JP3863282B2 - Non-aqueous electrolyte secondary battery and method of using non-aqueous electrolyte secondary battery - Google Patents

Description

【００６４】
図２から明らかなように、実施例１〜４の二次電池は、比較例１〜４に比べて充放電電位のヒステリシスが小さいことがわかる。中でも、比較例２の二次電池は、放電時に電圧が他のものに比べて急激に低下することがわかる。また、表１から、実施例１〜４の二次電池は、比較例１，３，４に比べて３００サイクル時の容量維持率が高いことがわかる。
【００６５】
なお、前記実施例では円筒形非水電解質二次電池に適用した例を説明したが、角形非水電解質二次電池にも同様に適用できる。また、前記電池の容器内に収納される電極群は渦巻形に限らず、正極、セパレータおよび負極をこの順序で複数積層した形態にしてもよい。
【００６６】
【発明の効果】
以上詳述したように、本発明によれば、高容量で、大電流放電特性に優れ、かつ長寿命な非水電解質二次電池を提供することができる。
【図面の簡単な説明】
【図１】本発明に係わる非水電解質二次電池の一例を示す部分断面図。
【図２】実施例１〜４及び比較例１〜４の非水電解質二次電池における充放電電圧の経時変化（充放電曲線）を示す特性図。
【符号の説明】
１…容器、
３…電極群、
４…正極、
６…負極、
８…封口板。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to a non-aqueous electrolyte secondary battery having an improved negative electrode containing a carbonaceous material.
[0002]
[Prior art]
In recent years, non-aqueous electrolyte batteries using lithium as a negative electrode active material have attracted attention as high energy density batteries. Manganese dioxide (MnO ₂ ), fluorocarbon [(CF ₂ ) _n ], thionyl chloride ( Primary batteries using SOCl ₂ ) and the like are already widely used as power sources for calculators, watches, and memory backup batteries.
[0003]
Furthermore, in recent years, with the reduction in size and weight of various electronic devices such as VTRs and communication devices, the demand for high energy density secondary batteries has increased, and research on lithium secondary batteries using lithium as a negative electrode active material has been made. Is being actively conducted.
[0004]
Lithium secondary batteries use lithium for the negative electrode, and in non-aqueous solvents such as propylene carbonate (PC), 1,2-dimethoxyethane (DME), γ-butyrolactone (γ-BL), and tetrahydrofuran (THF) as the electrolyte. A non-aqueous electrolyte solution or a lithium ion conductive solid electrolyte in which a lithium salt such as LiClO ₄ , LiBF ₄ or LiAsF ₆ is dissolved is used, and the positive electrode active materials are mainly TiS ₂ , MoS ₂ , V ₂ O ₅ , V _The use of compounds that undergo a topochemical reaction with lithium such as ₆ O ₁₃ and MnO ₂ has been studied.
[0005]
However, the above-described lithium secondary battery has not yet been put into practical use. The main reason is that the charge / discharge efficiency is low and the number of times (cycle life) that can be charged / discharged is short. The cause of this is thought to be largely due to the deterioration of lithium due to the reaction between lithium in the negative electrode and the non-aqueous electrolyte. That is, lithium dissolved in the non-aqueous electrolyte as lithium ions at the time of discharge reacts with the solvent when deposited at the time of charging, and the surface thereof is partially inactivated. For this reason, when charging and discharging are repeated, lithium is deposited in a dendritic shape (dendritic shape) or in a small spherical shape, and further, a phenomenon such that lithium is desorbed from the current collector occurs.
[0006]
For this reason, lithium and non-aqueous electrolysis can be obtained by using a carbonaceous material that occludes / releases lithium, such as coke, resin fired body, carbon fiber, pyrolytic vapor phase carbon, etc., as the negative electrode incorporated in the lithium secondary battery. It has been proposed to improve the deterioration of the negative electrode characteristics due to the reaction with the liquid and the dendrite precipitation.
[0007]
In the negative electrode containing the carbonaceous material, lithium ions enter and exit the portion between the layers in the structure (graphite structure) in which the hexagonal network layers mainly composed of carbon atoms are stacked among the carbonaceous materials. It is thought that charging / discharging is performed.
[0008]
By the way, a carbonaceous material obtained by heat-treating pitch, coke, resin or the like at 1000 ° C. or less has a large amount of hydrogen remaining, and H / C is 0.1 or more, so that a high capacity exceeding the capacity of graphite can be obtained. . However, since the carbonaceous material has low electronic conductivity and n-type semiconducting properties, the negative electrode including the carbonaceous material has a problem in that it has a large hysteresis in the charge / discharge potential and the charge / discharge efficiency is low. For this reason, the non-aqueous electrolyte secondary battery provided with the negative electrode is inferior in large current discharge characteristics and cycle life, and is practically used not only in small batteries for portable device power supply but also in large batteries used as electric vehicles and power storage power supplies. It was difficult.
[0009]
[Problems to be solved by the invention]
An object of the present invention is to provide a nonaqueous electrolyte secondary battery having a high capacity, excellent large current discharge characteristics, and a long life by improving a negative electrode containing a carbonaceous material.
[0010]
[Means for Solving the Problems]
A non-aqueous electrolyte secondary battery according to the present invention includes a container,
A positive electrode housed in the container;
The carbonaceous material A that is housed in the container and has an atomic ratio (H / C) of hydrogen (H) to carbon (C) of 0.1 to 0.4, and that absorbs and releases lithium ions, and the atomic ratio (H / C) less than 0.1, and a negative electrode containing carbonaceous material B that absorbs and releases lithium ions;
A non-aqueous electrolyte housed in the container;
And a temperature holding means for holding the temperature of the wall of the container at 50 ° C. or higher at the time of charging and holding at a higher temperature than at the time of charging at the time of discharging .
[0011]
The method of using the nonaqueous electrolyte secondary battery according to the present invention includes a container,
A positive electrode housed in the container;
The carbonaceous material A that is housed in the container and has an atomic ratio (H / C) of hydrogen (H) to carbon (C) of 0.1 to 0.4, and that absorbs and releases lithium ions, and the atomic ratio (H / C) less than 0.1, and a negative electrode containing carbonaceous material B that absorbs and releases lithium ions;
When performing a charge / discharge cycle on a non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte accommodated in the container, the temperature of the wall of the container is maintained at 50 ° C. or higher during charging and more than during charging during discharging. It is characterized by being kept at a high temperature .
[0012]
DETAILED DESCRIPTION OF THE INVENTION
(First nonaqueous electrolyte secondary battery)
Hereinafter, a first nonaqueous electrolyte secondary battery (for example, a cylindrical nonaqueous electrolyte secondary battery) according to the present invention will be described in detail with reference to FIG.
[0013]
For example, a bottomed cylindrical container 1 made of stainless steel has an insulator 2 disposed at the bottom. The electrode group 3 is accommodated in the container 1. The electrode group 3 has a structure in which a belt-like material in which the positive electrode 4, the separator 5, and the negative electrode 6 are laminated in this order is wound in a spiral shape.
[0014]
An electrolytic solution is accommodated in the container 1. The insulating paper 7 having a central opening is placed above the electrode group 3 in the container 1. The insulating sealing plate 8 is disposed in the upper opening of the container 1, and the sealing plate 8 is liquid-tightly fixed to the container 1 by caulking the vicinity of the upper opening inward. The positive terminal 9 is fitted in the center of the insulating sealing plate 8. One end of the positive electrode lead 10 is connected to the positive electrode 4, and the other end is connected to the positive electrode terminal 9. The negative electrode 6 is connected to the container 1 serving as a negative electrode terminal through a negative electrode lead (not shown).
[0015]
Next, the positive electrode 4, the separator 5, the negative electrode 6, and the electrolytic solution will be described in detail.
1) Positive electrode 4
The positive electrode 4 is produced by suspending a conductive agent and a binder in an appropriate solvent in a positive electrode active material, and applying this suspension to a current collector and drying to form a thin plate.
[0016]
Examples of the positive electrode active material include various oxides such as manganese dioxide, lithium manganese composite oxide, lithium-containing nickel oxide, lithium-containing cobalt compound, lithium-containing nickel cobalt oxide, lithium-containing iron oxide, and vanadium containing lithium. Examples thereof include oxides and chalcogen compounds such as titanium disulfide and molybdenum disulfide. Among them, when a lithium-containing cobalt oxide (for example, LiCoO ₂ ), a lithium-containing nickel oxide (for example, LiNiO ₂ ), or a lithium manganese composite oxide (for example, LiMn ₂ O ₄ , LiMnO ₂ ) is used, a high voltage can be obtained. Is preferable.
[0017]
Examples of the conductive agent include acetylene black, carbon black, and graphite.
Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), ethylene-propylene-diene copolymer (EPDM), and styrene-butadiene rubber (SBR).
[0018]
The blending ratio of the positive electrode active material, the conductive agent and the binder is preferably in the range of 80 to 95% by weight of the positive electrode active material, 3 to 20% by weight of the conductive agent, and 2 to 7% by weight of the binder.
[0019]
As the current collector, for example, aluminum foil, stainless steel foil, nickel foil or the like can be used.
2) Separator 5
As the separator 5, for example, a synthetic resin nonwoven fabric, a polyethylene porous film, a polypropylene porous film, or the like can be used.
[0020]
3) Negative electrode 6
The negative electrode 6 has an atomic ratio (H / C) of hydrogen (H) to carbon (C) of 0.1 to 0.4, a carbonaceous material A that absorbs and releases lithium ions, and the atomic ratio (H / C). ) Is less than 0.1 (including 0), and includes fibrous carbonaceous material B that absorbs and releases lithium ions.
[0021]
The smaller the H / C of the carbonaceous material, the closer the microstructure becomes to the graphite structure, and the higher the occlusion / release rate and electronic conductivity of lithium ions. On the other hand, as the H / C of the carbonaceous material increases, the amount of occlusion / release of lithium ions increases, but the occlusion / release rate and electron conductivity tend to decrease. When the H / C exceeds 0.4, it becomes difficult for the carbonaceous material to release lithium ions. Carbonaceous material A having H / C in the range of 0.1 to 0.4 can increase the amount of occlusion / release of lithium ions to 400 mAh / g or more, but is inferior in electron conductivity. On the other hand, the carbonaceous material B having H / C of less than 0.1 can efficiently store and release lithium, and has high electron conductivity, but has a small amount of storage and release.
[0022]
The specific surface area of the carbonaceous material A according to the BET method is preferably 10 to 500 m ² / g. This is due to the following reason. When the specific surface area exceeds 500 m ² / g, the progress rate of the self-discharge reaction increases, and the storage characteristics of the battery may be deteriorated. If the specific surface area is less than 10 m ² / g, the lithium occlusion / release rate becomes slow, and the large current discharge characteristics of the battery may be deteriorated. A more preferable range of the specific surface area is 20 to 400 m ² / g.
[0023]
The carbonaceous material A can be present in the negative electrode in the form of fibers, particles, or a mixture of fibers and particles.
The carbonaceous material A is, for example, petroleum, coal, synthetically obtained pitch, coke, mesophase pitch, mesophase microspheres, organic materials having aromatic condensation molecules such as phenol resin, novolac resin, furan resin, etc. Can be produced by heat treatment in an inert atmosphere at 500 to 1000 ° C.
[0024]
If the temperature of the heat treatment deviates from the above range, H / C may be out of the range of 0.1 to 0.4. A more preferable range of the heat treatment temperature is 550 to 800 ° C.
[0025]
The true density of the carbonaceous material B is preferably 2.0 g / cm ³ or more. When the true density is less than 2.0 g / cm ³ , the bulk density of the negative electrode may be lowered.
[0026]
The spacing (d ₀₀₂ ) between the (002) planes of the graphite structure of the carbonaceous material B is preferably 0.38 nm or less. If the interplanar spacing (d ₀₀₂ ) exceeds 0.38 nm, the lithium ion occlusion / release rate and electronic conductivity of the negative electrode may be reduced. From the viewpoint of improving the electron conductivity and lithium ion occlusion and release of the carbonaceous material B, the spacing d ₀₀₂ is preferably below 0.337 nm. The interplanar distance _d002 can be obtained from the peak position of a diffraction diagram obtained by powder X-ray diffraction, for example. As a calculation method, the half-value width midpoint method defined in the Gakushin Law is used. The half-width half-point method is described in the document “Tanso (carbon)”, 1963, p25.
[0027]
The average length of the fibrous carbonaceous material B is preferably in the range of 10 to 100 μm.
The average diameter of the fibrous carbonaceous material B is preferably in the range of 1 to 20 μm.
[0028]
Examples of the carbonaceous material B include petroleum, coal, synthesized pitch, coke, mesophase pitch, mesophase spherule, pitch fiber, mesophase pitch fiber, polyacrylonitrile fiber, vapor growth fiber, and phenol resin. It can be produced by using an organic substance having an aromatic condensation molecule such as a novolak resin or a furan resin as a raw material and heat-treating them in an inert atmosphere at 1000 ° C. or higher. If the temperature of the heat treatment is lower than the above range, H / C may exceed 0.1. Moreover, it is preferable that the temperature at the time of the said heat processing shall be 2000 degreeC or more, and a graphitization process is performed. As the carbonaceous material B, fibrous natural graphite (H / C is 0) can be used in addition to the carbon material produced by the above-described method. As the carbonaceous material B, either the natural graphite or the carbon material may be used, or both the natural graphite and the carbon material may be used. Among them, carbon fiber that has been graphitized and H / C is less than 0.1, particularly mesophase pitch that has been graphitized at 2500 ° C. or higher and H / C is less than 0.1. It is preferable to use a carbon fiber as the carbonaceous material B. By using this mesophase pitch-based carbon fiber as the carbonaceous material B, it is possible to realize a negative electrode having high electron conductivity, fast lithium occlusion / release reaction, and high electrode strength. Characteristics and cycle life can be greatly improved.
[0029]
The blending amount of the carbonaceous material B in the carbonaceous material A and the carbonaceous material B is preferably in the range of 5 to 50% by weight. This is due to the following reason. If the blending amount is less than 5% by weight, it may be difficult to improve the electronic conductivity of the negative electrode. On the other hand, if the amount exceeds 50% by weight, the capacity of the negative electrode may be reduced. A more preferable range of the blending amount is 10 to 40% by weight.
[0030]
For example, the negative electrode 6 is obtained by kneading the carbonaceous material and a binder in the presence of a solvent, applying the obtained suspension to a current collector, drying, and then pressing once or 2 at a desired pressure. It can be produced by performing multi-stage pressing up to 5 times.
[0031]
Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR), carboxymethylcellulose (CMC), poly Acrylonitrile and the like can be used.
[0032]
The blending ratio of the carbonaceous material and the binder is preferably in the range of 90 to 98% by weight of the carbon material and 2 to 10% by weight of the binder. In particular, the carbonaceous material is preferably in the range of 5 to ²⁰ mg / cm ² in a state where the negative electrode 6 is produced.
[0033]
As the current collector, for example, copper foil, stainless steel foil, nickel foil or the like can be used.
4) Solid or gel non-aqueous electrolyte This non-aqueous electrolyte is held by the separator.
[0034]
As the non-aqueous electrolyte, for example, a polymer solid electrolyte or an inorganic solid electrolyte can be used.
Examples of the polymer solid electrolyte include polymer materials such as polyacrylonitrile (PAN), polyvinylidene fluoride (PVdF), polyethylene oxide (PEO), and polypropylene oxide (PPO), LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , Solid electrolyte to which a lithium salt such as LiN (CF ₃ SO ₂ ) ₂ is added, the polymer material, the lithium salt and a non-aqueous solvent (for example, ethylene carbonate (EC), propylene carbonate (PC), trifluoropropylene carbonate ( TFPC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), acetonitrile (AN), room temperature molten salt, etc.).
[0035]
Examples of the inorganic solid electrolyte include lithium sulfide glass and lithium oxide glass. In particular, Li ₃ PO ₄ —Li ₂ S—SiS ₂ glass having high ion conductivity is preferable.
[0036]
Hereinafter, the second nonaqueous electrolyte secondary battery will be described.
(Second nonaqueous electrolyte secondary battery)
This second non-aqueous electrolyte secondary battery has a positive electrode, a carbon (A / C) atomic ratio (H / C) of hydrogen (H) to carbon (C) of 0.1 to 0.4, and a carbon that occludes and releases lithium ions. A material A and a negative electrode including a carbonaceous material B having an atomic ratio (H / C) of less than 0.1 and storing / releasing lithium ions, and a non-aqueous electrolyte, the positive electrode, the negative electrode, and the non-aqueous The electrolyte is held at 50 ° C. or higher at least during discharge.
[0037]
The application of the second non-aqueous electrolyte secondary battery is not particularly limited, but in addition to a portable device driving power source, it is a large power source that is particularly a power storage power source or a driving power source for an electric vehicle / hybrid vehicle. Suitable for use as a battery.
[0038]
Examples of the positive electrode and the negative electrode include the same as those described in the first non-aqueous electrolyte secondary battery. In addition, although the fibrous carbonaceous material B is used in the first nonaqueous electrolyte secondary battery described above, the particulate carbonaceous material B may be used in the second nonaqueous electrolyte secondary battery. .
[0039]
The nonaqueous electrolyte is held by a separator. Examples of the separator include the same ones as described for the first nonaqueous electrolyte secondary battery.
[0040]
As the non-aqueous electrolyte, a solid or gel non-aqueous electrolyte, a room temperature molten salt, or a non-aqueous electrolyte can be used. Examples of the solid or gel non-aqueous electrolyte include the same as those described in the first non-aqueous electrolyte secondary battery. The room temperature type molten salt exhibits high ionic conductivity in a high temperature range from room temperature to 100 ° C. or higher, and therefore, by combining with the negative electrode containing the carbonaceous material A and the carbonaceous material B, the capacity and the charge / discharge cycle are stable. A non-aqueous electrolyte secondary battery can be obtained.
[0041]
The nonaqueous electrolytic solution is prepared by dissolving an electrolyte in a nonaqueous solvent.
As the non-aqueous solvent, a known non-aqueous solvent can be used as a solvent for the non-aqueous electrolyte secondary battery, and is not particularly limited, but has a lower melting point than ethylene carbonate (EC) and the ethylene carbonate and the number of donors. It is preferable to use a non-aqueous solvent mainly composed of a mixed solvent with one or more kinds of non-aqueous solvents (hereinafter referred to as second solvent) having an A of 18 or less.
[0042]
As the second type of solvent, for example, chain carbon is preferable, among which dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), diethyl carbonate (DEC), ethyl propionate, methyl propionate, or propylene carbonate (PC). , Trifluoropropylene carbonate (TFPC), γ-butyrolactone (γ-BL), acetonitrile (AN), ethyl acetate (EA), toluene, xylene or methyl acetate (MA). These second solvents can be used alone or in the form of a mixture of two or more. In particular, the second type solvent preferably has a donor number of 16.5 or less.
[0043]
The viscosity of the second solvent is preferably 28 mp or less at 25 ° C. The blending amount of the ethylene carbonate in the mixed solvent is preferably 10 to 80% by volume ratio. The blending amount of the ethylene carbonate is more preferably 20 to 75% by volume ratio.
[0044]
A more preferable composition of the mixed solvent is EC and MEC, EC and PC and MEC, EC and MEC and DEC, EC and DEC, EC and MEC, PC and DEC, and the volume ratio of MEC is 30 to 80%. It is preferable that A more preferred MEC volume ratio is in the range of 40-75%.
[0045]
Examples of the electrolyte contained in the non-aqueous electrolyte include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium borofluoride (LiBF ₄ ), and lithium arsenic hexafluoride (LiAsF ₆ ). And lithium salts (electrolytes) such as lithium trifluorometasulfonate (LiCF ₃ SO ₃ ) and lithium bistrifluoromethylsulfonylimide [LiN (CF ₃ SO ₂ ) ₂ ]. Of these, LiPF ₆ and LiBF ₄ are preferably used.
[0046]
The amount of the electrolyte dissolved in the non-aqueous solvent is preferably 0.5 to 2.0 mol / 1.
In the second non-aqueous electrolyte secondary battery, the positive electrode, the negative electrode, and the non-aqueous electrolyte are held at 50 ° C. or higher at least during discharge. The holding temperature is set in the above range for the following reason. If the holding temperature is less than 50 ° C., it is difficult to reduce the hysteresis at the charge / discharge potential of the negative electrode and to lower the electron transfer resistance at the time of lithium ion release from the negative electrode. In addition, there is a risk that improvement of large current discharge characteristics cannot be achieved. The holding temperature is preferably 150 ° C. or lower in the case of a gel-like non-aqueous electrolyte and 300 ° C. or lower in the case of a solid non-aqueous electrolyte. When this temperature is exceeded, the stability of the positive electrode material is lowered, and therefore cycle deterioration is likely to occur. In particular, the holding temperature during discharge is preferably 80 to 120 ° C. However, the temperature range is not limited as long as the stability of the positive electrode material can be maintained. Moreover, when performing temperature control both at the time of charge and at the time of discharge, it is preferable to make holding temperature at the time of discharge higher than at the time of charge.
[0047]
The temperature of the positive electrode, the negative electrode, and the nonaqueous electrolyte can be maintained by installing a temperature maintaining means in the secondary battery. This temperature holding means can be comprised from the apparatus which controls the temperature of a secondary battery, a heater, and a heat insulating material, for example. A part of the charging current and discharging current may be used as the power source of the heater. This eliminates the need for a power source for the heater, thereby reducing the size of the holding means. Further, even if such a temperature holding means is not provided, if the secondary battery is mounted on a device or apparatus in which the secondary battery is exposed to a high temperature environment such as an electric vehicle or a hybrid vehicle, the positive electrode and the negative electrode And the temperature of a nonaqueous electrolyte is hold | maintained in the said range.
[0048]
The first nonaqueous electrolyte secondary battery according to the present invention described above has an atomic ratio (H / C) of hydrogen (H) to carbon (C) of 0.1 to 0.4, and occludes lithium ions. A carbonaceous material A to be released and a negative electrode containing a fibrous carbonaceous material B having an atomic ratio (H / C) of less than 0.1 and absorbing and releasing lithium ions, and a solid or gel nonaqueous electrolyte. It has. The carbonaceous material A having H / C in the range of 0.1 to 0.4 is inferior in electron conductivity, although it can increase the amount of occlusion / release of lithium to 400 mAh / g or more. On the other hand, the carbonaceous material B having an H / C of less than 0.1 can efficiently store and release lithium, and has high electron conductivity, and thus has an action of reducing the electron conduction resistance of the negative electrode. By making the carbonaceous material B into a fibrous form, the carbonaceous material B having high electron conductivity can be dispersed throughout the negative electrode, and the carbonaceous material A and the carbonaceous material B are sufficiently in contact with each other even in repeated charge / discharge cycles. A network structure can be taken. Therefore, since the electronic conductivity of the negative electrode can be improved uniformly and sufficiently, the hysteresis of the charge / discharge potential of the negative electrode can be reduced. For this reason, it is possible to improve the discharge capacity, large current discharge characteristics, and cycle life of the nonaqueous electrolyte secondary battery including the solid or gel nonaqueous electrolyte.
[0049]
The second nonaqueous electrolyte secondary battery according to the present invention has a positive electrode, an atomic ratio (H / C) of hydrogen (H) to carbon (C) of 0.1 to 0.4, and occludes lithium ions. A negative electrode containing a carbonaceous material A to be released and a carbonaceous material B having an atomic ratio (H / C) of less than 0.1, and storing and releasing lithium ions; and a non-aqueous electrolyte, the positive electrode, the negative electrode, The nonaqueous electrolyte is maintained at 50 ° C. or more at least during discharge. Such a secondary battery can greatly reduce the electron transfer resistance during lithium release of the carbonaceous material of the negative electrode and can reduce the hysteresis of the charge / discharge potential of the negative electrode. Capacitance, excellent large current discharge characteristics and long life can be realized.
[0050]
【Example】
Hereinafter, an embodiment of the present invention will be described in detail with reference to FIG.
Example 1
<Preparation of positive electrode>
First, 91% by weight of lithium cobalt oxide (LiCoO ₂ ) powder was mixed with 3.5% by weight of acetylene black, 3.5% by weight of graphite, 2% by weight of ethylene propylene diene monomer powder and toluene, and mixed together. 30 [mu] m) After applying to a current collector, the positive electrode was produced by pressing.
<Production of negative electrode>
A carbonaceous material A having an H / C of 0.25 and a specific surface area of 120 m ² / g was produced by heat-treating the synthetic pitch at 600 ° C. in an argon atmosphere. On the other hand, graphitization was performed at 3000 ° C., the average fiber length was 50 μm, the average fiber diameter was 8 μm, H / C was 0, the true density was 2.25 g / cm ³ , and d ₀₀₂ was 0.00. 336 nm mesophase pitch carbon fiber was prepared as carbonaceous material B.
[0051]
Next, 80% by weight of carbonaceous material A and 20% by weight of carbonaceous material B were mixed, and 96.7% by weight of the resulting carbonaceous material powder was mixed with 2.2% by weight of styrene-butadiene rubber and 1.1% by weight of carboxymethylcellulose. The negative electrode was produced by mixing, apply | coating this to the copper foil as a collector, drying, and pressing.
[0052]
The positive electrode, a separator made of a polyethylene porous film, and the negative electrode were laminated in this order, and then wound in a spiral shape to produce an electrode group.
Furthermore, 1.0 mol / l of lithium hexafluorophosphate (LiPF ₆ ) was dissolved in a mixed solvent of ethylene carbonate (EC) and dimethyl ethyl carbonate (DEC) (mixed volume ratio 50:50) to obtain a non-aqueous electrolyte. Was prepared.
[0053]
The electrode group and the electrolytic solution were respectively stored in a bottomed cylindrical container made of stainless steel to assemble the cylindrical nonaqueous electrolyte secondary battery having the structure shown in FIG.
Example 2
A cylindrical non-aqueous electrolyte secondary battery having the same configuration as in Example 1 was assembled except that the negative electrode described below was used.
[0054]
An average particle diameter of 3 [mu] m, at H / C is 0, the true density of 2.25g / cm ^3, d ₀₀₂ was prepared natural graphite 0.3354nm as carbonaceous material B. The same carbonaceous material A as in Example 1 was mixed with 30% by weight of the carbonaceous material B to obtain a carbonaceous material powder. A negative electrode was produced in the same manner as in Example 1 from the obtained carbonaceous material powder.
[0055]
Example 3
A cylindrical non-aqueous electrolyte secondary battery having the same configuration as in Example 1 was assembled except that the negative electrode described below was used.
[0056]
A carbonaceous material A having an H / C of 0.3 and a specific surface area of 200 m ² / g was produced by heat-treating the phenol resin at 600 ° C. in an argon atmosphere. On the other hand, coke was heat-treated at 1500 ° C. to obtain coke having an average particle diameter of 5 μm, H / C of 0.003, true density of 2.0 g / cm ³ and d ₀₀₂ of 0.345 nm. (Carbonaceous material B). 70% by weight of carbonaceous material A and 30% by weight of carbonaceous material B were mixed to obtain a carbonaceous material powder. A negative electrode was produced in the same manner as in Example 1 from the obtained carbonaceous material powder.
[0057]
Example 4
A gel electrolyte composed of PAN, TFPC, EC, and LiPF ₆ (molar ratio 11: 27: 54: 9) was prepared as a polymer solid electrolyte. A cylindrical non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 1 except that the same electrolyte as that in Example 1 was impregnated into the separator.
[0058]
Comparative Example 1
A cylindrical nonaqueous electrolyte secondary battery was assembled in the same manner as in Example 1 except that only the carbonaceous material A used in Example 1 was used as the carbonaceous material powder.
[0059]
Comparative Example 2
A cylindrical nonaqueous electrolyte secondary battery was assembled in the same manner as in Example 1 except that only the carbonaceous material B used in Example 1 was used as the carbonaceous material powder.
[0060]
Comparative Example 3
A cylindrical non-aqueous electrolyte secondary battery having the same configuration as in Example 1 was prepared except that the temperature at the time of charge / discharge cycle evaluation was 20 ° C.
[0061]
Comparative Example 4
A cylindrical non-aqueous electrolyte secondary battery having the same configuration as that of Comparative Example 1 was prepared except that the temperature at the time of charge / discharge cycle evaluation was the same as that of Example 1.
[0062]
A coiled heater is attached to the side of the battery can of the obtained secondary batteries of Examples 1 to 4 and Comparative Example 4, and the battery can wall temperature is controlled to 50 to 60 ° C. when charging the battery, and 80 ° C. when discharging. Controlled. On the other hand, about the secondary battery of Comparative Examples 1-3, the battery can wall temperature was controlled to 20 degreeC in both charge and discharge. The secondary batteries of Examples 1 to 4 and Comparative Examples 1 to 4 were charged at a charging current of 10A for 10 hours to 4.2V, and then charged and discharged at 10A to a voltage of 2.5V. FIG. 2 shows the change over time in the discharge voltage (charge / discharge curve), and Table 1 shows the capacity retention ratio (relative to the discharge capacity at the first cycle) at 300 cycles.
[0063]
[Table 1]

[0064]
As can be seen from FIG. 2, the secondary batteries of Examples 1 to 4 have smaller charge / discharge potential hysteresis than Comparative Examples 1 to 4. In particular, it can be seen that the voltage of the secondary battery of Comparative Example 2 is drastically reduced compared to other batteries during discharging. Moreover, it can be seen from Table 1 that the secondary batteries of Examples 1 to 4 have a higher capacity retention rate at 300 cycles than those of Comparative Examples 1, 3, and 4.
[0065]
In addition, although the example applied to the cylindrical nonaqueous electrolyte secondary battery has been described in the above embodiment, the present invention can be similarly applied to a prismatic nonaqueous electrolyte secondary battery. The electrode group housed in the battery container is not limited to a spiral shape, and a plurality of positive electrodes, separators, and negative electrodes may be stacked in this order.
[0066]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to provide a non-aqueous electrolyte secondary battery having a high capacity, excellent large current discharge characteristics, and a long life.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view showing an example of a nonaqueous electrolyte secondary battery according to the present invention.
FIG. 2 is a characteristic diagram showing a change with time (charge / discharge curve) of charge / discharge voltages in the nonaqueous electrolyte secondary batteries of Examples 1 to 4 and Comparative Examples 1 to 4.
[Explanation of symbols]
1 ... container,
3 ... Electrode group,
4 ... positive electrode,
6 ... negative electrode,
8 ... Sealing plate.

Claims (4)

A container,
A positive electrode housed in the container;
The carbonaceous material A that is housed in the container and has an atomic ratio (H / C) of hydrogen (H) to carbon (C) of 0.1 to 0.4, and that absorbs and releases lithium ions, and the atomic ratio (H / C) less than 0.1, and a negative electrode containing carbonaceous material B that absorbs and releases lithium ions;
A non-aqueous electrolyte housed in the container;
A non-aqueous electrolyte secondary battery comprising temperature holding means for holding the temperature of the wall of the container at 50 ° C. or higher during charging and holding at a higher temperature than during charging during discharging . A container,
A positive electrode housed in the container;
The carbonaceous material A that is housed in the container and has an atomic ratio (H / C) of hydrogen (H) to carbon (C) of 0.1 to 0.4, and that absorbs and releases lithium ions, and the atomic ratio (H / C) less than 0.1, and a negative electrode containing carbonaceous material B that absorbs and releases lithium ions;
When performing a charge / discharge cycle on a non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte accommodated in the container, the temperature of the wall of the container is maintained at 50 ° C. or higher during charging and more than during charging during discharging. A method of using a non-aqueous electrolyte secondary battery, characterized by being maintained at a high temperature . The non-aqueous electrolyte secondary battery according to claim 2, wherein the temperature holding is performed by mounting the non-aqueous electrolyte secondary battery in a device or apparatus that is exposed to an environment of 50 ° C. or more. How to use. 4. The method of using a nonaqueous electrolyte secondary battery according to claim 3 , wherein the device or apparatus to which the nonaqueous electrolyte secondary battery is exposed to an environment of 50 [deg.] C. or higher is an electric vehicle or a hybrid vehicle .

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