WO2010092815A1 - 非水電解質二次電池用負極及び非水電解質二次電池 - Google Patents
非水電解質二次電池用負極及び非水電解質二次電池 Download PDFInfo
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- WO2010092815A1 WO2010092815A1 PCT/JP2010/000856 JP2010000856W WO2010092815A1 WO 2010092815 A1 WO2010092815 A1 WO 2010092815A1 JP 2010000856 W JP2010000856 W JP 2010000856W WO 2010092815 A1 WO2010092815 A1 WO 2010092815A1
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- negative electrode
- active material
- secondary battery
- electrolyte secondary
- nonaqueous electrolyte
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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
- H01M10/052—Li-accumulators
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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
- H01M10/0567—Liquid materials characterised by the additives
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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
- 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
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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
- 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
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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
- 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
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- 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
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- 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
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
Definitions
- the present invention relates to a negative electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery. More specifically, the present invention mainly relates to an improvement in a negative electrode for a non-aqueous electrolyte secondary battery containing an alloy-based active material.
- Non-aqueous electrolyte secondary batteries are widely used as power sources for electronic equipment, electrical equipment, transportation equipment, machine tools, power storage equipment, etc. because they have high capacity and energy density, and are easy to reduce in size and weight.
- a lithium ion secondary battery including a positive electrode containing a lithium cobalt composite oxide, a negative electrode containing graphite, and a separator can be given.
- alloy-based active materials made of silicon, tin, oxides or alloys thereof are known as negative electrode active materials other than graphite.
- the alloy active material occludes lithium by alloying with lithium, and reversibly occludes and releases lithium.
- the alloy-based active material has a high discharge capacity.
- the theoretical discharge capacity of silicon is about 11 times the theoretical discharge capacity of graphite. Therefore, the nonaqueous electrolyte secondary battery using the alloy-based active material as the negative electrode active material has a high capacity.
- a non-aqueous electrolyte secondary battery using an alloy-based active material as a negative electrode active material exhibits high performance in the initial stage of use.
- alloy-based secondary battery exhibits high performance in the initial stage of use.
- the battery performance deteriorates with time due to electrode deterioration, battery deformation, and the like.
- the following methods have been proposed.
- Patent Document 1 discloses a negative electrode for a non-aqueous electrolyte secondary battery in which a polymer film layer formed of a polymer support and a crosslinkable monomer is provided on the surface of a negative electrode active material layer containing lithium alloy particles. To do.
- Patent Document 2 an oxide film made of an oxide of a metal selected from silicon, germanium, and tin is formed in a region that is supported on the surface of the current collector and in contact with the electrolyte on the surface of the negative electrode active material particles containing silicon or tin. Disclosed is a formed negative electrode for a non-aqueous electrolyte secondary battery.
- An object of the present invention is to provide a non-aqueous electrolyte secondary battery containing an alloy-based active material, and a non-aqueous electrolyte secondary battery having excellent life characteristics, including the negative electrode for a non-aqueous electrolyte secondary battery. It is.
- a negative electrode for a non-aqueous electrolyte secondary battery includes a negative electrode current collector and a negative electrode active material layer that is supported on the surface of the negative electrode current collector and includes an alloy-based active material that absorbs and releases lithium ions.
- the negative electrode active material layer is provided with a resin layer containing a resin component having lithium ion conductivity and an additive for nonaqueous electrolyte.
- the nonaqueous electrolyte secondary battery of the present invention includes a positive electrode that occludes and releases lithium ions, a negative electrode that occludes and releases lithium ions, and a lithium ion permeable electrode disposed so as to be interposed between the positive electrode and the negative electrode. And a lithium ion conductive nonaqueous electrolyte, wherein the negative electrode is used as a negative electrode.
- a nonaqueous electrolyte secondary battery having a negative electrode containing an alloy-based active material and having excellent life characteristics can be obtained.
- the inventors of the present invention have studied the cause of battery performance deterioration over time in alloy-based secondary batteries. As a result, the following knowledge was obtained.
- the alloy-based active material expands and contracts with the insertion and extraction of lithium, and generates a relatively large stress. For this reason, when the number of times of charging / discharging increases, cracks are generated on the surface and inside of the negative electrode active material layer made of the alloy-based active material. When a crack occurs, a surface that has not been in direct contact with the non-aqueous electrolyte (hereinafter referred to as “new surface”) appears.
- a resin containing a resin component having lithium ion conductivity and an additive added to the nonaqueous electrolyte on the surface of the negative electrode active material layer supported on the current collector surface and containing an alloy-based active material The inventors have come up with a negative electrode in which a layer (hereinafter simply referred to as “resin layer”) is formed.
- the resin layer is formed on the surface of the negative electrode active material layer, thereby preventing the new surface from contacting the nonaqueous electrolyte.
- the nonaqueous electrolyte used in the nonaqueous electrolyte secondary battery generally includes a supporting salt and a nonaqueous solvent, as well as an additive for nonaqueous electrolyte (hereinafter simply referred to as “additive”) for improving battery performance. Is).
- additive for nonaqueous electrolyte
- Such an additive is decomposed on the surface of the positive electrode active material layer or the negative electrode active material layer by repeating the charge / discharge cycle of the battery, and the concentration thereof gradually decreases. Therefore, the additive exhibits its effect sufficiently in the initial use of the battery, but as the charge / discharge cycle is repeated, the additive is decomposed and the effect is reduced.
- an additive is included in the resin layer formed on the surface of the negative electrode active material layer.
- the additive when the additive is contained in the resin layer, the additive can be held at a higher concentration than when the additive is contained in the nonaqueous electrolyte.
- the additive when the additive is contained in the non-aqueous electrolyte at a high concentration, the wettability of the non-aqueous electrolyte with respect to the separator decreases, the lithium ion conductivity decreases, and a side reaction tends to occur. Therefore, it is difficult to keep the additive at a high concentration in the nonaqueous electrolyte.
- the additive when the additive is retained at a high concentration in the resin layer, the additive is gradually supplied from the resin layer to the non-aqueous electrolyte, so that the above-described problem does not occur in the non-aqueous electrolyte. .
- FIG. 1 is a longitudinal sectional view schematically showing a configuration of a nonaqueous electrolyte secondary battery 1 according to the first embodiment of the present invention.
- the nonaqueous electrolyte secondary battery 1 is connected to a negative electrode 12, a stacked electrode group in which a positive electrode 11 and a negative electrode 12 are stacked with a separator 14 interposed therebetween, a positive electrode lead 15 connected to the positive electrode 11, and a negative electrode 12.
- the battery includes a negative electrode lead 16, a gasket 17 that seals the openings 18a and 18b of the outer case 18, and an outer case 18 that houses the laminated electrode group and a nonaqueous electrolyte (not shown). .
- One end of the positive electrode lead 15 is connected to the positive electrode current collector 11 a, and the other end is led out from the opening 18 a of the outer case 18 to the outside of the non-aqueous electrolyte secondary battery 1.
- One end of the negative electrode lead 16 is connected to the negative electrode current collector 12 a, and the other end is led out from the opening 18 b of the outer case 18 to the outside of the nonaqueous electrolyte secondary battery 1.
- the positive electrode lead 15 and the negative electrode lead 16 those commonly used in the field of lithium ion secondary batteries can be used.
- an aluminum lead can be used for the positive electrode lead 15, and a nickel lead can be used for the negative electrode lead 16.
- the openings 18 a and 18 b of the outer case 18 are sealed with a gasket 17.
- the gasket 17 can be made of various resin materials. Examples of the material of the outer case 18 include a metal material, a synthetic resin, and a laminate film.
- the openings 18a and 18b of the outer case 18 may be directly sealed by welding or the like without using the gasket 17.
- the nonaqueous electrolyte secondary battery 1 is manufactured as follows. One end of the positive electrode lead 15 is connected to the positive electrode current collector 11a of the electrode group. One end of the negative electrode lead 16 is connected to the negative electrode current collector 12a of the electrode group. The electrode group is inserted into the outer case 18, a nonaqueous electrolyte is injected, and the other ends of the positive electrode lead 15 and the negative electrode lead 16 are led out of the outer case 18. Next, the non-aqueous electrolyte secondary battery 1 is obtained by welding and sealing the openings 18 a and 18 b through the gasket 17 while vacuuming the inside of the outer case 18.
- the negative electrode 12 includes a negative electrode current collector 12a, a negative electrode active material layer 12b supported on the surface of the negative electrode current collector 12a, and a resin layer 13 formed on the surface of the negative electrode active material layer 12b. including.
- a conductive substrate is used as the negative electrode current collector 12a.
- the material of the conductive substrate include metal materials such as stainless steel, titanium, nickel, copper, and copper alloys.
- Examples of the form of the conductive substrate include a metal foil, a metal sheet, or a metal film.
- the thickness of the conductive substrate is not particularly limited, but is, for example, 1 to 500 ⁇ m, and more preferably 5 to 50 ⁇ m.
- the negative electrode active material layer 12b includes an alloy-based active material that occludes and releases lithium ions, and is formed on one or both surfaces of the negative electrode current collector 12a.
- the alloy-based active material has the following advantages. That is, since the alloy-based active material has a capacity much larger than that of graphite, the negative electrode active material layer 12b has a sufficient capacity even when the thickness is about 1 ⁇ m to several tens of ⁇ m. In the negative electrode active material layer 12b having a thickness of about 1 ⁇ m to several tens of ⁇ m, even if a new surface is generated, most of the new surface is exposed on the surface of the negative electrode active material layer 12b. Therefore, by protecting the surface of the negative electrode active material layer 12b with the resin layer 13, the new surface can be sufficiently protected.
- the alloy-based active material is preferably an amorphous or low crystalline active material that is alloyed with lithium by occlusion of lithium and reversibly occludes and releases lithium.
- Examples of the alloy-based active material include a silicon-based active material and a tin-based active material.
- An alloy type active material may be used individually by 1 type, or may be used in combination of 2 or more type.
- Examples of the silicon-based active material include silicon, silicon compounds, partially substituted products, solid solutions of the above-described silicon compounds and partially substituted products, and the like.
- Examples of the silicon compound include silicon oxide represented by the formula SiO a (0.05 ⁇ a ⁇ 1.95), silicon carbide represented by the formula SiC b (0 ⁇ b ⁇ 1), and formula SiN c (0 ⁇ a silicon nitride represented by c ⁇ 4/3), an alloy of silicon and a different element (A), and the like.
- Examples of the different element (A) include Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Sn, and Ti.
- the partially substituted body is a compound in which a part of silicon atoms contained in silicon and a silicon compound is substituted with a different element (B).
- a different element B
- the different element (B) include B, Mg, Ni, Ti, Mo, Co, Ca, Cr, Cu, Fe, Mn, Nb, Ta, V, W, Zn, C, N, or Sn. Is mentioned. Of these, silicon and silicon compounds are preferable, and silicon oxide is more preferable.
- tin-based active materials include tin, tin compounds, tin oxides represented by the formula SnO d (0 ⁇ d ⁇ 2), tin dioxide (SnO 2 ), tin nitride, Ni—Sn alloy, Mg—Sn alloy , Fe—Sn alloys, Cu—Sn alloys, Ti—Sn alloys and other tin alloys, SnSiO 3 , Ni 2 Sn 4 , Mg 2 Sn and other tin compounds, and solid solutions thereof.
- tin-based active materials tin oxide, tin alloy, tin compound, and the like are preferable.
- the form of the negative electrode active material layer 12b supported by the negative electrode current collector 12a is obtained by applying a mixture paste containing an alloy-based active material, a conductive material, and a binder to the surface of the negative electrode current collector 12a.
- a negative electrode active material layer formed of an aggregate of a plurality of columnar alloy-based active materials formed by a vapor phase method is preferable, and a negative electrode active material layer formed by a vapor phase method and including an assembly of a plurality of columnar alloy-based active materials is particularly preferable.
- the vapor phase method include, for example, a vacuum deposition method, a sputtering method, an ion plating method, a laser ablation method, a chemical vapor deposition (CVD) method, a plasma chemical vapor deposition method, a thermal spraying method, and the like. Is mentioned. Among these, the vacuum evaporation method is preferable. In addition, the manufacturing method of the negative electrode active material layer which consists of an alloy type active material by a vapor phase method is demonstrated in detail later.
- the negative electrode active material layer formed by the vapor phase method in the negative electrode active material layer 12b has a high surface roughness due to the presence of unevenness or cracks.
- the adhesion between the negative electrode active material layer 12b and the resin layer 13 is high, and even if the volume change of the alloy-based active material occurs, the resin layer 13 Is prevented from peeling.
- a negative electrode active material layer composed of an assembly of a plurality of columnar alloy active materials supported on the surface of the negative electrode current collector has voids between the columnar bodies.
- Such surface roughness and voids exert an anchor effect on the resin layer 13, thereby improving the adhesion between the negative electrode active material layer 12 b and the resin layer 13.
- contraction with charging / discharging peeling from the negative electrode active material layer 12b of the resin layer 13 is suppressed. As a result, the effect of protecting the new surface by the resin layer 13 is sustained.
- the dimensions of the concave and convex portions and cracks provided in advance on the surface of the negative electrode active material layer formed by the vapor phase method are not particularly limited, but the length is 0.1 to 20 ⁇ m, the width is 0.1 to 5 ⁇ m, and the depth is 0. It is preferably 1 to 20 ⁇ m. If at least one of the length, the width, and the depth is in the above range, an anchor effect occurs, and the adhesion between the negative electrode active material layer 12b and the resin layer 13 is reliably improved. In addition, the generation of cracks and the generation of new surfaces due to charge / discharge are reduced.
- a deposition method In order to form irregularities or cracks on the surface of the negative electrode active material layer formed by the vapor phase method, a deposition method, a surface adjustment method, or the like can be used. In the deposition method, a thin film of an alloy-based active material is formed in multiple times on the surface of the negative electrode current collector, as will be described later.
- the surface adjustment method first, the surface roughness of the negative electrode current collector is increased.
- the methods include mechanical grinding, chemical etching, electrochemical etching, polishing with an abrasive, plating, and the like.
- the thickness of the negative electrode active material layer is not particularly limited, but specifically, for example, it is 1 to several tens of ⁇ m, and more preferably 1 to 20 ⁇ m.
- the thickness of the negative electrode active material layer is within such a range, most of the new surface appears near the surface of the negative electrode active material layer.
- the new surface is sufficiently protected by the resin layer 13, so that the contact between the new surface and the nonaqueous electrolyte is suppressed. Thereby, the side reaction with a new surface and a nonaqueous electrolyte is suppressed.
- an amount of lithium corresponding to the irreversible capacity may be deposited on the negative electrode active material layer 12b.
- the irreversible capacity is the amount of lithium that is stored in the negative electrode active material layer 12b at the time of initial charge / discharge and is not subsequently released from the negative electrode active material layer 12b.
- the resin layer 13 formed on the surface of the negative electrode active material layer 12b will be described.
- the resin layer 13 suppresses the contact between the new surface and the non-aqueous electrolyte that occurs as the negative electrode active material expands and contracts.
- the resin layer 13 contains the additive for nonaqueous electrolytes.
- the additive for nonaqueous electrolyte contained in the resin layer 13 is gradually released into the nonaqueous electrolyte. Thereby, even if the density
- the resin layer 13 contains a resin component having lithium ion conductivity and a non-aqueous electrolyte additive.
- the resin component having lithium ion conductivity is not particularly limited as long as it is a resin component capable of conducting lithium ions.
- Specific examples of the resin component having lithium ion conductivity include a resin component that swells by contact with a non-aqueous electrolyte and exhibits lithium ion conductivity, and lithium ion conductivity is imparted by blending a supporting salt. Resin components and the like.
- the resin component for blending the supporting salt may be a resin component having lithium ion conductivity or a resin component not having it.
- Such resin components include fluororesin, polyacrylonitrile, polyethylene oxide, polypropylene oxide, and the like. These may be used alone or in combination of two or more. Among these, a fluororesin is preferable from the viewpoint of excellent adhesion to the negative electrode active material layer 12b, mechanical strength, compatibility with the nonaqueous electrolyte additive, and the like.
- the fluororesin include, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a copolymer of vinylidene fluoride and an olefin monomer, and the like.
- PVDF polyvinylidene fluoride
- PTFE polytetrafluoroethylene
- olefin monomer examples include tetrafluoroethylene, hexafluoropropylene (HFP), and ethylene.
- VDF vinylidene fluoride
- HFP copolymer of vinylidene fluoride
- HFP copolymer of VDF and HFP
- additives conventionally added to nonaqueous electrolytes can be used without any particular limitation.
- Specific examples thereof include carbonate compounds, sulfur-containing cyclic compounds, acid anhydrides, and nitrile compounds.
- the carbonate compound is an additive that improves the battery life characteristics by forming a film having high lithium ion conductivity on the negative electrode surface and suppressing side reactions.
- Specific examples of the carbonate compound include, for example, vinylene carbonate, 4-methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, 4-ethyl vinylene carbonate, 4,5-diethyl vinylene carbonate, 4-propyl vinylene carbonate, 4,5 -Dipropyl vinylene carbonate, 4-phenyl vinylene carbonate, 4,5-diphenyl vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, divinyl ethylene carbonate, trifluoropropylene carbonate and the like. These may be used alone or in combination of two or more.
- the sulfur-containing cyclic compound is an additive that forms a film on the positive electrode and suppresses gas generation inside the battery in a high temperature environment.
- the acid anhydride is an additive that forms a lithium ion conductive film on the negative electrode and suppresses the reductive decomposition of the nonaqueous solvent.
- Specific examples of the acid anhydride include succinic anhydride and maleic anhydride. These may be used alone or in combination of two or more.
- the nitrile compound is an additive that is adsorbed on the surface of the positive electrode and suppresses gas generation inside the battery in a high temperature environment.
- Specific examples of the nitrile compound include, for example, succinonitrile (NC—CH 2 —CH 2 —CN), glutaronitrile (NC—CH 2 —CH 2 —CH 2 —CN), adiponitrile (NC—CH 2 —) And nitrile compounds in which a cyano group is bonded to both ends of a linear alkylene group having 2 to 4 carbon atoms, such as CH 2 —CH 2 —CH 2 —CN).
- the content ratio of the non-aqueous electrolyte additive contained in the resin layer 13 is appropriately selected according to the type of the non-aqueous electrolyte additive, but is usually 0.1 to 50% by mass in the total amount of the resin layer 13. Yes, preferably 5 to 15% by mass.
- a lithium salt may be included in the resin layer 13 as a supporting salt.
- a lithium salt what is used as a support salt of a nonaqueous electrolyte secondary battery is used without particular limitation. Specific examples thereof include, for example, 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 lithium carboxylate, Examples include LiCl, LiBr, LiI, LiBCl 4 , borates, imide salts, and the like. These may be used alone or in combination of two or more.
- the resin layer 13 having lithium ion conductivity can be obtained without adding a lithium salt. That is, the resin layer 13 having lithium ion conductivity is obtained by swelling the resin layer 13 with the nonaqueous electrolyte.
- the thickness of the resin layer 13 is not particularly limited, but is usually 0.1 to 20 ⁇ m, preferably 1 to 10 ⁇ m.
- the thickness of the resin layer 13 is too thin, there is a tendency that the contact between the new surface and the nonaqueous electrolyte cannot be sufficiently suppressed. In addition, it tends to be difficult to control the release of the nonaqueous electrolyte additive in the resin layer 13.
- the thickness of the resin layer 13 is too thick, the lithium ion conductivity of the resin layer 13 is lowered, and thus the output characteristics, cycle characteristics, storage characteristics, etc. of the battery may be lowered.
- the resin layer 13 is formed by applying a resin solution containing a resin component having lithium ion conductivity and a non-aqueous electrolyte additive to the surface of the negative electrode active material layer 12b and drying the obtained coating film.
- a resin solution can be prepared by, for example, dissolving or dispersing a resin component, an additive for nonaqueous electrolyte, and a lithium salt blended as necessary in an organic solvent.
- organic solvent examples include carbonates such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate, amides such as dimethylformamide, dimethylacetamide, methylformamide, and N-methyl-2-pyrrolidone, dimethylamine, acetone, and cyclohexanone. .
- the concentration of the resin component in the resin solution is not particularly limited, but is preferably 1 to 10% by mass, for example.
- concentration of the resin component is within such a range, the adhesion with the surface of the negative electrode active material layer 12b is good, and the resin layer 13 having a uniform thickness is formed. Further, when the negative electrode active material layer 12b has voids or cracks, the resin component sufficiently enters the voids or cracks. Thereby, the anchor effect is exhibited and the adhesion between the negative electrode active material layer 12b and the resin layer 13 is sufficiently improved.
- the viscosity of the resin solution is preferably 0.1 to 10 cps.
- the viscosity is a value measured at 70 ° C. using a visco-viscoelasticity measuring apparatus (trade name: Leostress 600, manufactured by Eihiro Seiki Co., Ltd.).
- the viscosity range is as described above. It is particularly preferable to use a resin solution.
- the aggregate of the alloy-based active materials having a plurality of columnar bodies has voids between adjacent columnar bodies.
- the resin solution is applied to the surface of the negative electrode active material layer 12b by a known application method.
- Application methods include screen printing, die coating, comma coating, roll coating, bar coating, gravure coating, curtain coating, spray coating, air knife coating, reverse coating, dip squeeze coating, and the like.
- the thickness of the resin layer 13 can be adjusted, for example, by changing the coating amount of the resin solution, the synthetic resin content of the resin solution, the viscosity of the resin solution, and the like.
- the positive electrode 11 includes a positive electrode current collector 11a and a positive electrode active material layer 11b supported on the surface of the positive electrode current collector 11a.
- a conductive substrate is used as the positive electrode current collector 11a.
- the material of the conductive substrate include, for example, metal materials such as stainless steel, titanium, aluminum, and aluminum alloy, and conductive resins.
- a flat plate or a perforated plate is used as the conductive substrate.
- the perforated plate include a mesh body, a net body, a punching sheet, a lath body, a porous body, a foam, and a nonwoven fabric.
- the flat plate include a foil, a sheet, and a film.
- the thickness of the conductive substrate is not particularly limited, but is usually 1 to 500 ⁇ m, for example, and preferably 1 to 50 ⁇ m.
- the positive electrode active material layer 11b includes a positive electrode active material that occludes and releases lithium ions, and is formed on one or both surfaces of the positive electrode current collector 11a.
- the positive electrode active material various positive electrode active materials capable of inserting and extracting lithium ions can be used. Specific examples thereof include lithium-containing composite oxides and olivine type lithium phosphate.
- the lithium-containing composite oxide is a metal oxide containing lithium and a transition metal element, or a metal oxide in which a part of the transition metal element in the metal oxide is substituted with a different element.
- the transition metal element include Sc, Y, Mn, Fe, Co, Ni, Cu, and Cr.
- Mn, Co, Ni and the like are preferable.
- the different elements include Na, Mg, Zn, Al, Pb, Sb, and B.
- Mg, Al and the like are preferable.
- the transition metal element and the different element may be used alone or in combination of two or more.
- lithium-containing composite oxide for example, Li 1 CoO 2, Li l NiO 2, Li l MnO 2, Li l Co m Ni 1-m O 2, Li l Co m M 1-m O n, Li l Ni 1-m M m O n , Li l Mn 2 O 4 , Li l Mn 2 -m M m O 4 (wherein M is Sc, Y, Mn, Fe, Co, Ni, Cu, It represents at least one element selected from the group consisting of Cr, Na, Mg, Zn, Al, Pb, Sb and B. 0 ⁇ l ⁇ 1.2, 0 ⁇ m ⁇ 0.9, 2.0 ⁇ n ⁇ 2.3) and the like.
- Li l Co m M 1- m O n is preferred.
- olivine type lithium phosphate examples include LiXPO 4 , Li 2 XPO 4 F (wherein X represents at least one element selected from the group consisting of Co, Ni, Mn and Fe). Can be mentioned.
- the number of moles of lithium is a value immediately after the production of the positive electrode active material and increases or decreases due to charge / discharge.
- the positive electrode active materials may be used alone or in combination of two or more.
- the positive electrode active material layer 11b is formed by, for example, applying a positive electrode mixture slurry obtained by dispersing a positive electrode active material, a binder, a conductive agent and the like in an organic solvent to the surface of the positive electrode current collector 11a, and applying the obtained coating film. It is formed by drying and rolling.
- binder examples include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, polymethyl acrylate, polyethyl acrylate, poly Resin materials such as hexyl acrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, polyhexafluoropropylene; styrene butadiene rubber , Rubber materials such as modified acrylic rubber; water-soluble polymer materials such as carboxymethyl cellulose.
- a copolymer containing two or more types of monomer compounds can be used as the resin material.
- the monomer compound include tetrafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, and hexadiene.
- a binder may be used independently or may be used in combination of 2 or more type.
- the positive electrode active material layer 11b may contain a conductive agent as necessary.
- the conductive agent include, for example, graphites such as natural graphite and artificial graphite; carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; carbon fibers and metal fibers
- a conductive agent may be used independently or may be used in combination of 2 or more type.
- organic solvent examples include dimethylformamide, dimethylacetamide, methylformamide, N-methyl-2-pyrrolidone, dimethylamine, acetone, and cyclohexanone.
- the separator 14 is a lithium ion permeable insulating layer disposed so as to be interposed between the positive electrode 11 and the negative electrode 12. At least a part of the surface of the separator 14 on the negative electrode 12 side may be in contact with the surface of the resin layer 13.
- the separator 14 can be a porous sheet having predetermined ion permeability, mechanical strength, insulation, etc. and having pores.
- the porous sheet include a microporous film, a woven fabric, and a non-woven fabric.
- the microporous film may be either a single layer film or a multilayer film.
- the single layer film is made of one kind of material.
- the multilayer film is a laminate of a plurality of single layer films.
- the multilayer film includes a laminate of a plurality of single-layer films made of the same material, a laminate of single-layer films made of two or more different materials, and the like. Two or more layers of microporous membranes, woven fabrics, nonwoven fabrics, etc. may be laminated.
- the thickness of the separator 14 is usually 10 to 300 ⁇ m, preferably 10 to 30 ⁇ m.
- the porosity of the separator 14 is preferably 30 to 70%, more preferably 35 to 60%. The porosity is a percentage of the total volume of pores of the separator 14 with respect to the volume of the separator 14.
- Nonaqueous electrolytes include liquid nonaqueous electrolytes and gel-like nonaqueous electrolytes.
- the liquid non-aqueous electrolyte contains a solute (supporting salt) and a non-aqueous solvent, and further contains various additives as necessary.
- 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 lithium carboxylate, LiCl, LiBr, LiI, LiBCl 4 , borates, imide salts, and the like.
- Borate salts include lithium bis (1,2-benzenediolate (2-)-O, O ′) borate, bis (2,3-naphthalenedioleate (2-)-O, O ′) boric acid. Lithium, bis (2,2′-biphenyldiolate (2-)-O, O ′) lithium borate, bis (5-fluoro-2-olate-1-benzenesulfonic acid-O, O ′) lithium borate Etc.
- imide salts include lithium bistrifluoromethanesulfonate imide ((CF 3 SO 2 ) 2 NLi), lithium trifluoromethanesulfonate nonafluorobutanesulfonate ((CF 3 SO 2 ) (C 4 F 9 SO 2 ) NLi) ) Lithium bispentafluoroethanesulfonate ((C 2 F 5 SO 2 ) 2 NLi).
- Solutes can be used singly or in combination of two or more.
- the concentration of the solute in 1 liter of the non-aqueous solvent is preferably 0.5 to 2 mol.
- non-aqueous solvent examples include, for example, cyclic carbonates, chain carbonates, cyclic carboxylic acid esters and the like.
- cyclic carbonate examples include propylene carbonate and ethylene carbonate.
- chain carbonate examples include diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate and the like.
- cyclic carboxylic acid ester examples include ⁇ -butyrolactone and ⁇ -valerolactone. These may be used alone or in combination of two or more.
- Examples of the additive include the above-described additive for non-aqueous electrolyte, an additive for inactivating the battery (hereinafter referred to as “inactivating agent”), and the like.
- Deactivating agents include benzene compounds containing a phenyl group and a cyclic compound group adjacent to the phenyl group.
- Examples of the cyclic compound group include a phenyl group, a cyclic ether group, a cyclic ester group, a cycloalkyl group, and a phenoxy group.
- Examples of the benzene compound include cyclohexyl benzene, biphenyl, diphenyl ether and the like.
- An additive can be used individually by 1 type or in combination of 2 or more types.
- the gel-like non-aqueous electrolyte contains a liquid non-aqueous electrolyte and a resin material.
- the resin material include polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polytetrafluoroethylene, polyacrylonitrile, polyethylene oxide, polyvinyl chloride, and polyacrylate.
- the gelled nonaqueous electrolyte can also be used as the resin layer 13.
- a gel-like non-aqueous electrolyte containing an additive for non-aqueous electrolyte is prepared, this gel-like non-aqueous electrolyte is applied to the surface of the negative electrode active material layer 12b, and an appropriate amount of the non-aqueous solvent in the gel-like non-aqueous electrolyte is adjusted. What is necessary is just to remove by heating. Thereby, the gel-like nonaqueous electrolyte which serves as the resin layer 13 is formed on the surface of the negative electrode active material layer 12b.
- an electrode group is produced using the negative electrode 12 having the resin layer 13 formed on the surface of the negative electrode active material layer 12b, the electrode group is accommodated in a battery case, and a liquid nonaqueous electrolyte is injected into the battery case. Also good. Thereby, the resin layer 13 on the surface of the negative electrode active material layer 12b is gelled, and a gel-like nonaqueous electrolyte layer that also serves as the resin layer 13 is formed.
- the separator 14 is used as the lithium ion permeable insulating layer, but is not limited thereto, and an inorganic oxide particle layer may be used. Moreover, you may use together the separator 14 and an inorganic oxide particle layer.
- the inorganic oxide particle layer functions as a lithium ion permeable insulating layer and improves the safety of the battery when a short circuit occurs. Further, when the inorganic oxide particle layer and the separator 14 are used in combination, the durability of the separator 14 is significantly improved.
- the inorganic oxide particle layer can be formed on at least one surface of the positive electrode active material layer 11b and the negative electrode active material layer 12b, but is preferably formed on the surface of the positive electrode active material layer 11b.
- the inorganic oxide particle layer contains inorganic oxide particles and a binder.
- Inorganic oxides include alumina, titania, silica, magnesia, calcia and the like.
- the binder the same binder as that used for forming the positive electrode active material layer can be used.
- the inorganic oxide particles and the binder may be used singly or in combination of two or more.
- the content of the inorganic oxide particles in the inorganic oxide particle layer is preferably 90 to 99.5% by mass, more preferably 95 to 99% by mass with respect to the total amount of the inorganic oxide particle layer, and the balance is the binder. .
- the inorganic oxide particle layer can be formed in the same manner as the positive electrode active material layer 11b.
- an inorganic oxide and a binder are dissolved or dispersed in an organic solvent to prepare a slurry, the slurry is applied to the surface of the positive electrode active material layer 11b or the negative electrode active material layer 12b, and the obtained coating film is dried.
- an inorganic oxide particle layer can be formed.
- the organic solvent the same organic solvent contained in the positive electrode mixture slurry can be used.
- the thickness of the inorganic oxide particle layer is preferably 1 to 10 ⁇ m.
- the separator 14 is used as the lithium ion permeable insulating layer, but a solid electrolyte layer may be used instead of the separator 14.
- a solid electrolyte layer When a solid electrolyte layer is used, it is usually unnecessary to use a non-aqueous electrolyte, but a non-aqueous electrolyte and a solid electrolyte may be used in combination in order to further improve lithium ion conductivity in the battery.
- the solid electrolyte layer contains a solid electrolyte.
- Solid electrolytes include inorganic solid electrolytes and organic solid electrolytes.
- Inorganic solid electrolytes include sulfide-based inorganic solid electrolytes, oxide-based inorganic solid electrolytes, inorganic solid electrolytes other than sulfide-based and oxide-based electrolytes, and the like.
- a solid electrolyte layer made of an inorganic solid electrolyte can be formed by vapor deposition, sputtering, laser ablation, gas deposition, aerosol deposition, or the like.
- Organic solid electrolytes include ion conductive polymers and polymer electrolytes.
- Ion conductive polymers include polyethers with low phase transition temperatures, amorphous vinylidene fluoride copolymers, blends of different polymers, and the like.
- the polymer electrolyte includes a matrix polymer and a lithium salt.
- the matrix polymer include polyethylene oxide, polypropylene oxide, a copolymer of ethylene oxide and propylene oxide, and polycarbonate.
- the lithium salt the same lithium salt as contained in the liquid non-aqueous electrolyte can be used.
- the negative electrode active material layer 23 made of an aggregate of an alloy-based active material of a plurality of columnar bodies 24 was formed on the surface of the negative electrode current collector 21 used instead of the negative electrode 12 by a vapor phase method.
- An example of a method for forming the negative electrode 20 will be described in detail.
- FIG. 2 is a top view schematically showing the configuration of the negative electrode current collector 21.
- FIG. 3 is a longitudinal sectional view schematically showing the configuration of the negative electrode 20 in which the columnar body 24 made of an alloy-based active material is supported on the surface of the negative electrode current collector 21.
- FIG. 4 is a longitudinal sectional view schematically showing the configuration of the columnar body 24 included in the negative electrode 20.
- FIG. 7 is a side view schematically showing the configuration of the electron beam evaporation apparatus 30.
- the negative electrode 20 includes a negative electrode current collector 21 and a negative electrode active material layer 23 including a plurality of columnar bodies 24.
- the negative electrode active material layer 23 is an aggregate of a plurality of columnar bodies 24.
- a plurality of convex portions 22 are provided on the surface of the negative electrode current collector 21.
- the convex portion 22 is a projection extending outward from the surface 21a of the negative electrode current collector 21 (hereinafter simply referred to as “surface 21a”).
- the plurality of convex portions 22 are staggered on the surface 21a as shown in FIG. 2, but are not limited thereto, and may be a close-packed arrangement, a lattice arrangement, or the like.
- the height of the convex portion 22 is preferably 3 to 10 ⁇ m as an average height.
- the height of the convex portion 22 is defined in the cross section in the thickness direction of the negative electrode current collector 21.
- the cross section of the negative electrode current collector 21 is a cross section including the most distal point in the direction in which the convex portion 22 extends.
- the length of the perpendicular drawn from the foremost point to the surface 21 a is the height of the convex portion 22.
- the average height of the convex portions 22 is obtained by observing the cross section of the negative electrode current collector 21 with a scanning electron microscope to measure the height of 100 convex portions 22 and obtaining the average value of the obtained measurement values. .
- the width of the convex portion 22 is preferably 1 to 50 ⁇ m.
- the width of the convex portion 22 is the maximum length of the convex portion 22 in the direction parallel to the surface 21 a in the cross section of the negative electrode current collector 21 described above.
- the width of the convex portion 22 is also obtained as an average value of measured values by measuring the width of 100 convex portions 22. Note that it is not necessary to form all the plurality of convex portions 22 at the same height and / or the same width.
- the shape of the convex portion 22 is a rhombus in the present embodiment, but is not limited thereto, and may be a circle, a polygon, an ellipse, a parallelogram, a trapezoid, or the like.
- the shape of the convex portion 22 is a shape in an orthographic projection from the upper side in the vertical direction of the convex portion 22 in a state where the surface 21a is made to coincide with the horizontal plane.
- the convex portion 22 has a flat top portion (tip portion in the growth direction of the convex portion 22), and this plane is substantially parallel to the surface 21a.
- This plane may have micron-size or nano-size irregularities.
- the number of the protrusions 22 and the distance between the axes of the protrusions 22 are selected according to the dimensions (height, width, etc.) of the protrusions 22 and the dimensions of the columnar body 24 formed on the surface of the protrusions 22.
- the number of convex portions 22 is preferably 10,000 / cm 2 to 10 million / cm 2 .
- the distance between the axes of the protrusions 22 is preferably 2 ⁇ m to 100 ⁇ m.
- the axis of the convex portion 22 is an imaginary line that passes through the center of the smallest perfect circle containing the circle and extends in a direction perpendicular to the surface 21a.
- the axis of the convex portion 22 is an imaginary line that passes through the intersection point of the major axis and the minor axis of the ellipse and extends in a direction perpendicular to the surface 21a.
- the axis of the convex portion 22 passes through the diagonal of the shape and extends perpendicularly to the surface 21a. It is.
- the convex part 22 may have at least one protrusion on its surface (top part and side face). Thereby, the joint strength between the convex portion 22 and the columnar body 24 is further increased, and the separation of the columnar body 24 from the convex portion 22 is further remarkably suppressed.
- the protrusion extends outward from the surface of the convex portion 22 and has a smaller dimension than the convex portion 22. Examples of the three-dimensional shape of the protrusion include a cylindrical shape, a prismatic shape, a conical shape, a pyramid shape, a needle shape, and a hook shape (a mountain range extending in one direction).
- the hook-shaped protrusion formed on the side surface of the convex portion 22 may extend in either the circumferential direction or the growth direction of the convex portion 22.
- the negative electrode current collector 21 can be manufactured using a technique for forming irregularities on a metal plate.
- a metal foil, a metal sheet, a metal film, etc. can be used for a metal plate.
- the material of the metal plate is a metal material such as stainless steel, titanium, nickel, copper, or copper alloy.
- a technique for forming irregularities on a metal plate includes a roller processing method.
- a metal plate is mechanically pressed using a roller having a plurality of concave portions formed on the surface (hereinafter referred to as “convex roller”).
- convex roller a roller having a plurality of concave portions formed on the surface
- the convex roller is a ceramic roller having a concave portion formed on the surface.
- the ceramic roller includes a core roller and a sprayed layer.
- As the core roller an iron roller, a stainless steel roller, or the like can be used.
- the thermal spray layer can be formed by uniformly spraying a ceramic material such as chromium oxide on the surface of the core roller.
- a recess is formed in the sprayed layer.
- a laser used for forming a ceramic material or the like can be used for forming the recess.
- Another type of convex roller includes a core roller, an undercoat layer and a sprayed layer.
- the core roller is the same as the core roller of the ceramic roller.
- the base layer is a resin layer formed on the surface of the core roller.
- a recess is formed on the surface of the underlayer. After forming a recess on one surface of the resin sheet, the base layer is wound around the core roller so that the surface of the resin sheet on which the recess is not formed and the surface of the core roller are in contact with each other It is formed by adhering.
- thermoplastic resins such as thermosetting resins such as unsaturated polyesters, thermosetting polyimides, and epoxy resins, polyamides, polyether ketones, polyether ether ketones, and fluororesins. Can be mentioned.
- the sprayed layer is formed by spraying a ceramic material such as chromium oxide along the unevenness of the surface of the underlayer. Therefore, it is preferable that the concave portion formed in the underlayer is formed to be larger than the design dimension of the convex portion 22 by the layer thickness of the sprayed layer.
- the convex roller includes a core roller and a cemented carbide layer.
- the core roller is the same as the core roller of the ceramic roller.
- the cemented carbide layer is formed on the surface of the core roller and includes a cemented carbide such as tungsten carbide.
- the cemented carbide layer can be formed by shrink fitting and cold fitting. Shrink fitting is to warm and expand a cylindrical cemented carbide and fit it to a core roller. The cold fitting is to cool the core roller and contract it and insert it into a cemented carbide cylinder.
- a recess is formed on the surface of the cemented carbide layer by, for example, laser processing.
- convex roller is one in which a concave portion is formed on the surface of a hard iron-based roller.
- the hard iron-based roller is a roller having at least a surface layer portion made of high-speed steel, forged steel, or the like.
- High-speed steel is an iron-based material obtained by adding a metal such as molybdenum, tungsten, or vanadium to iron and heat-treating it to increase the hardness.
- Forged steel is an iron-based material manufactured by heating a steel ingot or steel slab, forging or rolling and forging, forging and further heat-treating.
- a steel ingot is manufactured by casting molten steel into a mold. The billet is manufactured from a steel ingot. Forging is performed by a press and a hammer. The recess is formed by laser processing.
- the negative electrode active material layer 23 includes a plurality of columnar bodies 24 as shown in FIG.
- the columnar body 24 extends from the surface of the convex portion 22 to the outside of the negative electrode current collector 21.
- the columnar body 24 extends in a direction perpendicular to the surface 21a or a direction inclined with respect to the perpendicular direction. Further, a gap exists between a pair of columnar bodies 24 adjacent to each other. This void relaxes the stress due to the volume change of the alloy-based active material. As a result, separation of the columnar body 24 from the convex portion 22, deformation of the negative electrode current collector 21 and the negative electrode 20, and the like are suppressed.
- the columnar body 24 is preferably a laminate of eight columnar chunks 24a, 24b, 24c, 24d, 24e, 24f, 24g, and 24h. More specifically, the columnar body 24 is formed as follows. First, the columnar mass 24a is formed so as to cover the top of the convex portion 22 and a part of the side surface following the top. Next, the columnar chunk 24b is formed so as to cover the remaining side surface of the convex portion 22 and a part of the top surface of the columnar chunk 24a. That is, in FIG. 4, the columnar block 24 a is formed at one end including the top of the convex portion 22. On the other hand, the columnar chunk 24 b partially overlaps the columnar chunk 24 a, but the portion not overlapping the columnar chunk 24 a is formed at the other end of the convex portion 22.
- the columnar chunk 24c is formed so as to cover the rest of the top surface of the columnar chunk 24a and a part of the top surface of the columnar chunk 24b. That is, the columnar chunk 24c is formed so as to mainly contact the columnar chunk 24a. Further, the columnar chunk 24d is formed so as to mainly contact the columnar chunk 24b.
- the columnar bodies 24 are formed by alternately stacking the columnar chunks 24e, 24f, 24g, and 24h. Note that the number of stacked columnar chunks is not limited to eight, and an arbitrary number of two or more columnar chunks can be stacked.
- the columnar body 24 can be formed by an electron beam vacuum deposition apparatus 30 (hereinafter, simply referred to as “deposition apparatus 30”) shown in FIG. In FIG. 7, each member inside the vapor deposition apparatus 30 is also shown by a solid line.
- the vapor deposition apparatus 30 includes a chamber 31, a first pipe 32, a fixing base 33, a nozzle 34, a target 35, an electron beam generator (not shown), a power source 36, and a second pipe (not shown).
- the chamber 31 is a pressure-resistant container, and the first pipe 32, the fixing base 33, the nozzle 34, the target 35, and the electron beam generator are accommodated in the internal space.
- the first pipe 32 has one end connected to the nozzle 34 and the other end extending outward from the chamber 31 and connected to a source gas cylinder or source gas manufacturing apparatus (not shown) via a mass flow controller (not shown).
- the first pipe 32 supplies the raw material gas to the nozzle 34.
- Source gas includes oxygen, nitrogen, and the like.
- the fixing base 33 is a plate-like member that is rotatably supported, and the negative electrode current collector 21 can be fixed to one surface in the thickness direction.
- the fixing base 33 rotates between a position indicated by a solid line and a position indicated by a one-dot chain line in FIG.
- the angle formed by the fixed base 33 and the horizontal line is ⁇ °.
- the angle formed by the fixed base 33 and the horizontal line is (180 ⁇ ) °.
- the angle ⁇ ° can be appropriately selected according to the size and shape of the columnar body 24, the number of stacked columnar blocks, and the like.
- the nozzle 34 is provided between the fixed base 33 and the target 35, and one end of the first pipe 32 is connected to discharge the raw material gas.
- the target 35 contains a raw material for the alloy-based active material.
- the electron beam generator irradiates and heats the raw material of the alloy active material accommodated in the target 35 with an electron beam. Thereby, the vapor
- the vapor rises toward the negative electrode current collector 21 and is mixed with the gas discharged from the nozzle 34.
- the power source 36 is provided outside the chamber 31 and applies a voltage to the electron beam generator.
- the second pipe introduces a gas that becomes the atmosphere in the chamber 31.
- An electron beam type vacuum deposition apparatus having the same configuration as the deposition apparatus 30 is commercially available from ULVAC, Inc., for example.
- the negative electrode current collector 21 is fixed to the fixing base 33, and oxygen gas is introduced into the chamber 31.
- the target 35 is irradiated with an electron beam to generate vapor of an alloy-based active material raw material.
- the alloy-based active material raw material is silicon.
- the vapor rises upward in the vertical direction and is mixed with the raw material gas around the nozzle 34.
- the mixture of the vapor and the source gas further rises and is supplied to the surface of the negative electrode current collector 21 fixed to the fixed base 33.
- a layer containing silicon and oxygen is formed on the surface of the projection 22 (not shown).
- the columnar block 25a shown in FIG. 4 is formed on the surface of the convex portion by arranging the fixing base 33 at the position of the solid line.
- the fixing base 33 is rotated to the position indicated by the alternate long and short dash line to form the columnar block 25b shown in FIG.
- the negative electrode active material layer 23 is obtained at the same time on the surface of the protrusions 22.
- the columnar body 24 made only of the raw material of the alloy-based active material is formed.
- the negative electrode active material layer 12b can be formed by using the negative electrode current collector 12a instead of the negative electrode current collector 21 and fixing the fixing base 33 in the horizontal direction without rotating.
- FIG. 5 schematically shows a configuration of a negative electrode 25 provided with a lithium ion conductive resin layer 28 (hereinafter referred to as “resin layer 28”) included in the nonaqueous electrolyte secondary battery according to the second embodiment of the present invention. It is a longitudinal cross-sectional view shown in FIG.
- the negative electrode current collector 21 side is the lowermost part and the resin layer 28 side is the uppermost part on the paper surface of FIG.
- the negative electrode 25 is similar to the negative electrode 23 of the first embodiment, and the same constituent members are denoted by the same reference numerals as those of the negative electrode 23 and the description thereof is omitted.
- the negative electrode 25 includes a negative electrode current collector 21, a negative electrode active material layer 26, and a resin layer 28 formed on the surface of the negative electrode active material layer 26.
- the negative electrode 25 has two major characteristics, and the other configuration is the same as that of the negative electrode 23.
- the negative electrode active material layer 26 includes a plurality of spindle-shaped columnar bodies 27 containing an alloy-based active material. On the surface of the negative electrode active material layer 26, portions where the columnar bodies 27 are present and portions where the columnar bodies 27 are not present alternately appear. This is an apparent unevenness. In addition, a gap exists between a pair of adjacent columnar bodies 27. The unevenness and voids exhibit a remarkable anchor effect, and further improve the adhesion between the negative electrode active material layer 26 and the resin layer 28.
- the distance between the axes between a pair of adjacent columnar bodies 27 is preferably 10 to 100 ⁇ m, more preferably 60 to 100 ⁇ m. Accordingly, the resin solution smoothly flows into the gaps between the columnar bodies 27, and the resin layer 28 can be easily formed between the columnar bodies 27.
- the axis of the columnar body 27 is an imaginary line that passes through the center of the contact surface with the surface of the convex portion 22 of the columnar body 27 and extends in a direction perpendicular to the surface 21a.
- the center of the contact surface is the center of the smallest circle that can contain the contact surface.
- the spindle-shaped columnar body 27 can be manufactured by adjusting the rotation angle of the turntable 33 and the number of stacked columnar chunks in the electron beam evaporation apparatus 30 shown in FIG. 7.
- the second feature is that the resin layer 28 enters not only the surface of the negative electrode active material layer 26 but also a gap between a pair of columnar bodies 27 adjacent to each other.
- the resin layer 28 exists only in the upper part between the columnar bodies 27 and does not reach the surface 21 a of the negative electrode current collector 21. Thereby, the anchor effect of the space
- the resin layer 28 has the same configuration as the resin layer 13.
- the resin layer 28 containing the non-aqueous electrolyte additive is formed almost all over the top surface of the columnar body 27.
- the total surface area of the columnar bodies 27 is larger than the surface area of the thin-film negative electrode active material layer made of an alloy-based active material. Therefore, the area of the resin layer 28 in contact with the columnar body 27 is also increased, and the effect of improving battery performance such as cycle characteristics becomes more remarkable.
- FIG. 6 is a longitudinal sectional view schematically showing the configuration of the negative electrode 29 provided in the nonaqueous electrolyte secondary battery according to the third embodiment of the present invention.
- the negative electrode current collector 21 side is the lowermost part and the lithium ion conductive resin layer 28a (hereinafter referred to as “resin layer 28a”) side is the uppermost part on the paper surface of FIG.
- the negative electrode 29 is similar to the negative electrode 25, and the same components as those of the negative electrode 25 are denoted by the same reference numerals as those of the negative electrode 25, and description thereof is omitted.
- the resin layer 28 a enters the gap between a pair of adjacent columnar bodies 27 and reaches the surface 21 a of the negative electrode current collector 21. That is, the gap between the columnar bodies 27 is filled with the resin layer 28a.
- the resin layer 28 a has the same configuration as the resin layers 13 and 28. Thereby, the same effect as the negative electrode 25 is acquired. Furthermore, since the gap between the columnar bodies 27 is filled with the resin layer 28a, the adhesion between the negative electrode active material layer 26 and the resin layer 28a is further enhanced.
- the resin layer 28a since the resin layer 28a has flexibility, it can follow the volume change of the alloy-based active material. Therefore, the resin layer 28a is effective in suppressing the occurrence of inconvenience associated with the volume change of the alloy-based active material.
- the inconvenience includes peeling of the columnar body 27 from the convex portion 22, deformation of the negative electrode current collector 21, generation of a new surface, deposition of lithium on the negative electrode current collector surface 21a, and the like.
- the suppression of the contact between the new surface and the non-aqueous electrolyte and the relaxation or absorption of the volume change of the alloy-based active material can be achieved at a high level. Further, similarly to the negative electrode 25 shown in FIG. 5, the contact area between the resin layer 28a containing the non-aqueous electrolyte additive and the columnar body 27 is further increased, so that the effect of the non-aqueous electrolyte additive is more remarkably exhibited.
- the resin layer 28a is formed so as to fill the gaps between the columnar bodies 27, but the present invention is not limited to this.
- the resin layer may be formed only on the surface of the columnar bodies 27.
- the resin layer is preferably configured such that a gap exists between the columnar bodies 27 by reducing the thickness of the resin layer.
- the nonaqueous electrolyte secondary battery 1 including the stacked electrode group has been described as an example.
- the present invention is not limited thereto, and the nonaqueous electrolyte secondary battery of the present invention is a wound electrode group or A flat electrode group may be included.
- the wound electrode group is an electrode group obtained by winding a lithium ion permeable insulating layer between a positive electrode and a negative electrode.
- the flat electrode group is, for example, an electrode group obtained by forming a wound electrode group into a flat shape.
- the flat electrode group can also be produced by interposing a lithium ion permeable insulating layer between the positive electrode and the negative electrode and winding them around a plate.
- the shape of the nonaqueous electrolyte secondary battery of the present invention includes a cylindrical shape, a square shape, a flat shape, a coin shape, a laminated film pack shape, and the like.
- This composite hydroxide was heated in the atmosphere at 900 ° C. for 10 hours to obtain a composite oxide having a composition represented by Ni 0.85 Co 0.15 O 2 .
- lithium hydroxide monohydrate is added so that the sum of the number of atoms of Ni and Co is equal to the number of atoms of Li, and heated at 800 ° C. in the atmosphere for 10 hours, thereby obtaining LiNi 0.85 Co 0.15.
- a positive electrode active material which is a lithium nickel-containing composite oxide having a composition represented by O 2 and having a volume average particle size of secondary particles of 10 ⁇ m was obtained.
- FIG. 8 is a side view schematically showing the configuration of an electron beam vacuum deposition apparatus 40 (hereinafter simply referred to as “deposition apparatus 40”).
- the vapor deposition apparatus 40 includes a chamber 41, a conveying means 42, a gas supply means 48, a plasma generating means 49, silicon targets 50a and 50b, a shielding plate 51, and an electron beam generator (not shown).
- the chamber 41 is a pressure-resistant container, and accommodates the transfer means 42, the gas supply means 48, the plasma generation means 49, the silicon targets 50a and 50b, the shielding plate 51, and the electron beam generator.
- the conveying means 42 includes an unwinding roller 43, a can 44, a take-up roller 45, and conveying rollers 46 and 47.
- the unwinding roller 43, the can 44, and the conveying rollers 46 and 47 are provided so as to be rotatable around the axis.
- a long negative electrode current collector 12 a is wound around the unwinding roller 43.
- the can 44 includes a cooling means (not shown) therein. When the surface of the can 44 is conveyed, the negative electrode current collector 12a is cooled, and an alloy-based active material is deposited on the surface of the negative electrode current collector 12a, thereby forming a thin-film negative electrode active material layer containing the alloy-based active material. .
- the take-up roller 45 is provided so as to be rotatable around an axis by a driving means (not shown).
- One end of the negative electrode current collector 12 a is fixed to the take-up roller 45, and when the take-up roller 45 rotates, the negative electrode current collector 12 a passes from the take-out roller 43 through the transport roller 46, the can 44, and the transport roller 47. Then transported. Then, the negative electrode 12 in which the thin film negative electrode active material layer is formed on the surface of the negative electrode current collector 12 a is wound around the winding roller 45.
- the gas supply means 48 supplies a source gas such as oxygen or nitrogen into the chamber 41.
- the plasma generating means 49 converts the raw material gas supplied from the gas supply means 48 into plasma.
- the silicon targets 50a and 50b are used when forming a thin film negative electrode active material layer containing silicon.
- the shielding plate 51 is provided movably in the horizontal direction between the can 44 and the silicon targets 50a and 50b. The position of the shielding plate 51 in the horizontal direction is adjusted according to the formation state of the thin film negative electrode active material layer.
- the electron beam generator irradiates the silicon targets 50a and 50b with an electron beam to generate silicon vapor.
- a thin-film negative electrode active material layer (silicon thin film, solid film) having a thickness of 6 ⁇ m was formed on the surface of the negative electrode current collector 12a under the following conditions, and the negative electrode 12 was produced.
- Pressure in chamber 41 8.0 ⁇ 10 ⁇ 5 Torr
- Negative electrode current collector 12a electrolytic copper foil having a length of 50 m, a width of 10 cm, and a thickness of 35 ⁇ m (manufactured by Furukawa Circuit Foil Co., Ltd.) Winding speed of the negative electrode current collector 12a: 2 cm / min
- Target 50a, 50b Silicon single crystal of purity 99.9999% (manufactured by Shin-Etsu Chemical Co., Ltd.)
- the obtained negative electrode 12 was cut into 35 mm ⁇ 35 mm to prepare a negative electrode plate.
- Lithium metal was vapor-deposited on the thin film negative electrode active material layer of this negative electrode plate, and lithium corresponding to the irreversible capacity stored at the time of the first charge / discharge was compensated.
- Vapor deposition of lithium metal was performed using a resistance heating vapor deposition apparatus (manufactured by ULVAC, Inc.). A tantalum boat in a resistance heating vapor deposition apparatus is loaded with lithium metal, a negative electrode plate is fixed so that the thin film negative electrode active material layer faces the tantalum boat, and a 50 A current is supplied to the tantalum boat in an argon atmosphere. Was evaporated for 10 minutes.
- the negative electrode plate on which lithium metal was deposited was immersed in a resin solution (80 ° C., viscosity 70 cps) for 1 minute. Thereafter, the negative electrode plate was taken out of the resin solution, placed on a glass plate, and subjected to hot air drying at 80 ° C. for 10 minutes.
- a resin layer having a thickness of about 2 ⁇ m was formed on the surface of the negative electrode plate.
- the adhesion amount of the resin layer was 0.34 mg / cm ⁇ 2 >. As described above, this resin layer swells upon contact with the non-aqueous electrolyte and becomes a lithium ion conductive resin layer.
- This electrode group was inserted into a laminated film outer case (size: 2 cm ⁇ 2 cm). Next, 0.5 ml of a liquid nonaqueous electrolyte was injected into the outer case. As a result, the resin layer on the surface of the negative electrode plate was impregnated with the liquid nonaqueous electrolyte.
- a non-aqueous electrolyte in which LiPF 6 was dissolved at a concentration of 1.0 mol / L in a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1: 1 was used.
- the other ends of the aluminum lead and nickel lead were led out from the openings at both ends of the outer case, respectively. Furthermore, the opening of the outer case was welded under vacuum decompression inside the outer case to produce a nonaqueous electrolyte secondary battery.
- Example 2 A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the negative electrode produced as follows was used.
- a ceramic layer having a thickness of 100 ⁇ m was formed by spraying chromium oxide on the surface of an iron roller having a diameter of 50 mm.
- a circular concave portion having a diameter of 12 ⁇ m and a depth of 8 ⁇ m was formed on the surface of the ceramic layer by laser processing to produce a convex roller.
- the recesses were arranged in a staggered manner, and the distance between the axes of a pair of recesses adjacent to each other was 20 ⁇ m.
- the center of the bottom of the concave portion is substantially planar, and the boundary between the bottom edge and the side surface is rounded.
- An alloy copper foil containing 0.03% by mass of zirconium (trade name: HCL-02Z, thickness 20 ⁇ m, manufactured by Hitachi Cable Ltd.) is heated at 600 ° C. for 30 minutes in an argon gas atmosphere and annealed. It was.
- This alloy copper foil was press-molded by passing it at a linear pressure of 2 t / cm through a press-contact portion formed by press-contacting the convex roller obtained above and an iron roller having a smooth surface with a diameter of 50 mm.
- a negative electrode current collector having a plurality of convex portions formed on one surface in the thickness direction was produced.
- a thin film negative electrode active material layer including a plurality of columnar bodies was formed.
- Negative electrode active material raw material silicon, purity 99.9999%, manufactured by Kojundo Chemical Laboratory Co., Ltd.
- Oxygen released from nozzle purity 99.7%, manufactured by Nippon Oxygen Co., Ltd.
- a cross section in the thickness direction of the obtained negative electrode was observed with a scanning electron microscope, and the heights of 10 columnar bodies (the length from the convex portion vertex to the columnar vertex) were measured, and the average value was obtained.
- This average value is the thickness of the thin film negative electrode active material layer, and was 22 ⁇ m.
- the composition of the columnar body was SiO 0.5 .
- Lithium metal was vapor-deposited on the surface of the thin-film negative electrode active material layer in the same manner as in Example 1, and lithium corresponding to the irreversible capacity stored in the thin-film negative electrode active material layer at the first charge / discharge was compensated.
- Example 1 A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the lithium ion conductive resin layer was not formed.
- Test Example 1 The nonaqueous electrolyte secondary batteries of Examples 1 and 2 and Comparative Example 1 were subjected to the following evaluation test.
- Constant current charging Current 0.7C, end-of-charge voltage 4.2V Constant voltage charging: Charging end current 0.05C, voltage 4.2V Constant current discharge: Current 0.2C, discharge end voltage 2.5V
- the batteries of Examples 1 and 2 maintain the cycle characteristics at a high level even after 100 cycles, and the swelling of the batteries is suppressed. This is because even if a lithium ion conductive resin layer is formed on the surface of the thin film negative electrode active material layer, cracks occur in the alloy-based active material and a new surface is generated, the lithium ion conductive resin layer becomes a new surface. It is presumed that this is for suppressing contact with the nonaqueous electrolyte.
- Example 2 when the thin-film negative electrode active material layer is not a solid film but a plurality of columnar bodies, the cycle characteristics are maintained at a higher level, and the battery swells. It can be seen that it is further suppressed. This is presumed to be because the adhesion between the thin film negative electrode active material layer and the lithium ion conductive resin layer is further improved since the thin film negative electrode active material layer includes a plurality of columnar bodies.
- the non-aqueous electrolyte secondary battery of the present invention can be used in the same applications as conventional non-aqueous electrolyte secondary batteries.
- Electronic devices include personal computers, mobile phones, mobile devices, portable information terminals, portable game devices, and the like.
- Electrical equipment includes vacuum cleaners and video cameras.
- Machine tools include electric tools and robots.
- Transportation equipment includes electric vehicles, hybrid electric vehicles, plug-in HEVs, fuel cell vehicles, and the like. Examples of power storage devices include uninterruptible power supplies.
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Abstract
Description
合金系活物質は、リチウムの吸蔵及び放出に伴って膨張及び収縮し、比較的大きな応力を発生させる。このため、充放電回数が増加すると、合金系活物質からなる負極活物質層の表面及びその内部にクラックが発生する。クラックが発生した場合、もともと非水電解質に直接触れていなかった面(以下「新生面」とする)が現れる。
[第1実施形態]
図1は、本発明の第1実施形態である非水電解質二次電池1の構成を模式的に示す縦断面図である。非水電解質二次電池1は、正極11と負極12とを両者の間にセパレータ14を介在させて積層した積層型電極群と、正極11に接続された正極リード15と、負極12に接続された負極リード16と、外装ケース18の開口18a、18bを封口するガスケット17と、前記積層型電極群及び非水電解質(不図示)を収容する外装ケース18と、を備えた扁平型電池である。
珪素化合物としては、式SiOa(0.05<a<1.95)で表される珪素酸化物、式SiCb(0<b<1)で表される珪素炭化物,式SiNc(0<c<4/3)で表される珪素窒化物,珪素と異種元素(A)との合金等が挙げられる。異種元素(A)としては、Fe,Co,Sb,Bi,Pb,Ni,Cu,Zn,Ge,In,Sn,又はTi等が挙げられる。また、部分置換体は、珪素及び珪素化合物に含まれる珪素原子の一部が、異種元素(B)で置換された化合物である。異種元素(B)の具体例としては、B,Mg,Ni,Ti,Mo,Co,Ca,Cr,Cu,Fe,Mn,Nb,Ta,V,W,Zn,C,N,又はSn等が挙げられる。これらの中では、珪素及び珪素化合物が好ましく、珪素酸化物が更に好ましい。
樹脂層13は、負極活物質の膨張及び収縮に伴って生じる新生面と非水電解質との接触を抑制する。また、樹脂層13は、非水電解質用添加剤を含有する。樹脂層13に含有される非水電解質用添加剤は、非水電解質に徐々に放出される。これにより、充放電サイクルを繰り返すことにより非水電解質中の非水電解質用添加剤の濃度が低減しても、非水電解質中に樹脂層13から非水電解質用添加剤が供給される。それにより、合金系活物質を含有する負極12を備えた非水電解質二次電池1において、寿命特性を向上させることができる。
リチウムイオン伝導性を有する樹脂成分は、リチウムイオンを伝導させることが可能な樹脂成分であれば特に限定されない。リチウムイオン伝導性を有する樹脂成分の具体例としては、非水電解質との接触により膨潤してリチウムイオン伝導性を示すようになる樹脂成分、支持塩を配合することによりリチウムイオン伝導性が付与された樹脂成分等が挙げられる。支持塩を配合する樹脂成分は、リチウムイオン伝導性を有する樹脂成分でもよく、有しない樹脂成分でも良い。
正極集電体11aとしては、導電性基板が用いられる。導電性基板の材質の具体例としては、例えば、ステンレス鋼、チタン、アルミニウム、アルミニウム合金等の金属材料、導電性樹脂等が挙げられる。導電性基板としては、平板や多孔板等が用いられる。多孔板の具体例としては、メッシュ体、ネット体、パンチングシート、ラス体、多孔質体、発泡体、不織布等が挙げられる。平板としては、箔、シート、フィルム等が挙げられる。導電性基板の厚さは特に限定されないが、例えば、通常1~500μmであり、好ましくは1~50μmである。
正極活物質は、リチウムイオンを吸蔵及び放出できる各種正極活物質を用いることができる。その具体例としては、リチウム含有複合酸化物、オリビン型リン酸リチウムが挙げられる。
遷移金属元素としては、Sc、Y、Mn、Fe、Co、Ni、Cu、Cr等が挙げられる。遷移金属元素の中では、Mn、Co、Ni等が好ましい。
また、異種元素としては、Na、Mg、Zn、Al、Pb、Sb、B等が挙げられる。異種元素の中では、Mg、Al等が好ましい。遷移金属元素及び異種元素は、それぞれ単独で用いても、2種以上を組み合わせて用いてもよい。
結着剤は単独で用いても、2種以上を組み合わせて用いてもよい。
セパレータ14は、正極11と負極12との間に介在するように配置されるリチウムイオン透過性の絶縁層である。セパレータ14は、負極12側ではその表面の少なくとも一部が樹脂層13の表面と接触していてもよい。
液状非水電解質は、溶質(支持塩)と非水溶媒とを含み、さらに必要に応じて各種添加剤を含む。
溶質は1種を単独で又は2種以上を組み合わせて使用できる。非水溶媒1リットルにおける溶質の濃度は、好ましくは0.5~2モルである。
負極20は、負極集電体21と、複数の柱状体24を含む負極活物質層23とからなる。負極活物質層23は、複数の柱状体24の集合体である。
凸部22は、負極集電体21の表面21a(以下単に「表面21a」とする)から、外方に向けて延びる突起である。本実施形態では、複数の凸部22は、図2に示すように、表面21aに千鳥配置されているが、それに限定されず、最密充填配置、格子配置等でもよい。
チャンバ31は耐圧性容器であり、その内部空間に第1配管32、固定台33、ノズル34、ターゲット35及び電子ビーム発生装置を収容する。
図5は、本発明の第2実施形態である非水電解質二次電池に備わる、リチウムイオン伝導性樹脂層28(以下「樹脂層28」とする)が形成された負極25の構成を模式的に示す縦断面図である。説明の都合上、図5の紙面において、負極集電体21側を最下部、樹脂層28側を最上部とする。負極25は第1実施形態の負極23に類似し、同じ構成部材には負極23と同一の参照符号を付して、説明を省略する。負極25は、負極集電体21、負極活物質層26、及び負極活物質層26の表面に形成される樹脂層28を含む。負極25は、2つの大きな特徴を有し、それ以外の構成は負極23と同じである。
図6は、本発明の第3実施形態である非水電解質二次電池に備わる、負極29の構成を模式的に示す縦断面図である。説明の都合上、図6の紙面において、負極集電体21側を最下部、リチウムイオン伝導性樹脂層28a(以下「樹脂層28a」とする)側を最上部とする。負極29は負極25に類似し、負極25と同じ構成部材には負極25と同一の参照符号を付して、説明を省略する。
(実施例1)
(1)正極活物質の作製
NiSO4水溶液に、Ni:Co=8.5:1.5(モル比)になるように硫酸コバルトを加えて金属イオン濃度2mol/Lの水溶液を調製した。この水溶液に撹拌下、2mol/Lの水酸化ナトリウム溶液を徐々に滴下して中和することにより、Ni0.85Co0.15(OH)2で示される組成を有する二元系の沈殿物を生成させた。この沈殿物をろ過により分離し、水洗し、80℃で乾燥し、複合水酸化物を得た。
前記で得られた正極活物質の粉末93g、アセチレンブラック(導電剤)3g、ポリフッ化ビニリデン粉末(結着剤)4g及びN-メチル-2-ピロリドン50mlを充分に混合して正極合剤スラリーを調製した。この正極合剤スラリーを厚さ15μmのアルミニウム箔(正極集電体)の片面に塗布し、得られた塗膜を乾燥及び圧延し、厚さ120μmの正極活物質層を形成した。
図8は、電子ビーム式真空蒸着装置40(以下単に「蒸着装置40」とする)の構成を模式的に示す側面図である。蒸着装置40は、チャンバ41、搬送手段42、ガス供給手段48、プラズマ化手段49、シリコンターゲット50a、50b、遮蔽板51及び不図示の電子ビーム発生装置を含む。
チャンバ41内の圧力:8.0×10-5Torr
負極集電体12a:長さ50m、幅10cm、厚さ35μmの電解銅箔(古河サーキットフォイル(株)製)
負極集電体12aの巻き取り速度:2cm/分
ターゲット50a、50b:純度99.9999%のシリコン単結晶(信越化学工業(株)製)
電子ビームの加速電圧:-8kV
電子ビームのエミッション:300mA
VDFとHFPとの共重合体(VDF:HFP=88質量%:12質量%)であるフッ素樹脂をジメチルカーボネートに溶解し、得られた溶液にビニレンカーボネート(以下「VC」とする)を添加し、80℃に加熱して樹脂溶液を調製した。この樹脂溶液を用いて形成される樹脂層は、後工程で非水電解質と接触することにより、リチウムイオン伝導性樹脂層になる。樹脂溶液中のフッ素樹脂及びVCの濃度は、リチウムイオン伝導性樹脂層におけるフッ素樹脂及びVCの含有割合がそれぞれ5質量%及び2質量%になるように調整した。
前記で得られた正極板及び負極板を、それぞれ、1.5cm×1.5cmの大きさに裁断した。その後、正極板と負極板とを、両者の間に厚さ20μmのポリエチレン微多孔膜(セパレータ、商品名:ハイポア、旭化成(株)製)を介在させて積層し、電極群を作製した。アルミニウムリードの一端を正極集電体に溶接し、ニッケルリードの一端を負極集電体に溶接した。
次のようにして作製した負極を使用する以外は、実施例1と同様にして非水電解質二次電池を作製した。
径50mmの鉄製ローラ表面に酸化クロムを溶射して厚さ100μmのセラミック層を形成した。このセラミック層の表面に、レーザ加工により、直径12μm、深さ8μmの円形の凹部を形成し、凸部用ローラを作製した。凹部は千鳥配置とし、互いに隣り合う一対の凹部の軸線間距離を20μmとした。この凹部の底部は中央がほぼ平面状であり、底部周縁部と側面との境界部分は丸みを帯びていた。
ノズルから放出される酸素:純度99.7%、日本酸素(株)製、
ノズルからの酸素放出流量:80sccm
角度α:60°
電子ビームの加速電圧:-8kV
エミッション:500mA
蒸着時間:3分
薄膜状負極活物質層の表面に実施例1と同様にしてリチウム金属を蒸着し、初回充放電時に薄膜状負極活物質層に蓄えられる不可逆容量に相当するリチウムを補填した。
リチウムイオン伝導性樹脂層を形成しない以外は、実施例1と同様にして非水電解質二次電池を作製した。
実施例1~2及び比較例1の各非水電解質二次電池を、次の評価試験に供した。
実施例1~2及び比較例1の各電池について、20℃環境下で、下記の条件で定電流充電、定電圧充電及び定電流放電を行い、1サイクル目の充放電を実施した。この時の放電容量を、初回放電容量とした。1Cとは、全電池容量を1時間で使い切ることができる電流値である。
定電圧充電:充電終止電流0.05C、電圧4.2V
定電流放電:電流0.2C、放電終止電圧2.5V
そして、初回放電容量に対する100サイクル後放電容量の百分率を容量維持率(%)として求めた。結果を表1に示す。
100サイクル後の電極群の厚さT及びサイクル特性の評価前の電極群の厚さT0を測定し、下記式から電池の膨れ(%)を求めた。結果を表1に示す。
電池の膨れ(%)=[(T-T0)/T0]×100
Claims (17)
- 負極集電体と、前記負極集電体表面に支持されてリチウムイオンを吸蔵及び放出する合金系活物質を含む負極活物質層と、を備え、
前記負極活物質層の表面に、リチウムイオン伝導性を有する樹脂成分と非水電解質用添加剤とを含有する樹脂層をさらに備える、非水電解質二次電池用負極。 - 前記非水電解質用添加剤の含有割合が前記樹脂層全量の0.1~50質量%である請求項1に記載の非水電解質二次電池用負極。
- 前記非水電解質用添加剤がカーボネート化合物を含有する請求項1又は2に記載の非水電解質二次電池用負極。
- 前記カーボネート化合物が、ビニレンカーボネート、4-メチルビニレンカーボネート、4,5-ジメチルビニレンカーボネート、4-エチルビニレンカーボネート、4,5-ジエチルビニレンカーボネート、4-プロピルビニレンカーボネート、4,5-ジプロピルビニレンカーボネート、4-フェニルビニレンカーボネート、4,5-ジフェニルビニレンカーボネート、ビニルエチレンカーボネート、フルオロエチレンカーボネート、ジビニルエチレンカーボネート及びトリフルオロプロピレンカーボネートよりなる群から選ばれる少なくとも1種である請求項3に記載の非水電解質二次電池用負極。
- 前記非水電解質用添加剤が含硫黄環状化合物を含有する請求項1又は2に記載の非水電解質二次電池用負極。
- 前記含硫黄環状化合物が、その分子中に基=SO2及び前記基=SO2に含有される酸素原子以外の酸素原子を含有する環状化合物である請求項5に記載の非水電解質二次電池用負極。
- 前記含硫黄環状化合物が、エチレンサルファイト及びスルトン類から選ばれる少なくとも1種である請求項5に記載の非水電解質二次電池用負極。
- 前記含硫黄環状化合物が、1,3-プロパンスルトン、1,4-ブタンスルトン、1,3-プロペンスルトン及び1,4-ブテンスルトンよりなる群から選ばれる少なくとも1種である請求項5に記載の非水電解質二次電池用負極。
- 前記非水電解質用添加剤が、酸無水物を含む請求項1又は2に記載の非水電解質二次電池用負極。
- 前記酸無水物が、無水コハク酸及び無水マレイン酸から選ばれる少なくとも1種である請求項9に記載の非水電解質二次電池用負極。
- 前記非水電解質用添加剤が、ニトリル化合物を含む請求項1又は2に記載の非水電解質二次電池用負極。
- 前記ニトリル化合物がスクシノニトリルである請求項11に記載の非水電解質二次電池用負極。
- 前記リチウムイオン伝導性を有する樹脂成分が、フッ素樹脂、ポリアクリロニトリル、ポリエチレンオキシド及びポリプロピレンオキシドから選ばれる少なくとも1種を含有する請求項1~12のいずれか1項に記載の非水電解質二次電池用負極。
- 前記樹脂層の厚さが0.1~10μmである請求項1~13のいずれか1項に記載の非水電解質二次電池用負極。
- 前記負極活物質層が、前記負極集電体表面に支持された複数の柱状体の合金系活物質の集合体からなる請求項1~14のいずれか1項に記載の非水電解質二次電池用負極。
- 前記合金系活物質が、珪素系活物質及び錫系活物質から選ばれる少なくとも1種を含有する請求項1~15のいずれか1項に記載の非水電解質二次電池用負極。
- リチウムイオンを吸蔵及び放出する正極と、リチウムイオンを吸蔵及び放出する負極と、前記正極と前記負極との間に介在するように配置されたリチウムイオン透過性絶縁層と、リチウムイオン伝導性非水電解質と、を備え
前記負極が、請求項1~16のいずれか1項に記載の負極である非水電解質二次電池。
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CN101960654A (zh) | 2011-01-26 |
US20110008673A1 (en) | 2011-01-13 |
CN101960654B (zh) | 2013-03-06 |
US8247096B2 (en) | 2012-08-21 |
KR20100120238A (ko) | 2010-11-12 |
JPWO2010092815A1 (ja) | 2012-08-16 |
EP2246923A1 (en) | 2010-11-03 |
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