hours.

The water content of the lithium metal composite oxide powder obtained by firing, measured at 110 to 300 ° C. by the Karl-Fisher method, was 340 ppm.
Chemical analysis of the lithium metal composite oxide powder obtained by firing showed that lithium metal composite oxide powder (sample) Li _1.05 Ni _0.46 Co _0.21 Mn _0.27 Al _0.01 It was O ₂ .

Next, 3.0 parts by mass of an aluminum coupling agent (Ajinomoto Fine Techno Co., Ltd. Prenact AL-M) as a surface treatment agent and 3.8 parts by mass of isopropyl alcohol as a solvent are mixed, and aluminum is added to the solvent A dispersion in which the coupling agent was dispersed was prepared. Thereafter, 6.8 parts by mass of the dispersion was added to 100 parts by mass of the lithium metal composite oxide powder obtained by firing, and mixed using a cutter mill (Mircer 720G manufactured by Iwatani Sangyo Co., Ltd.) .
Next, drying was performed by placing in an oven at 100 ° C. for 1 hour in the atmosphere. Thereafter, heat treatment was performed so as to maintain the product temperature at 770 ° C. for 5 hours in an atmosphere with an oxygen concentration of 100% to obtain a lithium metal composite oxide powder.
The lithium metal composite oxide obtained by the heat treatment was classified with a sieve having an opening of 53 μm to obtain a lithium metal composite oxide powder (sample) under the sieve.

Example 2
A lithium metal composite oxide powder (sample) was obtained in the same manner as in Example 1 except that the heat treatment temperature after the surface treatment was changed to 910 ° C. in Example 1.

Example 3
In Example 1, the amount 3.8 parts by mass of isopropyl alcohol used in the surface treatment is changed to 5.0 parts by mass, the amount of the added dispersion 6.8 parts by mass is changed to 8.0 parts by mass, and further In the same manner as in Example 1, except that the heat treatment conditions after the surface treatment were changed to “heat treatment so as to maintain the product temperature at 700 ° C. for 5 hours in an atmosphere with an oxygen concentration of 50%” A powder (sample) was obtained.

Example 4
In Example 1, 3.0 parts by mass of the aluminum coupling agent used in the surface treatment is changed to 1.0 parts by mass, and 3.8 parts by mass of the isopropyl alcohol is changed to 19.0 parts by mass, Furthermore, a lithium metal composite oxide powder (sample) was obtained in the same manner as in Example 1 except that the addition amount of 6.8 parts by mass of the dispersion was changed to 20.0 parts by mass.

Example 5
In Example 1, 3.0 parts by mass of the aluminum coupling agent used in the surface treatment is changed to 0.5 parts by mass, and 3.8 parts by mass of the isopropyl alcohol is changed to 2.5 parts by mass, Furthermore, a lithium metal composite oxide powder was prepared in the same manner as in Example 1, except that the amount of addition of the dispersion was changed to 3.0 parts by mass and the heat treatment temperature after surface treatment was changed to 810 ° C. (Sample) was obtained.

Example 6
In Example 1, 3.0 parts by mass of the aluminum coupling agent used in the surface treatment is changed to 4.0 parts by mass, and 3.8 parts by mass of the isopropyl alcohol is changed to 5.1 parts by mass, Change the 6.8 parts by mass addition of the dispersion to 9.1 parts by mass, and further, to maintain the material temperature at 770 ° C. for 5 hours under an atmosphere with an oxygen concentration of 80%. A lithium metal composite oxide powder (sample) was obtained in the same manner as in Example 1 except that the heat treatment was changed to "to perform heat treatment".

Example 7
In Example 1, 3.0 parts by mass of the aluminum coupling agent used in the surface treatment was changed to 1.0 parts by mass of a titanium coupling agent (Ajinomoto Fine Techno Co., Ltd. Prenact KR 46B), and the amount of isopropyl alcohol3. Lithium metal composite oxide powder (in the same manner as in Example 1) except that 8 parts by mass was changed to 5.0 parts by mass, and further, the addition amount of dispersion was changed to 6.0 parts by mass. I got a sample).

Example 8
In Example 1, 3.0 parts by mass of the aluminum coupling agent used in the surface treatment was replaced with a zirconium coupling agent (Kenrich Petrochemicals, Inc. Ken-React®) NZ (registered trademark) 12) Modified to 1.1 parts by mass, changed 3.8 parts by mass of isopropyl alcohol to 4.9 parts by mass, and further changed 6.8 parts by mass of added amount of dispersion to 6.0 parts by mass A lithium metal composite oxide powder (sample) was obtained in the same manner as in Example 1 except for the above.

Comparative Example 1
An aqueous solution of ammonium polycarboxylate as a dispersant (SN Disperse 5468 manufactured by San Nopco Co., Ltd.) was added to ion exchange water. The amount of the dispersant added was 6 wt% with respect to the total amount of Ni raw material, Mn raw material, Co raw material, Li raw material and the like described later, and was sufficiently dissolved and mixed in ion exchange water.
Lithium carbonate having an average particle diameter (D50) of 7 μm, electrolytic manganese dioxide having an average particle diameter (D50) of 23 μm and a specific surface area of 40 m ² / g, nickel hydroxide having an average particle diameter (D50) of 22 μm, D50) Weigh 14 μm of cobalt oxyhydroxide to a molar ratio of Li: Mn: Ni: Co = 1.04: 0.26: 0.51: 0.19, and it has a solid content concentration of 50 wt% The slurry was adjusted to a slurry and milled with a wet mill for 40 minutes at 1300 rpm to wet mill it to an average particle size (D50) of 0.55 μm.
The ground slurry thus obtained was granulated and dried using a thermal spray dryer (spray dryer, OC-16 manufactured by Ohkawara Kakohki Co., Ltd.). At this time, granulation drying was performed using a rotating disk for spraying, adjusting the temperature so that the rotation speed was 24000 rpm, the amount of supplied slurry was 20 kg / hr, and the outlet temperature of the drying tower was 100 ° C.
The obtained granulated powder was calcined at 450 ° C. in the air using a stationary electric furnace. Subsequently, the calcined powder was fired at 910 ° C. in the atmosphere for 20 hours using a stationary electric furnace.
The fired mass obtained by firing was put in a mortar and crushed, and classified using a sieve with an opening of 53 μm to recover a lithium metal composite oxide powder (sample) under the sieve.
Chemical analysis of the result of the recovered lithium metal composite oxide powder (sample) _{was Li 1.04 Ni 0.52 Co 0.19 Mn 0.25} O 2.

<Analysis of surface layer>
The cross section in the vicinity of the particle surface of the lithium metal composite oxide (sample) was observed with a transmission electron microscope ("JEM-ARM200F" manufactured by JEOL Ltd.) and analyzed by EDS (energy dispersive X-ray analysis).
As a result, with respect to the lithium metal composite oxides (samples) obtained in Examples 1 and 2, it was possible to confirm that a layer containing a large amount of Al element was present on the surface of each particle.

<D50 measurement>
A lithium metal composite oxide powder (sample) obtained in Examples and Comparative Examples was subjected to lithium metal composite oxide using an automatic sample feeder for laser diffraction particle size distribution measuring apparatus ("Microtorac SDC" manufactured by Nikkiso Co., Ltd.) The powder (sample) is introduced into a water-soluble solvent, and irradiated with 40 W ultrasonic waves for 360 seconds at a flow rate of 40%, and then the particle size distribution is measured using a laser diffraction particle size distribution analyzer "MT3000II" manufactured by Nikkiso Co., Ltd. D50 was determined from the obtained volume-based particle size distribution chart.
The water-soluble solvent used for measurement is a filter of 60 μm, solvent refractive index is 1.33, particle permeability is transmitted, particle refractive index is 2.46, shape is non-spherical, measurement range is 0.133. The measurement time was 30 seconds, and the average value measured twice was D50.

<Measurement of specific surface area>
0.5 g of lithium metal complex oxide powder (sample) was weighed, and put into a glass cell for flow type gas adsorption method specific surface area measurement device MONOSORB LOOP (product name MS-18 manufactured by Yuasa Ionics Co., Ltd.), After displacing the inside of the glass cell for 5 minutes while flowing nitrogen gas with a gas amount of 30 mL / min in the pretreatment device for MONOSORB LOOP, treatment was performed in the nitrogen gas atmosphere at 250 ° C. for 10 minutes. Thereafter, using the MONOSORB LOOP, a sample (powder) was measured by the BET single-point method.
In addition, mixed gas of nitrogen 30%: helium 70% was used as the adsorption gas at the time of measurement.

<Battery characteristic evaluation>
8.0 g of lithium metal complex oxide powder (sample) obtained in Examples and Comparative Examples and 1.0 g of acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd.) were accurately measured and mixed in a mortar for 10 minutes. Thereafter, 8.3 g of a solution in which 12 wt% of PVDF (manufactured by Kishida Chemical Co., Ltd.) was dissolved in NMP (N-methylpyrrolidone) was accurately measured, to which a mixture of lithium metal composite oxide powder and acetylene black was added and further mixed . Thereafter, 5 ml of NMP was added and thoroughly mixed to prepare a paste. The paste is placed on an aluminum foil as a current collector, coated with an applicator adjusted to a gap of 100 μm to 280 μm, dried at 140 ° C. overnight under vacuum, and then rolled so that the linear pressure becomes 0.3 t / cm ^2. It pressed, it pierced by (phi) 16 mm, and was set as the positive electrode.
Immediately before battery fabrication, vacuum drying was carried out at 200 ° C. for 300 minutes or more to remove attached moisture, and the battery was incorporated. In addition, an average value of the weight of the aluminum foil of φ 16 mm was obtained in advance, and the weight of the positive electrode mixture was calculated by subtracting the weight of the aluminum foil from the weight of the positive electrode. In addition, the content of the positive electrode active material was determined from the mixing ratio of the lithium metal composite oxide powder (positive electrode active material), acetylene black, and PVDF.
The negative electrode is a metal Li with a diameter of 19 mm and a thickness of 0.5 mm, and the electrolyte used is a mixture of EC and DMC in a volume of 3: 7 as a solvent, in which 1 mol / L of LiPF ₆ is dissolved as a solute. An electrochemical evaluation cell TOMCEL (registered trademark) shown in 1 was produced.

(Initial activity)
Initial activation was performed by the method described below using the electrochemical cell prepared as described above. After performing constant current constant potential charge to 4.3 V at 0.2 ° C. at 25 ° C., constant current discharge was performed to 3.0 V at 0.2 C. This was repeated 2 cycles. The current value actually set was calculated from the content of the positive electrode active material in the positive electrode.

(High temperature cycle life evaluation: 45 ° C high temperature cycle characteristics)
After the initial activation as described above, a charge / discharge test was performed by the method described below using the electrochemical cell to evaluate high temperature cycle life characteristics.
Place the cell in an environmental tester set to an environmental temperature of 45 ° C to charge and discharge the battery, prepare to be able to charge and discharge, stand for 4 hours so that the cell temperature becomes the environmental temperature, and then charge and discharge range The charge / discharge cycle was performed 40 times at 1 C after charge / discharge was performed at 0.2 C constant current constant potential and 0.2 C constant current for 1 cycle.
The percentage (%) of the value obtained by dividing the discharge capacity at the 40th cycle by the discharge capacity at the second cycle was determined as the high temperature cycle life characteristic value.
Table 1 shows the high temperature cycle life characteristic values of the respective examples and the comparative examples as relative values when the high temperature cycle life characteristic value of the comparative example 1 is 100.

(Output characteristic evaluation test)
Separately, the electrochemical cell after initial activation was subjected to constant current charging at 25 ° C. to a SOC of 50% at 0.2 C. After charging, discharge for 10 seconds at a current value of 3C, and after subtracting the potential after discharging from the potential after charging, the potential difference is divided by the current value of 3C to obtain the resistance value, and an indicator of output characteristics And Table 1 shows the relative value (%) when the resistance value of Comparative Example 1 is 100.0%. The smaller the numerical value, the better the output characteristics.

  In Table 1 below, “(M / lithium metal composite oxide powder) × 100” means the ratio of the total number of moles of aluminum, titanium and zirconium in the surface treatment agent to the number of moles of lithium metal composite oxide powder ( M: means Al, Ti, Zr), and “(M / Ni) × 100” means the sum of aluminum, titanium and zirconium in the surface treatment agent relative to the number of moles of nickel in the lithium metal composite oxide powder It means the ratio of the number of moles (M: Al, Ti, Zr)}, and the "addition amount of the surface treatment agent dispersion" means the lithium metal complex oxide of the dispersion in which the surface treatment agent is dispersed in an organic solvent It means the amount added to 100 parts by mass of the powder.

(Discussion)
As in the above-described example, the sintered lithium metal complex oxide powder is dispersed in a surface treatment agent or a surface treatment agent containing at least one of aluminum, titanium and zirconium in an organic solvent. The surface treatment of the lithium metal composite oxide powder is followed by heat treatment so as to maintain the temperature at 700 to 950 ° C. in an oxygen atmosphere, preferably in an atmosphere with an oxygen concentration of 20 to 100%. A surface layer containing at least one of aluminum, titanium and zirconium can be formed on the surface of the particles, and when used as a positive electrode active material of a lithium secondary battery, the reaction with the electrolytic solution is suppressed to prolong the life It has been found that the characteristics can be improved and the output characteristics can be made equal or higher.

  The above example is an example of a lithium metal composite oxide having a layered crystal structure of a specific composition, but according to the test results and technical common sense the present inventor has conducted so far, the layered crystal structure is Since the lithium metal complex oxide which it has has a common subject, and the influence by surface treatment and heat treatment is also the same, if it is a lithium metal complex oxide which has layered crystal structure, regardless of the composition, It can be considered that the same effect can be obtained in common.

Claims (10)

A surface treatment step of surface-treating lithium metal complex oxide powder using an organometallic compound containing at least one of aluminum, titanium and zirconium, and heat treatment of lithium metal complex oxide powder after the surface treatment A method for producing a lithium metal composite oxide having a layered crystal structure, comprising a heat treatment step, comprising:
In the heat treatment step, the lithium metal complex oxide powder after the surface treatment is heat treated so as to be maintained at a temperature of 700 to 950 ° C. in an oxygen-containing atmosphere having an oxygen concentration of 30 to 100%. The manufacturing method of lithium metal complex oxide which has a structure. After the heat treatment step, there is provided a crushing step of crushing the lithium metal composite oxide powder with a crushing strength such that the rate of change of the specific surface area (SSA) before and after the crushing is 100 to 250%. The manufacturing method of lithium metal complex oxide as described. The method for producing a lithium metal composite oxide according to claim 2, wherein the lithium metal composite oxide powder is crushed using a pin mill in the crushing step. The lithium according to any one of claims 1 to 3, wherein in the surface treatment step, a surface treatment agent equivalent to 0.1 to 20 parts by mass is brought into contact with 100 parts by mass of the lithium metal composite oxide powder. Method of producing metal complex oxide. In the surface treatment step, the ratio of the total number of moles of aluminum, titanium and zirconium in the surface treatment agent to the number of moles of the lithium metal composite oxide powder {(M / lithium metal composite oxide powder) × 100 (M: 4. The lithium according to any one of claims 1 to 3, characterized in that the lithium metal complex oxide powder and the surface treatment agent are brought into contact so that Al, Ti, Zr)} is 0.005 to 4%. Method of producing metal complex oxide. In the surface treatment step, the ratio of the total number of moles of aluminum, titanium and zirconium in the surface treatment agent to the number of moles of nickel in the lithium metal composite oxide powder {(M / Ni) × 100 (M: Al, The lithium metal composite oxide according to any one of claims 1 to 3 , wherein the lithium metal composite oxide powder and the surface treatment agent are brought into contact with each other such that Ti, Zr)} is 0.01 to 13%. Method of producing oxide Wherein in the surface treatment step, to a lithium metal composite oxide powder 100 parts by weight, claim and characterized in that the dispersion obtained by dispersing a surface treatment agent in an organic solvent is contacted 0.2 to 20 parts by weight 1-6 The manufacturing method of lithium metal complex oxide in any one of-. The method of producing a lithium metal composite oxide according to any one of claims 1 to 7, wherein the organic metal compound used for the surface treatment is an organic metal compound having phosphorus (P) in a side chain.   The method of producing a lithium metal composite oxide according to any one of claims 1 to 8, wherein the organic metal compound used for the surface treatment is a coupling agent. The lithium metal according to any one of claims 1 to 9, wherein, in the surface treatment step, the surface treatment agent is brought into contact with the lithium metal composite oxide powder, and then heated to 40 to 120 ° C and dried. Method of producing complex oxide.