JP2022064255A - Lithium-ion secondary battery using mixture of silicon monoxide and graphite as negative electrode active material and manufacturing method thereof - Google Patents

Abstract

To provide a lithium-ion secondary battery that has improved safety and a high battery capacity, and can suppress rapid capacity deterioration in a charge/discharge cycle of the mixture of silicon monoxide and graphite used as a negative electrode active material, and a manufacturing method of a lithium ion secondary battery that can use the current coating method.SOLUTION: In a lithium-ion secondary battery, and a manufacturing method thereof, a positive electrode current collector is changed from an aluminum foil of a positive electrode current collector to stainless steel 316L foil. In addition, a nano-level fibrous carbonaceous material is added to a mixture of silicon monoxide of a negative electrode active materials and graphite. Specific graphite is selected and used, and a lithium source consumed in the irreversible reaction is not used as an active material of the positive electrode, but a metallic lithium foil is attached to the surface of the negative electrode to perform electrochemical pretreatment charging. As thin a film as possible is used as a positive electrode current collector and a negative electrode current collector having through-hole pores. In this electrochemical pretreatment and the subsequent charge/discharge cycle, the retort pack type battery shape is used to suppress expansion, and mechanical treatment such as jigs is added to suppress dimensional changes in the thickness direction as much as possible. A higher capacity than that of a battery using graphite alone is exhibited, and a combination of complex operating factors is achieved such that the battery capacity can be maintained up to 300 cycles.

Description

The present invention relates to a lithium ion secondary battery and a method for manufacturing the same.
Specifically, the present invention relates to a high-capacity lithium-ion secondary battery that enhances the safety of the lithium-ion secondary battery.

In recent years, lithium-ion secondary batteries have become widespread as a main power source for portable electronic devices such as notebook personal computers, mobile phones, and integrated camcoders. There is a demand in the market for large lithium-ion secondary batteries with high battery safety and high capacity (increasing the mileage of electric vehicles (EV)) toward the EV shift.

Silicon metal nanoparticles and silicon monoxide have been proposed as negative electrode active materials to increase the capacity of lithium-ion secondary batteries, but there are difficulties in industrializing them as lithium-ion secondary batteries, and problems have been solved. The current situation is that it has not become.

Japanese Unexamined Patent Publication No. 2017-69118 Japanese Unexamined Patent Publication No. 2017-147247 Patent Document 1 proposes that the electrolytic solution contains ascorbic acid and vinylene carbonate in order to prevent a decrease in the initial battery capacity. The content of silicon monoxide in excess of 50% by mass has not been shown, and it is not mentioned that the capacity deterioration is caused by silicon monoxide.
Patent Document 2 proposes that a negative electrode is formed in a negative electrode active material with a mass ratio of a mixture of silicon monoxide and carbon 85: polyimide 15, and a silicon network containing a high concentration of silicon is formed by STEM-ADF measurement. ing.

GS Yuasa Technical Report, Vol. 15, No. 1 (June 2018) Lecture by Osaka Titanium Technologies Co., Ltd. Shingo Kizaki, February 2, 2018 National Institute of Advanced Industrial Science and Technology New Technology Briefing Material July 2, 2019 Non-Patent Document 1 shows the capacity deterioration behavior depending on the presence or absence of heat treatment of silicon monoxide, and shows that the remarkable capacity deterioration after 50 cycles of charge / discharge is caused by the structural change of silicon monoxide.
Non-Patent Document 2 introduces carbon-coated amorphous silicon monoxide fine particles as a negative electrode active material, but the volume change (expansion) associated with lithium occlusion is one of the reasons why the capacity retention rate cannot be improved in the charge / discharge cycle. It is pointed out that it has not been able to deal with.
Non-Patent Document 3 shows that silicon monoxide itself is a negative electrode active material that retains a high capacity by depositing a silicon monoxide film on a current collector foil.

As a negative electrode that can be manufactured by the conventional coating method by using a high-capacity battery to improve safety, large lithium that can eliminate sudden deterioration of battery capacity during the charge / discharge cycle of silicon monoxide and graphite mixture and maintain good capacity. It is to provide an ion secondary battery and a method for manufacturing the same.

The present inventor deprives the positive electrode current collector of the current lithium ion secondary battery of oxygen from the lithium transition metal oxide of the positive electrode active material at around 400 ° C, and reaches around 4.4 V without using an aluminum foil that emits high temperature. Since we have found a stainless steel 316L foil containing electrochemically stable molybdenum, we will change it. Further, the negative electrode is a mixture of silicon monoxide and graphite, and fibrous graphite is added in response to the remarkably repeated expansion and contraction of the coating film during the charge / discharge cycle. Further, a nano-level fibrous conductive auxiliary agent is added to silicon monoxide having poor electron conductivity, and silicon monoxide particles are present in the conductive network using a water-soluble binder that crosslinks after drying. For the graphite of the negative electrode active material, select rounded graphite or spherical graphite, core-shell carbon consisting of a shell in which a core of spherical graphite is coated with coke-carbon, and spherical graphite having a large number of pores. Instead of using the lithium of the positive electrode as in the current lithium ion secondary battery, the lithium source that is used and consumed by the irreversible reaction is a battery in which a very thin lithium metal foil is attached to the surface of the negative electrode under an inert gas. Pretreatment charging is performed. Use a thin-film stainless steel 316L foil that can be used as much as possible for the positive electrode current collector. Use a copper foil for the negative electrode current collector. .. In the first charge, silicon monoxide, graphite, and lithium metal are doped as lithium ions through the electrolytic solution due to the difference in potential, so the lithium metal foil dissolves and disappears after the subsequent charge. The voids of the lithium metal foil film and the voids after drying of water can partially absorb the volume expansion during discharge of silicon monoxide. In order to suppress shrinkage and expansion in this electrochemical pretreatment and the subsequent charge / discharge cycle, a retort pack type battery is formed, and a jig is prepared for the purpose of minimizing the dimensional change in the thickness direction, and mechanical treatment is performed. Add. (Remove this jig when making a module.) It develops a capacity 1.5 times or more higher than that of a graphite-only negative electrode, and retains a battery capacity of 70% or more up to at least 300 cycles without sudden capacity deterioration even after 50 cycles. We have found a lithium secondary battery in which a complex operating factor is combined and a method for manufacturing the same, and arrived at the present invention.

According to the battery and the manufacturing method of the present invention, the battery capacity can be increased by 1.3 times or more per the same internal volume of the current battery of the graphite negative electrode, and the mileage of the electric railcar can be significantly extended. The aluminum foil of the conventional positive electrode current collector can be replaced with a molybdenum-containing stainless steel 316L foil having a sufficient withstand voltage to improve battery safety. On the other hand, silicon monoxide and fibrous graphite are used as the negative electrode active material, and a lithium metal foil is attached to the negative electrode active material to generate a battery irreversible reaction by-product, so that the positive electrode active material has a battery capacity. Can be used more effectively. It enables industrial manufacturing that does not use the lithium source of the positive electrode active material, which is a burden on the battery weight. In addition, the exterior of the retort-pack type battery is provided with through-holes in the current collectors of both poles, and the dimensional change in the thickness direction of the battery is applied during charging / discharging while extending the charge / discharge cycle life. It is possible to suppress sudden deterioration of battery capacity by controlling the battery capacity.

Next, the lithium ion secondary battery of the present invention and a method for manufacturing the same will be described in detail. First, the main substances used will be described.

[1] A mixture of silicon monoxide silicon powder and silicon dioxide powder is produced by precipitating silicon monoxide with a vacuum aggregator. Use a crusher to obtain the desired particle size. The particle size is not particularly limited as long as it is in the range of 1 μm to 10 μm, but preferably, fine amorphous particles of 1 μm to 2 μm or less are used for good dispersion with the conductive auxiliary agent. Heat-treated or carbon surface coated.

[2] If the battery temperature rises to 400 ° C due to misuse of the current collector for the positive electrode, aluminum that deprives the oxygen of the lithium transition metal oxide of the positive electrode active material and causes rapid heat generation (behavior is explosive combustion). Foil is not used. A molybdenum-containing stainless steel foil that has almost no electrochemical corrosion with the electrolytic solution up to around 4.4 V is used as the collector material for the thin metal foil that does not have to worry about explosive combustion. For example, a stainless steel 316L foil having a thickness of 3 μm to 10 μm is further punched with pores of 0.1 mm to 0.5 mm, or the foil obtained by dissolution by electrolytic corrosion or acid and pore formation has through holes. The porosity is increased from 1% or more to 30%. A thickness of 5 μm or less, which has the same mass as or less than that of the 15 μm aluminum foil and is in the range of 3-10% porosity, is preferable. If the porosity is less than 1%, it becomes difficult to significantly improve the battery capacity retention in the charge / discharge cycle. If it exceeds 30%, the rigidity required for the foil battery assembly operation is lost, and the work speed is reduced, which is not preferable.

[3] The current collector for the negative electrode preferably has a copper foil of 20 to 4 μm, preferably 13 to 6 μm with through pores. Alternatively, it is preferable to have through pores in 10 to 5 μm of a stainless steel foil of 20 to 5 μm, for example, stainless steel 304.

[4] Binder (binder)
An alternating copolymer of fluoroalkylethylene and fluorovinyl ether A binder (binding agent) that develops adhesion and binding force between electrode active material particles and a metal current collector by cross-linking the latex with an isocyanate group during drying. Since it was found, it is used in the present invention. The bond between the positive electrode active material particles and the metal current collector is 6% by mass or less, preferably 3 to 2% by mass. Further, it is used in an amount of 6% by mass or less, preferably 4 to 3% by mass, for binding the negative electrode active material and the metal current collector. For example, AGC's Lumiflon Latex one-component FE4300 and two-component 4400 can be used. Since it is a latex and does not use an organic solvent, it has environmentally friendly characteristics as a coating liquid. The dissociated lithium cations of the electrolytic solution are localized in the ether bond portion of the polymer, and high lithium ion conductivity is expected.・ Facilitates liquid retention. It is a binder that can be used in common for both positive and negative electrodes. When dried, it is cross-linked by isocyanate groups, so voids and nano-level conductive graphite fiber network structure (network structure) are fixed in three dimensions, and charging and discharging are repeated. By minimizing the disconnection of the conductive circuit as an electronic conductive network in response to the dimensional change of the coating film of the positive electrode and the negative electrode due to expansion and contraction during the period, the sudden decrease in battery capacity during the charge / discharge cycle is eliminated. Use in anticipation of that. Polymer latex that crosslinks during drying can be used. For example, an acrylate having an acrylic group of 2 to 4 functional groups in a fluoroalkyl polymer, an acrylate having a metal group of 2 to 4 functional groups, a polyvinylidene polyfluoride polymer latex, a latex knitted with an isocyanate group in poly, ethylene tetrafluoride. Isocyanate groups on latex, ethylene / tetrafluoroethylene (ETFE) copolymer latex, ethylene / chlorotrifluoroethylene (ECTFE) copolymer latex, tetrafluoroethylene / hexafluoropropylene (FEP) copolymer latex, perfluoroalkoxyfluoropolymer latex, etc. You can use the latex modified and knitted in. A combination system of carboxy-modified SBR latex and CMC (sodium carboxymethyl cellulose) and a combination system of carboxy-modified polybutadiene latex and CMC (sodium carboxymethyl cellulose salt) may also be used.

[5] Negative Electrode Active Material In the present invention, a moderately high battery capacity is exhibited without making a new capital investment in the production of a negative electrode of a lithium ion secondary battery for a vapor deposition (blasting) device when a single silicon monoxide is used. A mixture of silicon monoxide and graphite is used as the negative electrode active material, and the negative electrode can be manufactured by the conventional coating method using the existing coating / drying equipment. As the graphite active material, those used for the lithium ion secondary battery can be used, but in order to maintain the high battery capacity retention rate and the high battery capacity, which is the object of the present invention, silicon monoxide is 30% by mass to 95% by mass. The specific graphite preferable for use in the mixture of% by mass and 70% by mass to 5% by mass of graphite is graphite fiber treated at a high temperature under an inert gas at 2600 ° C to 2800 ° C (formerly manufactured by Petka Material Co., Ltd.). , Rounded natural graphite (manufactured by Nippon Graphite Co., Ltd.) or spherical artificial graphite (manufactured by JFE Chemical Co., Ltd.), Spherical massive artificial graphite with many pores (currently manufactured by Showa Denko Materials Co., Ltd., former Hitachi Kasei Co., Ltd.) Co., Ltd.), core-shell carbon (manufactured by Mitsui Mining Co., Ltd.) having a coke-like shell carbonized by spraying toluene or the like on the core of spherical graphite particles, or the core of spherical graphite particles coated with a curable phenol resin and carbonized. Core shell carbon (manufactured by Asahi Organic Materials Co., Ltd.) having a graphite-quality shell is used. Taking advantage of the high coating film density of the coating film obtained by drying from the coating liquid. The charge / discharge cycle life (retention rate of battery capacity) can be improved. It is also important to select the shape of the active material particles that can be bonded to the collector foil as the negative electrode active material coating film with a small amount of binder and can increase the density of the coating film in order to maintain the electrode capacity. If carbon having a fiber diameter at the nano level, for example, VGCF manufactured by Showa Denko Corporation or VGCF-H of nanotubes, is added to the active material particles of graphite, the contact resistance with the copper foil collector can be reduced.

[6] Positive Electrode Active Material In the present invention, a ternary lithium transition metal oxide of lithium cobalt oxide, manganese, nickel, and cobalt is used. An olivine type such as ferrous phosphate can also be used, but in order to obtain a high-capacity battery, it is preferable to use a transition metal lithium oxide such as lithium cobalt oxide. The positive electrode active material is not particularly limited as long as it can be used as the positive electrode active material of the lithium ion secondary battery, but for example, LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , LiCoO ₂ , LiNiMgMO ₂ ,
Lithium metal oxides such as Li (MnM) ₂ O ₄ , Li ₂ (NiMnCo) O ₃ , or LiFePO ₄ , LiMnPO ₄ , LiNiPO ₄ , LiCoPO ₄ , Li ₃ Fe ₂ (PO ₄ ) ₃ , and Li ₃ V ₂ (PO ₄ ) There is lithium metal phosphate such as ₃ . The form of the positive electrode active material is preferably powder. The average particle size of the positive electrode active material is, for example, in the range of 1 μm to 20 μm, preferably 1 μm to 10 μm, and more preferably 1 μm to 6 μm.

[7] Electrolytic solution In the present invention, an electrolytic solution used in a lithium ion secondary battery can be used. From the viewpoint of battery capacity retention, LiBF ₄ of 1.5M to 0.8M, preferably LiBF ₄ of 1.2M to 1.0M and γ-butyrolactone were added in 50% by volume in a non-aqueous organic solvent and 10 volumes of polyethylene carbonate. A composition containing% or more is preferable (for example, manufactured by Toyama Yakuhin Kogyo Co., Ltd.), or 1.5 M to 0.8 M LiPF ₆ , preferably 1.2 M to 1.0 M LiPF ₆ and 10% by volume in a non-aqueous organic solvent. A composition containing 20% by volume of ethylene carbonate, 10% by volume to 20% by volume of propylene ethylene carbonate and 80 to 20% by volume of methyl ethyl carbonate (ethylmethyl carbonate) is preferable (for example, manufactured by Toyama Yakuhin Kogyo Co., Ltd.).

[8] Metallic Lithium Foil A metallic lithium metal foil is used to serve as a lithium source for irreversible by-products of the negative electrode of the present battery without using the lithium source of the positive electrode. Of the 4 mol of silicon monoxide, 1 mol becomes the irreversible by-product Li ₄ SiO ₄ and 3 mol becomes the reversible negative electrode active material Li _4.25 Si. Assuming that the molecular weight of the lithium metal is 6.941 g and the density is 0.534 g / cm ³ , the foil thickness of the lithium metal purity of 99.9 to 99.0% is calculated and used. For the metallic lithium foil to be used, about 30 μm to 10 μm of the commercially available foil is sandwiched between a polyacetal roll press or a polyacetal sheet in an inert gas atmosphere such as argon gas, and the film is pressed down with a small lab compression molding machine to finely adjust the film thickness. .. After cutting to the specified size and confirming that it is the required weight, it is attached on the negative electrode dry coating film. Preferably, metallic lithium is deposited on a polypropylene film by a gas deposition method to have a desired thickness (mass) and transferred to a dry negative electrode coating film. In addition, lithium, which is a passivation film formed on the surface of graphite particles as an irreversible by-product of the graphite used, is considered to be consumed as irreversible lithium, which is equivalent to 52 mAh / g with respect to the theoretical capacity of graphite of 372 mAh / g. Add to the thickness of the lithium foil that is crimped to the coating film.

[9] Conductive Auxiliary Agent In the mixture of silicon monoxide and graphite used for the negative electrode active material, the mixture of silicon monoxide and silicon monoxide with good electron conductivity is more electron-conducting than the silicon monoxide alone with poor electron conductivity. Although it should be better in terms of properties, the contact resistance between the graphite particles and the silicon monoxide particles is reduced so as to exceed the mixing effect, and the conductive network due to volume expansion during charging and discharging of the silicon monoxide particles. A large amount of nano-level fibrous graphite is added for the purpose of suppressing cutting as much as possible.
Finely pulverized graphite, pulverized carbon fiber, VGCF, VGCF-H, carbon nanofiber (CNF), carbon nanotube (CNT), kechen black, super made by the gas phase method to make the positive electrode active material electronically conductive. S, Super P, Super C45, Super C65, acetylene black and the like can be used.
Preferred are nano-level fibrous carbonaceous and nano-level fibrous graphite. Particularly preferred is VGCF-H of nanotube graphite. In particular, it adheres to silicon monoxide particles to supplement the electron conductivity imparted at the initial stage of charging, and at the same time, the volume expands rapidly during discharge, and even if voids are generated in the negative electrode coating film due to rapid shrinkage during charging, the amount added is large. If so, it is considered that the disconnection of the conductive network is unlikely to occur. It is presumed that the electron conductivity from the current collector can be ensured by forming a network structure between the negative electrode active material particles by mechanically suppressing the dimensional change of the negative electrode together with the negative electrode active material particles. From 10 parts by mass to 100 parts by mass can be added to 100 parts by mass of silicon monoxide particles. Preferably, 30 to 80 parts by mass is used.

[10] Separator It is an essential requirement that the separator has electronic insulation and lithium ion conductivity. A thin film is preferable for increasing the capacity of the present invention. For example, it seems possible as a product improvement technique to reduce the film thickness of a 12 μm-thick ceramic-coated polyethylene separator to about 9 μm. However, the base material is a polyethylene separator, and the polyimide of the binder and the ceramic coating film are used for the purpose of improving the heat resistance of polyethylene, and if an attempt is made to reduce the coating film thickness, the heat resistance will be lowered, and the film. There is a limit to reducing the thickness. Preferably, if the base material is a heat-resistant polyolefin separator containing 30% by mass or more and 60% by mass of polymethylpentene even if the film thickness is reduced, the thickness is 12 μm or less without the need for ceramic coating, which is the current lower limit of manufactureability. It can be appropriately used within a film thickness range of 3 μm in thickness. The film thickness is preferably 4-5 μm. The lithium ion secondary battery having a high battery capacity of the present invention and a moderately good capacity retention rate in a charge / discharge cycle for repeated use is suitably manufactured by a manufacturing method including the following steps. Hereinafter, each step will be described in detail in sequence.
(Step 1) 95% by mass to 30% by mass of silicon monoxide and 5% by mass to 70% by mass of graphite are added with a binder latex and an appropriate amount of deionized water, and the mixture is uniformly stirred and mixed to prepare a negative electrode coated esly slurry. .. It is applied on a copper foil having penetrating pores to remove and dry residual moisture at a temperature not exceeding 130 ° C. This is cut out to the desired size, and a metal lithium foil of the desired thickness is attached using a roll press or a roller in an atmosphere of an inert gas such as dry argon gas to control the porosity of the negative electrode. The process of manufacturing;
(Step 2) After stirring and mixing the lithium transition metal composite oxide particle powder with the conductive additive powder and the powder, the binder latex is uniformly stirred and mixed to adjust the positive electrode coating liquid. For example, it is applied on a stainless steel 316L foil having a penetrating pore with a thickness of 5 μm to remove and dry residual moisture at a temperature not exceeding 130 ° C. A step of cutting this into a desired size and rolling it to produce a positive electrode of a positive electrode coating film having a controlled porosity with a smooth surface;
(Step 3) An unpainted (solid) heat-resistant polyolefin separator in the range of 30% by mass or more and 60% by mass of 4-methylpentene-1 between the electrodes obtained in Step 1 and Step 2 is appropriately provided from a thickness of 9 μm to 3 μm. The process of selecting, sandwiching the separator, and assembling the battery;
(Step 4) The battery obtained in Step 3 is inserted into a retort pack type outer bag of a laminated multilayer film made of a metal foil thin film such as aluminum foil or stainless steel 304, nylon, a polyester film and polypropylene as the innermost interior. Process.
(Step 5) A step of heat-sealing and sealing a part other than the electrolytic solution injection hole of the retort pack.
(Step 6) A step of injecting an electrolytic solution from an electrolytic solution injection hole of a retort pack and temporarily sealing the injection hole.
(Step 7) In the first charge (pretreatment charge), the charge potential does not cause structural collapse of the positive electrode active material at a charge rate of 0.05 C to 0.1 C, and the charge / discharge potential determined from the negative electrode lower limit potential of 0.047 V is used. Processing charge / discharge process.
(Step 8) After exhausting the gas generated in the initial stage (pretreatment charge) from the retort pack that has completed step 7, the electrolytic solution injection hole is completely closed. In addition, the process of fixing the retort pack with a metal plate and pressing down the four corners to suppress the change in the thickness direction (do not change the dimensions) and then subject it to the charge / discharge operation. For example, thumbscrews are attached to the four corners of a metal plate to prevent dimensional changes. Alternatively, the module may be placed in a container having high consistency and capable of suppressing changes in the thickness direction. Alternatively, the process of mechanically adjusting and controlling changes in the thickness direction by reducing the pressure on a metal plate so that the gauge pressure can be detected. If gas is hardly generated in step 7 and no swelling is observed in the retort pack bag, the electrolytic solution injection hole may be completely closed immediately.
(Step 9) A discharge step in which the discharge voltage is not reduced to 2.7 V or less when the charge / discharge cycle is charged and discharged in the CCCV mode.
In the present invention, the operation is changed to step 1 and step 7 for the operation normally performed, a fluoropolymer having an ether group is used for the binder lattice, and the coating material is crosslinked with isocyanate when it is dried to make it three-dimensional. Fix it. The purpose is to constitute a complex comprehensive process such that the potential of the negative electrode active material of the battery is not set to 0.047 V (vs. Li / Li ⁺ ) or less.

The mechanical means of the present invention means a means for suppressing a change in the thickness direction of a battery, preferably hardly changing the dimensions. For example, the retort pack battery is fixed with a metal plate and tightened with thumbscrews at the four corners to suppress the change in the thickness direction. Alternatively, put it in a container that can suppress the change in the thickness direction with high consistency. Alternatively, the gauge pressure can be detected on the metal plate, and the change in the thickness direction is mechanically adjusted and controlled by a reduction operation such as a press.
It is estimated that the silicon monoxide is changed to Li _4.25 Si, which can be charged and discharged, and Li ₄ SiO ₄ , which is irreversibly generated, by the charge / discharge operation of the pretreatment, and the second discharge of the pretreatment. From the thickness of the battery in the above, it is expected that the dimensional fluctuation during charging and discharging will be small.

As the charging / discharging method of the lithium ion secondary battery in the present invention, the conventionally adopted method of the lithium ion secondary battery may be used. In particular, in the present invention, it is preferable to charge and discharge a battery having a retort pack type battery configuration. The positive electrode coated with the positive electrode active material and the negative electrode coated with the negative electrode active material are confronted with each other, and a separator is sandwiched between them to impregnate the electrolytic solution. The negative electrode size is slightly larger than the positive electrode size, and the separator is larger in size to ensure electronic insulation. The separator and the negative electrode are overlapped so as to be exactly overlapped with the positive electrode, and the outermost positive electrodes are laminated so that the negative electrode coated on one side is provided via the separator. In the present invention, in order to increase the battery capacity of a mixture of silicon monoxide and graphite as the negative electrode active material, charge / discharge is performed at least once, preferably twice in the pretreatment. Here, the standard of the battery capacity is that the third charge is the first charge capacity and the third discharge capacity is the first battery capacity. A metallic lithium foil is attached to the surface of Li ₄ SiO ₄ , which is an irreversible by-product that is inactive during charging and discharging without using the lithium source of the positive electrode active material, and to form a passivation film made of an electrolytic solution on the surface of the graphite particles. Keep it. The first and second charge / discharge operations until the formation of the passivation film and the formation of Li ₄ SiO ₄ and the lithium-silicon alloy are stabilized are adopted as the pretreatment operation for stabilizing the negative electrode behavior. In addition, mechanical operation is applied as a device to forcibly suppress the volume change of the battery during charging and discharging. Mechanical operation, for example, the exterior of the retort pack battery is sandwiched between metal plates and tightened with thumbscrews or the like so as to cope with the change in battery volume during charging and discharging. By suppressing the dimensional change in the thickness direction as much as possible, the metallic lithium foil is doped into the graphite particles by passing the electrolytic solution, and at the same time, it changes to Li ₄ SiO ₄ and disappears, and the thin film component causes volume expansion of silicon monoxide. I think it will contribute to absorption. Preferably, when the second charge as the pretreatment is completed, the electrolytic solution injection hole that was temporarily sealed is opened, the pressure is slightly reduced, the gas generated in the battery is sucked and removed, and then the seal is heat-sealed. Then tighten. For the exterior of the retort pack, the laminated multilayer sheet ropylene contains metal foils such as aluminum foil, stainless steel 304 foil and nylon film, and the interior is polypropylene film. During charging, silicon monoxide changes to Li _x Si (0 <x ≤ 4.4), but after changing to Li _4.25 Si in the negative electrode, for example, Li _325-4.4 Si. The potential (V) of is 0.047V vs. Li / Li ⁺ , and since the LiC ₆ of graphite is 0.01V, when silicon monoxide-graphite is used for the negative electrode, the charging voltage is preferable. Is preferably 0.047 V lower than that of the graphite-only negative electrode. In the case of the positive electrode of another positive electrode active material, it is preferable to set 0.047 V or slightly lower than the charging potential in combination with the graphite-only negative electrode. The first and second charges and discharges are treated as pretreatment assuming that they are carried out in the battery factory. When the positive electrode uses lithium cobalt oxide as the active material in the CCCV (constant current-constant voltage charge / discharge) mode with a current value of 0.2 C, the charge / discharge cycle is performed in the charge / discharge voltage range of 4.15 V to 2.75 V. .. The charge / discharge voltage range is preferably 4.10V to 2.90V. The astringent current is 0.01 mA, and the rest time (the time when no current flows in the charge / discharge circuit when switching between charging and discharging) is 15 minutes. It is preferable that the battery capacity retention rate at the 300th charge / discharge cycle is 70% or more and 80% or more.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

The negative electrode coating film is prepared from a negative electrode active material having a mass ratio of coated silicon monoxide and carbons of 90:10 as follows. 205.6 g of carbon-coated silicon monoxide particles (manufactured by Osaka Titanium Technologies Co., Ltd.) and 88.3 g of nano-level fibrous graphite nanotubes, VGCF-H (manufactured by Showa Denko KK) are mixed with a sealed mixer. 11.0 g of graphite fiber (formerly manufactured by Petka Material Co., Ltd.) and 11.0 g of core (graphite) -shell (coke carbon) carbon (manufactured by Mitsui Mining Co., Ltd.) are mixed with a high-speed mixer. AGC Lumiflon FE4300 latex is diluted with 39.1 g (solid content 25%) with deionized water, the graphite powder mixture is added to the binder, and a 6.0 μm thick copper foil (0.3 mmφ punching hole is made). (With a porosity of 9.1%), apply on top and dry. Under an argon atmosphere, 23.7 μm of a metallic lithium foil was pressure-bonded onto a copper foil coating film by a roll press. The film thickness of the double-sided coating product was 91.6 μm, and that of the single-sided coating product was 48.8 μm. 14 double-sided coating films and 2 single-sided coating films are cut into dimensions of 10.4 cm in length and 20.4 cm in width. For the positive electrode, 930.0 g of lithium cobalt oxide (LiCoO ₂ ) particle powder, 27.5 g of Super P as a conductive auxiliary agent, and 10.0 g of finely pulverized graphite (SP270 manufactured by Nippon Graphite Co., Ltd.) are mixed with a high-speed mixer. Add 90.0 g of Lumiflon Latex FE4300 (diluted from 50% to 25% solid content) as a binder to form a slurry. It is applied and dried on a stainless steel 316L foil having 5.0 μm through pores so as to obtain a desired coating film. The thickness of the double-sided coating film after roll pressing was 176.8 μm. Cut 15 pieces into dimensions of 10.0 cm in length and 20.0 cm in width. It faces the negative electrode through the separator. The negative electrodes to be stacked are accurately positioned and stacked on the positive electrode. 4 30 pieces of 5.0 μm thick unpainted heat-resistant polyolefin separator manufactured by KEE, whose end face is 0.5 mm larger, are interposed between the positive electrode and the negative electrode, and the positive electrode and the negative electrode face each other accurately. Insert it into an aluminum laminated bag as a laminated retort pack. Inject the electrolyte and temporarily close the injection port. The first and second charge / discharge are assumed to be carried out in the battery factory in the CCCV (constant current-constant voltage charge / discharge) mode with a current value of 0.1C and 4.10V-2.90V. The convergence current is 0.01 mA. From the third time onward, the converging current is set to 0.01 mA in the CCCV (constant current-constant voltage charge / discharge) mode of 4.10V-2.90V with a current value of 0.2C. From the third time onward, the CCCV (constant current-constant voltage charge / discharge) mode with a current value of 0.2C, the convergence current is 0.01mA, and the rest time (switching between charging and discharging). The time during which no current sometimes flows through the charge / discharge circuit) is set to 15 minutes. During the rest time after the first and second charges are completed, the electrolytic solution injection port in the retort pack is opened and the pressure is slightly reduced to suck and remove the gas generated from the inside of the retort pack. During the rest time before starting the third charge, the electrolyte inlet is heat-sealed and sealed. Also, attach thumbscrews to the four corners of the metal plate of the retort pack battery sandwiched between the metal plates and tighten. By introducing this mechanical operation, the change in the void in the negative electrode generated during charging and discharging is suppressed, and it is fixed and restrained in order to maintain good electronic conductivity. The standard of the battery capacity is that the third charge is regarded as the first charge, and the corresponding discharge capacity at the time of the first discharge is the battery capacity. The battery discharge capacity for the first time (third charge) was 24.0 Ah. Compared to the 16.0 Ah battery using graphite as the negative electrode active material in Comparative Example 1, the battery capacity was 1.5 times that of the battery having almost the same volume. An electric vehicle that can travel 500 km on a single charge can travel up to 750 km. Electrodes obtained by electrochemically treating the material in the current battery manufacturing equipment, and by mechanically suppressing the volume change during charging, the silicon monoxide and graphite system have a high battery capacity and sudden capacity deterioration as in the past. The result (Table 1) was obtained that exceeded the capacity retention rate of the negative electrode of graphite alone. The battery capacity retention rate in the 300th charge / discharge cycle was 90%. In addition, no sudden decrease in battery capacity was observed from around the 50th cycle.

The negative electrode coating film is prepared from a negative electrode active material having a mass ratio of coated silicon monoxide to carbons of 70:30. 195.7 g of carbon-coated silicon monoxide particles (manufactured by Osaka Titanium Technologies Co., Ltd.) and 108.1 g of nano-level fibrous graphite and VGCF-H (manufactured by Showa Denko KK) are mixed with a sealed mixer. 40.5 g of graphite fiber (formerly manufactured by Petka Material Co., Ltd.) and 40.5 g of core (graphite) -shell (coke carbon) carbon (manufactured by Mitsui Mining Co., Ltd.) are mixed with a high-speed mixer. AGC Lumiflon FE4300 latex was diluted with 47.6 g (50% solid content was diluted to 25%) in a binder, diluted with deionized water, and the graphite powder mixture was added to make a 6.0 μm thick copper foil (0. It is made into a 3 mmφ pad, has a punching hole, and has a porosity of 9.1%.) It is applied on top and dried. A metal lithium foil of 22.8 μm was pressure-bonded onto a copper foil coating film by a roll press in an argon stream. The double-sided coating was 96.5 μm, and the single-sided coating was 51.3 μm. 14 double-sided coating films and 2 single-sided coating films are cut into dimensions of 10.4 cm in length and 20.4 cm in width. Fifteen positive electrodes having the same composition as in Example 1 and having a film thickness of 176.8 μm were used. The negative electrodes to be stacked are accurately positioned and stacked on the positive electrode.
4 30 pieces of 5.0 μm thick unpainted heat-resistant polyolefin separator manufactured by KEE, whose end face is 0.5 mm larger, are interposed between the positive electrode and the negative electrode, and the positive electrode and the negative electrode face each other accurately. Insert it into an aluminum laminated bag as a laminated retort pack. , Inject the electrolyte and temporarily close the injection port. In the first and second charge / discharge, as a pretreatment, the CCCV (constant current-constant voltage charge) convergence current of 4.10V-2.90V at a current value of 0.1C is set to 0.01mA, and the rest time. (Time during which no current flows through the charge / discharge circuit when switching between charging and discharging) is set to 15 minutes. During the rest time after the first and second charges are completed, the electrolytic solution injection port in the retort pack is opened and the pressure is slightly reduced to suck and remove the gas generated from the inside of the retort pack. The electrolytic solution injection port is heat-sealed and sealed at the rest time before charging is started at the third current value of 0.2 C. In addition, a thumbscrew is attached to the four corners of the metal plate of the retort pack battery sandwiched between the metal plates, and it is fixed and restrained so that there is almost no dimensional change in the thickness direction while charging and discharging are repeated at a current value of 0.2C. do. By introducing this mechanical operation, we tried to suppress the volume change in the negative electrode generated during charging and maintain good electron conductivity. The standard of the battery capacity is that the third charge is regarded as the first charge, and the corresponding discharge capacity at the time of the first discharge is the battery capacity. The battery discharge capacity for the first time (third charge) was 24.0 Ah. Compared with the battery using graphite as the negative electrode active material of Comparative Example 1, the battery capacity was 1.5 times as large as 16.0 Ah in almost the same volume. An electric vehicle that can travel 500 km on a single charge can travel up to 750 km. By using electrodes with an electrochemical material changed to the current battery manufacturing equipment and mechanically suppressing volume expansion during charging, silicon monoxide and graphite-based batteries with high battery capacity can undergo sudden capacity deterioration as in the past. The result (Table 1) was obtained that exceeded the capacity retention rate of the negative electrode of graphite alone. The battery capacity retention rate in the 300th charge / discharge cycle was 89%. In addition, no sudden decrease in battery capacity was observed from around the 50th cycle.

The negative electrode coating film is prepared from a negative electrode active material having a mass ratio of coated silicon monoxide and carbons of 50:50. 180.1 g of carbon-coated silicon monoxide particles (manufactured by Osaka Titanium Technologies Co., Ltd.) and 139.3 g of nano-level fibrous graphite and VGCF-H (manufactured by Showa Denko KK) are mixed with a sealed mixer. 87.0 g of graphite fiber (formerly manufactured by Petka Material Co., Ltd.) and 87.0 g of core (graphite) -shell (coke carbon) carbon (manufactured by Mitsui Mining Co., Ltd.) are mixed with a high-speed mixer. AGC Lumiflon FE4300 latex was diluted with 60.3 g (diluted solid content from 50% to 25%) with ionized water, and the graphite powder mixture was added to the binder to make a 6.0 μm thick copper foil (0.3 mmφ punching). A hole is made to make the void ratio 9.1%), and the mixture is applied and dried. A metal lithium foil of 21.32 μm was pressure-bonded onto a copper foil coating film in an argon air stream by a roll press. The double-sided coating was 108.4 μm, and the single-sided coating was 57.2 μm. Cut out 13 double-sided coating films and 2 single-sided coating films to a length of 10.4 cm and a width of 20.4 cm. The negative electrodes to be stacked are accurately positioned and stacked on the positive electrode. As the positive electrode, 14 sheets having the same composition as in Example 1 and having a film thickness of 176.8 μm were used. 4 KEE's unpainted heat-resistant polyolefin separator with a large end face of 0.5 mm has 28 sheets with a thickness of 5.0 μm interposed between the positive electrode and the negative electrode, and the positive electrode and the negative electrode face each other accurately. Insert it into an aluminum laminated bag as a laminated retort pack. , Inject the electrolyte and temporarily close the injection port. The first and second charges and discharges of the current value of 0.1 C are handled assuming implementation in the battery factory. The CCCV (constant current-constant voltage charge) convergence current of 4.15V-2.80V is 0.01mA, and the rest time (time when no current flows in the charge / discharge circuit when switching between charging and discharging) is 15 minutes. During the rest time after the first and second charges are completed, the electrolytic solution injection port in the retort pack is opened and the pressure is slightly reduced to suck and remove the gas generated from the inside of the retort pack. During the rest time before starting the third charge, the electrolyte inlet is heat-sealed and sealed. In addition, a thumbscrew is attached to the four corners of the metal plate of the retort pack battery sandwiched between the metal plates, and fixed and restrained so that the dimensional change in the thickness direction hardly occurs while charging and discharging are repeated. By introducing this mechanical operation, we tried to suppress the volume change in the negative electrode generated during charging and maintain good electron conductivity. The standard of the battery capacity is that the third charge is regarded as the first charge, and the corresponding discharge capacity at the time of the first discharge is the battery capacity. The battery discharge capacity for the first time (third charge) was 22.4 Ah. Compared to the battery using graphite as the negative electrode active material in Comparative Example 1, the battery capacity was 1.4 times that of the battery having almost the same volume and 16.0 Ah. An electric vehicle that can travel 500 km on a single charge can travel up to 700 km. By using electrodes with an electrochemical material changed to the current battery manufacturing equipment and mechanically suppressing volume expansion during charging, silicon monoxide and graphite-based batteries with high battery capacity can undergo sudden capacity deterioration as in the past. The result (Table 1) was obtained that exceeded the capacity retention rate of the negative electrode of graphite alone. The battery capacity retention rate in the 300th charge / discharge cycle was 88%. In addition, no sudden decrease in battery capacity was observed from around the 50th cycle.

The negative electrode coating film is prepared from a negative electrode active material having a mass ratio of coated silicon monoxide to carbons of 30:70. 151.9 g of carbon-coated silicon monoxide particles (manufactured by Osaka Titanium Technologies Co., Ltd.) and 73.4 g of nano-level fibrous graphite and VGCF-H (manufactured by Showa Denko KK) are mixed with a sealed mixer. 171.3 g of graphite fiber (formerly manufactured by Petka Material Co., Ltd.) and 171.3 g of core (graphite) -shell (coke carbon) carbon (manufactured by Mitsui Mining Co., Ltd.) are mixed with a high-speed mixer. AGC Lumiflon FE4300 latex was diluted with 65.4 g (diluted from 50% solid content to 25% solid content) with deionized water, and the graphite powder mixture was added to the binder to make a 6.0 μm thick copper foil (0.3 mmφ). (Punching holes are made to make the void ratio 9.1%), and the mixture is applied and dried. A metal lithium foil of 18.36 μm was pressure-bonded onto a copper foil coating film by a roll press using a polyacetal roller under an argon atmosphere. The double-sided coating was 127.3 μm, and the single-sided coating was 66.7 μm. Twelve double-sided coating films and two single-sided coating films are cut into dimensions of 10.4 cm in length and 20.4 cm in width. The negative electrodes to be stacked are accurately positioned and stacked on the positive electrode. Thirteen positive electrodes having the same composition as in Example 1 and having a film thickness of 176.8 μm were used.
4 KEE's unpainted heat-resistant polyolefin separator with a large end face of 0.5 mm is sandwiched between 26 sheets of 5.0 μm between the positive electrode and the negative electrode, and the positive electrode and the negative electrode face each other accurately. Insert it into an aluminum laminated bag as a laminated retort pack. , Inject the electrolyte and temporarily close the injection port. The first and second charges and discharges of the current value of 0.1 C are treated as pretreatment. During the rest time after the first and second charges are completed, the electrolytic solution injection port in the retort pack is opened and the pressure is slightly reduced to suck and remove the gas generated from the inside of the retort pack. CCCV (constant current-constant voltage charge) convergence current of 4.15V-2.80V with a current value of 0.2C is 0.01mA, and rest time (time when no current flows in the charge / discharge circuit when switching between charging and discharging). ) Is 15 minutes. During the rest time before starting the third charge, the electrolyte inlet is heat-sealed and sealed. In addition, a thumbscrew is attached to the four corners of the metal plate of the retort pack battery sandwiched between the metal plates, and fixed and restrained so that the dimensional change in the thickness direction hardly occurs while charging and discharging are repeated. By introducing this mechanical operation, we tried to suppress the volume increase in the negative electrode generated during charging and maintain good electron conductivity. As for the standard of battery capacity, the third charge is regarded as the first charge, and the corresponding discharge capacity at the time of the first discharge is regarded as the first battery capacity. The battery discharge capacity for the first time (third charge) was 20.8 Ah. Compared with the battery using graphite as the negative electrode active material in Comparative Example 1, the battery capacity was 1.3 times as large as 16.0 Ah in almost the same volume. An electric vehicle that can travel 500 km on a single charge can travel up to 650 km. By using electrodes with an electrochemical material changed to the current battery manufacturing equipment and mechanically suppressing volume expansion during charging, silicon monoxide and graphite-based batteries with high battery capacity can undergo sudden capacity deterioration as in the past. The result (Table 1) was obtained that exceeded the capacity retention rate of the negative electrode of graphite alone. The battery capacity retention rate in the 300th charge / discharge cycle was 84%. In addition, no sudden decrease in battery capacity was observed from around the 50th cycle.

A water-soluble coated paste of a negative electrode active material having a mass ratio of carbon-coated silicon monoxide particles (manufactured by Osaka Titanium Technologies Co., Ltd.) and graphite of 95: 5 is prepared and applied to a punching copper foil. 207.5 g of carbon-coated silicon monoxide particles (manufactured by Osaka Titanium Technologies Co., Ltd.) and 95.0 g of nano-level fibrous graphite nanotubes, VGCF-H (manufactured by Showa Denko KK) are mixed in a closed mixer. Mix the powder with 5.3 g of graphite fiber (formerly manufactured by Petka Material Co., Ltd.) and 5.3 g of core (graphite) -shell (coke carbon) carbon (manufactured by Mitsui Mining Co., Ltd.) with a high-speed mixer. AGC Lumiflon FE4300 latex was diluted with 38.7 g (diluted from 50% solid content to 25% solid content) with deionized water, and the graphite powder mixture was added to the binder to make a 6.0 μm thick copper foil (0.3 mmφ). Punching holes are made to make the porosity 9.1%), and the mixture is applied and dried. A metal lithium foil of 23.7 μm was pressure-bonded onto the copper foil coating film. The double-sided coating was 89.9 μm, and the single-sided coating was 48.0 μm. 14 double-sided coating films and 2 single-sided coating films are cut into dimensions of 10.4 cm in length and 20.4 cm in width. The negative electrodes to be stacked are accurately positioned and stacked on the same positive electrode as in the first embodiment. As the positive electrode, 15 double-sided coated products were used. 4 30 pieces of 5.0 μm thick unpainted heat-resistant polyolefin separator manufactured by KEE, whose end face is 0.5 mm larger, are interposed between the positive electrode and the negative electrode, and the positive electrode and the negative electrode face each other accurately. Insert it into an aluminum laminated bag as a laminated retort pack. , Inject the electrolyte and temporarily close the injection port. The convergence current is set to 0.01 mA in the CCCV (constant current-constant voltage charge / discharge) mode of 4.10V-2.90V with the current value of 0.1C in the first and second times, and it is treated as a pretreatment. From the third time onward, charging / discharging is repeated with a converging current of 0.01 mA in a CCCV (constant current-constant voltage charge / discharge) mode of 4.10 V-2.90 V with a current value of 0.2 C and the same voltage range. The rest time (the time during which no current flows through the charge / discharge circuit when switching between charging and discharging) is set to 15 minutes. During the rest time after the first and second charges are completed, the electrolytic solution injection port in the retort pack is opened and the pressure is slightly reduced to suck and remove the gas generated from the inside of the retort pack. During the rest time before starting the third charge, the electrolyte inlet is heat-sealed and sealed. In addition, a thumbscrew is attached to the four corners of the metal plate of the retort pack battery sandwiched between the metal plates, and fixed and restrained so that the dimensional change in the thickness direction hardly occurs while charging and discharging are repeated. By introducing this mechanical operation, we tried to suppress the volume change in the negative electrode generated during charging and maintain good electron conductivity. As for the standard of battery capacity, the third charge is regarded as the first charge, and the corresponding discharge capacity at the time of the first discharge is regarded as the first battery capacity. The battery discharge capacity for the first time (third charge) was 24.0 Ah. Compared to the battery using graphite as the negative electrode active material in Comparative Example 1, the battery capacity is 1.5 times that of the battery having almost the same volume and 16.0 Ah. An electric vehicle that can travel 500 km on a single charge can travel up to 750 km. By using electrodes with an electrochemical material changed to the current battery manufacturing equipment and mechanically suppressing volume expansion during charging, silicon monoxide and graphite-based batteries with high battery capacity can undergo sudden capacity deterioration as in the past. The result (Table 1) was obtained that exceeded the capacity retention rate of the negative electrode of graphite alone. The battery capacity retention rate in the 300th charge / discharge cycle was 90%. In addition, no sudden decrease in battery capacity was observed from around the 50th cycle.

A water-soluble coated paste of a negative electrode active material having a mass ratio of 80:20 between uncoated silicon monoxide particles (manufactured by Osaka Titanium Technologies Co., Ltd.) and graphite is prepared and applied to a punching copper foil. 194.4 g of pure silicon monoxide particles (manufactured by Osaka Titanium Technologies Co., Ltd.) without carbon coating and 97.2 g of nano-level fibrous graphite, VGCF-H (manufactured by Showa Denko KK) are mixed in a closed mixer. 24.30 g of graphite fiber (formerly manufactured by Petka Material Co., Ltd.) and 23.30 g of core (graphite) -shell (coke carbon) carbon (manufactured by Mitsui Mining Co., Ltd.) are mixed with a high-speed mixer. AGC Lumiflon FE4300 latex was diluted with 42.1 g (diluted 50% solid content to 25%) with deionized water, and the graphite powder mixture was added to the binder to make a 6.0 μm thick copper foil (0.3 mmφ). Punching holes are made to make the porosity 9.1%), and the mixture is applied and dried. A metal lithium foil of 23.13 μm was pressure-bonded onto the copper foil coating film by a roll press in an argon stream. The double-sided coating was 94.2 μm, and the single-sided coating was 47.1 μm. 14 double-sided coating films and 2 single-sided coating films are cut into dimensions of 10.4 cm in length and 20.4 cm in width. The negative electrodes to be stacked are accurately positioned and stacked on the same positive electrode as in the first embodiment. As the positive electrode, 15 double-sided coated products were used. 4 30 pieces of 5.0 μm thick unpainted heat-resistant polyolefin separator manufactured by KEE, whose end face is 0.5 mm larger, are interposed between the positive electrode and the negative electrode, and the positive electrode and the negative electrode face each other accurately. Insert it into an aluminum laminated bag as a laminated retort pack. , Inject the electrolyte and temporarily close the injection port. For the first and second charge / discharge at a current value of 0.1 C, CCCV (constant current-constant voltage charge / discharge) of 4.10 V-2.90 V, the convergence current is 0.01 mA, and the rest time (rest time ( The time during which no current flows through the charge / discharge circuit when switching between charging and discharging) is set to 15 minutes. Treat as preprocessing. From the third time onward, charging and discharging were performed in the same voltage range with a current value of 0.2C. During the rest time after the first and second charges are completed, the electrolytic solution injection port in the retort pack is opened and the pressure is slightly reduced to suck and remove the gas generated from the inside of the retort pack. During the rest time before starting the third charge, the electrolyte inlet is heat-sealed and sealed. In addition, a thumbscrew is attached to the four corners of the metal plate of the retort pack battery sandwiched between the metal plates, and fixed and restrained so that the dimensional change in the thickness direction hardly occurs while charging and discharging are repeated. By introducing this mechanical operation, we tried to suppress the volume change in the negative electrode generated during charging and maintain good electron conductivity. As for the standard of battery capacity, the third charge is regarded as the first charge, and the corresponding discharge capacity at the time of the first discharge is regarded as the first battery capacity. The battery discharge capacity for the first time (third charge) was 24.0 Ah. Compared with the battery using graphite as the negative electrode active material of Comparative Example 1, the battery capacity was 1.5 times as large as 16.0 Ah in almost the same volume. An electric vehicle that can travel 500 km on a single charge can travel up to 750 km. By using electrodes with an electrochemical material changed to the current battery manufacturing equipment and mechanically suppressing volume expansion during charging, silicon monoxide and graphite-based batteries with high battery capacity can undergo sudden capacity deterioration as in the past. The result (Table 1) was obtained that exceeded the capacity retention rate of the negative electrode of graphite alone. The battery capacity retention rate in the 300th charge / discharge cycle was 89%. In addition, no sudden decrease in battery capacity was observed from around the 50th cycle.

A water-soluble coated paste of a negative electrode active material having a mass ratio of carbon-coated silicon monoxide particles (manufactured by Osaka Titanium Technologies Co., Ltd.) and graphite of 95: 5 is prepared and applied to a punching copper foil. 207.5 g of carbon-coated silicon monoxide particles (manufactured by Osaka Titanium Technologies) and 95.0 g of nano-level fibrous graphite, VGCF-H (manufactured by Showa Denko) are mixed with a high-speed mixer, and further. 10.6 g of artificial graphite (currently manufactured by Showa Denko Materials Co., Ltd., formerly manufactured by Hitachi Kasei Co., Ltd.) was added and mixed. As a binder, 38.7 g of AGC Lumiflon FE4300 latex (diluted solid content from 50% to 25%) is added to the graphite powder mixture and mixed by stirring, and deionized water is added to adjust the slurry concentration. .. It is applied on a copper foil having a thickness of 6.0 μm (a punching hole of 0.3 mmφ is formed to have a porosity of 9.1%) and dried. A 23.13 μm metallic lithium foil deposited on a polypropylene film by a gas deposition method is pressed down while being transferred onto a copper foil by a roll press. The double-sided coating was 90.4 μm, and the single-sided coating was 48.2 μm. 14 double-sided coating films and 2 single-sided coating films are cut into dimensions of 10.4 cm in length and 20.4 cm in width. The negative electrodes to be stacked are accurately positioned and stacked on the same positive electrode as in the first embodiment. As the positive electrode, 15 double-sided coated products were used. 4 30 pieces of 5.0 μm thick unpainted heat-resistant polyolefin separator manufactured by KEE, whose end face is 0.5 mm larger, are interposed between the positive electrode and the negative electrode, and the positive electrode and the negative electrode face each other accurately. Insert it into an aluminum laminated bag as a laminated retort pack. Inject the electrolyte and temporarily close the injection port. The first and second charge / discharge are treated as pretreatment in the CCCV (constant current-constant voltage charge / discharge) mode of 4.10-2.90V with a current value of 0.1C. After the third charge / discharge, the convergence current of 4.10-2.90V CCCV (constant current-constant voltage charge / discharge) mode at a current value of 0.2C is set to 0.01mA, and the rest time (rest time ( The time during which no current flows through the charge / discharge circuit when switching between charging and discharging) is set to 15 minutes. During the rest time after the first and second charges are completed, the electrolytic solution injection port in the retort pack is opened and the pressure is slightly reduced to suck and remove the gas generated from the inside of the retort pack. During the rest time before starting the third charge, the electrolyte inlet is heat-sealed and sealed. Furthermore, a thumbscrew is attached to the four corners of the metal plate of the retort pack battery sandwiched between the metal plates, and fixed and restrained so that the dimensional change in the thickness direction hardly occurs while charging and discharging are repeated. By introducing this mechanical operation, we tried to suppress the increase of voids in the negative electrode generated during charging and maintain good electron conductivity. The standard of the battery capacity is that the third charge is the initial charge and the charge capacity is set, and the corresponding initial discharge capacity is the initial battery capacity. The battery capacity for the first time (third charge) was 24.0 Ah. Compared with the battery using graphite as the negative electrode active material of Comparative Example 1, the battery capacity was 1.5 times as large as 16.0 Ah in almost the same volume. An electric vehicle that can travel 500 km on a single charge can travel up to 750 km. By using electrodes with an electrochemical material changed to the current battery manufacturing equipment and mechanically suppressing volume expansion during charging, silicon monoxide and graphite-based batteries with high battery capacity can undergo sudden capacity deterioration as in the past. The result (Table 1) was obtained that exceeded the capacity retention rate of the negative electrode of graphite alone. The battery capacity retention rate in the 300th charge / discharge cycle was 90%. In addition, no sudden decrease in battery capacity was observed from around the 50th cycle.

Comparative Example 1

The positive electrode coating film is a binder previously dissolved in NMP (N-methylpyrrolidone) in 450.0 g of lithium cobalt oxide (LiCoO ₂ ) (manufactured by Yumicoa) having an average particle diameter of 5 μm and SuperP, 25.0 g of a conductive auxiliary agent. Mix and stir with 25.0 g of polymer PVDF. It was applied to both sides of a 15 μm aluminum foil of a positive electrode current collector, and rolled and pressed. The thickness of the positive electrode coating film per 1 cm ² was 94.9 μm. Cut out 10 sheets by the method with dimensions of 10.0 cm in length and 20.0 cm in width. For the negative electrode coating film, 485.0 g of natural graphite pulverized particles having an average particle diameter of 10 μm of the active material were removed from 5.0 g of CMC (sodium carboxymethyl cellulose) and 20.8 g of carboxylic acid-modified polystyrene-butadiene copolymer latex (solid content 48%). Mix with ionized water to make a slurry. Double-sided coating was applied to 13 μm of copper foil without punching, and after drying, the film was pressed down with a roll press to a film thickness of 200 μm, and single-sided coating was 106.5 μm. Nine double-sided coating films and two single-sided coating films are cut into dimensions of 10.4 cm in length and 20.4 cm in width. The negative electrodes to be stacked are accurately positioned and stacked on the positive electrode. As the positive electrode, 10 double-sided coated products were used.
4 Alumina-coated polyimide binder polyethylene separator with an end face 0.5 mm larger, 20 sheets with a thickness of 12 m are interposed between the positive and negative electrodes, and the positive and negative electrodes are laminated so that they face each other exactly. Insert it into an aluminum laminate bag as a retort pack. Inject the electrolyte and temporarily close the injection port. Pretreatment The first charge / discharge is treated as pretreatment. In the CCCV (constant current-constant voltage charge / discharge) mode of 4.20V 2.75V with a current value of 0.2C, the convergence current is set to 0.01mA, and the rest time (current flows in the charge / discharge circuit when switching between charging and discharging). No time) is 15 minutes. After the first charge was completed, the electrolyte injection port in the retort pack was opened during the rest time, the pressure was slightly reduced, and the gas generated from the inside of the retort pack was sucked off and then sealed. Discharge to 2.75V, rest for 15 minutes, and then measure the second charge and discharge capacity. The second charge was regarded as the first charge, and the corresponding discharge capacity at the time of the first discharge was taken as the battery capacity. The battery capacity for the first time (second discharge) was 16.0 Ah. When the battery of Comparative Example 1 was used as a built-in battery in an electric vehicle (EV) as a power source, it was used as a standard for initially traveling 500 km on a single charge.

Comparative Example 2

As the negative electrode coating film, a negative electrode active material having a mass ratio of coated silicon monoxide and carbons of 30:70 is prepared as follows. 151.9 g of carbon-coated silicon monoxide particles (manufactured by Osaka Titanium Technologies Co., Ltd.) and 342.5 g of natural graphite having an average particle diameter of 20 μm are mixed with a high-speed mixer. Mix 5.1 g of binder CMC (sodium carboxymethyl cellulose), 40.8 g of carboxylic acid-modified polystyrene-butadiene copolymer latex (solid content 48%) and deionized water to make a slurry. A copper foil having no punching pores was coated on both sides of 13 μm, dried, and then pressed down with a roll press to obtain a film thickness of 83.9 μm for double-sided coating and 46.2 μm for single-sided coating. Nine double-sided coating films and two single-sided coating films are cut into dimensions of 10.4 cm in length and 20.4 cm in width. The negative electrodes to be stacked are accurately positioned and stacked on the positive electrode. As the positive electrode, 10 double-sided coated products as in Comparative Example 1 were used. 4. 20 sheets of 12 μm thickness of polyethylene separator (ceramic coated polyethylene separator) coated with alumina particles whose end face is 0.5 mm larger are interposed between the positive electrode and the negative electrode, and the positive electrode and the negative electrode face each other accurately. Insert it into an aluminum laminated bag as a laminated retort pack. , Inject the electrolyte and temporarily close the injection port. The first and second charge / discharge are 4.20V-2.50V CCCV (constant current-constant voltage charging / discharging) mode with a current value of 0.1C, the convergence current is 0.01mA, and the rest time. (Time during which no current flows through the charging / discharging circuit when switching between charging and discharging) was set to 115 minutes and treated as pretreatment. After the first charge is completed and during the rest time, the electrolytic solution injection port in the retort pack is opened and the pressure is slightly reduced to suck and remove the gas generated from the inside of the retort pack. During the rest time before starting the second charge, the electrolyte inlet is heat-sealed and sealed. As the standard of the battery capacity, the second charge was regarded as the first charge, and the corresponding discharge capacity at the time of the first discharge was taken as the battery capacity. The battery capacity for the first time (second charge) was 19.2 Ah, but the battery capacity retention rate for the 20th charge / discharge cycle was less than 30%, so the charge / discharge was terminated.

According to the present invention, silicon monoxide and graphite are used for the negative electrode, the positive electrode current collector is changed from an aluminum foil to a stainless steel 316L foil having through holes, and the separator is a thin film of an unpainted heat-resistant polyolefin separator. It is said that a mixture of silicon monoxide and graphite was observed as the negative electrode active material, which is higher than the safety desired for a high-performance lithium-ion secondary battery with increased energy density and size by dramatically increasing the battery capacity. We have found a method for manufacturing a lithium ion secondary battery that does not cause a sudden decrease in battery capacity from around the 50th cycle, and have reached the present invention. It is especially useful as a power source for electric vehicles.

Claims (10)

The negative electrode is composed of 95% by mass to 30% by mass of silicon monoxide, 5% by mass to 70% by mass of graphite, and nano-level fibrous carbonaceous material or nano-level fibrous graphite, and the positive electrode is a lithium transition metal oxide. A lithium-ion secondary battery characterized by containing a separator and an electrolytic solution. The lithium ion II according to claim 1, wherein the active material of the negative electrode contains 10 parts by mass to 100 parts by mass of nano-level fibrous carbonaceous material or nano-level fibrous graphite per 100 parts by mass of silicon monoxide. Next battery. The lithium ion secondary battery according to claim 1, wherein the negative electrode contains a mixture of graphite fibers and rounded graphite in the range of 5% by mass to 70% by mass. The lithium ion secondary battery according to claim 1, wherein the negative electrode contains a mixture of graphite fibers and graphite coated with spherical coke in the range of 5% by mass to 70% by mass. The lithium ion secondary battery according to claim 1, further comprising spherical artificial graphite having a large number of pores in the negative electrode in the range of 5% by mass to 70% by mass. Stainless steel 316L foil with a thickness of 10 μm or less and up to 3 μm and a porosity of 1 to 30% for the positive electrode collector and copper foil or stainless steel with a thickness of 15 to 5 μm and a porosity of 1 to 30% for the negative electrode collector. Lithium ion di of claims 1 to 5, which comprises a heat-resistant polyolefin microporous film having a thickness of 3 to 15 μm containing 30 to 60% by mass of poly 4-methyl-1-pentene in a 304 foil and a separator. Next battery. A method for manufacturing a lithium ion secondary battery according to claim 1 to 6, wherein a metallic lithium foil is attached to a negative electrode film and charging / discharging of the pretreatment is performed. In a method for manufacturing a retort-pack type lithium-ion secondary battery using a metal foil and a plastic laminated outer bag made of nylon, polypropylene, etc., the entire battery is mechanically formed in the thickness direction after the pretreatment discharge according to claim 7. A method for manufacturing a lithium ion secondary battery, which is characterized by suppressing an increase. A method for producing a lithium ion secondary battery according to claims 1 to 8, wherein a latex of a crosslinkable fluoroalkyl polymer is used as an electrode binder. A lithium ion secondary battery, wherein the battery according to any one of claims 1 to 9 is used as a power source for an electric vehicle.