WO2011052126A1 - 電極、二次電池、および二次電池の製造方法 - Google Patents
電極、二次電池、および二次電池の製造方法 Download PDFInfo
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- WO2011052126A1 WO2011052126A1 PCT/JP2010/005320 JP2010005320W WO2011052126A1 WO 2011052126 A1 WO2011052126 A1 WO 2011052126A1 JP 2010005320 W JP2010005320 W JP 2010005320W WO 2011052126 A1 WO2011052126 A1 WO 2011052126A1
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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
- H01M10/058—Construction or manufacture
- H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
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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
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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
- H01M4/139—Processes of manufacture
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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
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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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
- H01M4/621—Binders
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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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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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
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49002—Electrical device making
- Y10T29/49108—Electric battery cell making
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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
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49002—Electrical device making
- Y10T29/49108—Electric battery cell making
- Y10T29/49115—Electric battery cell making including coating or impregnating
Definitions
- the present invention relates to a secondary battery provided with a wound electrode group, and more particularly to an improvement of an electrode constituting the electrode group.
- high energy density non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries are widely used.
- an electrode group having a folded structure, a laminated structure, or a wound structure is used.
- the electrode group having a wound structure is common.
- the electrode group having a wound structure is an electrode group in which a positive electrode and a negative electrode are wound in a spiral shape between both electrodes via a separator.
- Patent Document 1 in order to improve the output characteristics of a battery, it is proposed to increase the thickness of the electrode from the inner side toward the outer side in an electrode group having a wound structure. Accordingly, it has been proposed to make the bulk density of the mixture layer substantially uniform.
- Patent Document 2 in order to improve the charge / discharge cycle characteristics of the battery, in the electrode constituting the wound electrode group, the thickness of the mixture layer disposed on the outer peripheral side of the current collector is set to It has been proposed to make it larger than the thickness of the mixture layer arranged on the circumferential side. Thereby, the amount of active materials in the outer peripheral side mixture layer can be made larger than the amount of active materials in the inner peripheral side mixture layer.
- the radius of curvature of the electrode becomes smaller from the outside toward the inside (closer to the winding axis).
- the difference in active material density (capacity density) between the inner mixture layer and the outer mixture layer becomes large, and the reaction tends to be non-uniform.
- the weight of the mixture layer (active material) that is, the capacity density per unit area
- the reaction tends to be non-uniform.
- the weight of the mixture layer (active material) differs between the inner mixture layer and the outer mixture layer. For this reason, the capacity design of the counter electrode becomes complicated, and it is difficult to ensure the uniformity of the electrode reaction.
- the present invention provides a highly reliable electrode in which the capacity density per unit volume of the mixture layer is uniform when the electrode group is configured, and a secondary battery including the electrode.
- the present invention provides a method for manufacturing a secondary battery that can easily configure an electrode group including electrodes having a uniform capacity density per unit volume of a mixture layer.
- the present invention is an electrode used in a wound electrode group, It includes a current collector, a first mixture layer containing a first active material formed on one surface of the current collector, and a second active material formed on the other surface of the current collector.
- a second mixture layer At the time of electrode group configuration, the first mixture layer is wound so as to be located outside the second mixture layer, In a portion corresponding to a predetermined region having a radius of curvature of 3.0 ⁇ 10 ⁇ 3 m or less in a cross section perpendicular to the winding axis of the electrode group, the capacity C v1 per unit volume of the first mixture layer is It is characterized by being larger than the capacity C v2 per unit volume of the two mixture layers.
- the present invention is a secondary battery comprising an electrode group in which a pair of electrodes are wound via a separator between both electrodes, At least one of the pair of electrodes is formed on a current collector, a first mixture layer containing a first active material formed on one surface of the current collector, and the other surface of the current collector And a second mixture layer containing a second active material,
- the first mixture layer is wound so as to be located outside the second mixture layer,
- the ratio of the capacity C v1 per unit volume of the first mixture layer to the capacity C v2 per unit volume of the second mixture layer: C v1 / C v2 is more than 0.97 and less than 1.03 It is characterized by being.
- the method for producing the secondary battery of the present invention includes: (1) A first mixture layer containing a first active material is formed on one surface of a current collector, and a second mixture layer containing a second active material is formed on the other surface of the current collector, A first step of forming an electrode A having the following polarity: (2) The electrode A and the electrode B having the other polarity are wound so that the first mixture layer is positioned outside the second mixture layer via a separator between the two, A second step of constituting an electrode group, In the step (1), in a portion corresponding to a predetermined region having a curvature radius of 3.0 ⁇ 10 ⁇ 3 m or less in a cross section perpendicular to the winding axis of the electrode group, per unit volume of the first mixture layer.
- the electrode A is configured such that the capacity C v1 is larger than the capacity C v2 per unit volume of the second mixture layer, In the step (2), in the predetermined region, the ratio of the capacity C v1 per unit volume of the first mixture layer to the capacity C v2 per unit volume of the second mixture layer: C v1 / C
- the electrode group is configured so that v2 is greater than 0.97 and less than 1.03.
- the mixture layer disposed on the inside of the current collector includes the mixture layer disposed on the outside of the current collector, Can be made substantially uniform. Therefore, the electrode reaction in the electrode group is made uniform, and a secondary battery excellent in charge / discharge cycle characteristics is obtained.
- the present invention relates to a strip-shaped electrode used for a wound electrode group.
- the electrode includes a band-shaped current collector, a first mixture layer containing a first active material formed on one surface of the current collector, and a first current layer formed on the other surface of the current collector. And a second mixture layer containing two active materials.
- the first mixture layer is wound so as to be located outside the second mixture layer.
- shaft of an electrode group is 3.0x10 ⁇ -3> m or less.
- capacitance per unit volume of a mixture layer is a capacity
- the first active material may be the same as or different from the second active material.
- the first capacitor is formed in the portion corresponding to the region X so that the first capacitance density is substantially the same as the second capacitance density when the electrode is wound.
- the density is set larger than the second capacity density.
- the first mixture layer is a dense layer and the second mixture layer is a sparse layer.
- the first mixture layer located outside the current collector, and the capacity density per unit volume slightly decreases.
- the first mixture layer has substantially the same capacity density per unit volume as the second mixture layer.
- C v1 / C v2 is preferably more than 1.01 and 1.05 or less. If C v1 / C v2 exceeds 1.01, the difference between the first capacity density and the second capacity density at the time of winding the electrode becomes small, and the electrode reaction can be made uniform. When C v1 / C v2 exceeds 1.05, the first capacity density becomes considerably larger than the second capacity density even when the electrode is wound, and the electrode reaction may become non-uniform. In order to make the electrode reaction more uniform, C v1 / C v2 is more preferably more than 1.01 and 1.04 or less.
- the first capacity density and the second capacity density may be the same.
- the first capacity density and the second capacity density are substantially the same when the electrode group is configured, and the effect of improving the charge / discharge cycle characteristics by homogenizing the electrode reaction can be obtained, Similarly to the portion corresponding to the region X, the first capacity density may be larger than the second capacity density.
- the first capacity density may be the same as the second capacity density, and the first capacity density may be larger than the second capacity density as long as C v1 / C v2 does not exceed 1.05.
- the unit areas of the first mixture layer and the second mixture layer in the electrode before winding It is preferable that the per capita density is substantially the same, and the thickness of the second mixture layer is larger than the thickness of the first mixture layer.
- Ratio of the capacity C a1 per unit area of the first mixture layer and the capacity C A2 per unit area of the second mixture layer in the portion corresponding to the region X of the electrode before winding: C a1 / C a2 is preferably more than 0.97 and less than 1.03.
- the thickness T 2 of the second Go adhesive layer, the ratio between the thickness T 1 of the first Go adhesive layer: T 2 / T 1 is preferably 1.01 to 1.05. If C a1 / C a2 and T 2 / T 1 are within the above range in the portion corresponding to the region X of the electrode before winding, the first capacitance density and the second capacitance density are set in the electrode after winding. It is easy to make substantially the same.
- the present invention relates to a secondary battery using the above electrode. That is, the secondary battery of the present invention includes an electrode group in which a pair of electrodes are wound with a separator between both electrodes. At least one of the pair of electrodes is formed on the current collector, the first mixture layer containing the first active material formed on one surface of the current collector, and the other surface of the current collector. And a second mixture layer containing a second active material. In the electrode group, the first mixture layer is wound so as to be positioned outside the second mixture layer.
- the capacity C v1 per 1 cm 3 of the first mixture layer (first capacity density)
- the capacity C v2 per second Go adhesive layer 1 cm 3 (second capacity density) and the ratio of: C v1 / C v2 is less than 0.97 ultra 1.03.
- C v1 / C v2 is greater than 0.97 and less than 1.03.
- C v1 / C v2 in the electrode group of the secondary battery is more than 0.97 and less than 1.03, the difference between the first capacity density and the second capacity density is small, so the electrode reaction becomes uniform, and the charge / discharge cycle Improved characteristics.
- C v1 / C v2 in the electrode group of the secondary battery is preferably 0.98 or more and 1.02 or less, more preferably 0.99 or more and 1.01 or less, and particularly preferably 1.00.
- the secondary battery of the present invention only needs to have an electrode group in which a positive electrode and a negative electrode are wound via a separator between both electrodes, and has any structure such as a cylindrical shape, a square shape, and a sheet shape. Also good.
- Examples of the secondary battery of the present invention include a non-aqueous electrolyte secondary battery and a water-soluble electrolyte secondary battery.
- the method for producing the secondary battery of the present invention includes: (1) A first mixture layer containing a first active material is formed on one surface of a current collector, and a second mixture layer containing a second active material is formed on the other surface of the current collector, Forming an electrode A having the following polarity: (2) The electrode A and the electrode B having the other polarity are wound so that the first mixture layer is positioned outside the second mixture layer with a separator between them, Configuring.
- the unit volume of the first mixture layer in a portion corresponding to a predetermined region (region X) having a radius of curvature of 3.0 ⁇ 10 ⁇ 3 m or less in a cross section perpendicular to the winding axis of the electrode group.
- the electrode A is configured so that the per capita capacity C v1 (first capacity density) is larger than the capacity C v2 (second capacity density) per unit volume of the second mixture layer.
- the electrode group is configured so that C v2 is more than 0.97 and less than 1.03.
- the electrode A By using the electrode A, an electrode group having a uniform capacity density per unit volume can be easily obtained. Therefore, the electrode reaction in the electrode group is made uniform, and a secondary battery excellent in charge / discharge cycle characteristics is obtained.
- the electrode B is preferably produced by the same method as the electrode A.
- the first capacity density may be made larger than the second capacity density in the portion other than the region X as long as the effect of improving the charge / discharge cycle characteristics due to the uniform electrode reaction can be obtained.
- Step (1) (A) applying a first mixture containing a first active material to one surface of the current collector, drying, and forming a first coating film; (B) applying a second mixture containing a second active material to the other surface of the current collector, drying, and forming a second coating film; (C) The same pressure is applied to the first coating film and the second coating film, respectively, to compress the first coating film and the second coating film to form the first mixture layer and the second mixture layer, and to form the electrode A It is preferable to include the process of obtaining.
- the electrode precursor comprising the current collector, the first coating film, and the second coating film obtained in steps (a) and (b) is passed between a pair of rollers.
- the electrode precursor is pressed with a press.
- the compression rate of a 1st coating film is made higher than the compression rate of a 2nd coating film, and a 1st capacity density is made larger than a 2nd capacity density.
- the ratio of the compression ratio P2 of the second coating film to the compression ratio P1 of the first coating film: P2 / P1 is preferably 0.6 or less and less than 1.
- a compression rate is represented by the following formula
- equation. Compression rate (%) (Thickness of coating film before compression ⁇ Thickness of mixture layer after compression) / Thickness of coating film before compression ⁇ 100
- a first binder and a second binder are prepared, and a material having a lower elastic modulus than that of the second binder is used as the first binder.
- the first binder is added to the first mixture.
- the second binder is added to the second mixture.
- the elastic modulus is a physical property value indicating the difficulty of deformation of the material. The higher the modulus of elasticity, the harder the material is to deform and the harder the mixture layer becomes.
- the ratio E1 / E2 of the elastic modulus E1 of the first binder and the elastic modulus E2 of the second binder is preferably 0.6 or more and less than 1.
- the elastic modulus here refers to the flexural modulus at 20 ° C.
- the first coating film is more compressed than the second coating film. This is because the same pressure is applied to both sides of the current collector during compression, but due to the action of the binder, a difference occurs in the compressibility of the mixture layer. Therefore, in the region X, the electrode A having the first capacitance density larger than the second capacitance density can be easily manufactured.
- the elastic modulus of the binder can be adjusted, for example, by changing the material used for the binder. Since the adjustment of the capacity density is easy, it is preferable to use the same material as the second active material for the first active material.
- a material having a higher filling property than the second active material that is, a material having a higher tap density is used for the first active material.
- a tap density Td 2 of the second active material, the ratio of tap density Td 1 of the first active material: Td 2 / Td 1 is preferably 0.6 or more and less than 1.
- the first coating film is compressed more than the second coating film. This is because, during compression, the same pressure is applied to both sides of the current collector, but due to the action of the active material, a difference occurs in the compression ratio of the mixture layer. Therefore, in the region X, the electrode A having the first capacitance density larger than the second capacitance density can be easily manufactured.
- the fillability (tap density) of the active material can be adjusted, for example, by changing the particle size, the particle shape, or the mixing ratio of two or more active materials having different particle sizes or shapes.
- the first mixture is applied to the entire surface of the current collector to form the first mixture layer
- the second mixture is applied to the entire other surface of the current collector. It is preferable to apply and form the second mixture layer.
- one of the first mixture and the second mixture is applied to one surface of the portion corresponding to the region X of the current collector, and the other portions of the first mixture and the second mixture are applied. The other may be applied.
- the winding method in the step (2) is not particularly limited as long as the positive electrode and the negative electrode are wound so that a separator exists between the positive electrode and the negative electrode during winding.
- the winding method for obtaining the cylindrical electrode group is, for example, (I) a step of sandwiching two separators with a pair of cores; (II) a step of disposing one of the positive electrode and the negative electrode between the two separators, disposing the other of the positive electrode and the negative electrode on one outer side of the two separators, and forming a laminate; (III) rotating the pair of winding cores to wind the laminate, and obtaining an electrode group; including.
- the region X is a predetermined region at one end in the longitudinal direction of the positive electrode, and the predetermined region is a region near the central axis of the electrode group.
- the flat elliptical columnar electrode group can be obtained by, for example, pressing the cylindrical electrode group obtained by the above method into a flat shape.
- the region X exists intermittently along the longitudinal direction of the positive electrode.
- the location is a region corresponding to the bent side surface of the electrode group.
- the non-aqueous electrolyte secondary battery includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte.
- the positive electrode is composed of a positive electrode current collector and a positive electrode mixture layer formed on both surfaces of the positive electrode current collector.
- the thickness of one side of the positive electrode mixture layer is, for example, 50 to 80 ⁇ m.
- the positive electrode mixture layer includes a positive electrode active material and a positive electrode binder. If necessary, the positive electrode mixture layer may further contain a positive electrode conductive material.
- a lithium-containing transition metal composite oxide or a transition metal polyanion compound is used as the positive electrode active material.
- a positive electrode active material may be used individually by 1 type, and may be used in combination of 2 or more type.
- the lithium-containing transition metal composite oxide include lithium cobaltate (LiCoO 2 ), lithium nickelate (LiNiO 2 ), lithium manganate (LiMnO 2 , LiMn 2 O 4 ), and modified products thereof. Some of Co, Ni, and Mn in these oxides may be replaced with other transition metal elements, typical metals such as Al, or alkaline earth metals such as Mg.
- the transition metal polyanion compound include a phosphate compound or a sulfate compound having a NASICON structure or an olivine structure and containing transition metals such as Mn, Fe, Co, and Ni.
- the capacity density of the positive electrode can be adjusted by changing the filling property of the positive electrode active material.
- the filling property of the positive electrode active material can be adjusted by changing the particle size or particle shape of the positive electrode active material or the mixing ratio of two or more active materials having different particle sizes or shapes.
- the positive electrode active material (first positive electrode active material) powder having a high filling property has, for example, an average particle diameter of 8 to 20 ⁇ m, an average circularity of 0.85 to 1, and a tap density of 2.5 to 3.0 g / cm 3 . Also, the positive electrode active material P A having an average particle size of 8 ⁇ 20 [mu] m, by mixing the positive electrode active material P B having an average particle size of 2 ⁇ 5 [mu] m, the tap density of the first cathode active material to 3.3 g / cm 3 Can be increased.
- the weight ratio of the positive electrode active material P A to the positive electrode active material P B : P A / P B is preferably 90/10 to 60/40.
- the positive electrode active material (second positive electrode active material) powder having a low filling property has, for example, an average particle diameter of 1 to 12 ⁇ m, an average circularity of 0.7 to 0.95, and a tap density of 2.0 g / cm 3 to 3.0 g. / Cm ⁇ 3 .
- the positive electrode current collector is preferably a metal foil or alloy foil that is chemically stable in the positive electrode potential region.
- the positive electrode current collector is preferably an aluminum foil or an aluminum alloy foil, and more preferably an aluminum foil.
- the thickness of the positive electrode current collector is, for example, 5 to 20 ⁇ m.
- a metal layer that is stable under the positive electrode potential may be formed on the surface of a film-like substrate made of various materials, and this may be used as a current collector. In order to improve the current collecting property, irregularities may be formed on the surface of the current collector, or the current collector may be provided with perforations.
- the positive electrode binder for example, polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE) is used.
- PVDF polyvinylidene fluoride
- PTFE polytetrafluoroethylene
- the content of the positive electrode binder in the positive electrode mixture layer is preferably 0.5 to 3 parts by weight per 100 parts by weight of the positive electrode active material.
- the capacity density of the positive electrode can be adjusted by changing the material (elastic modulus) of the positive electrode binder.
- the positive electrode binder having a low elastic modulus preferably has an elastic modulus of 500 MPa or more and less than 800 MPa, and the material is PVDF having an average molecular weight of less than 1 million.
- the positive electrode binder (second binder) having a high elastic modulus preferably has an elastic modulus of 800 to 1100 MPa, and the material is preferably PVDF having an average molecular weight of 1,000,000 or more.
- the positive electrode conductive material those generally used in non-aqueous electrolyte secondary batteries may be used, and for example, graphite, acetylene black, and ketjen black are used.
- the content of the positive electrode conductive material in the positive electrode mixture layer is preferably 0.5 to 3.0 parts by weight per 100 parts by weight of the positive electrode active material.
- a slurry-like positive electrode mixture containing a positive electrode active material and a positive electrode binder is prepared, and the positive electrode mixture is applied to a positive electrode current collector and dried to form a coating film. This coating film is compressed to form a positive electrode mixture layer.
- the positive electrode mixture is prepared, for example, by mixing a positive electrode active material and a positive electrode binder together with an appropriate dispersion medium.
- an organic solvent such as N-methyl-2-pyrrolidone (NMP) or water is used.
- NMP N-methyl-2-pyrrolidone
- a positive electrode material such as a conductive material may be further added to the positive electrode mixture.
- an additive such as a surfactant may be added to the positive electrode mixture.
- the negative electrode includes a negative electrode current collector and a negative electrode mixture layer formed on both surfaces of the negative electrode current collector.
- the thickness per side of the negative electrode mixture layer is, for example, 60 to 90 ⁇ m.
- the negative electrode mixture layer includes a negative electrode active material and a negative electrode binder.
- the negative electrode active material for example, a carbon material or an alloy-based active material capable of reversibly inserting and extracting lithium ions is used. Examples of the carbon material include natural graphite, artificial graphite, petroleum coke, carbon fiber, organic polymer fired product, carbon nanotube, and carbon nanohorn.
- the alloy-based active material for example, metal oxides such as silicon oxide and tin oxide, silicon compounds, or tin compounds are used.
- the capacity density of the negative electrode can be adjusted by changing the filling property of the negative electrode active material.
- the fillability of the negative electrode active material can be adjusted by changing the particle size or particle form of the negative electrode active material, or the mixing ratio of two or more active materials having different particle sizes or forms.
- the highly active negative electrode active material (first negative electrode active material) powder has, for example, an average particle size of 10 to 20 ⁇ m, an average circularity of 0.85 to 1, and a tap density of 1.2 to 1.5 g / cm 3 .
- the weight ratio between the negative electrode active material N A and the negative electrode active material N B: N A / N B is preferably 90 / 10-60 / 40.
- the negative electrode active material powder (second negative electrode active material) having a low filling property has, for example, an average particle diameter of 1 ⁇ m to 15 ⁇ m, an average circularity of 0.6 to 0.95, and a tap density of 0.8 g / cm 3 to 1.
- An average particle size An 1 of the first negative electrode active material, the ratio of the average particle size An 2 of the second negative electrode active material: An 1 / An 2, and a circularity of Cn 1 of the first anode active material, a second negative electrode Ratio with active material Cn 2 : Cn 1 / Cn 2 is 1.0 or more and 1.5 or less, and at least one of An 1 / An 2 and Cn 1 / Cn 2 is preferably more than 1.0.
- the negative electrode binder is not particularly limited, but a particulate rubber material is preferable from the viewpoint of exhibiting binding properties in a small amount.
- the rubber material is preferably a material containing a styrene unit and a butadiene unit, and more preferably a styrene-butadiene copolymer (SBR) or a modified product thereof.
- SBR styrene-butadiene copolymer
- a thickener composed of a water-soluble polymer.
- a cellulose-based resin is preferable, and carboxymethyl cellulose (CMC) is particularly preferable.
- PVDF or a modified product thereof may be used for the negative electrode binder.
- the negative electrode current collector for example, a metal foil that is stable in the potential range of the negative electrode is used.
- the negative electrode current collector is preferably a copper foil.
- the thickness of the negative electrode current collector is, for example, 5 to 20 ⁇ m.
- a metal layer that is stable in the potential range of the negative electrode, such as copper, may be formed on the surface of the film-like substrate, and this may be used as the negative electrode current collector. In order to improve current collection, irregularities may be formed on the surface of the negative electrode current collector, or perforations may be provided.
- a slurry-like negative electrode mixture containing a negative electrode active material and a negative electrode binder is prepared, and the negative electrode mixture is applied to the negative electrode current collector and dried to form a coating film. This coating film is compressed to form a negative electrode mixture layer.
- the negative electrode mixture is prepared, for example, by mixing a negative electrode active material and a negative electrode binder together with a suitable dispersion medium.
- a suitable dispersion medium for example, an organic solvent such as N-methyl-2-pyrrolidone (NMP) or water is used.
- a microporous membrane or a nonwoven fabric is used for the separator of the nonaqueous electrolyte secondary battery.
- the microporous membrane and the nonwoven fabric are made of a material that can withstand the use environment of the battery, have ion permeability, and have a function of insulating the positive and negative electrodes.
- a microporous film made of a polyolefin resin is used.
- the polyolefin resin for example, polyethylene or polypropylene is used.
- the microporous membrane may be composed of a single layer made of one kind of resin or may be made of a multilayer composed of two or more kinds of resins.
- the microporous film may be composed of an insulating inorganic material such as alumina, or may be composed of an insulating inorganic material and a resin.
- the nonaqueous electrolyte includes a nonaqueous solvent and a solute dissolved in the nonaqueous solvent.
- the non-aqueous solvent is not particularly limited, and for example, carbonates, halogenated hydrocarbons, ethers, ketones, nitriles, lactones, oxolane compounds and the like are used.
- the nonaqueous solvent is preferably composed of a mixed solvent of a high dielectric constant solvent A having a relative dielectric constant (20 ° C.) of 20 or more and a low viscosity solvent B having a viscosity (25 ° C.) of 0.001 Pa ⁇ s or less. .
- the high dielectric constant solvent A for example, ethylene carbonate (EC) or propylene carbonate (PC) is used.
- low-viscosity solvent B for example, dimethyl carbonate (DMC), diethyl carbonate (DEC), or ethyl methyl carbonate (EMC) is used. Dimethoxyethane (DME), tetrahydrofuran (THF), and ⁇ -butyrolactone (GBL) may be added to the solvents A and B described above.
- DMC dimethyl carbonate
- DEC diethyl carbonate
- EMC ethyl methyl carbonate
- DME dimethoxyethane
- THF tetrahydrofuran
- GBL ⁇ -butyrolactone
- an inorganic salt As the solute, an inorganic salt, an organic salt, or a derivative thereof is used.
- LiPF 6 , LiBF 4 , LiClO 4 , or LiAsF 6 is used as the inorganic salt.
- the organic salt include LiSO 3 CF 3 , LiC (SO 3 CF 3 ) 2 , LiN (SO 3 CF 3 ) 2 , LiN (SO 2 C 2 F 5 ) 2 , LiN (SO 2 CF 3 ) (SO 2 C 4 F 9 ) is used.
- the concentration of the solute in the nonaqueous electrolyte is usually 0.5 to 2.0 mol / L.
- additives may be added to the non-aqueous electrolyte for the purpose of improving the characteristics of the non-aqueous electrolyte secondary battery (for example, improvement of storage characteristics, cycle characteristics, and safety).
- examples of such additives include vinylene carbonate (VC), cyclohexylbenzene (CHB), and derivatives thereof.
- a battery is manufactured by the following procedure.
- the electrode group is accommodated in the battery case.
- the battery case for example, an aluminum alloy, a nickel-plated iron alloy, or a laminate of various resins and metals is used.
- the shape of the battery case is, for example, a bottomed cylindrical shape or a bottomed rectangular tube shape.
- One of the positive electrode lead and the negative electrode lead is electrically connected to the positive electrode current collector and the negative electrode current collector.
- the other of the positive electrode lead and the negative electrode lead is electrically connected to the positive electrode terminal and the negative electrode terminal, respectively.
- a nonaqueous electrolyte is injected into the battery case.
- the battery case is sealed using a sealing member such as a battery lid.
- Example 1 (1) Preparation of positive electrode mixture A
- the positive electrode active material lithium nickelate powder having an average particle diameter of 12 ⁇ m, an average circularity of 0.95, and a tap density of 2.9 g / cm 3
- positive electrode binder A first 1 binder
- PVDF positive electrode binder A
- first 1 binder PVDF having an average molecular weight of 600,000 (elastic modulus 700 MPa)
- acetylene black as a conductive material
- NMP an appropriate amount of NMP
- positive electrode mixture B lithium nickelate as described above, PVDF (elastic modulus 1000 MPa) having an average molecular weight of 1,000,000 as positive electrode binder B (second binder), and conductive material Acetylene black and an appropriate amount of NMP were stirred in a double-arm kneader to prepare a slurry-like positive electrode mixture B (second mixture).
- the weight ratio of the positive electrode active material, the positive electrode binder B, and the conductive material was 100: 2: 2.
- the same pressure (linear pressure 1.5 ⁇ 10 2 N / cm) is applied to the coating film A and the coating film B, the coating film A and the coating film B are compressed, and the mixture layer A (first mixture), respectively. Layer) and mixture layer B (second mixture layer).
- the positive electrode was obtained. Thereafter, the positive electrode was cut into a band shape so that it could be inserted into a battery case of a cylindrical battery (Part No. 18650). Specifically, the longitudinal dimension of the positive electrode was 660 mm, and the width dimension was 55 mm.
- the thickness of the mixture layer A after compression was 59 ⁇ m.
- the thickness of the mixture layer B after compression was 60 ⁇ m.
- the capacity (volume density A1) per unit volume 1 cm 3 of the mixture layer A after compression was 630 mAh.
- the capacity (volume density B1) per unit volume 1 cm 3 of the mixture layer B after compression was 620 mAh.
- the ratio of capacity density A1 to capacity density B1: A1 / B1 was 1.016.
- the capacity per unit area 1 cm 2 of the mixture layer A (capacity density A2) was 3.8 mAh.
- the capacity per unit area 1 cm 2 of the mixture layer B (capacity density B2) was 3.8 mAh.
- an area here refers to an area parallel to the main surface of a collector. Ratio of capacity density A2 to capacity density B2: A2 / B2 was 1.00.
- negative electrode active material 300 g of artificial graphite having an average particle size of 15 ⁇ m, an average circularity of 0.95, and a tap density of 1.4 g / cm 3 , and Nippon Zeon Co., Ltd., which is a negative electrode binder “BM-400B (trade name)” (7.5 g of an aqueous dispersion containing 40% by weight of a modified styrene-butadiene copolymer), 3 g of CMC as a thickener, and an appropriate amount of water The mixture was stirred with an arm kneader to prepare a slurry-like negative electrode mixture.
- BM-400B trade name
- This negative electrode mixture was applied to both surfaces of a 10 ⁇ m thick copper foil as a negative electrode current collector and dried to obtain a coating film.
- This coating film was compressed at a linear pressure of 40 N / cm to form a negative electrode mixture layer.
- the thickness of the negative electrode which consists of a negative electrode electrical power collector and the negative mix layer formed in both surfaces was 180 micrometers.
- the negative electrode was cut into a strip shape in a size that could be inserted into a battery case of a cylindrical battery (Part No. 18650). Specifically, the dimension of the negative electrode in the longitudinal direction was 750 mm, and the width was 57 mm.
- a non-aqueous electrolyte prepared EC, DMC, and EMC mixed solvent (volume ratio 2: 3: 3), the LiPF 6 as a solute was dissolved at a concentration of 1 mol / L, to prepare a nonaqueous electrolyte.
- 3 parts by weight of VC was added per 100 parts by weight of the nonaqueous electrolyte.
- a cylindrical non-aqueous electrolyte secondary battery having a product number of 18650 shown in FIG. 1 was prepared by the following procedure.
- One end of the positive electrode lead 5 a was connected to the positive electrode lead connection portion of the positive electrode 5.
- One end of the negative electrode lead 6 a was connected to the negative electrode lead connection portion of the negative electrode 5.
- the positive electrode 5 and the negative electrode 6 were wound with the separator 7 disposed between the positive electrode 5 and the negative electrode 6 to form a cylindrical electrode group.
- a microporous film (thickness 15 ⁇ m) made of polyethylene resin was used for the separator 7, a microporous film (thickness 15 ⁇ m) made of polyethylene resin was used.
- the electrode group was configured as follows. With the two separators sandwiched between a pair of cores, the positive electrode is placed between the two separators, and the negative electrode is placed outside one of the two separators so that the negative electrode is inside the positive electrode And wound around a pair of cores. At this time, the positive electrode was disposed such that the mixture layer A (first mixture layer) was located outside and the mixture layer B (second mixture layer) was located inside.
- Region X in the positive electrode region having a radius of curvature of 3.0 ⁇ 10 ⁇ 3 m or less in the cross section perpendicular to the winding axis when the electrode group is configured
- Region X in the positive electrode region having a radius of curvature of 3.0 ⁇ 10 ⁇ 3 m or less in the cross section perpendicular to the winding axis when the electrode group is configured
- the capacity densities A and B in the region X after winding the positive electrode were determined from the amount of the active material in the region X in the mixture layers A and B and the volume of the region X determined by image analysis.
- the ratio of the capacity density A1 and the capacity density B1 after winding the positive electrode (after the electrode group configuration): A1 / B1 was 0.985.
- the upper insulating ring 8a and the lower insulating ring 8b were arranged above and below the electrode group, respectively, and then accommodated in a low-cylindrical battery case 1 made of stainless steel.
- the other end of the positive electrode lead 5 a was welded to the lower surface of the battery lid 2.
- the other end of the negative electrode lead 5 b was welded to the inner bottom surface of the battery case 1.
- 5 g of the nonaqueous electrolyte was injected into the battery case 1, the inside of the battery case 1 was decompressed to 133 Pa, and the electrode group was impregnated with the nonaqueous electrolyte.
- the opening end of the battery case was caulked to the peripheral edge of the battery lid 2 via the insulating packing 3 to seal the battery case 1.
- a cylindrical lithium ion secondary battery (part number 18650) having a diameter of 18 mm and a height of 65 mm was completed.
- Example 2 A positive electrode was produced in the same manner as in Example 1 except that PVDF (elastic modulus: 500 MPa) having an average molecular weight of 300,000 was used as the positive electrode binder A.
- the thickness of the mixture layer A after compression was 58 ⁇ m.
- the capacity (volume density A1) per unit volume 1 cm 3 of the mixture layer A after compression was 640 mAh.
- Ratio of capacity density A1 and capacity density B1 before winding of the positive electrode: A1 / B1 was 1.032.
- An electrode group was produced in the same manner as in Example 1 except that the positive electrode was used.
- Ratio of capacity density A1 and capacity density B1 after winding of the positive electrode: A1 / B1 was 1.00.
- a battery was produced in the same manner as in Example 1 except that the above electrode group was used.
- Example 3 PVDF (elastic modulus 500 MPa) having an average molecular weight of 300,000 was used for the positive electrode binder A. PVDF (elastic modulus 1100 MPa) having an average molecular weight of 1,200,000 was used for the positive electrode binder B.
- a positive electrode was produced in the same manner as in Example 1 except for the above.
- the thickness of the mixture layer A after compression was 58 ⁇ m.
- the capacity (volume density A1) per unit volume 1 cm 3 of the mixture layer A after compression was 640 mAh.
- the thickness of the mixture layer B after compression was 61 ⁇ m.
- the capacity (volume density B1) per unit volume 1 cm 3 of the mixture layer B after compression was 610 mAh.
- Ratio of capacity density A1 and capacity density B1 before winding of the positive electrode was 1.049.
- An electrode group was produced in the same manner as in Example 1 except that the positive electrode was used.
- Ratio of capacity density A1 and capacity density B1 after winding of the positive electrode: A1 / B1 was 1.025.
- a battery was produced in the same manner as in Example 1 except that the above electrode group was used.
- Comparative Example 1 A battery was produced in the same manner as in Example 1 except that the positive electrode having the mixture layer B formed on both sides of the current collector was used. Ratio of capacity density A1 and capacity density B1 before winding of the positive electrode: A1 / B1 was 1.00. Ratio of capacity density A1 and capacity density B1 after winding of the positive electrode: A1 / B1 was 0.97.
- the batteries of Examples 1 to 3 in which A1 / B1 after electrode winding is more than 0.97 and less than 1.03 are compared with the battery of Comparative Example 1 in which A1 / B1 after electrode winding is 0.97.
- the electrode reaction was made uniform and the charge / discharge cycle characteristics were improved.
- A1 / B1 after electrode winding was 0.980 or more and 1.020 or less
- excellent charge / discharge cycle characteristics were obtained.
- the battery of Example 2 in which A1 / B1 after electrode winding was 1 exhibited the most excellent charge / discharge cycle characteristics.
- the electrode of the present invention was used for the positive electrode. However, even when the electrode of the present invention is used for the negative electrode or both the positive electrode and the negative electrode, the charge / discharge cycle characteristics are improved.
- Example 4 As the positive electrode active material C (first active material), lithium nickelate powder having an average particle size of 12 ⁇ m, an average circularity of 0.95, and a tap density of 2.9 g / cm 3 , and an average molecular weight of 600,000 as a positive electrode binder Of PVDF (elastic modulus 700 MPa), acetylene black as a conductive material, and an appropriate amount of NMP were stirred in a double-arm kneader to prepare a slurry-like positive electrode mixture C (first mixture).
- the weight ratio of the positive electrode active material C, the positive electrode binder, and the conductive material was 100: 2: 2.
- the positive electrode active material D (second active material) lithium nickelate having an average particle diameter of 10 ⁇ m, an average circularity of 0.80, and a tap density of 2.3 g / cm 3 , the same positive electrode binder and conductive material as described above And an appropriate amount of NMP was stirred with a double arm kneader to prepare a slurry-like positive electrode mixture D (second mixture).
- the weight ratio of the positive electrode active material D, the positive electrode binder, and the conductive material was 100: 2: 2.
- An aluminum foil having a thickness of 15 ⁇ m was prepared as a positive electrode current collector.
- the positive electrode mixture C was applied to one surface of the positive electrode current collector and dried to form a coating film C (thickness 89 ⁇ m).
- the positive electrode mixture D was applied to the other surface of the positive electrode current collector and dried to form a coating film D (thickness 91 ⁇ m).
- the positive electrode precursor which has a positive electrode electrical power collector, the coating film C, and the coating film D was obtained.
- the positive electrode precursor was compressed with a pair of rollers.
- the same pressure (linear pressure 1.5 ⁇ 10 2 N / cm) is applied to the coating film C and the coating film D, the coating film C and the coating film D are compressed, and the mixture layer C (first mixture) Layer) and mixture layer D (second mixture layer).
- a positive electrode was obtained.
- the positive electrode was cut to a size (longitudinal dimension 660 mm, width dimension 55 mm) that can be inserted into a battery case of a cylindrical battery (Part No. 18650).
- the thickness of the mixture layer C after compression was 59 ⁇ m.
- the thickness of the mixture layer D after compression was 61 ⁇ m.
- the capacity (capacity density C1) per unit volume 1 cm 3 of the mixture layer C after compression was 640 mAh.
- the capacity (capacity density D1) per unit volume 1 cm 3 of the mixture layer D after compression was 620 mAh.
- Ratio of capacity density C1 to capacity density D1: C1 / D1 was 1.032.
- the capacity per unit area 1 cm 2 of the mixture layer C (capacity density C2) was 3.8 mAh.
- the capacity per unit area 1 cm 2 of the mixture layer D (capacity density D2) was 3.8 mAh.
- an area here refers to an area parallel to the main surface of a collector. Ratio of capacity density C2 to capacity density D2: C2 / D2 was 1.00.
- Region X in the positive electrode region having a radius of curvature of 3.0 ⁇ 10 ⁇ 3 m or less in the cross section perpendicular to the winding axis when the electrode group is configured
- Region X in the positive electrode region having a radius of curvature of 3.0 ⁇ 10 ⁇ 3 m or less in the cross section perpendicular to the winding axis when the electrode group is configured
- Example 5 As positive electrode active material C (first positive electrode active material), lithium nickelate powder (positive electrode active material P A ) having an average particle size of 20 ⁇ m and an average circularity of 0.95, an average particle size of 5 ⁇ m and an average circularity of 0.95 Lithium nickelate (tap density: 3.0 g / cm 3 ) mixed with a lithium nickelate powder (positive electrode active material P B ) at a weight ratio of 9: 1 was used.
- the positive electrode active material D (second positive electrode active material) lithium nickelate powder having an average particle diameter of 12 ⁇ m, an average circularity of 0.95, and a tap density of 2.9 g / cm 3 was used.
- a positive electrode was obtained in the same manner as in Example 4 except for the above.
- the thickness of the mixture layer C after compression was 58 ⁇ m.
- the thickness of the mixture layer D after compression was 59 ⁇ m.
- the capacity (capacity density C1) per unit volume 1 cm 3 of the mixture layer C after compression was 650 mAh.
- the capacity (volume density D1) per unit volume 1 cm 3 of the mixture layer D after compression was 640 mAh.
- the ratio of the capacity density C1 and the capacity density D1 before winding the positive electrode: C1 / D1 was 1.017.
- An electrode group was produced in the same manner as in Example 4 except that the positive electrode was used.
- Ratio of capacity density C1 and capacity density D1 after winding of the positive electrode: C1 / D1 was 0.980.
- a battery was produced in the same manner as in Example 1 except that the above electrode group was used.
- Example 6 As positive electrode active material C (first positive electrode active material), lithium nickelate powder (positive electrode active material P A ) having an average particle diameter of 20 ⁇ m and an average circularity of 0.95, an average particle diameter of 5 ⁇ m and an average circularity of 0.1.
- a lithium nickelate (tap density of 3.1 g / cm 3 ) obtained by mixing lithium nickelate powder (positive electrode active material P B ) of 95 at a weight ratio of 8: 2 was used.
- a positive electrode was produced in the same manner as in Example 5.
- the thickness of the mixture layer C after compression was 57 ⁇ m.
- the capacity per unit volume 1 cm 3 of the mixture layer C after compression was 660 mAh (capacity density C1).
- the ratio of the capacity density C1 and the capacity density D1 before winding the positive electrode: C1 / D1 was 1.031.
- An electrode group was produced in the same manner as in Example 5 except that the positive electrode was used.
- Ratio of capacity density C1 and capacity density D1 after winding of the positive electrode: C1 / D1 was 1.000.
- a battery was produced in the same manner as in Example 1 except that the above electrode group was used.
- Example 7 As positive electrode active material C (first positive electrode active material), lithium nickelate powder (positive electrode active material P A ) having an average particle size of 20 ⁇ m and an average circularity of 0.95, an average particle size of 5 ⁇ m and an average circularity of 0.95 Lithium nickelate (tap density: 3.2 g / cm 3 ) mixed with lithium nickelate powder (positive electrode active material P B ) at a weight ratio of 7: 3 was used. Other than this, a positive electrode was produced in the same manner as in Example 5. The thickness of the mixture layer C after compression was 56 ⁇ m. The capacity per unit volume of 1 cm 3 of the mixture layer C after compression was 670 mAh (capacity density C1).
- the ratio of the capacity density C1 and the capacity density D1 before winding the positive electrode: C1 / D1 was 1.046.
- An electrode group was produced in the same manner as in Example 5 except that the positive electrode was used.
- Ratio of capacity density C1 and capacity density D1 after winding of the positive electrode: C1 / D1 was 1.025.
- a battery was produced in the same manner as in Example 1 except that the above electrode group was used.
- Example 8 (1) Production of positive electrode mixture C Lithium nickelate having an average particle diameter of 12 ⁇ m, an average circularity of 0.95, and a tap density of 2.9 g / cm 3 using positive electrode active material C (first positive electrode active material)
- positive electrode active material C first positive electrode active material
- the powder, PVDF having an average molecular weight of 600,000 as a positive electrode binder (elastic modulus 700 MPa), acetylene black as a conductive material, and an appropriate amount of NMP are stirred in a double-arm kneader to form a slurry-like positive electrode composite.
- Agent C (first mixture) was prepared.
- the weight ratio of the positive electrode active material C, the positive electrode binder, and the conductive material was 100: 2: 2.
- the coating weight of the positive electrode was 0.0200 g / cm 2 .
- positive electrode active material D (second positive electrode active material), lithium nickelate having an average particle diameter of 10 ⁇ m, an average circularity of 0.90, and a tap density of 2.7 g / cm 3 ;
- positive electrode binder and conductive material as above and an appropriate amount of NMP were stirred with a double-arm kneader to prepare a slurry-like positive electrode mixture D (second mixture).
- the weight ratio of the positive electrode active material D, the positive electrode binder, and the conductive material was 100: 2: 2.
- the coating weight of the positive electrode was 0.0206 g / cm 2 .
- the same pressure is applied to the coating film C and the coating film D to compress the coating film C and the coating film D, and the mixture layer C (first mixture layer) and the mixture layer D (second mixture layer), respectively. ) was formed.
- a positive electrode was obtained.
- the positive electrode was cut to a size (longitudinal dimension 660 mm, width dimension 55 mm) that can be inserted into a battery case of a cylindrical battery (Part No. 18650).
- the thickness of the mixture layer C after compression was 59 ⁇ m.
- the thickness of the mixture layer D after compression was 62 ⁇ m.
- the capacity per unit volume 1 cm 3 of the mixture layer C after compression (capacity density C1) was 640 mAh.
- the capacity (volume density D1) per unit volume 1 cm 3 of the mixture layer D after compression was 630 mAh.
- Ratio of capacity density C1 to capacity density D1: C1 / D1 was 1.015.
- the capacity per unit area 1 cm 2 of the mixture layer C (capacity density C2) was 3.8 mAh.
- the capacity per unit area 1 cm 2 of the mixture layer D (capacity density D2) was 3.9 mAh.
- an area here refers to an area parallel to the main surface of a collector.
- Ratio of capacity density C2 to capacity density D2: C2 / D2 was 0.974.
- Region X in the positive electrode region having a radius of curvature of 3.0 ⁇ 10 ⁇ 3 m or less in the cross section perpendicular to the winding axis when the electrode group is configured
- Region X in the positive electrode region having a radius of curvature of 3.0 ⁇ 10 ⁇ 3 m or less in the cross section perpendicular to the winding axis when the electrode group is configured
- the electrode of the present invention is used for the positive electrode. However, even when the electrode of the present invention is used for both the negative electrode or the positive electrode and the negative electrode, the charge / discharge cycle characteristics are improved.
- Example 9 (1) Production of negative electrode mixture E As negative electrode active material E (first negative electrode active material), artificial graphite having an average particle diameter of 15 ⁇ m, an average circularity of 0.95, and a tap density of 1.4 g / cm 3 , and a negative electrode SBR as a binder, CMC as a thickener, and an appropriate amount of water were stirred with a double-arm kneader to prepare a slurry-like negative electrode mixture E (first mixture).
- the weight ratio of the negative electrode active material E, the negative electrode binder, and CMC was 100: 2.5: 1.
- negative electrode active material F (second negative electrode active material)
- artificial graphite having an average particle diameter of 15 ⁇ m, an average circularity of 0.85, and a tap density of 1.2 g / cm 3
- a negative electrode SBR as a binder
- CMC as a thickener
- an appropriate amount of water were stirred with a double-arm kneader to prepare a slurry-like negative electrode mixture E (second mixture).
- the weight ratio of the negative electrode active material F, the negative electrode binder, and CMC was 100: 2.5: 1.
- a copper foil having a thickness of 10 ⁇ m was prepared as a negative electrode current collector.
- a negative electrode mixture E was applied to one surface of the negative electrode current collector and dried to form a coating film E (thickness: 101 ⁇ m).
- a negative electrode mixture F was applied to the other surface of the negative electrode current collector and dried to form a coating film F (thickness: 106 ⁇ m).
- the negative electrode precursor which has a negative electrode collector, the coating film E, and the coating film F was obtained.
- the negative electrode precursor was compressed with a pair of rollers.
- the same pressure (linear pressure 40 N / cm) is applied to the coating film E and the coating film F, the coating film E and the coating film F are compressed, and the mixture layer E (first mixture layer) and the mixture layer, respectively. F (second mixture layer) was formed. In this way, a negative electrode was obtained. Thereafter, the negative electrode was cut into a size (longitudinal dimension 750 mm, width dimension 57 mm) that can be inserted into a battery case of a cylindrical battery (Part No. 18650).
- the thickness of the mixture layer E after compression was 84 ⁇ m.
- the thickness of the mixture layer F after compression was 86 ⁇ m.
- the capacity per unit volume 1 cm 3 of the mixture layer E after compression (capacity density E1) was 640 mAh.
- the capacity (capacity density F1) per unit volume 1 cm 3 of the mixture layer F after compression was 630 mAh.
- Ratio of capacity density E1 to capacity density F1: E1 / F1 was 1.015.
- the capacity (capacity density E2) per unit area 1 cm 2 of the mixture layer E was 3.8 mAh.
- the capacity (capacity density F2) per unit area 1 cm 2 of the mixture layer E was 3.8 mAh.
- an area here refers to an area parallel to the main surface of a collector. Ratio of capacity density E2 to capacity density F2: E2 / F2 was 1.00.
- positive electrode As a positive electrode active material, lithium nickelate powder having an average particle size of 12 ⁇ m, an average circularity of 0.95, and a tap density of 2.9 g / cm 3 , and PVDF having an average molecular weight of 600,000 as a positive electrode binder Then, acetylene black as a conductive material and an appropriate amount of NMP were stirred with a double-arm kneader to prepare a slurry-like positive electrode mixture. The weight ratio of the positive electrode active material, the positive electrode binder, and the conductive material was 100: 2: 2. This positive electrode mixture was applied to both surfaces of a 15 ⁇ m thick aluminum foil serving as a positive electrode current collector and dried to obtain a coating film.
- This coating film was compressed at a linear pressure of 1.5 ⁇ 10 2 N / cm to form a positive electrode mixture layer.
- the thickness of the positive electrode which consists of a positive electrode electrical power collector and the positive mix layer formed in the both surfaces was 133 micrometers.
- the positive electrode was cut into a band shape so that it could be inserted into a battery case of a cylindrical battery (Part No. 18650). Specifically, the longitudinal dimension of the positive electrode was 660 mm, and the width dimension was 55 mm.
- An electrode group was constructed in the same manner as in Example 1 except that the positive electrode and the negative electrode were used.
- Region X in the negative electrode region having a radius of curvature of 3.0 ⁇ 10 ⁇ 3 m or less in the cross section perpendicular to the winding axis when the electrode group is configured
- E1 / F1 was 0.986.
- a battery was produced in the same manner as in Example 1 except that the above electrode group was used.
- Example 10 As the negative electrode active material E (first negative electrode active material), artificial graphite having an average particle diameter of 15 ⁇ m, an average circularity of 0.95, and a tap density of 1.4 g / cm 3 , SBR which is a negative electrode binder, CMC, which is a viscous agent, and an appropriate amount of water were stirred with a double-arm kneader to prepare a slurry-like negative electrode mixture E (first mixture). The weight ratio of the negative electrode active material E, the negative electrode binder, and CMC was 100: 2.5: 1.
- the negative electrode active material F (second negative electrode active material)
- artificial graphite having an average particle diameter of 15 ⁇ m, an average circularity of 0.7, and a tap density of 1.0 g / cm 3
- SBR as a negative electrode binder
- CMC which is a viscous agent
- an appropriate amount of water were stirred with a double-arm kneader to prepare a slurry-like negative electrode mixture E (second mixture).
- the weight ratio of the negative electrode active material F, the negative electrode binder, and CMC was 100: 2.5: 1.
- a copper foil having a thickness of 10 ⁇ m was prepared as a negative electrode current collector.
- a negative electrode mixture E was applied to one surface of the negative electrode current collector and dried to form a coating film E (thickness: 101 ⁇ m).
- a negative electrode mixture F was applied to the other surface of the negative electrode current collector and dried to form a coating film F (thickness: 108 ⁇ m).
- the negative electrode precursor which has a negative electrode collector, the coating film E, and the coating film F was obtained.
- the negative electrode precursor was compressed with a pair of rollers.
- the same pressure (linear pressure 40 N / cm) is applied to the coating film E and the coating film F, the coating film E and the coating film F are compressed, and the mixture layer E (first mixture layer) and the mixture layer, respectively. F (second mixture layer) was formed. In this way, a negative electrode was obtained. Thereafter, the negative electrode was cut into a size (longitudinal dimension 750 mm, width dimension 57 mm) that can be inserted into a battery case of a cylindrical battery (Part No. 18650).
- the thickness of the mixture layer E after compression was 84 ⁇ m.
- the thickness of the mixture layer F after compression was 87 ⁇ m.
- the capacity per unit volume 1 cm 3 of the mixture layer E after compression (capacity density E1) was 640 mAh.
- the capacity (capacity density F1) per unit volume 1 cm 3 of the mixture layer F after compression was 620 mAh.
- Ratio of capacity density E1 to capacity density F1: E1 / F1 was 1.032.
- the capacity (capacity density E2) per unit area 1 cm 2 of the mixture layer E was 3.8 mAh.
- the capacity (capacity density F2) per unit area 1 cm 2 of the mixture layer E was 3.8 mAh.
- an area here refers to an area parallel to the main surface of a collector. Ratio of capacity density E2 to capacity density F2: E2 / F2 was 1.000.
- An electrode group was constructed in the same manner as in Example 9 except that the above negative electrode was used.
- Region X in the negative electrode region having a radius of curvature of 3.0 ⁇ 10 ⁇ 3 m or less in the cross section perpendicular to the winding axis when the electrode group is configured
- E1 / F1 was 1.000.
- a battery was produced in the same manner as in Example 1 except that the above electrode group was used.
- Example 11 As the negative electrode active material E (first negative electrode active material), artificial graphite (negative electrode active material N A ) having an average particle diameter of 20 ⁇ m and an average circularity of 0.95, an average particle diameter of 5 ⁇ m and an average circularity of 0.95 Artificial graphite (tap density 1.5 g / cm 3 ) mixed with artificial graphite (negative electrode active material N B ) at a weight ratio of 8: 2 was used.
- a negative electrode binder E (first mixture) was prepared by stirring SBR as a negative electrode binder, CMC as a thickener, and an appropriate amount of water with a double-arm kneader. .
- the weight ratio of the negative electrode active material E, the negative electrode binder, and CMC was 100: 2.5: 1.
- the negative electrode active material F (second negative electrode active material)
- artificial graphite having an average particle diameter of 15 ⁇ m, an average circularity of 0.95, and a tap density of 1.4 g / cm 3
- SBR as a negative electrode binder
- CMC which is a viscous agent
- an appropriate amount of water were stirred with a double-arm kneader to prepare a slurry-like negative electrode mixture E (second mixture).
- the weight ratio of the negative electrode active material F, the negative electrode binder, and CMC was 100: 2.5: 1.
- a copper foil having a thickness of 10 ⁇ m was prepared as a negative electrode current collector.
- a negative electrode mixture E was applied to one surface of the negative electrode current collector and dried to form a coating film E (thickness 99 ⁇ m).
- a negative electrode mixture F was applied to the other surface of the negative electrode current collector and dried to form a coating film F (thickness: 101 ⁇ m).
- the negative electrode precursor which has a negative electrode collector, the coating film E, and the coating film F was obtained.
- the negative electrode precursor was compressed with a pair of rollers. That is, the same pressure (linear pressure 40 N / cm) is applied to the coating film E and the coating film F, the coating film E and the coating film F are compressed, and the mixture layer E (first mixture layer) and the mixture layer, respectively.
- the thickness of the mixture layer E after compression was 83 ⁇ m.
- the thickness of the mixture layer F after compression was 84 ⁇ m.
- the capacity per unit volume 1 cm 3 (capacity density E1) of the mixture layer E after compression was 650 mAh.
- the capacity (capacity density F1) per unit volume 1 cm 3 of the mixture layer F after compression was 640 mAh.
- Ratio of capacity density E1 to capacity density F1: E1 / F1 was 1.015.
- the capacity (capacity density E2) per unit area 1 cm 2 of the mixture layer E was 3.8 mAh.
- the capacity (capacity density F2) per unit area 1 cm 2 of the mixture layer E was 3.8 mAh.
- an area here refers to an area parallel to the main surface of a collector. Ratio of capacity density E2 to capacity density F2: E2 / F2 was 1.000.
- An electrode group was constructed in the same manner as in Example 9 except that the above negative electrode was used.
- Region X in the negative electrode region having a radius of curvature of 3.0 ⁇ 10 ⁇ 3 m or less in the cross section perpendicular to the winding axis when the electrode group is configured
- E1 / F1 was 0.986.
- a battery was produced in the same manner as in Example 1 except that the above electrode group was used.
- Example 12 A battery was produced in the same manner as in Example 1 except that the positive electrode of Example 6 and the negative electrode of Example 10 were used. Table 4 shows values of (first capacity density / second capacity density) at the time of preparing the positive electrode and the negative electrode and at the time of forming the electrode group. The battery of Example 12 was evaluated in the same manner as described above. The results are shown in Table 4.
- the battery of Example 12 in which both C1 / D1 and E1 / F1 in the electrode group configuration were 1 showed higher charge / discharge efficiency than the battery of Example 6 and the battery of Example 10.
- the secondary battery of the present invention Since the secondary battery of the present invention has high capacity and high reliability, it is suitably used as a power source for portable devices such as mobile phones, digital cameras, camcorders, electric vehicles, and hybrid vehicles.
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Abstract
Description
特許文献2では、電池の充放電サイクル特性を改善するため、捲回構造の電極群を構成する電極において、集電体の外周側に配された合剤層の厚みを、集電体の内周側に配された合剤層の厚みよりも大きくすることが提案されている。これにより、外周側の合剤層の活物質量を、内周側の合剤層の活物質量よりも多くすることができる。
特許文献1記載の方法では、集電体の同一面において合剤層(活物質)の重量、すなわち単位面積あたりの容量密度が変化するため、反応が不均一となり易い。
特許文献2記載の方法では、内側の合剤層と、外側の合剤層とで合剤層(活物質)の重量が異なる。このため、対極の容量設計が複雑になり、電極反応の均一性を確保することが困難である。
集電体と、前記集電体の一方の面に形成された、第1活物質を含む第1合剤層と、前記集電体の他方の面に形成された、第2活物質を含む第2合剤層とを有し、
電極群構成時において、前記第1合剤層は、前記第2合剤層よりも外側に位置するように捲回され、
電極群の捲回軸に垂直な断面における曲率半径が3.0×10-3m以下の所定領域に対応する部分において、前記第1合剤層の単位体積あたりの容量Cv1は、前記第2合剤層の単位体積あたりの容量Cv2よりも、大きいことを特徴とする。
前記一対の電極の少なくとも一方は、集電体と、前記集電体の一方の面に形成された、第1活物質を含む第1合剤層と、前記集電体の他方の面に形成された、第2活物質を含む第2合剤層とを有し、
前記電極群において、前記第1合剤層は、前記第2合剤層よりも外側に位置するように捲回され、
前記電極群の捲回軸に垂直な断面における曲率半径が3.0×10-3m以下の所定領域において、
前記第1合剤層の単位体積あたりの容量Cv1と、前記第2合剤層の単位体積あたりの容量Cv2との比:Cv1/Cv2は、0.97超1.03未満であることを特徴とする。
(1)集電体の一方の面に第1活物質を含む第1合剤層を形成し、集電体の他方の面に第2活物質を含む第2合剤層を形成し、一方の極性を有する電極Aを構成する第1の工程と、
(2)前記電極Aと、他方の極性を有する電極Bとを、両者間にセパレータを介して、前記第1合剤層が前記第2合剤層よりも外側に位置するように捲回し、電極群を構成する第2の工程と、を含み、
前記工程(1)では、電極群の捲回軸に垂直な断面における曲率半径が3.0×10-3m以下の所定領域に対応する部分において、前記第1合剤層の単位体積あたりの容量Cv1が、前記第2合剤層の単位体積あたりの容量Cv2よりも大きくなるように、前記電極Aを構成し、
前記工程(2)では、前記所定領域において、前記第1合剤層の単位体積あたりの容量Cv1と、前記第2合剤層の単位体積あたりの容量Cv2との比:Cv1/Cv2が0.97超1.03未満となるように、前記電極群を構成する。
本発明の新規な特徴を添付の請求の範囲に記述するが、本発明は、構成および内容の両方に関し、本発明の他の目的および特徴と併せ、図面を照合した以下の詳細な説明によりさらによく理解されるであろう。
これに対して、本発明の電極では、当該電極の捲回時おいて、第1容量密度が、第2容量密度と、略同一となるように、領域Xに対応する部分において、第1容量密度は、第2容量密度よりも、大きく設定される。捲回前の電極では、第1合剤層は密な層であり、第2合剤層は疎な層である。電極を捲回すると、集電体の内側に位置する第2合剤層には圧縮応力が発生し、単位体積あたりの容量密度が若干増大する。一方、集電体の外側に位置する第1合剤層には引張応力が発生し、単位体積あたりの容量密度が若干低下する。その結果、捲回後の電極では、第1合剤層は、第2合剤層と、単位体積あたりの容量密度が略同一となる。これにより、電極群内において、電極反応が均一化し、二次電池の充放電サイクル特性を改善することが可能となる。
例えば、捲回前の電極における領域X以外に対応する部分が、電極群の捲回軸に垂直な断面における曲率半径が3mm超9mm以下の領域に対応する部分である場合、その部分では、第1容量密度および第2容量密度は同じでもよく、Cv1/Cv2が1.05を超えない程度で、第1容量密度を第2容量密度よりも大きくしてもよい。
第2合剤層の厚みT2と、第1合剤層の厚みT1との比:T2/T1は、1.01以上1.05以下が好ましい。
捲回前の電極の領域Xに対応する部分において、Ca1/Ca2およびT2/T1が上記範囲内であれば、捲回後の電極において、第1容量密度および第2容量密度を略同一とすることが容易である。
(1)集電体の一方の面に第1活物質を含む第1合剤層を形成し、集電体の他方の面に第2活物質を含む第2合剤層を形成し、一方の極性を有する電極Aを構成する工程と、
(2)電極Aと、他方の極性を有する電極Bとを、両者間にセパレータを介して、第1合剤層が第2合剤層よりも外側に位置するように捲回し、電極群を構成する工程と、を含む。
工程(1)では、電極群の捲回軸に垂直な断面における曲率半径が3.0×10-3m以下の所定領域(領域X)に対応する部分において、第1合剤層の単位体積あたりの容量Cv1(第1容量密度)が、第2合剤層の単位体積あたりの容量Cv2(第2容量密度)よりも大きくなるように、電極Aを構成する。
工程(2)では、所定領域(領域X)において、第1合剤層の単位体積あたりの容量Cv1と、第2の合剤層の単位体積あたりの容量Cv2との比:Cv1/Cv2が0.97超1.03未満となるように、電極群を構成する。
(a)集電体の一方の面に第1活物質を含む第1合剤を塗布し、乾燥し、第1塗膜を形成する工程と、
(b)集電体の他方の面に第2活物質を含む第2合剤を塗布し、乾燥し、第2塗膜を形成する工程と、
(c)第1塗膜および第2塗膜にそれぞれ同じ圧力を加えることにより第1塗膜および第2塗膜を圧縮し、第1合剤層および第2合剤層を形成し、電極Aを得る工程と、を含むのが好ましい。
圧縮率(%)=(圧縮前の塗膜の厚み-圧縮後の合剤層の厚み)/圧縮前の塗膜の厚み×100
活物質の充填性(タップ密度)は、例えば、活物質の、粒子サイズ、粒子形態、または粒子のサイズもしくは形態の異なる2種以上の活物質の混合比率を変えることにより調整可能である。
円柱形の電極群を得るための捲回方法は、例えば、
(I)2枚のセパレータを一対の巻芯で挟む工程と、
(II)2枚のセパレータの間に正極および負極の一方を配置し、2枚のセパレータの一方の外側に、正極および負極の他方を配置し、積層体を構成する工程と、
(III)一対の巻芯を回転させて積層体を捲回し、電極群を得る工程と、
を含む。
この場合、領域Xは、正極の長手方向における一端部の所定領域であり、その所定領域は電極群の中心軸近傍領域である。
非水電解質二次電池は、正極、負極、正極と負極との間に配されるセパレータ、および非水電解質を備える。
リチウム含有遷移金属複合酸化物としては、例えば、コバルト酸リチウム(LiCoO2)、ニッケル酸リチウム(LiNiO2)、マンガン酸リチウム(LiMnO2、LiMn2O4)、またはこれらの変性体が挙げられる。これらの酸化物中のCo、Ni、およびMnの一部を、他の遷移金属元素、Alなどの典型金属、またはMgなどのアルカリ土類金属で置換してもよい。
遷移金属ポリアニオン化合物としては、例えば、ナシコン構造またはオリビン構造を有し、Mn、Fe、Co、およびNiのような遷移金属を含むリン酸化合物または硫酸化合物が挙げられる。
充填性の低い正極活物質(第2正極活物質)粉末は、例えば、平均粒径1~12μm、平均円形度0.7以上0.95以下、タップ密度2.0g/cm3以上3.0g/cm3未満である。
第1正極活物質の平均粒径Ap1と第2正極活物質の平均粒径Ap2との比:Ap1/Ap2、および第1正極活物質の円形度Cp1と、第2正極活物質の円形度Cp2との比:Cp1/Cp2は、1.0以上1.5以下であり、かつAp1/Ap2およびCp1/Cp2の少なくとも一方は、1.0超が好ましい。
正極集電体は、アルミニウム箔またはアルミニウム合金箔が好ましく、アルミニウム箔がより好ましい。正極集電体の厚みは、例えば、5~20μmである。
また、様々な材質のフィルム状の基材の表面に、正極電位下で安定な金属層を形成し、これを集電体として用いてもよい。集電性を向上させるために、集電体表面に凹凸を形成してもよく、集電体に穿孔を設けてもよい。
非水電解質二次電池用正極の場合、弾性率の低い正極結着剤(第1結着剤)は、弾性率500MPa以上800MPa未満が好ましく、材料としては、平均分子量が100万未満のPVDFが好ましい。弾性率の高い正極結着剤(第2結着剤)は、弾性率800~1100MPaが好ましく、材料としては、平均分子量が100万以上のPVDFが好ましい。
例えば、正極活物質および正極結着剤を含むスラリー状の正極合剤を調製し、正極合剤を正極集電体に塗布し、乾燥して、塗膜を形成する。この塗膜を圧縮して、正極合剤層を形成する。
正極合剤は、例えば、正極活物質および正極結着剤を、適当な分散媒とともに混合して調製される。分散媒には、例えば、N-メチル-2-ピロリドン(NMP)などの有機溶媒や水が用いられる。正極合剤には、さらに導電材等の正極材料を加えてもよい。正極合剤の安定性および活物質等の分散性の向上のために、正極合剤に界面活性剤などの添加剤を加えてもよい。
負極活物質には、例えば、リチウムイオンを可逆的に吸蔵・脱離可能な炭素材料または合金系活物質が用いられる。炭素材料としては、例えば、天然黒鉛、人造黒鉛、石油コークス、炭素繊維、有機高分子焼成物、カーボンナノチューブ、カーボンナノホーンが用いられる。合金系活物質としては、例えば、珪素酸化物および錫酸化物のような金属酸化物、珪素化合物、または錫化合物が用いられる。
充填性の高い負極活物質(第1負極活物質)粉末は、例えば、平均粒径10~20μm、平均円形度0.85~1、タップ密度1.2~1.5g/cm3である。また、平均粒径10~20μmの負極活物質NAと、平均粒径1μm以上10μm未満の負極活物質NBとを混合して、第1負極活物質のタップ密度を1.8g/cm3まで高めることができる。負極活物質NAと負極活物質NBとの重量比:NA/NBは、90/10~60/40が好ましい。
充填性の低い負極活物質粉末(第2負極活物質)は、例えば、平均粒径1μm以上15μm以下、平均円形度0.6以上0.95以下、タップ密度0.8g/cm3以上1.4g/cm3以下である。
第1負極活物質の平均粒径An1と、第2負極活物質の平均粒径An2との比:An1/An2、および第1負極活物質の円形度Cn1と、第2負極活物質Cn2との比:Cn1/Cn2は、1.0以上1.5以下であり、かつAn1/An2およびCn1/Cn2の少なくとも一方は、1.0超が好ましい。
負極結着剤にゴム材料を用いる場合、水溶性高分子からなる増粘剤を併用することが望ましい。水溶性高分子としては、セルロース系樹脂が好ましく、特にカルボキシメチルセルロース(CMC)が好ましい。上記以外に、負極結着剤に、PVDFまたはその変性体を用いてもよい。
例えば、負極活物質および負極結着剤を含むスラリー状の負極合剤を調製し、負極合剤を負極集電体に塗布し、乾燥して、塗膜を形成する。この塗膜を圧縮して、負極合剤層を形成する。負極合剤は、例えば、負極活物質および負極結着剤を、適当な分散媒とともに混合して調製される。分散媒には、例えば、N-メチル-2-ピロリドン(NMP)などの有機溶媒や水が用いられる。
例えば、ポリオレフィン樹脂からなる微多孔膜が用いられる。ポリオレフィン樹脂としては、例えば、ポリエチレン、ポリプロピレンが用いられる。微多孔膜は、1種の樹脂からなる単層で構成してもよく、2種以上の樹脂からなる複層で構成してもよい。微多孔膜は、アルミナなどの絶縁性無機材料で構成してもよく、絶縁性無機材料および樹脂で構成してもよい。
非水電解質二次電池特性の改善(例えば、保存特性、サイクル特性、および安全性の向上)を目的として、種々の添加剤を非水電解質に添加してもよい。このような添加剤としては、例えば、ビニレンカーボネート(VC)、シクロヘキシルベンゼン(CHB)、またはこれらの誘導体が挙げられる。
電極群を電池ケース内に収容する。電池ケースには、例えば、アルミニウム合金、ニッケルめっきを施した鉄合金、各種樹脂と金属との積層体が用いられる。電池ケースの形状は、例えば、有底円筒状または有底角筒状である。
正極リードおよび負極リードの一方を、正極集電体および負極集電体に電気的に接続する。正極リードおよび負極リードの他方を、それぞれ正極端子および負極端子に電気的に接続する。非水電解質を電池ケース内に注入する。筒状の電池ケースを用いる場合には、電池蓋等の封口部材を用いて電池ケースを密閉する。
《実施例1》
(1)正極合剤Aの作製
正極活物質として、平均粒径12μm、平均円形度0.95、およびタップ密度2.9g/cm3であるニッケル酸リチウム粉末と、正極結着剤A(第1結着剤)として平均分子量60万のPVDF(弾性率700MPa)と、導電材としてアセチレンブラックと、適量のNMPとを、双腕式練合機にて攪拌し、スラリー状の正極合剤A(第1合剤)を調製した。正極活物質、正極結着剤A、および導電材の重量比は、100:2:2とした。
正極活物質として、上記と同じニッケル酸リチウムと、正極結着剤B(第2結着剤)として平均分子量100万のPVDF(弾性率1000MPa)と、導電材であるアセチレンブラックと、適量のNMPとを、双腕式練合機にて攪拌し、スラリー状の正極合剤B(第2合剤)を調製した。正極活物質、正極結着剤B、および導電材の重量比は、100:2:2とした。
正極集電体として、厚み15μmのアルミニウム箔を準備した。正極集電体の一方の面に正極合剤Aを塗布し、乾燥して、塗膜A(厚み89μm)を形成した。正極集電体の他方の面に正極合剤Bを塗布し、乾燥して、塗膜B(厚み90μm)を形成した。このようにして、正極集電体、塗膜A、および塗膜Bを有する正極前駆体を得た。
正極前駆体を一対のローラにて圧縮した。すなわち、塗膜Aおよび塗膜Bに同じ圧力(線圧1.5×102N/cm)を加えて、塗膜Aおよび塗膜Bを圧縮し、それぞれ合剤層A(第1合剤層)および合剤層B(第2合剤層)を形成した。このようにして正極を得た。その後、円筒型電池(品番18650)の電池ケースに挿入可能なサイズに正極を帯状に切断した。具体的には、正極の長手方向の寸法660mm、および幅の寸法55mmとした。
負極活物質として、平均粒子径15μm、平均円形度0.95、およびタップ密度1.4g/cm3である人造黒鉛300gと、負極結着剤である日本ゼオン(株)製の「BM-400B(商品名)」(スチレン-ブタジエン共重合体の変性体を40重量%含む水性分散液)7.5gと、増粘剤であるCMC3gと、適量の水とを、双腕式練合機にて攪拌し、スラリー状の負極合剤を調製した。この負極合剤を、負極集電体である厚み10μmの銅箔の両面に塗布し、乾燥して、塗膜を得た。この塗膜を線圧40N/cmで圧縮して、負極合剤層を形成した。このとき、負極集電体およびその両面に形成された負極合剤層からなる負極の厚みは180μmであった。その後、円筒型電池(品番18650)の電池ケースに挿入可能なサイズに負極を帯状に切断した。具体的には、負極の長手方向の寸法750mm、および幅の寸法57mmとした。
EC、DMC、およびEMCの混合溶媒(体積比2:3:3)に、溶質としてLiPF6を1mol/Lの濃度で溶解し、非水電解質を調製した。非水電解質100重量部あたりVCを3重量部添加した。
上記で得られた正極、負極、および非水電解質を用いて、以下の手順で、図1に示す品番18650の円筒型非水電解質二次電池を作製した。
正極5の正極リード接続部に正極リード5aの一端を接続した。負極5の負極リード接続部に負極リード6aの一端を接続した。その後、正極5と負極6とを、正極5と負極6との間にセパレータ7を配置して捲回し、円筒状の電極群を構成した。セパレータ7には、ポリエチレン樹脂製の微多孔膜(厚み15μm)を用いた。
2枚のセパレータを一対の巻芯で挟み、2枚のセパレータの間に正極を配置し、2枚のセパレータの一方の外側に負極を配置した状態で、負極が正極よりも内側になるように、一対の巻芯を中心にして捲回した。このとき、合剤層A(第1合剤層)は外側、合剤層B(第2合剤層)が内側に位置するように正極を配置した。
合剤層AおよびBにおける、領域Xの活物質量、および画像解析より求めた領域Xの体積から、正極捲回後の領域Xにおける容量密度AおよびBを求めた。その結果、正極捲回後(電極群構成後)における容量密度A1と容量密度B1との比:A1/B1は、0.985であった。
正極結着剤Aに、平均分子量30万のPVDF(弾性率500MPa)を用いた以外、実施例1と同様の方法により正極を作製した。圧縮後の合剤層Aの厚みは、58μmであった。圧縮後の合剤層Aの単位体積1cm3あたりの容量(容量密度A1)は、640mAhであった。正極捲回前における容量密度A1と容量密度B1との比:A1/B1は、1.032であった。
上記正極を用いた以外、実施例1と同様の方法により電極群を作製した。正極捲回後における容量密度A1と容量密度B1との比:A1/B1は、1.00であった。
上記電極群を用いた以外、実施例1と同様の方法により電池を作製した。
正極結着剤Aに平均分子量30万のPVDF(弾性率500MPa)を用いた。正極結着剤Bに平均分子量120万のPVDF(弾性率1100MPa)を用いた。上記以外、実施例1と同様の方法により正極を作製した。
圧縮後の合剤層Aの厚みは、58μmであった。圧縮後の合剤層Aの単位体積1cm3あたりの容量(容量密度A1)は、640mAhであった。圧縮後の合剤層Bの厚みは、61μmであった。圧縮後の合剤層Bの単位体積1cm3あたりの容量(容量密度B1)は、610mAhであった。正極捲回前における容量密度A1と容量密度B1との比:A1/B1は、1.049であった。
上記正極を用いた以外、実施例1と同様の方法により電極群を作製した。正極捲回後における容量密度A1と容量密度B1との比:A1/B1は、1.025であった。
上記電極群を用いた以外、実施例1と同様の方法により電池を作製した。
集電体の両面に合剤層Bが形成された正極を用いた以外、実施例1と同様の方法により電池を作製した。正極捲回前における容量密度A1と容量密度B1との比:A1/B1は、1.00であった。正極捲回後における容量密度A1と容量密度B1との比:A1/B1は、0.97であった。
25℃の環境下において、各電池について、下記条件で充放電を1000回繰り返し実施し、1サイクル目および1000サイクル目の放電容量を求めた。
充電電流:3000mA
放電電流:3000mA
充電終止電圧:4.2V
放電終止電圧:2.5V
そして、下記式より容量維持率を求めた。
容量維持率(%)=(1000サイクル目の放電容量/1サイクル目の放電容量)×100
上記試験結果を表1に示す。
なお、本実施例では、正極に本発明の電極を用いたが、負極または正極および負極の両方に、本発明の電極を用いても、充放電サイクル特性は向上する。
正極活物質C(第1活物質)として、平均粒径12μm、平均円形度0.95、およびタップ密度2.9g/cm3であるニッケル酸リチウム粉末と、正極結着剤として平均分子量60万のPVDF(弾性率700MPa)と、導電材としてアセチレンブラックと、適量のNMPとを、双腕式練合機にて攪拌し、スラリー状の正極合剤C(第1合剤)を調製した。正極活物質C、正極結着剤、および導電材の重量比は、100:2:2とした。
正極前駆体を一対のローラにて圧縮した。すなわち、塗膜Cおよび塗膜Dに同じ圧力(線圧1.5×102N/cm)を加えて、塗膜Cおよび塗膜Dを圧縮し、それぞれ合剤層C(第1合剤層)および合剤層D(第2合剤層)を形成した。このようにして正極を得た。その後、円筒型電池(品番18650)の電池ケースに挿入可能なサイズ(長手方向の寸法660mm、幅の寸法55mm)に正極を切断した。
正極における領域X(電極群構成時の捲回軸に垂直な断面における曲率半径が3.0×10-3m以下の領域)は、正極の巻芯側の端部から長手方向に沿って10mmの幅の領域であった。
合剤層CおよびDにおける、領域Xの活物質量、および画像解析より求めた領域Xの体積から、正極捲回後の領域Xにおける容量密度C1およびD1を求めた。その結果、正極捲回後(電極群構成後)における容量密度C1と容量密度D1との比:C1/D1は、1.00であった。
上記電極群を用いた以外、実施例1と同様の方法により電池を作製した。
正極活物質C(第1正極活物質)として、平均粒径20μmおよび平均円形度0.95であるニッケル酸リチウム粉末(正極活物質PA)と、平均粒径5μmおよび平均円形度0.95であるニッケル酸リチウム粉末(正極活物質PB)とを9:1の重量比で混合したニッケル酸リチウム(タップ密度3.0g/cm3)を用いた。
正極活物質D(第2正極活物質)として、平均粒径12μm、平均円形度0.95、タップ密度2.9g/cm3であるニッケル酸リチウム粉末を用いた。
上記以外、実施例4と同様の方法により正極を得た。圧縮後の合剤層Cの厚みは、58μmであった。圧縮後の合剤層Dの厚みは、59μmであった。圧縮後の合剤層Cの単位体積1cm3あたりの容量(容量密度C1)は、650mAhであった。圧縮後の合剤層Dの単位体積1cm3あたりの容量(容量密度D1)は、640mAhであった。正極捲回前における容量密度C1と容量密度D1との比:C1/D1は、1.017であった。
上記正極を用いた以外、実施例4と同様の方法により電極群を作製した。正極捲回後における容量密度C1と容量密度D1との比:C1/D1は、0.980であった。
上記電極群を用いた以外、実施例1と同様の方法により電池を作製した。
正極活物質C(第1正極活物質)として、平均粒径20μmおよび平均円形度0.95、であるニッケル酸リチウム粉末(正極活物質PA)と、平均粒径5μmおよび平均円形度0.95であるニッケル酸リチウム粉末(正極活物質PB)とを8:2の重量比で混合したニッケル酸リチウム(タップ密度3.1g/cm3)を用いた。これ以外、実施例5と同様の方法により正極を作製した。
圧縮後の合剤層Cの厚みは、57μmであった。圧縮後の合剤層Cの単位体積1cm3あたりの容量は、660mAh(容量密度C1)であった。正極捲回前における容量密度C1と容量密度D1との比:C1/D1は、1.031であった。
上記正極を用いた以外、実施例5と同様の方法により電極群を作製した。正極捲回後における容量密度C1と容量密度D1との比:C1/D1は、1.000であった。
上記電極群を用いた以外、実施例1と同様の方法により電池を作製した。
正極活物質C(第1正極活物質)として、平均粒径20μmおよび平均円形度0.95であるニッケル酸リチウム粉末(正極活物質PA)と、平均粒径5μmおよび平均円形度0.95であるニッケル酸リチウム粉末(正極活物質PB)とを7:3の重量比で混合したニッケル酸リチウム(タップ密度3.2g/cm3)を用いた。これ以外、実施例5と同様の方法により正極を作製した。
圧縮後の合剤層Cの厚みは、56μmであった。圧縮後の合剤層Cの単位体積1cm3あたりの容量は、670mAh(容量密度C1)であった。正極捲回前における容量密度C1と容量密度D1との比:C1/D1は、1.046であった。
上記正極を用いた以外、実施例5と同様の方法により電極群を作製した。正極捲回後における容量密度C1と容量密度D1との比:C1/D1は、1.025であった。
上記電極群を用いた以外、実施例1と同様の方法により電池を作製した。
(1)正極合剤Cの作製
正極活物質C(第1正極活物質)を用いて、平均粒径12μm、平均円形度0.95、およびタップ密度2.9g/cm3であるニッケル酸リチウム粉末と、正極結着剤として平均分子量60万のPVDF(弾性率700MPa)と、導電材としてアセチレンブラックと、適量のNMPとを、双腕式練合機にて攪拌し、スラリー状の正極合剤C(第1合剤)を調製した。正極活物質C、正極結着剤、および導電材の重量比は、100:2:2とした。正極の塗工重量を0.0200g/cm2とした。
正極活物質D(第2正極活物質)として、平均粒径10μm、平均円形度0.90、およびタップ密度2.7g/cm3であるニッケル酸リチウムと、上記と同じ正極結着剤および導電材と、適量のNMPとを、双腕式練合機にて攪拌し、スラリー状の正極合剤D(第2合剤)を調製した。正極活物質D、正極結着剤、および導電材の重量比は、100:2:2とした。正極の塗工重量を0.0206g/cm2とした。
正極集電体として、厚み15μmのアルミニウム箔を準備した。正極集電体の一方の面に正極合剤Cを塗布し、乾燥して、塗膜C(厚み89μm)を形成した。正極集電体の他方の面に正極合剤Dを塗布し、乾燥して、塗膜D(厚み91μm)を形成した。このようにして、正極集電体、塗膜C、および塗膜Dを有する正極前駆体を得た。
正極前駆体を一対のローラにて圧縮した。すなわち、塗膜Cおよび塗膜Dに同じ圧力を加えて、塗膜Cおよび塗膜Dを圧縮し、それぞれ合剤層C(第1合剤層)および合剤層D(第2合剤層)を形成した。このようにして正極を得た。その後、円筒型電池(品番18650)の電池ケースに挿入可能なサイズ(長手方向の寸法660mm、幅の寸法55mm)に正極を切断した。
合剤層Cの単位面積1cm2あたりの容量(容量密度C2)は、3.8mAhであった。合剤層Dの単位面積1cm2あたりの容量(容量密度D2)は、3.9mAhであった。なお、ここでいう面積とは、集電体の主面に平行な面積を指す。容量密度C2と容量密度D2との比:C2/D2は、0.974であった。
正極における領域X(電極群構成時の捲回軸に垂直な断面における曲率半径が3.0×10-3m以下の領域)は、正極の巻芯側の端部から長手方向に沿って10mmの幅の領域であった。
合剤層CおよびDにおける、領域Xの活物質量、および画像解析より求めた領域Xの体積から、正極捲回後の領域Xにおける容量密度C1およびD1を求めた。その結果、正極捲回後(電極群構成後)における容量密度C1と容量密度D1との比:C1/D1は、0.985であった。
上記電極群を用いた以外、実施例1と同様の方法により電池を作製した。
なお、本実施形態では、正極に本発明の電極を用いたが、負極または正極および負極の両方に、本発明の電極を用いても、充放電サイクル特性は向上する。
(1)負極合剤Eの作製
負極活物質E(第1負極活物質)として、平均粒子径15μm、平均円形度0.95、およびタップ密度1.4g/cm3である人造黒鉛と、負極結着剤であるSBRと、増粘剤であるCMCと、適量の水とを、双腕式練合機にて攪拌し、スラリー状の負極合剤E(第1合剤)を調製した。負極活物質E、負極結着剤、およびCMCの重量比は、100:2.5:1とした。
負極活物質F(第2負極活物質)として、平均粒子径15μm、平均円形度0.85、およびタップ密度1.2g/cm3である人造黒鉛と、負極結着剤であるSBRと、増粘剤であるCMCと、適量の水とを、双腕式練合機にて攪拌し、スラリー状の負極合剤E(第2合剤)を調製した。負極活物質F、負極結着剤、およびCMCの重量比は、100:2.5:1とした。
負極集電体として、厚み10μmの銅箔を準備した。負極集電体の一方の面に負極合剤Eを塗布し、乾燥して、塗膜E(厚み101μm)を形成した。負極集電体の他方の面に負極合剤Fを塗布し、乾燥して、塗膜F(厚み106μm)を形成した。このようにして、負極集電体、塗膜E、および塗膜Fを有する負極前駆体を得た。
負極前駆体を一対のローラにて圧縮した。すなわち、塗膜Eおよび塗膜Fに同じ圧力(線圧40N/cm)を加えて、塗膜Eおよび塗膜Fを圧縮し、それぞれ合剤層E(第1合剤層)および合剤層F(第2合剤層)を形成した。このようにして負極を得た。
その後、円筒型電池(品番18650)の電池ケースに挿入可能なサイズ(長手方向の寸法750mm、幅の寸法57mm)に負極を切断した。
正極活物質として、平均粒径12μm、平均円形度0.95、タップ密度2.9g/cm3であるニッケル酸リチウム粉末と、正極結着剤として平均分子量60万のPVDFと、導電材としてアセチレンブラックと、適量のNMPとを、双腕式練合機にて攪拌し、スラリー状の正極合剤を調製した。正極活物質、正極結着剤、および導電材の重量比は、100:2:2とした。この正極合剤を、正極集電体である厚み15μmのアルミニウム箔の両面に塗布し、乾燥して、塗膜を得た。この塗膜を線圧1.5×102N/cmで圧縮して、正極合剤層を形成した。このとき、正極集電体およびその両面に形成された正極合剤層からなる正極の厚みは133μmであった。その後、円筒型電池(品番18650)の電池ケースに挿入可能なサイズに正極を帯状に切断した。具体的には、正極の長手方向の寸法660mm、および幅の寸法55mmとした。
上記正極および負極を用いた以外、実施例1と同様の方法により電極群を構成した。
負極における領域X(電極群構成時の捲回軸に垂直な断面における曲率半径が3.0×10-3m以下の領域)は、負極の巻芯側の端部から長手方向に沿って10mmの幅の領域であった。
負極捲回後(電極群構成後)における容量密度E1と容量密度F1との比:E1/F1は、0.986であった。
上記電極群を用いた以外、実施例1と同様の方法により電池を作製した。
負極活物質E(第1負極活物質)として、平均粒子径15μm、平均円形度0.95、およびタップ密度1.4g/cm3である人造黒鉛と、負極結着剤であるSBRと、増粘剤であるCMCと、適量の水とを、双腕式練合機にて攪拌し、スラリー状の負極合剤E(第1合剤)を調製した。負極活物質E、負極結着剤、およびCMCの重量比は、100:2.5:1とした。
負極前駆体を一対のローラにて圧縮した。すなわち、塗膜Eおよび塗膜Fに同じ圧力(線圧40N/cm)を加えて、塗膜Eおよび塗膜Fを圧縮し、それぞれ合剤層E(第1合剤層)および合剤層F(第2合剤層)を形成した。このようにして負極を得た。その後、円筒型電池(品番18650)の電池ケースに挿入可能なサイズ(長手方向の寸法750mm、幅の寸法57mm)に負極を切断した。
負極における領域X(電極群構成時の捲回軸に垂直な断面における曲率半径が3.0×10-3m以下の領域)は、負極の巻芯側の端部から長手方向に沿って10mmの幅の領域であった。
負極捲回後(電極群構成後)における容量密度E1と容量密度F1との比:E1/F1は、1.000であった。
上記電極群を用いた以外、実施例1と同様の方法により電池を作製した。
負極活物質E(第1負極活物質)として、平均粒子径20μmおよび平均円形度0.95である人造黒鉛(負極活物質NA)と、平均粒径5μmおよび平均円形度0.95である人造黒鉛(負極活物質NB)とを8:2の重量比で混合した人造黒鉛(タップ密度1.5g/cm3)を用いた。負極結着剤であるSBRと、増粘剤であるCMCと、適量の水とを、双腕式練合機にて攪拌し、スラリー状の負極合剤E(第1合剤)を調製した。負極活物質E、負極結着剤、およびCMCの重量比は、100:2.5:1とした。
負極前駆体を一対のローラにて圧縮した。すなわち、塗膜Eおよび塗膜Fに同じ圧力(線圧40N/cm)を加えて、塗膜Eおよび塗膜Fを圧縮し、それぞれ合剤層E(第1合剤層)および合剤層F(第2合剤層)を形成した。このようにして負極を得た。その後、円筒型電池(品番18650)の電池ケースに挿入可能なサイズ(長手方向の寸法750mm、幅の寸法57mm)に負極を切断した。
負極における領域X(電極群構成時の捲回軸に垂直な断面における曲率半径が3.0×10-3m以下の領域)は、負極の巻芯側の端部から長手方向に沿って10mmの幅の領域であった。
負極捲回後(電極群構成後)における容量密度E1と容量密度F1との比:E1/F1は、0.986であった。
上記電極群を用いた以外、実施例1と同様の方法により電池を作製した。
実施例6の正極および実施例10の負極を用いた以外、実施例1と同様の方法により電池を作製した。正極および負極の電極作製時および電極群構成時の(第1容量密度/第2容量密度)の値を表4に示す。
実施例12の電池について、上記と同様の評価を行った。その結果を表4に示す。
以上のことより、正極のみに本発明の電極を用いた場合、負極のみに本発明の電極を用いた場合、および正負極の両方に本発明の電極を用いた場合のいずれにおいても、充放電効率が向上することがわかった。
Claims (13)
- 捲回型電極群に用いられる電極であって、
集電体と、前記集電体の一方の面に形成された、第1活物質を含む第1合剤層と、前記集電体の他方の面に形成された、第2活物質を含む第2合剤層とを有し、
電極群構成時において、前記第1合剤層は、前記第2合剤層よりも外側に位置するように捲回され、
電極群の捲回軸に垂直な断面における曲率半径が3.0×10-3m以下の所定領域に対応する部分において、前記第1合剤層の単位体積あたりの容量Cv1は、前記第2合剤層の単位体積あたりの容量Cv2よりも、大きいことを特徴とする電極。 - 前記所定領域に対応する部分において、前記第1合剤層の単位体積あたりの容量Cv1と、前記第2合剤層の単位体積あたりの容量Cv2との比:Cv1/Cv2は、1.01超1.05以下である請求項1記載の電極。
- 前記所定領域に対応する部分において、前記第1合剤層の単位体積あたりの容量Cv1と、前記第2合剤層の単位体積あたりの容量Cv2との比:Cv1/Cv2は、1.01超1.04以下である請求項1記載の電極。
- 前記所定領域に対応する部分において、前記第1合剤層の単位面積あたりの容量Ca1と、前記第2合剤層の単位面積あたりの容量Ca2との比:Ca1/Ca2は、0.97超1.03未満である請求項1記載の電極。
- 前記第1および第2合剤層は、それぞれ第1および第2結着剤を含み、
前記第1結着剤は、前記第2結着剤よりも、弾性率が低い請求項1記載の電極。 - 前記第1活物質は、前記第2活物質よりも、充填性が高い請求項1に記載の電極。
- 一対の電極を、両電極間にセパレータを介して、捲回した電極群を備えた二次電池であって、
前記一対の電極の少なくとも一方は、集電体と、前記集電体の一方の面に形成された、第1活物質を含む第1合剤層と、前記集電体の他方の面に形成された、第2活物質を含む第2合剤層とを有し、
前記電極群において、前記第1合剤層は、前記第2合剤層よりも外側に位置するように捲回され、
前記電極群の捲回軸に垂直な断面における曲率半径が3.0×10-3m以下の所定領域において、前記第1合剤層の単位体積あたりの容量Cv1と、前記第2合剤層の単位体積あたりの容量Cv2との比:Cv1/Cv2は、0.97超1.03未満であることを特徴とする二次電池。 - 前記電極群において、前記第1合剤層の単位体積あたりの容量Cv1と、前記第2合剤層の単位体積あたりの容量Cv2との比:Cv1/Cv2は、0.98以上1.02以下である請求項7記載の二次電池。
- 前記電極群において、前記第1合剤層の単位体積あたりの容量Cv1と、前記第2合剤層の単位体積あたりの容量Cv2との比:Cv1/Cv2は、0.99以上1.01以下である請求項7記載の二次電池。
- 前記電極群において、前記第1合剤層の単位体積あたりの容量Cv1と、前記第2合剤層の単位体積あたりの容量Cv2との比:Cv1/Cv2は、1.00である請求項7記載の二次電池。
- (1)集電体の一方の面に第1活物質を含む第1合剤層を形成し、集電体の他方の面に第2活物質を含む第2合剤層を形成し、一方の極性を有する電極Aを構成する工程と、
(2)前記電極Aと、他方の極性を有する電極Bとを、両者間にセパレータを介して、前記第1合剤層が前記第2合剤層よりも外側に位置するように捲回し、電極群を構成する工程と、を含み、
前記工程(1)では、電極群の捲回軸に垂直な断面における曲率半径が3.0×10-3m以下の所定領域に対応する部分において、前記第1合剤層の単位体積あたりの容量Cv1が、前記第2合剤層の単位体積あたりの容量Cv2よりも大きくなるように、前記電極Aを構成し、
前記工程(2)では、前記所定領域において、前記第1合剤層の単位体積あたりの容量Cv1と、前記第2合剤層の単位体積あたりの容量Cv2との比:Cv1/Cv2が0.97超1.03未満となるように、前記電極群を構成することを特徴とする二次電池の製造方法。 - 前記工程(1)は、
(a)前記集電体の一方の面に前記第1活物質を含む第1合剤を塗布し、乾燥し、第1塗膜を形成する工程と、
(b)前記集電体の他方の面に前記第2活物質を含む第2合剤を塗布し、乾燥し、第2塗膜を形成する工程と、
(c)前記第1塗膜および前記第2塗膜にそれぞれ同じ圧力を加えることにより前記第1塗膜および前記第2塗膜を圧縮し、第1合剤層および第2合剤層を形成する工程と、
を含み、
前記第1合剤および第2合剤は、それぞれ第1および第2結着剤を含み、
前記第1結着剤は、前記第2結着剤よりも、弾性率が低く、
前記工程(c)において、前記第1塗膜は、前記第2塗膜よりも圧縮される請求項11記載の二次電池の製造方法。 - 前記工程(1)は、
(A)前記集電体の一方の面に前記第1活物質を含む第1合剤を塗布し、乾燥し、第1塗膜を形成する工程と、
(B)前記集電体の他方の面に前記第2活物質を含む第2合剤を塗布し、乾燥し、第2塗膜を形成する工程と、
(C)前記第1塗膜および前記第2塗膜にそれぞれ同じ圧力を加えることにより前記第1塗膜および前記第2塗膜を圧縮し、第1合剤層および第2合剤層を形成する工程と、
を含み、
前記第1活物質は、前記第2活物質よりも、充填性が高く、
前記工程(C)において、前記第1塗膜は、前記第2塗膜よりも圧縮される請求項11記載の二次電池の製造方法。
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JPWO2017150264A1 (ja) * | 2016-02-29 | 2018-12-27 | パナソニックIpマネジメント株式会社 | 電気化学デバイスおよびこれに用いる負極とその製造方法 |
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