WO2015118833A1 - Non-aqueous electrolyte secondary battery - Google Patents

Non-aqueous electrolyte secondary battery Download PDF

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WO2015118833A1
WO2015118833A1 PCT/JP2015/000340 JP2015000340W WO2015118833A1 WO 2015118833 A1 WO2015118833 A1 WO 2015118833A1 JP 2015000340 W JP2015000340 W JP 2015000340W WO 2015118833 A1 WO2015118833 A1 WO 2015118833A1
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negative electrode
aqueous electrolyte
graphite
particles
secondary battery
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PCT/JP2015/000340
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French (fr)
Japanese (ja)
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泰典 渡邉
泰三 砂野
山本　諭
安展 岩見
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三洋電機株式会社
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a non-aqueous electrolyte secondary battery.
  • Metal materials that can be alloyed with lithium such as silicon, germanium, tin and zinc instead of carbonaceous materials such as graphite as negative electrode active materials, and these metals for higher energy density and higher output of lithium ion batteries
  • silicon, germanium, tin and zinc instead of carbonaceous materials such as graphite as negative electrode active materials, and these metals for higher energy density and higher output of lithium ion batteries
  • carbonaceous materials such as graphite
  • Patent Document 1 proposes a composite of a material containing Si and O as a constituent element and a carbon material, and a negative electrode for a nonaqueous electrolyte secondary battery containing a graphitic carbon material as a negative electrode active material. .
  • the non-aqueous electrolyte secondary battery of Patent Document 1 has problems in that the cycle characteristics are not sufficiently improved and gas is generated during high-temperature storage.
  • a non-aqueous electrolyte secondary battery includes a positive electrode, a negative electrode, and a non-aqueous electrolyte
  • the negative electrode includes a negative electrode current collector and a negative electrode mixture layer
  • the negative electrode includes particles containing silicon and graphite particles whose surfaces are coated with a material containing cellulose.
  • the non-aqueous electrolyte includes a cyclic carbonate and a chain carbonate.
  • the cyclic carbonate is propylene. With carbonate.
  • the non-aqueous electrolyte secondary battery of the present invention has improved cycle characteristics and suppresses gas generation during high-temperature storage.
  • FIG. 2 is a schematic cross-sectional view along the line AA in FIG. 1. It is sectional drawing which shows the negative electrode which is an example of embodiment of this invention.
  • a nonaqueous electrolyte secondary battery which is an example of an embodiment includes a positive electrode, a negative electrode, and a nonaqueous electrolyte containing a nonaqueous solvent.
  • a separator is preferably provided between the positive electrode and the negative electrode.
  • As an example of the structure of the nonaqueous electrolyte secondary battery there is a structure in which an electrode body in which a positive electrode and a negative electrode are wound via a separator, and a nonaqueous electrolyte are housed in an exterior body.
  • other types of electrode bodies such as a stacked electrode body in which a positive electrode and a negative electrode are stacked via a separator may be applied.
  • the nonaqueous electrolyte secondary battery may have any form such as a cylindrical type, a square type, a coin type, a button type, and a laminate type.
  • the specific structure of the nonaqueous electrolyte secondary battery 11 is such that the positive electrode 1 and the negative electrode 2 are wound so as to face each other with a separator 3 therebetween.
  • a flat electrode body composed of the positive and negative electrodes 1 and 2 and the separator 3 is impregnated with a non-aqueous electrolyte.
  • a positive electrode current collecting tab 4 and a negative electrode current collecting tab 5 are connected to the positive electrode 1 and the negative electrode 2, respectively, so that a secondary battery can be charged and discharged.
  • the said electrode body is arrange
  • the positive electrode is preferably composed of a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector.
  • a positive electrode current collector for example, a conductive thin film, particularly a metal foil or alloy foil that is stable in the potential range of the positive electrode such as aluminum, or a film having a metal surface layer such as aluminum is used.
  • the positive electrode active material layer preferably contains a conductive material and a binder in addition to the positive electrode active material.
  • the positive electrode active material includes an oxide including lithium and a metal element M, and the metal element M includes at least one selected from the group including cobalt and nickel.
  • Preferred is a lithium-containing transition metal oxide.
  • the lithium-containing transition metal oxide may contain non-transition metal elements such as Mg and Al. Specific examples include lithium-containing transition metal oxides such as lithium cobaltate, Ni—Co—Mn, Ni—Mn—Al, and Ni—Co—Al. These positive electrode active materials may be used alone or in combination of two or more.
  • the negative electrode 2 preferably includes a negative electrode current collector 21 and a negative electrode mixture layer 22 formed on the negative electrode current collector 21.
  • a conductive thin film particularly a metal foil or alloy foil that is stable in the potential range of the negative electrode such as copper, or a film having a metal surface layer such as copper is used.
  • the negative electrode mixture layer preferably contains a thickener and a binder in addition to the negative electrode active material.
  • the thickener it is preferable to use carboxymethylcellulose ammonium salt, ruboxymethylcellulose sodium salt, or the like.
  • the binder styrene-butadiene rubber (SBR), polyimide, or the like is preferably used.
  • the negative electrode active material 23 includes a negative electrode active material 23a which is a particle containing silicon and a negative electrode active material 23b which is a particle containing graphite.
  • the surface of graphite is preferably coated with a material containing cellulose.
  • a material containing cellulose By covering the surface with a material containing cellulose, the insertion of propylene carbonate between the graphite layers is suppressed, and the deterioration of the graphite due to the cycle is suppressed. Further, the adsorption of the thickener and the binder is promoted, the adhesion between the negative electrode current collector 21 and the negative electrode mixture layer 22 is improved, and the current collecting property is improved. That the surface of graphite is covered with a material containing cellulose includes the case where a material containing cellulose is adsorbed on the graphite surface.
  • the surface of graphite being coated with a material containing cellulose means that the outermost surface of graphite is coated with a material containing cellulose.
  • the material containing cellulose is preferably a water-soluble cellulose derivative having C 6 H 10 O 5 as a basic structure, and is preferably carboxyalkyl cellulose, hydroxyalkyl cellulose, or alkoxy cellulose. Examples thereof include carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose. Of these, carboxymethylcellulose is preferable.
  • covers the graphite surface is not restricted to the material containing cellulose, It is possible to use as long as it is a polymer material which has ion permeability and does not react with lithium.
  • Polymer materials that do not react with lithium are starch derivatives having a basic structure of C 6 H 10 O 5 , such as starch acetate, phosphate starch, carboxymethyl starch, hydroxyethyl starch, and the like, C 6 H 10 O Viscous polysaccharides such as pullulan and dextrin having a basic structure of 5 , water-soluble acrylic resin, water-soluble epoxy resin, water-soluble polyester resin, water-soluble polyamide resin, vinylidene fluoride / hexafluoropropylene copolymer and polyvinylidene fluoride, Is mentioned.
  • the material containing cellulose relative to graphite is preferably 0.1 to 2.0% by mass, and more preferably 0.3 to 1.5% by mass. If the mass ratio is too small, the amount of gas generated during high-temperature storage tends to increase, and if the mass ratio is too large, the resistance of the negative electrode mixture layer tends to increase and cycle characteristics tend to decrease.
  • the surface of graphite 100% or less than 90% of a material containing cellulose, preferably, it is preferably covered approximately 100%. If the coverage is too small, the gas generated during high-temperature storage tends to increase. Note that the surface of graphite is covered with a material containing cellulose when the particle cross section is observed by SEM, the surface of the graphite is covered with a film made of a material containing cellulose at least 50 nm thick. It is.
  • Examples of the method of coating the graphite surface with a material containing cellulose include a spray dryer method and a stirring-drying method.
  • the negative electrode active material 23a preferably contains SiO x (preferably 0.5 ⁇ X ⁇ 1.5), Si or Si alloy.
  • Si alloys include solid solutions of silicon and one or more other elements, intermetallic compounds of silicon and one or more other elements, and eutectic alloys of silicon and one or more other elements. It is done. Among these, it is preferable to use SiO x particles.
  • the surface of the SiO x particles is covered with carbon at 50% or more and 100% or less, preferably 100%.
  • the SiO X particle surface is coated with carbon, when the particle cross sections were observed by SEM, SiO X particle surfaces, is that covered by at least 1nm thick or more carbon coating.
  • the SiO x surface is covered with carbon by 100%.
  • the carbon coating is preferably 1 to 200 nm, more preferably 5 to 100 nm. If the thickness of the carbon film becomes too thin, the conductivity decreases. On the other hand, if the thickness of the carbon film becomes too thick, the diffusion of Li + into SiO x tends to be inhibited and the capacity tends to decrease.
  • the carbon coating is preferably composed of amorphous carbon.
  • amorphous carbon By using amorphous carbon, it is possible to form a good and uniform film on the surface of SiO x , and it is possible to further promote the diffusion of Li + into SiO x .
  • the amorphous carbon film is produced, for example, by immersing SiO X particles to be coated in a solution such as coal tar and then performing a high temperature treatment under an inert atmosphere.
  • the heat treatment temperature at this time is preferably about 900 ° C. to 1100 ° C.
  • the surface of the negative electrode active material 23a may be coated with a material containing cellulose.
  • a material containing cellulose By covering the reaction active part of the surface of the particle
  • the negative electrode active material 23a is SiO x particles, it is preferable that the surface of the amorphous carbon coating on the surface of the SiO x particles is coated with a material containing cellulose.
  • the average particle diameter of the negative electrode active material particles 23a is preferably 1 to 15 ⁇ m and more preferably 4 to 10 ⁇ m from the viewpoint of increasing the capacity. If the particle size of the negative electrode active material particles 23a becomes too small, the particle surface area increases, and therefore the reaction amount with the electrolyte tends to increase and the capacity tends to decrease. On the other hand, if the particle size becomes too large, Li + cannot diffuse to the vicinity of the center of the particle, and the capacity tends to decrease and the load characteristics tend to deteriorate.
  • the average particle diameter of the negative electrode active material particles 23b is preferably 15 to 25 ⁇ m.
  • the mass ratio between the particles containing silicon and the graphite whose surface is coated with a material containing cellulose is preferably 1:99 to 50:50, more preferably 3:97 to 20:80. If mass ratio is in the said range, it will become easy to make high capacity
  • the mass of the thickener in the negative electrode mixture layer is preferably larger than the mass of the binder.
  • the mass ratio of the thickener to the binder is 98: 2 to less than 50:50, more preferably 80:20 to 60:40.
  • Non-aqueous electrolyte examples include LiClO 4 , LiBF 4 , LiPF 6 , LiAlCl 4 , LiSbF 6 , LiSCN, LiCF 3 SO 3 , LiCF 3 CO 2 , LiAsF 6 , LiB 10 Cl 10 , lower aliphatic carboxylic acid.
  • Lithium, LiCl, LiBr, Lii, chloroborane lithium, borates, imide salts, and the like can be used.
  • LiPF 6 is preferably used from the viewpoints of ion conductivity and electrochemical stability.
  • One electrolyte salt may be used alone, or two or more electrolyte salts may be used in combination. These electrolyte salts are preferably contained at a ratio of 0.8 to 1.5 mol with respect to 1 L of the nonaqueous electrolyte.
  • cyclic carbonates and chain carbonates are used as the solvent for the nonaqueous electrolyte.
  • cyclic carbonate examples include propylene carbonate (PC), ethylene carbonate (EC), and fluoroethylene carbonate (FEC).
  • chain carbonate examples include diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC).
  • the cyclic carbonate preferably contains propylene carbonate.
  • propylene carbonate When propylene carbonate is used, the reaction between the material containing cellulose and the electrolytic solution is less likely to occur during charge storage, and gas generation is suppressed.
  • Propylene carbonate is preferably contained in an amount of 1 to 40% by volume, more preferably 1 to 30% by volume, based on the entire non-aqueous solvent. If it is less than 1% by volume, the effect of suppressing gas generation tends to be reduced. When it exceeds 40 volume%, the viscosity of electrolyte solution will become high and there exists a tendency for charging / discharging capacity to fall.
  • the cyclic carbonate is preferably contained in an amount of 1 to 50% by volume based on the entire non-aqueous solvent. If the amount is less than 1% by volume, oxidative decomposition of the chain carbonate ester is likely to occur, which causes an increase in the generated gas. If it exceeds 50% by volume, the viscosity of the electrolytic solution tends to increase, and the charge / discharge capacity tends to decrease.
  • the ratio of propylene carbonate with respect to the cyclic carbonate in the non-aqueous solvent is preferably 1 to 100% by volume, more preferably 10 to 50% by volume.
  • the volume ratio of the cyclic carbonate and the chain carbonate in the non-aqueous solvent is preferably 1:90 to 70:30, more preferably 50:50.
  • cyclic carboxylic acid ester chain
  • the cyclic carboxylic acid ester include ⁇ -butyrolactone (GBL) and ⁇ -valerolactone (GVL).
  • chain carboxylic acid esters include methyl propionate (MP), fluoromethyl propionate (FMP), and methyl trimethyl acetate (MTMA).
  • fluoroarene include monofluorobenzene (FB).
  • separator a porous sheet having ion permeability and insulating properties is used.
  • the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric.
  • material of the separator polyolefin such as polyethylene and polypropylene is suitable.
  • Example 1> (Preparation of positive electrode) Weigh and mix lithium cobaltate, acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., HS100) and polyvinylidene fluoride (PVdF) so that the mass ratio is 95.0: 2.5: 2.5. Then, N-methyl-2-pyrrolidone (NMP) as a dispersion medium was added. Next, this was stirred using a mixer (Primix Co., Ltd., TK Hibismix) to prepare a positive electrode slurry.
  • NMP N-methyl-2-pyrrolidone
  • this positive electrode slurry is applied to both surfaces of a positive electrode current collector made of aluminum foil, dried, and then rolled by a rolling roller to produce a positive electrode in which a positive electrode mixture layer is formed on both surfaces of the positive electrode current collector. did.
  • the filling density in the positive electrode mixture layer was 3.60 g / ml.
  • the negative electrode active material, carboxymethyl cellulose, and styrene butadiene rubber were mixed at a mass ratio of 98: 1.5: 0.5 with a suitable amount of water with a mixer to prepare a negative electrode mixture slurry.
  • This negative electrode mixture slurry was applied to both sides of a negative electrode current collector sheet made of a copper foil having a thickness of 10 ⁇ m, dried and rolled.
  • the packing density of the negative electrode active material layer was 1.60 g / mL.
  • Ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), monofluorobenzene (FB), and methyltrimethylacetate (MTMA) with a volume ratio of 30: 20: 40: 5: 5 1.2 mol / liter of lithium hexafluorophosphate (LiPF 6 ) is added to the mixed solvent, and 1% by volume each of vinylene carbonate (VC) and fluoroethylene carbonate (FEC) is added.
  • LiPF 6 lithium hexafluorophosphate
  • VC vinylene carbonate
  • FEC fluoroethylene carbonate
  • a tab was attached to each of the electrodes, and the positive electrode and the negative electrode were wound in a spiral shape through a separator so that the tab was positioned on the outermost periphery, thereby preparing a wound electrode body.
  • the electrode body is inserted into an exterior body made of an aluminum laminate sheet and vacuum-dried at 105 ° C. for 2 hours, and then the non-aqueous electrolyte is injected, and the opening of the exterior body is sealed to prepare the battery A1.
  • the design capacity of the battery A1 is 800 mAh.
  • Capacity maintenance rate (%) at the 100th cycle (discharge capacity at the 100th cycle / discharge capacity at the first cycle) ⁇ 100 (2)
  • the battery after the first charge / discharge is charged at a constant current of 1.0 it (800 mA) until the battery voltage becomes 4.2 V, and then the current value becomes 0.05 it (40 mA) at a voltage of 4.2 V. After performing constant voltage charging, it was stored at 60 ° C. for 2 days.
  • Battery swelling rate (%) ((Battery thickness after storage ⁇ Battery thickness before storage) / Battery thickness before storage) ⁇ 100 (3) The thickness of each battery was measured using a micrometer.
  • coated graphite particles When PC is not used for the cyclic carbonate in the non-aqueous solvent, the reaction between the material containing cellulose and the electrolytic solution is likely to occur during charge storage, and it is considered that the swelling of the battery due to gas generation increased.
  • CMC in the negative electrode mixture is easily adsorbed by graphite having the film containing cellulose. Therefore, in the negative electrode mixture, CMC is diffused as the graphite diffuses. Is easily diffused. Then, the diffused CMC is adsorbed by SiO x which is more easily adsorbed by CMC than graphite.
  • the charge potential differs between graphite and SiO x , so that selective charge / discharge to the SiO x is performed, in the cell A2 with the graphite particles and the SiO X particles as a negative electrode active material, since the charging potential of the SiO X is in the CMC coated-adsorption polarization increases it is close to graphite, selective charging of the SiO X It is thought that the discharge was suppressed. As described above, since the uneven charge / discharge reaction is alleviated, the suppression of the deterioration of the SiO x particles is one factor that did not decrease the capacity retention rate.
  • the thickener and the binder are easily adsorbed, the adhesion and the flexibility of the electrode plate are improved, and the destruction of the electrode plate structure due to charge / discharge is suppressed. This is also cited as one factor that did not decrease the capacity maintenance rate.
  • CMC When CMC is contained as a binder in the negative electrode mixture layer, CMC exists around the graphite particles without using the coated graphite particles. However, in this case, since a sufficient amount of CMC is not coated on the surface of graphite, it is considered that there are no effects such as suppression of deterioration of graphite particles and relaxation of non-uniform charging as described above.
  • the FB and MTMA used as the solvent for the battery A1 are used as regulators for the electrolyte viscosity equal to those of the batteries B1 and B2, and do not affect the capacity retention rate and the swelling rate.
  • a battery A2 was produced in the same manner as the battery A1, except that the negative electrode active material, carboxymethyl cellulose, and styrene butadiene rubber were mixed at a mass ratio of 98: 1: 1.
  • the swelling rate during high-temperature storage is particularly reduced when the thickener is contained in the negative electrode mixture in a larger amount than the binder.
  • the thickener is contained in a larger amount than the binder, a good pseudo film is easily formed on the surface of the coated graphite particles and the particles containing Si, and the decomposition reaction of the electrolytic solution due to the reaction between the active material and the electrolytic solution It is thought that it became difficult to occur.

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Abstract

The present invention suppresses the generation of gas when a non-aqueous electrolyte secondary battery is stored at high temperatures. The present invention comprises a positive electrode, a negative electrode, and a non-aqueous electrolyte. The negative electrode comprises a negative electrode current collector and a negative electrode mixture layer. The negative electrode mixture layer comprises particles that include silicon and comprises graphite particles that are coated with a material that includes cellulose. The non-aqueous electrolyte comprises a cyclic carbonate ester and a chain carbonate ester. The cyclic carbonate ester comprises propylene carbonate. The negative electrode mixture layer comprises a thickening agent and a binding agent, the mass of the thickening agent preferably being greater than the mass of the binding agent.

Description

非水電解質二次電池Nonaqueous electrolyte secondary battery
　本発明は、非水電解質二次電池に関する。 The present invention relates to a non-aqueous electrolyte secondary battery.
　リチウムイオン電池の高エネルギー密度化、高出力化に向け、負極活物質として、黒鉛等の炭素質材料に替えてケイ素、ゲルマニウム、錫及び亜鉛などのリチウムと合金化する金属材料や、これらの金属の酸化物などを用いることが検討されている。 Metal materials that can be alloyed with lithium such as silicon, germanium, tin and zinc instead of carbonaceous materials such as graphite as negative electrode active materials, and these metals for higher energy density and higher output of lithium ion batteries The use of these oxides is being studied.
　リチウムと合金化する金属材料やこれらの金属の酸化物からなる負極活物質は、充放電時において負極活物質が膨張収縮するため、サイクル特性が低下することが知られている。下記特許文献１には、ＳｉとＯとを構成元素に含む材料と炭素材料との複合体、および黒鉛質炭素材料を負極活物質として含有する非水電解質二次電池用負極が提案されている。 It is known that a negative electrode active material made of a metal material alloyed with lithium or an oxide of these metals is deteriorated in cycle characteristics because the negative electrode active material expands and contracts during charge and discharge. Patent Document 1 listed below proposes a composite of a material containing Si and O as a constituent element and a carbon material, and a negative electrode for a nonaqueous electrolyte secondary battery containing a graphitic carbon material as a negative electrode active material. .
国際公開第２０１３／０９４６６８号International Publication No. 2013/094668
　特許文献１の非水電解質二次電池では、サイクル特性の改善が十分ではなく、また、高温保存時においてガスが発生するという課題があった。 The non-aqueous electrolyte secondary battery of Patent Document 1 has problems in that the cycle characteristics are not sufficiently improved and gas is generated during high-temperature storage.
　上記課題を解決すべく、本発明に係る非水電解質二次電池は、正極と、負極と、非水電解質とを備え、前記負極は、負極集電体及び負極合剤層を備え、前記負極合剤層は、シリコンを含む粒子と、セルロースを含む材料で表面が被覆された黒鉛粒子とを備え、前記非水電解質は環状炭酸エステル及び鎖状炭酸エステルを備え、前記環状炭酸エステルは、プロピレンカーボネートを備える。 In order to solve the above problems, a non-aqueous electrolyte secondary battery according to the present invention includes a positive electrode, a negative electrode, and a non-aqueous electrolyte, and the negative electrode includes a negative electrode current collector and a negative electrode mixture layer, and the negative electrode The mixture layer includes particles containing silicon and graphite particles whose surfaces are coated with a material containing cellulose. The non-aqueous electrolyte includes a cyclic carbonate and a chain carbonate. The cyclic carbonate is propylene. With carbonate.
　本発明の非水電解質二次電池は、サイクル特性が向上すると共に、高温保存時のガス発生が抑制される。 The non-aqueous electrolyte secondary battery of the present invention has improved cycle characteristics and suppresses gas generation during high-temperature storage.
本発明の実施形態の一例である非水電解質二次電池を示す模式的正面図である。It is a typical front view showing a nonaqueous electrolyte secondary battery which is an example of an embodiment of the present invention. 図１のＡ－Ａ線に沿った模式的断面図である。FIG. 2 is a schematic cross-sectional view along the line AA in FIG. 1. 本発明の実施形態の一例である負極を示す断面図である。It is sectional drawing which shows the negative electrode which is an example of embodiment of this invention.
　以下、本発明の実施形態について詳細に説明する。
　実施形態の説明で参照する図面は、模式的に記載されたものであり、図面に描画された構成要素の寸法比率などは、現物と異なる場合がある。具体的な寸法比率等は、以下の説明を参酌して判断されるべきである。本明細書において、略１００％とは、１００％はもとより、実質的に１００％と認められるものを含む意図である。 Hereinafter, embodiments of the present invention will be described in detail.
The drawings referred to in the description of the embodiments are schematically described, and the dimensional ratios of the components drawn in the drawings may be different from the actual products. Specific dimensional ratios and the like should be determined in consideration of the following description. In the present specification, “approximately 100%” is intended to include not only 100% but also what is substantially recognized as 100%.
　実施形態の一例である非水電解質二次電池は、正極と、負極と、非水溶媒を含む非水電解質とを備える。正極と負極との間には、セパレータを設けることが好適である。非水電解質二次電池の構造の一例としては、正極及び負極がセパレータを介して巻回されてなる電極体と、非水電解質とが外装体に収容された構造が挙げられる。或いは、巻回型の電極体の代わりに、正極及び負極がセパレータを介して積層されてなる積層型の電極体など、他の形態の電極体が適用されてもよい。非水電解質二次電池は、例えば円筒型、角型、コイン型、ボタン型、ラミネート型など、いずれの形態であってもよい。 A nonaqueous electrolyte secondary battery which is an example of an embodiment includes a positive electrode, a negative electrode, and a nonaqueous electrolyte containing a nonaqueous solvent. A separator is preferably provided between the positive electrode and the negative electrode. As an example of the structure of the nonaqueous electrolyte secondary battery, there is a structure in which an electrode body in which a positive electrode and a negative electrode are wound via a separator, and a nonaqueous electrolyte are housed in an exterior body. Alternatively, instead of the wound electrode body, other types of electrode bodies such as a stacked electrode body in which a positive electrode and a negative electrode are stacked via a separator may be applied. The nonaqueous electrolyte secondary battery may have any form such as a cylindrical type, a square type, a coin type, a button type, and a laminate type.
　ここで、図１及び図２に示すように、非水電解質二次電池１１の具体的な構造は、正極１と負極２とがセパレータ３を介して対向配置されて巻回されており、これら正負両極１、２とセパレータ３とからなる扁平型の電極体には非水電解液が含浸されている。上記正極１と負極２には、それぞれ、正極集電タブ４と負極集電タブ５が接続され、二次電池として充放電可能な構造となっている。尚、上記電極体は、周縁同士がヒートシールされたヒートシール部７を備えるアルミラミネート外装体６の収納空間内に配置されている。 Here, as shown in FIGS. 1 and 2, the specific structure of the nonaqueous electrolyte secondary battery 11 is such that the positive electrode 1 and the negative electrode 2 are wound so as to face each other with a separator 3 therebetween. A flat electrode body composed of the positive and negative electrodes 1 and 2 and the separator 3 is impregnated with a non-aqueous electrolyte. A positive electrode current collecting tab 4 and a negative electrode current collecting tab 5 are connected to the positive electrode 1 and the negative electrode 2, respectively, so that a secondary battery can be charged and discharged. In addition, the said electrode body is arrange | positioned in the storage space of the aluminum laminate exterior body 6 provided with the heat seal part 7 by which the periphery heat-sealed.
〔正極〕
　正極は、正極集電体と、正極集電体上に形成された正極活物質層とで構成されることが好適である。正極集電体には、例えば、導電性を有する薄膜体、特にアルミニウムなどの正極の電位範囲で安定な金属箔や合金箔、アルミニウムなどの金属表層を有するフィルムが用いられる。正極活物質層は、正極活物質の他に、導電材及び結着剤を含むことが好ましい。 [Positive electrode]
The positive electrode is preferably composed of a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector. For the positive electrode current collector, for example, a conductive thin film, particularly a metal foil or alloy foil that is stable in the potential range of the positive electrode such as aluminum, or a film having a metal surface layer such as aluminum is used. The positive electrode active material layer preferably contains a conductive material and a binder in addition to the positive electrode active material.
　正極活物質は、リチウムと、金属元素Ｍとを含む酸化物を含み、前記金属元素Ｍは、コバルト、ニッケルを含む群より選択される少なくとも一種を含む。好ましくはリチウム含有遷移金属酸化物である。リチウム含有遷移金属酸化物は、Ｍｇ、Ａｌ等の非遷移金属元素を含有するものであってもよい。具体例としては、コバルト酸リチウム、Ｎｉ－Ｃｏ－Ｍｎ、Ｎｉ－Ｍｎ－Ａｌ、Ｎｉ－Ｃｏ－Ａｌ等のリチウム含有遷移金属酸化物が挙げられる。正極活物質は、これらを１種単独で用いてもよいし、複数種を混合して用いてもよい。 The positive electrode active material includes an oxide including lithium and a metal element M, and the metal element M includes at least one selected from the group including cobalt and nickel. Preferred is a lithium-containing transition metal oxide. The lithium-containing transition metal oxide may contain non-transition metal elements such as Mg and Al. Specific examples include lithium-containing transition metal oxides such as lithium cobaltate, Ni—Co—Mn, Ni—Mn—Al, and Ni—Co—Al. These positive electrode active materials may be used alone or in combination of two or more.
　〔負極〕
　図３に例示するように、負極２は、負極集電体２１と、負極集電体２１上に形成された負極合剤層２２とを備えることが好適である。負極集電体２１には、例えば、導電性を有する薄膜体、特に銅などの負極の電位範囲で安定な金属箔や合金箔、銅などの金属表層を有するフィルムが用いられる。負極合剤層は、負極活物質の他に、増粘剤及び結着剤を含むことが好適である。増粘剤としては、カルボキシメチルセルロースアンモニウム塩やルボキシメチルセルロースナトリウム塩等を用いることが好ましい。結着剤としてはスチレン－ブタジエンゴム（ＳＢＲ）やポリイミド等を用いることが好ましい。 [Negative electrode]
As illustrated in FIG. 3, the negative electrode 2 preferably includes a negative electrode current collector 21 and a negative electrode mixture layer 22 formed on the negative electrode current collector 21. For the negative electrode current collector 21, for example, a conductive thin film, particularly a metal foil or alloy foil that is stable in the potential range of the negative electrode such as copper, or a film having a metal surface layer such as copper is used. The negative electrode mixture layer preferably contains a thickener and a binder in addition to the negative electrode active material. As the thickener, it is preferable to use carboxymethylcellulose ammonium salt, ruboxymethylcellulose sodium salt, or the like. As the binder, styrene-butadiene rubber (SBR), polyimide, or the like is preferably used.
　負極活物質２３は、シリコンを含む粒子である負極活物質２３ａ及び黒鉛を含む粒子である負極活物質２３ｂを備える。 The negative electrode active material 23 includes a negative electrode active material 23a which is a particle containing silicon and a negative electrode active material 23b which is a particle containing graphite.
　黒鉛は、セルロースを含む材料で表面が被覆されていることが好ましい。セルロースを含む材料で表面が被覆されていることにより、黒鉛の層間へプロピレンカーボネートが挿入されるのが抑制されて、サイクルに伴う黒鉛の劣化が抑制される。また、増粘剤や結着剤の吸着が促されて、負極集電体２１と負極合剤層２２との密着性が向上し、集電性が向上する。黒鉛表面がセルロースを含む材料で被覆されているとは、黒鉛表面に、セルロースを含む材料が吸着されている場合も含む。また、黒鉛の表面がセルロースを含む材料で表面が被覆されているとは、黒鉛の最表面がセルロースを含む材料で被覆されているということである。セルロースを含む材料で表面が被覆されている黒鉛を用いて負極を作製する際、溶媒等と混合させても、セルロースを含む材料は黒鉛表面を被覆した状態は保持される。 The surface of graphite is preferably coated with a material containing cellulose. By covering the surface with a material containing cellulose, the insertion of propylene carbonate between the graphite layers is suppressed, and the deterioration of the graphite due to the cycle is suppressed. Further, the adsorption of the thickener and the binder is promoted, the adhesion between the negative electrode current collector 21 and the negative electrode mixture layer 22 is improved, and the current collecting property is improved. That the surface of graphite is covered with a material containing cellulose includes the case where a material containing cellulose is adsorbed on the graphite surface. Further, the surface of graphite being coated with a material containing cellulose means that the outermost surface of graphite is coated with a material containing cellulose. When a negative electrode is produced using graphite whose surface is coated with a material containing cellulose, the material containing cellulose is maintained in a state of covering the graphite surface even when mixed with a solvent or the like.
　セルロースを含む材料は、Ｃ6Ｈ10Ｏ5を基本構造とした水溶性セルロース誘導体であることが好ましく、カルボキシアルキルセルロース、ヒドロキシアルキルセルロースまたはアルコキシセルロースであることが好ましい。カルボキシメチルセルロース、メチルセルロース、ヒドロキシエチルセルロース、ヒドロキシプロピルセルロース、が挙げられる。このうち、好ましくは、カルボキシメチルセルロースである。 The material containing cellulose is preferably a water-soluble cellulose derivative having C 6 H 10 O 5 as a basic structure, and is preferably carboxyalkyl cellulose, hydroxyalkyl cellulose, or alkoxy cellulose. Examples thereof include carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose. Of these, carboxymethylcellulose is preferable.
　なお、黒鉛表面を被覆する材料は、セルロースを含む材料に限らず、イオン透過性があって、リチウムと反応しないポリマー材料であれば使用することが可能である。リチウムと反応しないポリマー材料は、Ｃ6Ｈ10Ｏ5を基本構造とした澱粉の誘導体である酢酸澱粉、リン酸澱粉、カルボキシメチル澱粉、ヒドロキシエチル澱粉などのヒドロキシアルキル澱粉類、Ｃ6Ｈ10Ｏ5を基本構造としたプルランやデキストリンなどの粘性多糖類、水溶性アクリル樹脂、水溶性エポキシ樹脂、水溶性ポリエステル樹脂、水溶性ポリアミド樹脂、フッ化ビニリデン／ヘキサフルオロプロピレン共重合体及びポリフッ化ビニリデン、が挙げられる。 In addition, the material which coat | covers the graphite surface is not restricted to the material containing cellulose, It is possible to use as long as it is a polymer material which has ion permeability and does not react with lithium. Polymer materials that do not react with lithium are starch derivatives having a basic structure of C 6 H 10 O 5 , such as starch acetate, phosphate starch, carboxymethyl starch, hydroxyethyl starch, and the like, C 6 H 10 O Viscous polysaccharides such as pullulan and dextrin having a basic structure of 5 , water-soluble acrylic resin, water-soluble epoxy resin, water-soluble polyester resin, water-soluble polyamide resin, vinylidene fluoride / hexafluoropropylene copolymer and polyvinylidene fluoride, Is mentioned.
　黒鉛に対するセルロースを含む材料は、０．１～２．０質量％であることが好ましく、さらに好ましくは、０．３～１．５質量％である。上記質量比が小さくなりすぎると、高温保存時における発生ガスが増加する傾向があり、上記質量比が大きくなりすぎると、負極合剤層の抵抗が上昇してサイクル特性が低下する傾向がある。 The material containing cellulose relative to graphite is preferably 0.1 to 2.0% by mass, and more preferably 0.3 to 1.5% by mass. If the mass ratio is too small, the amount of gas generated during high-temperature storage tends to increase, and if the mass ratio is too large, the resistance of the negative electrode mixture layer tends to increase and cycle characteristics tend to decrease.
　黒鉛の表面は、セルロースを含む材料で９０％以上１００％以下、好ましくは、略１００％被覆されていることが好ましい。被覆率が小さくなりすぎると、高温保存時における発生ガスが増加する傾向がある。なお、黒鉛の表面がセルロースを含む材料で被覆されているとは、粒子断面をＳＥＭ観察した場合に、黒鉛表面が、少なくとも５０ｎｍ厚以上のセルロースを含む材料からなる被膜で覆われているということである。 The surface of graphite, 100% or less than 90% of a material containing cellulose, preferably, it is preferably covered approximately 100%. If the coverage is too small, the gas generated during high-temperature storage tends to increase. Note that the surface of graphite is covered with a material containing cellulose when the particle cross section is observed by SEM, the surface of the graphite is covered with a film made of a material containing cellulose at least 50 nm thick. It is.
　セルロースを含む材料で黒鉛表面を被覆する方法としては、スプレードライヤー法や、攪拌－乾燥法が例示される。 Examples of the method of coating the graphite surface with a material containing cellulose include a spray dryer method and a stirring-drying method.
　負極活物質２３ａは、ＳｉＯX（好ましくは０．５≦Ｘ≦１．５）、ＳｉまたはＳｉ合金を含有することが好ましい。Ｓｉ合金としては、ケイ素と他の１種以上の元素との固溶体、ケイ素と他の１種以上の元素との金属間化合物、ケイ素と他の１種以上の元素との共晶合金などが挙げられる。このうち、ＳｉＯX粒子を用いることが好適である。 The negative electrode active material 23a preferably contains SiO x (preferably 0.5 ≦ X ≦ 1.5), Si or Si alloy. Examples of Si alloys include solid solutions of silicon and one or more other elements, intermetallic compounds of silicon and one or more other elements, and eutectic alloys of silicon and one or more other elements. It is done. Among these, it is preferable to use SiO x particles.
　ＳｉＯX粒子は、表面が炭素で５０％以上１００％以下、好ましくは、１００％被覆されていることが好ましい。なお、ＳｉＯX粒子表面が炭素で被覆されているとは、粒子断面をＳＥＭ観察した場合に、ＳｉＯX粒子表面が、少なくとも１ｎｍ厚以上の炭素被膜で覆われているということである。本発明において、ＳｉＯX表面が炭素で１００％被覆されているとは、粒子断面をＳＥＭ観察した場合に、ＳｉＯX粒子表面の略１００％が、少なくとも１ｎｍ厚以上の炭素被膜で覆われているということである。炭素被膜は１～２００ｎｍが好ましく、５～１００ｎｍがより好ましい。炭素被膜の厚みが薄くなり過ぎると、導電性が低下し、一方、炭素被膜の厚みが厚くなり過ぎると、ＳｉＯXへのＬｉ+の拡散が阻害されて容量が低下する傾向にある。 It is preferable that the surface of the SiO x particles is covered with carbon at 50% or more and 100% or less, preferably 100%. Note that the SiO X particle surface is coated with carbon, when the particle cross sections were observed by SEM, SiO X particle surfaces, is that covered by at least 1nm thick or more carbon coating. In the present invention, the SiO x surface is covered with carbon by 100%. When the particle cross section is observed by SEM, almost 100% of the SiO x particle surface is covered with a carbon film having a thickness of at least 1 nm. That's what it means. The carbon coating is preferably 1 to 200 nm, more preferably 5 to 100 nm. If the thickness of the carbon film becomes too thin, the conductivity decreases. On the other hand, if the thickness of the carbon film becomes too thick, the diffusion of Li + into SiO x tends to be inhibited and the capacity tends to decrease.
　炭素被膜は、非晶質炭素から構成されることが好ましい。非晶質炭素を用いることで、ＳｉＯX表面に良好かつ均一な被膜を形成することが可能となり、ＳｉＯXへのＬｉ+の拡散をより促進させることが可能である。 The carbon coating is preferably composed of amorphous carbon. By using amorphous carbon, it is possible to form a good and uniform film on the surface of SiO x , and it is possible to further promote the diffusion of Li + into SiO x .
　非晶質炭素被膜は、例えば、コールタール等の溶液に被覆対象であるＳｉＯX粒子を浸漬した後、不活性雰囲気下で高温処理して作製される。このときの熱処理温度は、９００℃～１１００℃程度が好ましい。 The amorphous carbon film is produced, for example, by immersing SiO X particles to be coated in a solution such as coal tar and then performing a high temperature treatment under an inert atmosphere. The heat treatment temperature at this time is preferably about 900 ° C. to 1100 ° C.
　負極活物質２３ａは、セルロースを含む材料で表面が被覆されていてもよい。シリコンを含む粒子の表面の反応活性部をセルロースを含む材料で覆うことにより、シリコンを含む粒子と電解液との反応性が抑制され、電解液の分解によるガス発生が低減する。負極活物質２３ａがＳｉＯX粒子である場合には、ＳｉＯX粒子表面の非晶質炭素被膜上が、セルロースを含む材料で表面が被覆されていることが好ましい。 The surface of the negative electrode active material 23a may be coated with a material containing cellulose. By covering the reaction active part of the surface of the particle | grains containing silicon with the material containing cellulose, the reactivity of the particle | grains containing silicon | silicone and electrolyte solution is suppressed, and the gas generation by decomposition | disassembly of electrolyte solution reduces. When the negative electrode active material 23a is SiO x particles, it is preferable that the surface of the amorphous carbon coating on the surface of the SiO x particles is coated with a material containing cellulose.
　負極活物質粒子２３ａの平均粒径は、高容量化の観点から、１～１５μｍが好ましく、４～１０μｍがより好ましい。負極活物質粒子２３ａの粒径が小さくなり過ぎると、粒子表面積が大きくなるため、電解質との反応量が増大して容量が低下する傾向にある。一方、粒径が大きくなり過ぎると、Ｌｉ+が粒子の中心付近まで拡散できず、 容量が低下し負荷特性が悪くなる傾向にある。 The average particle diameter of the negative electrode active material particles 23a is preferably 1 to 15 μm and more preferably 4 to 10 μm from the viewpoint of increasing the capacity. If the particle size of the negative electrode active material particles 23a becomes too small, the particle surface area increases, and therefore the reaction amount with the electrolyte tends to increase and the capacity tends to decrease. On the other hand, if the particle size becomes too large, Li + cannot diffuse to the vicinity of the center of the particle, and the capacity tends to decrease and the load characteristics tend to deteriorate.
　負極活物質粒子２３ｂの平均粒径は、１５～２５μｍが好ましい。 The average particle diameter of the negative electrode active material particles 23b is preferably 15 to 25 μm.
　シリコンを含む粒子とセルロースを含む材料で表面が被覆された黒鉛との質量比は、好ましくは、１：９９～５０：５０、さらに好ましくは３：９７～２０：８０である。質量比が当該範囲内であれば、高容量化と初回充放電特性向上を両立し易くなる。 The mass ratio between the particles containing silicon and the graphite whose surface is coated with a material containing cellulose is preferably 1:99 to 50:50, more preferably 3:97 to 20:80. If mass ratio is in the said range, it will become easy to make high capacity | capacitance and initial charge / discharge characteristic improvement compatible.
　負極合剤層中における増粘剤の質量は結着剤の質量よりも多いことが好ましい。増粘剤と結着剤との質量比は、９８：２～５０：５０未満、より好ましくは　８０：２０～６０：４０である。増粘剤が結着剤の質量よりも少ないと、極板抵抗が上昇しサイクル特性が悪化する傾向がある。 The mass of the thickener in the negative electrode mixture layer is preferably larger than the mass of the binder. The mass ratio of the thickener to the binder is 98: 2 to less than 50:50, more preferably 80:20 to 60:40. When the thickener is less than the mass of the binder, the electrode plate resistance increases and the cycle characteristics tend to deteriorate.
〔非水電解質〕
　非水電解質の電解質塩としては、例えばＬｉＣｌＯ4、ＬｉＢＦ4、ＬｉＰＦ6、ＬｉＡｌＣｌ4、ＬｉＳｂＦ6、ＬｉＳＣＮ、ＬｉＣＦ3ＳＯ3、ＬｉＣＦ3ＣＯ2、ＬｉＡｓＦ6、ＬｉＢ10Ｃｌ10、低級脂肪族カルボン酸リチウム、ＬｉＣｌ、ＬｉＢｒ、Ｌｉｉ、クロロボランリチウム、ホウ酸塩類、イミド塩類などを用いることができる。この中でも、イオン伝導性と電気化学的安定性の観点から、ＬｉＰＦ6を用いることが好ましい。電解質塩は、１種を単独で用いてもよく、２種以上を組み合わせて用いてもよい。これら電解質塩は、非水電解質１Ｌに対し０．８～１．５ｍｏｌの割合で含まれていることが好ましい。 [Non-aqueous electrolyte]
Examples of the electrolyte salt of the non-aqueous electrolyte include LiClO 4 , LiBF 4 , LiPF 6 , LiAlCl 4 , LiSbF 6 , LiSCN, LiCF 3 SO 3 , LiCF 3 CO 2 , LiAsF 6 , LiB 10 Cl 10 , lower aliphatic carboxylic acid. Lithium, LiCl, LiBr, Lii, chloroborane lithium, borates, imide salts, and the like can be used. Among these, LiPF 6 is preferably used from the viewpoints of ion conductivity and electrochemical stability. One electrolyte salt may be used alone, or two or more electrolyte salts may be used in combination. These electrolyte salts are preferably contained at a ratio of 0.8 to 1.5 mol with respect to 1 L of the nonaqueous electrolyte.
　非水電解質の溶媒としては、環状炭酸エステル及び鎖状炭酸エステルを用いる。環状炭酸エステルとしては、プロピレンカーボネート（ＰＣ）、エチレンカーボネート（ＥＣ）、フルオロエチレンカーボネート（ＦＥＣ）、などが挙げられる。鎖状炭酸エステルとしては、ジエチルカーボネート（ＤＥＣ）、エチルメチルカーボネート（ＥＭＣ）、ジメチルカーボネート（ＤＭＣ）などが挙げられる。 As the solvent for the nonaqueous electrolyte, cyclic carbonates and chain carbonates are used. Examples of the cyclic carbonate include propylene carbonate (PC), ethylene carbonate (EC), and fluoroethylene carbonate (FEC). Examples of the chain carbonate include diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC).
　環状炭酸エステルは、プロピレンカーボネートを含むことが好ましい。プロピレンカーボネートを用いると、充電保存時において、セルロースを含む材料と電解液との反応が起こりにくくなり、ガス発生が抑制される。 The cyclic carbonate preferably contains propylene carbonate. When propylene carbonate is used, the reaction between the material containing cellulose and the electrolytic solution is less likely to occur during charge storage, and gas generation is suppressed.
　プロピレンカーボネートは、非水溶媒全体に対し、１～４０体積％含まれることが好ましく、さらに好ましくは、１～３０体積％である。１体積％を下回ると、ガス発生を抑制する効果が低減する傾向がある。４０体積％を上回ると、電解液の粘性が高くなり、充放電容量が低下する傾向がある。 Propylene carbonate is preferably contained in an amount of 1 to 40% by volume, more preferably 1 to 30% by volume, based on the entire non-aqueous solvent. If it is less than 1% by volume, the effect of suppressing gas generation tends to be reduced. When it exceeds 40 volume%, the viscosity of electrolyte solution will become high and there exists a tendency for charging / discharging capacity to fall.
　環状炭酸エステルは、非水溶媒全体に対し１～５０体積％含まれることが好ましい。１体積％を下回ると、鎖状炭酸エステルの酸化分解が起こりやすくなり、発生ガス増加の原因となる。５０体積％を上回ると、電解液の粘性が高くなり、充放電容量が低下する傾向がある。 The cyclic carbonate is preferably contained in an amount of 1 to 50% by volume based on the entire non-aqueous solvent. If the amount is less than 1% by volume, oxidative decomposition of the chain carbonate ester is likely to occur, which causes an increase in the generated gas. If it exceeds 50% by volume, the viscosity of the electrolytic solution tends to increase, and the charge / discharge capacity tends to decrease.
　非水溶媒中の環状炭酸エステルに対するプロピレンカーボネートの割合は、１～１００体積％であることが好ましく、さらに好ましくは、１０～５０体積％である。 The ratio of propylene carbonate with respect to the cyclic carbonate in the non-aqueous solvent is preferably 1 to 100% by volume, more preferably 10 to 50% by volume.
　非水溶媒中の環状炭酸エステル及び鎖状炭酸エステルの体積比は、１：９０～７０：３０であることが好ましく、より好ましくは、５０：５０である。 The volume ratio of the cyclic carbonate and the chain carbonate in the non-aqueous solvent is preferably 1:90 to 70:30, more preferably 50:50.
また、溶媒として、環状カルボン酸エステルや鎖状カルボン酸エステル、フルオロアーレン等がさらに用いられていても良い。環状カルボン酸エステルとしては、γ－ブチロラクトン（ＧＢＬ）、γ－バレロラクトン（ＧＶＬ）などが挙げられる。鎖状カルボン酸エステルとしては、メチルプロピオネート（ＭＰ）フルオロメチルプロピオネート（ＦＭＰ）、メチルトリメチルアセテート（ＭＴＭＡ）などが挙げられる。フルオロアーレンとしては、モノフルオロベンゼン（ＦＢ）などが挙げられる。 Moreover, cyclic carboxylic acid ester, chain | strand-shaped carboxylic acid ester, fluoroarene, etc. may further be used as a solvent. Examples of the cyclic carboxylic acid ester include γ-butyrolactone (GBL) and γ-valerolactone (GVL). Examples of chain carboxylic acid esters include methyl propionate (MP), fluoromethyl propionate (FMP), and methyl trimethyl acetate (MTMA). Examples of fluoroarene include monofluorobenzene (FB).
〔セパレータ〕
　セパレータには、イオン透過性及び絶縁性を有する多孔性シートが用いられる。多孔性シートの具体例としては、微多孔薄膜、織布、不織布等が挙げられる。セパレータの材質としては、ポリエチレン、ポリプロピレン等のポリオレフィンが好適である。 [Separator]
As the separator, a porous sheet having ion permeability and insulating properties is used. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. As the material of the separator, polyolefin such as polyethylene and polypropylene is suitable.
　以下、実施例により本発明をさらに説明するが、本発明はこれらの実施例に限定されるものではない。 Hereinafter, the present invention will be further described with reference to examples, but the present invention is not limited to these examples.
　　　　　　　　　　　　　　　＜実施例１＞
＜実験１＞
（正極の作製）
　コバルト酸リチウムと、アセチレンブラック（電気化学工業社製、ＨＳ１００）と、ポリフッ化ビニリデン(ＰＶｄＦ)とを、質量比が９５．０：２．５：２．５の割合になるように秤量、混合し、分散媒としてのＮ－メチル－２－ピロリドン（ＮＭＰ）を添加した。次に、これを混合機（プライミクス社製、Ｔ．Ｋ．ハイビスミックス）を用いて攪拌し、正極スラリーを調製した。次に、この正極スラリーを、アルミニウム箔から成る正極集電体の両面に塗布、乾燥した後、圧延ローラにより圧延して、正極集電体の両面に正極合剤層が形成された正極を作製した。尚、正極合剤層における充填密度は３．６０ｇ／ｍｌとした。 <Example 1>
<Experiment 1>
(Preparation of positive electrode)
Weigh and mix lithium cobaltate, acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., HS100) and polyvinylidene fluoride (PVdF) so that the mass ratio is 95.0: 2.5: 2.5. Then, N-methyl-2-pyrrolidone (NMP) as a dispersion medium was added. Next, this was stirred using a mixer (Primix Co., Ltd., TK Hibismix) to prepare a positive electrode slurry. Next, this positive electrode slurry is applied to both surfaces of a positive electrode current collector made of aluminum foil, dried, and then rolled by a rolling roller to produce a positive electrode in which a positive electrode mixture layer is formed on both surfaces of the positive electrode current collector. did. The filling density in the positive electrode mixture layer was 3.60 g / ml.
　（負極の作製）
　　[黒鉛への被覆]
　純水１リットルに対し、カルボキシメチルセルロースナトリウム(ダイセル製＃１３８０)を所定量加えて溶解し、黒鉛粉末（平均粒径（Ｄ50）２０μｍ）を１ｋｇ投入した後、ホモジナイザーで６０分間攪拌して分散させた。スプレードライヤーを用い、得られた分散液を１００℃で乾燥させ、黒鉛の乾燥粉を得た。なお、黒鉛表面の被覆率は１００％となるように乾燥粉を作製した。 (Preparation of negative electrode)
[Coating on graphite]
Dissolve by adding a predetermined amount of sodium carboxymethylcellulose (Daicel # 1380) to 1 liter of pure water, add 1 kg of graphite powder (average particle size (D 50 ) 20 μm), and then disperse by stirring for 60 minutes with a homogenizer I let you. Using a spray dryer, the obtained dispersion was dried at 100 ° C. to obtain a dry powder of graphite. A dry powder was prepared so that the coverage of the graphite surface was 100%.
[質量比の測定]
　得られた黒鉛の乾燥粉の重量（Ｗ1）およびそれらを大気中において１００℃で３時間熱処理を施した黒鉛の重量（Ｗ2）から、下記（１）式より被覆量を算出し、黒鉛に対する被覆量とした。
　被覆量［重量％］＝〔（Ｗ1－Ｗ2）／Ｗ1〕×１００・・・（１）
　黒鉛に対するカルボキシメチルセルロース被覆量は、０．５質量％であった。 [Measurement of mass ratio]
From the weight (W 1 ) of the obtained graphite dry powder and the weight (W 2 ) of the graphite subjected to heat treatment at 100 ° C. for 3 hours in the air, the coating amount was calculated from the following formula (1). It was set as the coating amount with respect to.
Covering amount [wt%] = [(W 1 −W 2 ) / W 1 ] × 100 (1)
The coating amount of carboxymethyl cellulose relative to graphite was 0.5% by mass.
　得られた黒鉛粉末と、非晶質炭素材料で被覆された平均粒径（Ｄ50）６μｍのＳｉＯX（Ｘ＝１）粒子とを９５：５で混合したものを負極活物質として用いた。上記負極活物質と、カルボキシメチルセルロースと、スチレンブタジエンラバーとを、質量比で９８：１．５：０．５の割合で、適量の水とともにミキサーで混合し、負極合剤スラリーを調製した。この負極合剤スラリーを厚さ１０μｍの銅箔からなる負極集電体シートの両面に塗布し、乾燥させ、圧延後した。負極活物質層の充填密度は、１．６０ｇ／ｍＬであった。 A mixture of the obtained graphite powder and SiO x (X = 1) particles having an average particle diameter (D 50 ) of 6 μm coated with an amorphous carbon material at a ratio of 95: 5 was used as the negative electrode active material. The negative electrode active material, carboxymethyl cellulose, and styrene butadiene rubber were mixed at a mass ratio of 98: 1.5: 0.5 with a suitable amount of water with a mixer to prepare a negative electrode mixture slurry. This negative electrode mixture slurry was applied to both sides of a negative electrode current collector sheet made of a copper foil having a thickness of 10 μm, dried and rolled. The packing density of the negative electrode active material layer was 1.60 g / mL.
　〔非水電解液の調製〕
　エチレンカーボネート（ＥＣ）とプロピレンカーボネート（ＰＣ）とジエチルカーボネート（ＤＥＣ）と、モノフルオロベンゼン（ＦＢ）と、メチルトリメチルアセテート（ＭＴＭＡ）を、体積比が３０：２０：４０：５：５の割合となるように混合した混合溶媒に、六フッ化リン酸リチウム（ＬｉＰＦ6）を、１．２モル／リットル添加し、さらに、ビ
ニレンカーボネート（ＶＣ）及びフルオロエチレンカーボネート（ＦＥＣ）をそれぞれ１体積％添加して、非水電解液を調製した。 (Preparation of non-aqueous electrolyte)
Ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), monofluorobenzene (FB), and methyltrimethylacetate (MTMA) with a volume ratio of 30: 20: 40: 5: 5 1.2 mol / liter of lithium hexafluorophosphate (LiPF 6 ) is added to the mixed solvent, and 1% by volume each of vinylene carbonate (VC) and fluoroethylene carbonate (FEC) is added. Thus, a non-aqueous electrolyte was prepared.
〔電池の組み立て〕
　上記各電極にタブをそれぞれ取り付け、タブが最外周部に位置するようにセパレータを介して上記正極及び上記負極を渦巻き状に巻回して巻回電極体を作製した。当該電極体をアルミニウムラミネートシートで構成される外装体に挿入して、１０５℃で２時間真空乾燥した後、上記非水電解液を注入し、外装体の開口部を封止して電池Ａ１を作製した。電池Ａ１の設計容量は８００ｍＡｈである。 [Assembling the battery]
A tab was attached to each of the electrodes, and the positive electrode and the negative electrode were wound in a spiral shape through a separator so that the tab was positioned on the outermost periphery, thereby preparing a wound electrode body. The electrode body is inserted into an exterior body made of an aluminum laminate sheet and vacuum-dried at 105 ° C. for 2 hours, and then the non-aqueous electrolyte is injected, and the opening of the exterior body is sealed to prepare the battery A1. Produced. The design capacity of the battery A1 is 800 mAh.
＜実験２＞
　非水電解液の調製において、ＥＣ：ＰＣ：ＤＥＣ：ＦＢ：ＭＴＭＡ＝３０：２０：４０：５：５の混合溶媒に代えて、ＥＣ：ＤＥＣ＝３０：７０の混合溶媒を用いたこと以外は、電池Ａ１と同様にして電池Ｂ１を作製した。 <Experiment 2>
In the preparation of the non-aqueous electrolyte, instead of using a mixed solvent of EC: PC: DEC: FB: MTMA = 30: 20: 40: 5: 5, a mixed solvent of EC: DEC = 30: 70 was used. A battery B1 was produced in the same manner as the battery A1.
＜実験３＞
　負極の作製において、カルボキシメチルセルロースナトリウムで被覆した黒鉛粉末に代えて、未処理の黒鉛粉末（表面をカルボキシメチルセルロースナトリウムで被覆していない黒鉛粉末）を用いたこと、及び、非水電解液の調製において、ＥＣ：ＰＣ：ＤＥＣ：ＦＢ：ＭＴＭＡ＝３０：２０：４０：５：５の混合溶媒に代えて、ＥＣ：ＤＥＣ＝３０：７０の混合溶媒を用いたこと以外は、電池Ａ１と同様にして電池Ｂ２を作製した。 <Experiment 3>
In the preparation of the negative electrode, in place of the graphite powder coated with sodium carboxymethylcellulose, untreated graphite powder (graphite powder whose surface was not coated with sodium carboxymethylcellulose) was used, and in the preparation of the non-aqueous electrolyte , EC: PC: DEC: FB: MTMA = In the same manner as battery A1, except that a mixed solvent of EC: DEC = 30: 70 was used instead of the mixed solvent of 30: 20: 40: 5: 5 Battery B2 was produced.
（実験）
上記の各電池を、以下の条件で保存した後、下記（２）式で示す１００サイクル後の容量維持率（％）及び下記（３）式で示す高温保存時の膨れ率（％）を調べたので、その結果を表１に示す。 (Experiment)
After each battery is stored under the following conditions, the capacity retention rate (%) after 100 cycles shown by the following formula (2) and the swelling rate (%) during high temperature storage shown by the following formula (3) are examined. The results are shown in Table 1.
〔充放電条件〕
　１．０ｉｔ（８００ｍＡ）電流で電池電圧が４．２Ｖとなるまで定電流充電を行った後、４．２Ｖの電圧で電流値が０．０５ｉｔ（４０ｍＡ）となるまで定電圧充電を行った。１０分間休止した後、１．０ｉｔ（８００ｍＡ）電流で電池電圧が２．７５Ｖとなるまで定電流放電を行った。 (Charging / discharging conditions)
The battery was charged at a constant current of 1.0 it (800 mA) until the battery voltage was 4.2 V, and then charged at a voltage of 4.2 V until the current value was 0.05 it (40 mA). After resting for 10 minutes, constant current discharge was performed at a current of 1.0 it (800 mA) until the battery voltage reached 2.75V.
　〔１００サイクル目の容量維持率の算出式〕
　１００サイクル目の容量維持率（％）＝（１００サイクル目の放電容量／１サイクル目の放電容量）×１００・・・（２） [Calculation formula of capacity maintenance rate at 100th cycle]
Capacity maintenance rate (%) at the 100th cycle = (discharge capacity at the 100th cycle / discharge capacity at the first cycle) × 100 (2)
　初回充放電後の電池を１．０ｉｔ（８００ｍＡ）電流で電池電圧が４．２Ｖとなるまで定電流充電を行った後、４．２Ｖの電圧で電流値が０．０５ｉｔ（４０ｍＡ）となるまで定電圧充電を行った後、６０℃で２日間保存した。 The battery after the first charge / discharge is charged at a constant current of 1.0 it (800 mA) until the battery voltage becomes 4.2 V, and then the current value becomes 0.05 it (40 mA) at a voltage of 4.2 V. After performing constant voltage charging, it was stored at 60 ° C. for 2 days.
〔電池の膨れ率（％）の算出式〕
　電池の膨れ率（％）＝（（保存後の電池厚み－保存前の電池厚み）／保存前の電池厚み）×１００・・・（３）
　各電池の厚みは、マイクロメータを用いて測定した。 [Calculation formula for battery swelling rate (%)]
Battery swelling rate (%) = ((Battery thickness after storage−Battery thickness before storage) / Battery thickness before storage) × 100 (3)
The thickness of each battery was measured using a micrometer.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　非水溶媒中の環状炭酸エステルとしてＰＣを用いていない場合、セルロースを含む材料で表面が被覆された黒鉛粒子（以下、被覆黒鉛粒子）とＳｉＯX粒子とを負極活物質として用いた電池Ｂ１と未処理の黒鉛粒子とＳｉＯX粒子とを負極活物質として用いた電池Ｂ２を比較すると、被覆黒鉛粒子を用いると容量維持率は向上するものの、高温保存後の膨れ率が大きくなることがわかる。非水溶媒中の環状炭酸エステルにＰＣを用いない場合は、充電保存時において、セルロースを含む材料と電解液との反応が起こりやすく、ガス発生による電池膨れが増大したと考えられる。 When PC is not used as the cyclic carbonate in the non-aqueous solvent, a battery B1 using graphite particles whose surfaces are coated with a material containing cellulose (hereinafter, coated graphite particles) and SiO x particles as a negative electrode active material; Comparing the battery B2 using untreated graphite particles and SiO x particles as the negative electrode active material, it can be seen that when the coated graphite particles are used, the capacity retention rate is improved, but the swelling rate after high-temperature storage is increased. When PC is not used for the cyclic carbonate in the non-aqueous solvent, the reaction between the material containing cellulose and the electrolytic solution is likely to occur during charge storage, and it is considered that the swelling of the battery due to gas generation increased.
　被覆黒鉛粒子とＳｉＯX粒子とを負極活物質として用いた場合、電池Ａ１と電池Ｂ１とを比較すると、非水溶媒中の環状炭酸エステルとしてＰＣを用いることで、保存後の膨れ率が大きく低減された。非水溶媒中の環状炭酸エステルにＰＣを用いた電池Ａ１においては、充電保存時においてセルロースを含む材料と電解液との反応が起こりにくく、ガス発生による電池膨れ抑制されたと考えられる。 When coated graphite particles and SiO x particles are used as the negative electrode active material, when battery A1 and battery B1 are compared, the use of PC as a cyclic carbonate in a non-aqueous solvent greatly reduces the swelling rate after storage. It was done. In the battery A1 using PC as the cyclic carbonate in the non-aqueous solvent, the reaction between the material containing cellulose and the electrolytic solution hardly occurs during charge storage, and it is considered that the battery swelling due to gas generation was suppressed.
　非水溶媒としてＰＣを用いた電池Ａ１においては、容量維持率が低下していない。これは、以下の複数の理由によると考えられる。 In the battery A1 using PC as the non-aqueous solvent, the capacity retention rate is not lowered. This is considered to be due to the following reasons.
　セルロースを含む被膜により、黒鉛の層間へＰＣが挿入されるのが抑制されて、サイクルに伴う黒鉛の劣化が抑制されたことが、容量維持率が低下しなかった１つの要因として挙げられる。 One reason that the capacity retention rate did not decrease is that the film containing cellulose suppressed the insertion of PC between the graphite layers and the deterioration of the graphite accompanying the cycle.
　セルロースを含む被膜を黒鉛表面に設けることによって、負極合剤中のＣＭＣが、セルロースを含む被膜を備える黒鉛に吸着されやすくなり、従って、負極合剤中においては、黒鉛の拡散に伴って、ＣＭＣが拡散されやすくなる。そして、拡散したＣＭＣは、黒鉛よりもＣＭＣに吸着されやすいＳｉＯXに吸着されていく。黒鉛粒子とＳｉＯX粒子とを負極活物質として用いた電池Ｂ２においては、黒鉛とＳｉＯXとで充電電位に相異があるため、ＳｉＯXへの選択的充放電が行われていく一方、被覆黒鉛粒子とＳｉＯX粒子とを負極活物質として用いた電池Ａ２においては、ＣＭＣが被覆・吸着しては分極が大きくなってＳｉＯXの充電電位が黒鉛に近づいたため、ＳｉＯXへの選択的充放電が抑制されたと考えられる。このように、不均一な充放電反応が緩和されたので、ＳｉＯX粒子の劣化が抑制されたことが、容量維持率が低下しなかった１つの要因として挙げられる。 By providing a film containing cellulose on the graphite surface, CMC in the negative electrode mixture is easily adsorbed by graphite having the film containing cellulose. Therefore, in the negative electrode mixture, CMC is diffused as the graphite diffuses. Is easily diffused. Then, the diffused CMC is adsorbed by SiO x which is more easily adsorbed by CMC than graphite. In the battery B2 using graphite particles and SiO x particles as the negative electrode active material, the charge potential differs between graphite and SiO x , so that selective charge / discharge to the SiO x is performed, in the cell A2 with the graphite particles and the SiO X particles as a negative electrode active material, since the charging potential of the SiO X is in the CMC coated-adsorption polarization increases it is close to graphite, selective charging of the SiO X It is thought that the discharge was suppressed. As described above, since the uneven charge / discharge reaction is alleviated, the suppression of the deterioration of the SiO x particles is one factor that did not decrease the capacity retention rate.
　さらに、被膜黒鉛粒子を用いることにより、増粘剤及び結着剤が吸着されやすくなって、密着性および極板の柔軟性が向上して、充放電に伴う極板構造の破壊を抑制されたことも、容量維持率が低下しなかった１つの要因として挙げられる。 Furthermore, by using the coated graphite particles, the thickener and the binder are easily adsorbed, the adhesion and the flexibility of the electrode plate are improved, and the destruction of the electrode plate structure due to charge / discharge is suppressed. This is also cited as one factor that did not decrease the capacity maintenance rate.
　負極合剤層中に結着剤としてＣＭＣが含まれる場合、被覆黒鉛粒子を用いなくても、黒鉛粒子周辺にはＣＭＣが存在する。しかし、この場合は、黒鉛の表面に十分な量のＣＭＣが被覆されていないので、上述したような、黒鉛粒子の劣化抑制及び不均一充電の緩和等の効果はないと考えられる。 When CMC is contained as a binder in the negative electrode mixture layer, CMC exists around the graphite particles without using the coated graphite particles. However, in this case, since a sufficient amount of CMC is not coated on the surface of graphite, it is considered that there are no effects such as suppression of deterioration of graphite particles and relaxation of non-uniform charging as described above.
　電池Ａ１の溶媒として使用したＦＢおよびＭＴＭＡは、電池Ｂ１及びＢ２と同等の電解液粘度とするための調整剤として用いたものであり、上記容量維持率及び膨れ率に影響を与えるものではない。 The FB and MTMA used as the solvent for the battery A1 are used as regulators for the electrolyte viscosity equal to those of the batteries B1 and B2, and do not affect the capacity retention rate and the swelling rate.
　　　　　　　　　　　　　　　　＜実施例２＞
＜実験４＞
　負極の作製において、負極活物質と、カルボキシメチルセルロースと、スチレンブタジエンラバーとを、質量比で９８：１：１の割合で混合したこと以外は、電池Ａ１と同様にして電池Ａ２を作製した。 <Example 2>
<Experiment 4>
A battery A2 was produced in the same manner as the battery A1, except that the negative electrode active material, carboxymethyl cellulose, and styrene butadiene rubber were mixed at a mass ratio of 98: 1: 1.
（実験）
　実施例１と同様にして、膨れ率（％）を調べたので、その結果を電池Ａ１の結果と共に表２に示す。 (Experiment)
Since the swelling rate (%) was examined in the same manner as in Example 1, the result is shown in Table 2 together with the result of the battery A1.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　高温保存時の膨れ率は、負極合剤中に増粘剤が結着剤よりも多く含まれる場合に、特に低減されることがわかる。増粘剤が結着剤よりも多く含まれる場合には、被覆黒鉛粒子やＳｉを含む粒子の表面に良好な擬似被膜が形成されやすく、活物質と電解液との反応による電解液の分解反応が起こりにくくなったと考えられる。 It can be seen that the swelling rate during high-temperature storage is particularly reduced when the thickener is contained in the negative electrode mixture in a larger amount than the binder. When the thickener is contained in a larger amount than the binder, a good pseudo film is easily formed on the surface of the coated graphite particles and the particles containing Si, and the decomposition reaction of the electrolytic solution due to the reaction between the active material and the electrolytic solution It is thought that it became difficult to occur.
　１　正極、２　負極、３　セパレータ、４　正極集電タブ、５　負極集電タブ、６　アルミラミネート外装体、７　ヒートシール部、１１　非水電解質二次電池、２１　負極集電体、２２　負極合剤層、２３，２３ａ，２３ｂ　負極活物質。 1 positive electrode, 2 negative electrode, 3 separator, 4 positive electrode current collecting tab, 5 negative electrode current collecting tab, 6 aluminum laminate outer package, 7 heat seal part, 11 nonaqueous electrolyte secondary battery, 21 negative electrode current collector, 22 negative electrode mixture Layer, 23, 23a, 23b negative electrode active material.

Claims (3)

  1. 　正極と、負極と、非水電解質とを備える非水電解質二次電池において、
    　前記負極は、負極集電体及び負極合剤層を備え、
    　前記負極合剤層は、シリコンを含む粒子と、セルロースを含む材料で表面が被覆された黒鉛粒子とを備え、
    　前記非水電解質は環状炭酸エステル及び鎖状炭酸エステルを備え、
    　前記環状炭酸エステルは、プロピレンカーボネートを備える、非水電解質二次電池。     In a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte,
    The negative electrode includes a negative electrode current collector and a negative electrode mixture layer,
    The negative electrode mixture layer includes particles containing silicon and graphite particles whose surfaces are coated with a material containing cellulose.
    The non-aqueous electrolyte comprises a cyclic carbonate and a chain carbonate,
    The cyclic carbonate is a non-aqueous electrolyte secondary battery comprising propylene carbonate.
  2. 　前記負極合剤層は、増粘剤及び結着剤を備え、
    　前記増粘剤の質量は前記結着剤の質量よりも多い、請求項１に記載の非水電解質二次電池。     The negative electrode mixture layer includes a thickener and a binder,
    The non-aqueous electrolyte secondary battery according to claim 1, wherein a mass of the thickener is greater than a mass of the binder.
  3. 　前記シリコンを含む粒子は、ＳｉＯX（０．５≦Ｘ≦１．５）粒子を含む、請求項１または請求項２に記載の非水電解質二次電池。 The non-aqueous electrolyte secondary battery according to claim 1, wherein the silicon-containing particles include SiO x (0.5 ≦ X ≦ 1.5) particles.
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