WO2017212594A1 - 非水電解質二次電池 - Google Patents
非水電解質二次電池 Download PDFInfo
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- WO2017212594A1 WO2017212594A1 PCT/JP2016/067136 JP2016067136W WO2017212594A1 WO 2017212594 A1 WO2017212594 A1 WO 2017212594A1 JP 2016067136 W JP2016067136 W JP 2016067136W WO 2017212594 A1 WO2017212594 A1 WO 2017212594A1
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- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
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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
- H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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- 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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- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
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- H—ELECTRICITY
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- 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
- H01M10/052—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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
- H01M10/0585—Construction or manufacture of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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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
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
- H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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- H—ELECTRICITY
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- 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
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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- H—ELECTRICITY
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- 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
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M2010/4292—Aspects relating to capacity ratio of electrodes/electrolyte or anode/cathode
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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
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0025—Organic electrolyte
- H01M2300/0028—Organic electrolyte characterised by the solvent
- H01M2300/0037—Mixture of solvents
- H01M2300/004—Three solvents
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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
Definitions
- the present invention relates to a non-aqueous electrolyte secondary battery.
- a nonaqueous electrolyte secondary battery generally includes a positive electrode obtained by applying a positive electrode active material or the like to a current collector, and a negative electrode obtained by applying a negative electrode active material or the like to a current collector. It has the structure connected through the electrolyte layer holding electrolyte gel. Then, when ions such as lithium ions are occluded / released in the electrode active material, a charge / discharge reaction of the battery occurs.
- non-aqueous electrolyte secondary batteries with a low environmental load are being used not only for portable devices, but also for power supply devices for electric vehicles such as hybrid vehicles (HEV), electric vehicles (EV), and fuel cell vehicles. .
- HEV hybrid vehicles
- EV electric vehicles
- fuel cell vehicles fuel cell vehicles.
- Non-aqueous electrolyte secondary batteries intended for application to electric vehicles are required to have high output and high capacity. Furthermore, non-aqueous electrolyte secondary batteries intended for application to electric vehicles are required to have cycle characteristics capable of maintaining capacity even when charge / discharge cycles are repeated for a long period of time.
- the density of the positive electrode active material layer is increased and the porosity of the active material layer is decreased, so that the penetration of the non-aqueous electrolyte in the active material layer is hindered.
- Patent Document 1 in the lithium ion secondary battery in which the active material density of the positive electrode active material layer is 3.65 g / cm 3 or more, as the positive electrode active material, large particle size particles having a crushing strength of 85 MPa or more and small particles A mixture of diameter particles is used. With such a configuration, even when a positive electrode having a high active material density in the positive electrode active material layer is provided, cracking of the positive electrode active material is suppressed and a battery having excellent cycle characteristics can be obtained. is there.
- non-aqueous electrolyte secondary batteries for electric vehicles are required to have high capacity and high output in order to extend the cruising distance in one charge.
- improvement in battery durability (cycle characteristics in repeated charge / discharge) is required so that a sufficient cruising distance can be secured even under repeated charge / discharge.
- the lithium ion secondary battery described in Patent Document 1 cannot be said to have sufficient cycle characteristics, and further improvement is demanded.
- an object of the present invention is to provide a non-aqueous electrolyte secondary battery having improved battery durability in a high capacity, high density, and large area battery.
- the present invention is characterized in that, in a battery having a high capacity, a high density, and a large area, a variation in porosity in the positive electrode active material layer is 6.0% or less.
- FIG. 1 is a schematic cross-sectional view showing a basic configuration of a non-aqueous electrolyte lithium ion secondary battery that is not a flat (stacked) bipolar type, which is an embodiment of a non-aqueous electrolyte secondary battery. It is explanatory drawing for demonstrating the method of selecting five area
- the first embodiment of the present invention includes a positive electrode in which a positive electrode active material layer containing a positive electrode active material is formed on the surface of a positive electrode current collector, and a negative electrode active material layer containing a negative electrode active material on the surface of the negative electrode current collector.
- the power generation element includes a negative electrode formed and a separator, the ratio of the rated capacity to the pore volume of the positive electrode active material layer is 1.40 Ah / cc or more, and the ratio of the battery area to the rated capacity is 4
- Non-aqueous electrolyte secondary battery having a capacity of 0.0 cm 2 / Ah or more and a rated capacity of 30 Ah or more, wherein the non-aqueous electrolyte has a variation in porosity of the positive electrode active material layer of 6.0% or less It is a secondary battery. In 1st embodiment, it becomes a nonaqueous electrolyte secondary battery which durability improved notably by making the dispersion
- Non-aqueous electrolyte secondary batteries particularly non-aqueous electrolyte secondary batteries for electric vehicles, are required to have high output and high capacity in order to increase the cruising distance in one charge.
- improvement of durability is an important issue for a battery mounted on an electric vehicle so that high output and high capacity are not lowered by repeated charging and discharging with a large current for a short time.
- the capacity maintenance rate after 500 cycles is about 80 to 83% (Patent Document 1: Table 1), but further life extension is required for the popularization of electric vehicles.
- the inventors of the present invention have a capacity ratio of the positive electrode active material layer to the pore volume of 1.40 Ah / cc (Ah / cm 3 ) or more, and a ratio of the battery area to the rated capacity of 4.0 cm 2 / Ah or more.
- the distribution of pores in the positive electrode active material layer It has been found that the cycle characteristics are remarkably improved by setting the variation to 6.0% or less.
- the positive electrode active material is likely to be burdened during charge and discharge, and the life is likely to deteriorate.
- the diffusibility of Li ions Since it is bad, the battery life is likely to deteriorate due to particle cracking of the positive electrode active material.
- the current concentration in the positive electrode active material layer is alleviated, the deterioration due to the side reaction due to the overvoltage variation is suppressed, and the durability is improved. It is considered possible.
- the variation in the porosity of the positive electrode active material layer is allowed to 6.0%.
- the variation in the porosity in the positive electrode active material layer exceeds 6.0%, the capacity retention rate after repeated charge / discharge is remarkably reduced (see Comparative Examples 1 to 3 described later).
- the present invention can be said to be a problem solving means specialized for high capacity density, large area, high capacity non-aqueous electrolyte secondary batteries.
- the electrode As a structure of the electrode, there is a flat rectangular structure in addition to a wound type. Among these, in the wound type battery, the pressure distribution hardly occurs in the positive electrode surface as described above due to its structure. On the other hand, the flat rectangular electrode has a larger surface area and a shorter distance between the battery surface and the center than the wound electrode. For this reason, the heat generated inside the battery can be easily released to the outside, and the heat can be prevented from staying in the center of the battery. In an electric vehicle, charging and discharging are performed with a large current, and thus high heat dissipation is required. However, by using a flat rectangular electrode, a rise in battery temperature can be suppressed and deterioration in battery performance can be suppressed. be able to.
- the area of the non-aqueous electrolyte secondary battery used for the electric vehicle is very large compared to the consumer battery.
- a high-capacity, high-capacity density, large-area flat rectangular battery further improvement in battery durability is required.
- the problem of the pressure distribution in the positive electrode surface and hence the deterioration of the cycle characteristics becomes obvious because of the size of the area.
- the nonaqueous electrolyte secondary battery of the present invention can be particularly suitably used for a flat type nonaqueous electrolyte secondary battery.
- FIG. 1 is a schematic cross-sectional view schematically showing an outline of a flat laminated battery which is an embodiment of the battery of the present invention.
- the battery can be made compact and have a high capacity.
- the flat-stacked lithium ion secondary battery shown in FIG. 1 that is not a bipolar type battery will be described in detail as an example.
- the lithium ion secondary battery is not limited to a stacked flat shape, but the pressure in the surface direction is likely to be non-uniform, and the effects of the present invention are more easily exhibited.
- a flat shape is preferable, and since a high capacity can be easily achieved, a laminated type is more preferable.
- the wound lithium ion secondary battery may have a cylindrical shape, or may have a shape that is a flattened rectangular shape by deforming such a cylindrical shape.
- a laminate film may be used for the exterior material, and the conventional cylindrical can (metal can) may be used, for example, It does not restrict
- the power generation element is covered with an aluminum laminate film. With this configuration, weight reduction can be achieved.
- FIG. 1 is a schematic cross-sectional view schematically illustrating a basic configuration of a non-aqueous electrolyte lithium ion secondary battery (hereinafter also simply referred to as “stacked battery”) that is not a flat stacked bipolar type.
- the stacked battery 10 of the present embodiment has a structure in which a flat, substantially rectangular power generation element 21 in which a charge / discharge reaction actually proceeds is sealed inside a battery exterior material 29 that is an exterior body.
- the power generation element 21 has a configuration in which a positive electrode, a separator 17, and a negative electrode are stacked.
- the separator 17 contains a nonaqueous electrolyte (for example, a liquid electrolyte).
- the positive electrode has a structure in which the positive electrode active material layers 15 are disposed on both surfaces of the positive electrode current collector 12.
- the negative electrode has a structure in which the negative electrode active material layer 13 is disposed on both surfaces of the negative electrode current collector 11.
- the negative electrode, the electrolyte layer, and the positive electrode are laminated in this order so that one positive electrode active material layer 15 and the negative electrode active material layer 13 adjacent thereto face each other with a separator 17 therebetween.
- the adjacent positive electrode, electrolyte layer, and negative electrode constitute one unit cell layer 19. Therefore, it can be said that the stacked battery 10 shown in FIG. 1 has a configuration in which a plurality of single battery layers 19 are stacked and electrically connected in parallel.
- the negative electrode active material layer 13 is arrange
- the positive electrode current collector 12 and the negative electrode current collector 11 are each provided with a positive electrode current collector plate (tab) 27 and a negative electrode current collector plate (tab) 25 that are electrically connected to the respective electrodes (positive electrode and negative electrode). It has the structure led out of the battery exterior material 29 so that it may be pinched
- the positive electrode current collector 27 and the negative electrode current collector 25 are ultrasonically welded to the positive electrode current collector 12 and the negative electrode current collector 11 of each electrode, respectively, via a positive electrode lead and a negative electrode lead (not shown) as necessary. Or resistance welding or the like.
- FIG. 1 shows a flat battery that is not a flat stacked bipolar battery, but a positive electrode active material layer that is electrically coupled to one surface of the current collector and a surface opposite to the current collector.
- a bipolar battery including a bipolar electrode having a negative electrode active material layer that is electrically coupled may be used.
- one current collector also serves as a positive electrode current collector and a negative electrode current collector.
- the positive electrode has a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material formed on the surface of the positive electrode current collector.
- a metal is preferably used.
- the metal include aluminum, nickel, iron, stainless steel, titanium, copper, and other alloys.
- a clad material of nickel and aluminum, a clad material of copper and aluminum, or a plating material of a combination of these metals can be preferably used.
- covered on the metal surface may be sufficient.
- aluminum, stainless steel, and copper are preferable from the viewpoints of electronic conductivity and battery operating potential.
- the size of the current collector is determined according to the intended use of the battery. For example, if it is used for a large battery that requires a high energy density, a current collector having a large area is used. There is no particular limitation on the thickness of the current collector.
- the thickness of the current collector is usually about 1 to 100 ⁇ m.
- the positive electrode active material layer 15 includes a positive electrode active material, and, if necessary, a binder; a conductive additive, an electrolyte (polymer matrix, ion conductive polymer, electrolytic solution, etc.), and a lithium salt for increasing ion conductivity. And other additives.
- the positive electrode active material examples include LiMn 2 O 4 , LiCoO 2 , LiNiO 2 , Li (Ni—Mn—Co) O 2, and lithium-- such as those in which some of these transition metals are substituted with other elements.
- Examples include transition metal composite oxides, lithium-transition metal phosphate compounds, and lithium-transition metal sulfate compounds.
- a lithium-transition metal composite oxide is used as the positive electrode active material.
- two or more positive electrode active materials may be used in combination.
- NMC composite oxide Li (Ni—Mn—Co) O 2 and those in which some of these transition metals are substituted with other elements (hereinafter also simply referred to as “NMC composite oxide”) are used.
- the NMC composite oxide has a layered crystal structure in which lithium atomic layers and transition metal (Mn, Ni, and Co are arranged in order) atomic layers are alternately stacked via oxygen atomic layers.
- one Li atom is contained per one atom of the transition metal, and the amount of Li that can be taken out is twice that of the spinel-based lithium manganese oxide, that is, the supply capacity is doubled, so that a high capacity can be obtained.
- the NMC composite oxide includes a composite oxide in which a part of the transition metal element is substituted with another metal element.
- Other elements in that case include Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, Cr, Fe, B, Ga, In, Si, Mo, Y, Sn, V, Cu , Ag, Zn and the like.
- Preferred are Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, and Cr. More preferred are Ti, Zr, P, Al, Mg, and Cr. From the viewpoint of improving cycle characteristics, Ti, Zr, Al, Mg, and Cr are more preferable.
- the NMC composite oxide has a high theoretical discharge capacity, it is preferable that the general formula (1): Li a Ni b Mn c Co d M x O 2 (where a, b, c, d, x Satisfies 0.9 ⁇ a ⁇ 1.2, 0 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 0.5, 0 ⁇ d ⁇ 0.5, and 0 ⁇ x ⁇ 0.3, where M is Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr and Cr.
- a represents the atomic ratio of Li
- b represents the atomic ratio of Ni
- c represents the atomic ratio of Mn
- d represents the atomic ratio of Co
- x represents the atomic ratio of M.
- the composition of each element can be measured by, for example, inductively coupled plasma (ICP) emission spectrometry.
- ICP inductively coupled plasma
- Ni nickel
- Co cobalt
- Mn manganese
- Ti or the like partially replaces the transition metal in the crystal lattice. From the viewpoint of cycle characteristics, a part of the transition element may be substituted with another metal element. In this case, it is preferable that 0 ⁇ x ⁇ 0.3 in the general formula (1). Since at least one selected from the group consisting of Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, and Cr is dissolved, the crystal structure is stabilized. It is considered that the battery capacity can be prevented from decreasing even if the above is repeated, and that excellent cycle characteristics can be realized.
- the NMC composite oxide can be prepared by selecting various known methods such as a coprecipitation method and a spray drying method.
- the coprecipitation method is preferably used because the composite oxide is easy to prepare.
- a nickel-cobalt-manganese composite hydroxide is produced by a coprecipitation method as in the method described in JP2011-105588A. Thereafter, the nickel-cobalt-manganese composite hydroxide and the lithium compound are mixed and fired to obtain an NMC composite oxide.
- positive electrode active materials other than those described above may be used.
- the average particle diameter of the positive electrode active material contained in the positive electrode active material layer is not particularly limited, but is preferably 1 to 100 ⁇ m, more preferably 1 to 25 ⁇ m from the viewpoint of increasing the output.
- the average particle diameter is measured by a particle size distribution measuring apparatus using a laser diffraction / scattering method.
- the content of the positive electrode active material (in terms of solid content) is preferably 80 to 99.5% by weight, and more preferably 85 to 99.5% by weight.
- Density of the positive electrode active material layer is preferably 2.5 ⁇ 3.8g / cm 3, more preferably 2.6 ⁇ 3.7g / cm 3, 2 . More preferably, it is 8 to 3.7 g / cm 3 .
- the binder used for the positive electrode active material layer is not particularly limited.
- polyethylene, polypropylene, polyethylene terephthalate (PET), polyether nitrile, polyacrylonitrile, polyimide, polyamide, cellulose, carboxymethyl cellulose (CMC) and a salt thereof Ethylene-vinyl acetate copolymer, polyvinyl chloride, styrene-butadiene rubber (SBR), isoprene rubber, butadiene rubber, ethylene-propylene rubber, ethylene-propylene-diene copolymer, styrene-butadiene-styrene block copolymer and Its hydrogenated product, thermoplastic polymer such as styrene / isoprene / styrene block copolymer and its hydrogenated product, polyvinylidene fluoride (PVdF), polytetrafluoroethylene ( TFE), tetrafluoro
- the amount of the binder contained in the positive electrode active material layer is not particularly limited as long as it is an amount capable of binding the active material, but preferably 0.5 to 15% by weight with respect to the active material layer. More preferably, it is 1 to 10% by weight.
- the conductive assistant refers to an additive that is blended in order to improve the conductivity of the positive electrode active material layer or the negative electrode active material layer.
- the conductive auxiliary agent include carbon materials such as carbon black such as ketjen black and acetylene black, graphite, and carbon fiber.
- the amount of the conductive auxiliary agent contained in the positive electrode active material layer is not particularly limited, but is preferably 0.5 to 15% by weight, more preferably 1 to 10% by weight with respect to the active material layer. It is.
- electrolyte salt examples include Li (C 2 F 5 SO 2 ) 2 N, LiPF 6 , LiBF 4 , LiClO 4 , LiAsF 6 , LiCF 3 SO 3 and the like.
- Examples of the ion conductive polymer include polyethylene oxide (PEO) and polypropylene oxide (PPO) polymers.
- the compounding ratio of the components contained in the positive electrode active material layer and the negative electrode active material layer described later is not particularly limited.
- the blending ratio can be adjusted by appropriately referring to known knowledge about lithium ion secondary batteries.
- the thickness of each active material layer is not particularly limited, and conventionally known knowledge about the battery can be appropriately referred to. As an example, the thickness of each active material layer is about 2 to 100 ⁇ m.
- variation in the porosity in a positive electrode active material layer is 6.0% or less.
- the ratio of the rated capacity to the pore volume of the positive electrode active material layer is 2.20 Ah / cc or more, and the variation in the porosity in the positive electrode active material layer is 5.0% or less.
- the variation in the porosity of the positive electrode active material layer is 5.0% or less.
- the capacity retention rate is significantly improved. This is because a battery having a high capacity density has a more remarkable effect on the cycle characteristics due to the variation in the porosity, and thus it is considered that the uniformity of the porosity is required to be 5.0%.
- the variation in porosity in the positive electrode active material layer is 4.0% or less.
- the variation in the porosity in the positive electrode active material layer is 4.0% or less, so that the cycle characteristics are further improved (comparison with Examples 1 to 6 and Examples 7 to 12 described later).
- the variation in the porosity in the positive electrode active material layer is preferably as low as possible from the viewpoint of improving the cycle characteristics, but is usually 0.5% or more.
- the variation in porosity in the positive electrode active material layer is more preferably 2.0% or more, and further preferably 3.0% or more. 3.5% or more is particularly preferable.
- the variation in porosity in the positive electrode active material layer is calculated by the following formula
- the porosity is measured (total number of measurements: 5 points ⁇ number of stacked layers), the maximum porosity and the minimum porosity are determined, and the average porosity is calculated. From these values, the variation is calculated by applying the above formula.
- the pore volume of the sample is measured.
- the pore volume of the sample is measured as follows.
- the volume of pores (micropores) existing inside the sample is measured by measuring the pore distribution by a mercury intrusion method using a mercury intrusion porosimeter.
- the mercury porosimeter utilizes this, and mercury is injected into the pores, and the diameter of the pores is determined from the required pressure, and the pore volume (sample pore volume) is determined from the amount of injection.
- the negative electrode has a negative electrode current collector and a negative electrode active material layer formed on the surface of the negative electrode current collector.
- the negative electrode active material layer contains a negative electrode active material and, if necessary, other materials such as a conductive aid, a binder, an electrolyte (polymer matrix, ion conductive polymer, electrolyte, etc.), and a lithium salt for increasing ion conductivity. Further includes an additive. Other additives such as conductive assistants, binders, electrolytes (polymer matrix, ion conductive polymers, electrolytes, etc.) and lithium salts for improving ion conductivity are those described in the above positive electrode active material layer column. It is the same.
- the negative electrode active material examples include artificial graphite, coated natural graphite, graphite such as natural graphite, carbon materials such as soft carbon and hard carbon, and lithium-transition metal composite oxide (for example, Li 4 Ti 5 O 12 ), Metal materials, lithium alloy negative electrode materials, and the like.
- two or more negative electrode active materials may be used in combination.
- a carbon material or a lithium-transition metal composite oxide is used as the negative electrode active material.
- negative electrode active materials other than those described above may be used.
- the average particle diameter of the negative electrode active material is not particularly limited, but is preferably 1 to 100 ⁇ m, more preferably 1 to 30 ⁇ m from the viewpoint of increasing the output.
- the negative electrode active material layer preferably contains at least an aqueous binder.
- a water-based binder has a high binding power.
- it is easy to procure water as a raw material and since steam is generated at the time of drying, the capital investment in the production line can be greatly suppressed, and the environmental load can be reduced. There is.
- the water-based binder refers to a binder using water as a solvent or a dispersion medium, and specifically includes a thermoplastic resin, a polymer having rubber elasticity, a water-soluble polymer, or a mixture thereof.
- the binder using water as a dispersion medium refers to a polymer that includes all expressed as latex or emulsion and is emulsified or suspended in water.
- kind a polymer latex that is emulsion-polymerized in a system that self-emulsifies.
- water-based binders include styrene polymers (styrene-butadiene rubber (SBR), styrene-vinyl acetate copolymer, styrene-acrylic copolymer, etc.), acrylonitrile-butadiene rubber, and methyl methacrylate-butadiene rubber.
- SBR styrene-butadiene rubber
- styrene-vinyl acetate copolymer styrene-acrylic copolymer
- acrylonitrile-butadiene rubber acrylonitrile-butadiene rubber
- methyl methacrylate-butadiene rubber methyl methacrylate-butadiene rubber
- (Meth) acrylic polymers (polyethyl acrylate, polyethyl methacrylate, polypropyl acrylate, polymethyl methacrylate (methyl methacrylate rubber), polypropyl methacrylate, polyisopropyl acrylate, polyisopropyl methacrylate, polybutyl acrylate, polybutyl methacrylate, Polyhexyl acrylate, polyhexyl methacrylate, polyethylhexyl acrylate, polyethylhexyl methacrylate, polylauryl acrylate, poly Uryl methacrylate, etc.), polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene copolymer, polybutadiene, butyl rubber, fluororubber, polyethylene oxide, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene-propylene-diene copolymer
- the aqueous binder may contain at least one rubber binder selected from the group consisting of styrene-butadiene rubber, acrylonitrile-butadiene rubber, methyl methacrylate-butadiene rubber, and methyl methacrylate rubber from the viewpoint of binding properties. preferable. Furthermore, it is preferable that the water-based binder contains styrene-butadiene rubber (SBR) because of good binding properties.
- SBR styrene-butadiene rubber
- Water-soluble polymers suitable for use in combination with styrene-butadiene rubber include polyvinyl alcohol and modified products thereof, starch and modified products thereof, cellulose derivatives (carboxymethylcellulose (CMC), methylcellulose, hydroxyethylcellulose, and salts thereof) ), Polyvinylpyrrolidone, polyacrylic acid (salt), or polyethylene glycol. Among them, it is preferable to combine styrene-butadiene rubber and carboxymethyl cellulose (CMC) (salt) as a binder.
- CMC carboxymethyl cellulose
- the content of the aqueous binder is preferably 80 to 100% by weight, more preferably 90 to 100% by weight, and preferably 100% by weight.
- the density of the negative electrode active material layer is preferably 1.2 to 1.8 g / cm 3 from the viewpoint of increasing the capacity.
- the basis weight (one-side coating amount) of the negative electrode active material layer is preferably 6.0 to 15.0 mg / cm 2 from the viewpoint of increasing the capacity.
- the separator has a function of holding an electrolyte and ensuring lithium ion conductivity between the positive electrode and the negative electrode, and a function as a partition wall between the positive electrode and the negative electrode.
- the thickness of the microporous (microporous membrane) separator cannot be uniquely defined because it varies depending on the intended use. For example, in applications such as secondary batteries for driving motors such as electric vehicles (EV), hybrid electric vehicles (HEV), and fuel cell vehicles (FCV), it is 4 to 60 ⁇ m in a single layer or multiple layers. Is desirable.
- the fine pore diameter of the microporous (microporous membrane) separator is desirably 1 ⁇ m or less (usually a pore diameter of about several tens of nm).
- nonwoven fabric separator cotton, rayon, acetate, nylon, polyester; polyolefins such as PP and PE; conventionally known ones such as polyimide and aramid are used alone or in combination.
- the bulk density of the nonwoven fabric is not particularly limited as long as sufficient battery characteristics can be obtained by the impregnated polymer gel electrolyte.
- the thickness of the nonwoven fabric separator may be the same as that of the electrolyte layer, and is preferably 5 to 200 ⁇ m, particularly preferably 10 to 100 ⁇ m.
- the separator includes an electrolyte.
- the electrolyte is not particularly limited as long as it can exhibit such a function, but a liquid electrolyte or a gel polymer electrolyte is used.
- a gel polymer electrolyte By using the gel polymer electrolyte, the distance between the electrodes is stabilized, the occurrence of polarization is suppressed, and the durability (cycle characteristics) is improved.
- the liquid electrolyte functions as a lithium ion carrier.
- the liquid electrolyte constituting the electrolytic solution layer has a form in which a lithium salt as a supporting salt is dissolved in an organic solvent as a plasticizer.
- organic solvent include carbonates such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC).
- EC ethylene carbonate
- PC propylene carbonate
- DMC dimethyl carbonate
- DEC diethyl carbonate
- EMC ethyl methyl carbonate
- Li (CF 3 SO 2) 2 N Li (C 2 F 5 SO 2) 2 N
- LiPF 6, LiBF 4, LiClO 4, LiAsF 6, LiTaF such 6 LiCF 3 SO 3
- a compound that can be added to the active material layer of the electrode can be similarly employed.
- the liquid electrolyte may further contain additives other than the components described above.
- additives include, for example, vinylene carbonate, methyl vinylene carbonate, dimethyl vinylene carbonate, phenyl vinylene carbonate, diphenyl vinylene carbonate, ethyl vinylene carbonate, diethyl vinylene carbonate, vinyl ethylene carbonate, 1,2-divinyl ethylene carbonate.
- vinylene carbonate, methyl vinylene carbonate, and vinyl ethylene carbonate are preferable, and vinylene carbonate and vinyl ethylene carbonate are more preferable.
- These cyclic carbonates may be used alone or in combination of two or more.
- the gel polymer electrolyte has a configuration in which the above liquid electrolyte is injected into a matrix polymer (host polymer) made of an ion conductive polymer.
- a gel polymer electrolyte as the electrolyte is superior in that the fluidity of the electrolyte is lost and the ion conductivity between the layers is easily cut off.
- the matrix polymer of gel electrolyte can express excellent mechanical strength by forming a crosslinked structure.
- thermal polymerization, ultraviolet polymerization, radiation polymerization, electron beam polymerization, etc. are performed on a polymerizable polymer (for example, PEO or PPO) for forming a polymer electrolyte using an appropriate polymerization initiator.
- a polymerization treatment may be performed.
- the separator is less likely to curl in the battery manufacturing process due to the effect of suppressing thermal shrinkage and high mechanical strength.
- the inorganic particles in the heat resistant insulating layer contribute to the mechanical strength and heat shrinkage suppressing effect of the heat resistant insulating layer.
- the material used as the inorganic particles is not particularly limited. Examples thereof include silicon, aluminum, zirconium, titanium oxides (SiO 2 , Al 2 O 3 , ZrO 2 , TiO 2 ), hydroxides and nitrides, and composites thereof. These inorganic particles may be derived from mineral resources such as boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine and mica, or may be artificially produced. Moreover, only 1 type may be used individually for these inorganic particles, and 2 or more types may be used together. Of these, silica (SiO 2 ) or alumina (Al 2 O 3 ) is preferably used, and alumina (Al 2 O 3 ) is more preferably used from the viewpoint of cost.
- the basis weight of the inorganic particles is not particularly limited, but is preferably 5 to 15 g / m 2 . If it is this range, sufficient ion conductivity will be acquired and it is preferable at the point which maintains heat resistant strength.
- the binder in the heat-resistant insulating layer has a role of adhering the inorganic particles and the inorganic particles to the resin porous substrate layer. With the binder, the heat-resistant insulating layer is stably formed, and peeling between the porous substrate layer and the heat-resistant insulating layer is prevented.
- the binder used for the heat-resistant insulating layer is not particularly limited.
- a compound such as butadiene rubber, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), or methyl acrylate can be used as a binder.
- PVDF polyvinylidene fluoride
- PTFE polytetrafluoroethylene
- PVF polyvinyl fluoride
- methyl acrylate methyl acrylate
- PVDF polyvinylidene fluoride
- these compounds only 1 type may be used independently and 2 or more types may be used together.
- the binder content in the heat resistant insulating layer is preferably 2 to 20% by weight with respect to 100% by weight of the heat resistant insulating layer.
- the binder content is 2% by weight or more, the peel strength between the heat-resistant insulating layer and the porous substrate layer can be increased, and the vibration resistance of the separator can be improved.
- the binder content is 20% by weight or less, the gaps between the inorganic particles are appropriately maintained, so that sufficient lithium ion conductivity can be ensured.
- the thermal contraction rate of the separator with a heat-resistant insulating layer is preferably 10% or less for both MD and TD after holding for 1 hour at 150 ° C. and 2 gf / cm 2 .
- the material which comprises a current collector plate (25, 27) is not restrict
- a constituent material of the current collector plate for example, metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof are preferable. From the viewpoint of light weight, corrosion resistance, and high conductivity, aluminum and copper are more preferable, and aluminum is particularly preferable.
- the same material may be used for the positive electrode current collecting plate 27 and the negative electrode current collecting plate 25, and different materials may be used.
- Battery exterior material battery exterior body 29
- a known metal can case can be used, and a bag-like case using a laminate film containing aluminum that can cover the power generation element can be used.
- a laminate film having a three-layer structure in which PP, aluminum, and nylon are laminated in this order can be used as the laminate film, but the laminate film is not limited thereto.
- a laminate film is desirable from the viewpoint of high output and excellent cooling performance, and can be suitably used for a battery for large-size equipment for EV and HEV, and an aluminum laminate film is more preferable from the viewpoint of weight reduction.
- the ratio of the rated capacity to the pore volume of the positive electrode active material layer is 1.40 Ah / cc or more.
- the ratio of the capacity of the positive electrode active material layer to the pore volume is an index indicating an increase in capacity of the positive electrode active material layer.
- g / cc which shows the active material density of a positive electrode active material layer
- the density of positive electrode active material itself needs to be considered. For example, in a material with a low active material density, even if the same volume of active material is filled in the same volume, the density of the positive electrode active material layer is lower than that of a material with a high active material density, so the density is low.
- hole volume is prescribed
- the upper limit of the ratio of the rated capacity to the vacancy volume of the positive electrode active material layer is not particularly limited, but considering the diffusibility of Li ions, the ratio of the capacity to the vacancy volume of the positive electrode is 3.2 Ah / cc. Or less, more preferably 3.0 Ah / cc or less. Further, from the viewpoint of high density, it is preferably 1.2 Ah / cc or more, and more preferably 1.5 Ah / cc or more because the effect of the present invention is more easily exhibited.
- the pore volume of the positive electrode active material layer is measured as follows; the positive electrode active material layer is extracted from the nonaqueous electrolyte secondary battery and cut into a 10 cm ⁇ 10 cm sample.
- the volume of pores (micropores) existing inside the sample is measured by measuring the pore distribution by a mercury intrusion method using a mercury intrusion porosimeter.
- the mercury porosimeter utilizes this, and mercury is injected into the pores, and the pore diameter is determined from the required pressure, and the pore volume of the sample is determined from the amount of injection. From the hole volume of this sample, the hole volume of the positive electrode active material layer is calculated in consideration of the area of the positive electrode active material layer and the number of stacked layers.
- the rated capacity is measured as follows by the following procedures 1 and 2 at a temperature of 25 ° C and a predetermined voltage range.
- Procedure 1 After reaching the upper limit voltage by constant current charging at 0.2 C, charge for 2.5 hours by constant voltage charging, and then rest for 10 seconds.
- Procedure 2 Stop for 10 seconds after reaching the lower limit voltage by constant current discharge of 0.2C.
- the discharge capacity in constant current discharge in step 2 is the rated capacity.
- the battery storage space is about 170L. Since auxiliary devices such as cells and charge / discharge control devices are stored in this space, the storage efficiency of a normal cell is about 50%. The efficiency of loading cells into this space is a factor that governs the cruising range of electric vehicles. If the size of the single cell is reduced, the loading efficiency is impaired, so that the cruising distance cannot be secured.
- the battery structure in which the power generation element is covered with the exterior body is preferably large. Further, as described above, the effect of the present invention is exhibited in a large battery. Specifically, in this embodiment, the enlargement of the battery is defined from the relationship between the battery area and the battery capacity. Specifically, in the nonaqueous electrolyte secondary battery according to this embodiment, the ratio of the battery area to the rated capacity is 4.0 cm 2 / Ah or more. In the present invention, since the rated capacity is as large as 30 Ah or more, the battery area inevitably becomes as large as 120 cm 2 or more.
- the ratio of the battery area to the rated capacity is preferably as large as possible, but is usually 18 cm 2 / Ah or less because of the in-vehicle capacity.
- the value of the ratio of the battery area to the rated capacity is preferably 5.0 to 15 cm 2 / Ah.
- the battery area refers to the area of the positive electrode (in the plane direction).
- the maximum positive electrode area is defined as the battery area.
- the rated capacity is 30 Ah or more.
- a high capacity can be maintained by repeating charge and discharge cycles. It becomes even more difficult, and the problem of improving cycle characteristics can be even more pronounced.
- the rated capacity is preferably as large as possible, and the upper limit is not particularly limited.
- the rated capacity is preferably 30 to 150 Ah, more preferably 40 to 100 Ah.
- the value measured by the method as described in the following Example is employ
- the length of the short side of the battery is preferably 100 mm or more. Such a large battery can be used for vehicle applications.
- the length of the short side of the battery refers to the side having the shortest length.
- the upper limit of the short side length is not particularly limited, but is usually 400 mm or less.
- the size of the electrode is defined as the size of the positive electrode.
- the positive electrode and the negative electrode may be the same size or different sizes, but it is preferable that both are the sizes described above.
- the aspect ratio of the rectangular electrode is preferably 1 to 3, and more preferably 1 to 2.
- the electrode aspect ratio is defined as the aspect ratio of the rectangular positive electrode active material layer.
- the assembled battery is configured by connecting a plurality of batteries. Specifically, at least two or more are used, and are configured by serialization, parallelization, or both. Capacitance and voltage can be freely adjusted by paralleling in series.
- a small assembled battery that can be attached and detached by connecting a plurality of batteries in series or in parallel. Then, a plurality of small assembled batteries that can be attached and detached are connected in series or in parallel to provide a large capacity and large capacity suitable for vehicle drive power supplies and auxiliary power supplies that require high volume energy density and high volume output density.
- An assembled battery having an output can also be formed. How many batteries are connected to make an assembled battery, and how many small assembled batteries are stacked to make a large-capacity assembled battery depends on the battery capacity of the mounted vehicle (electric vehicle) It may be determined according to the output.
- the cell unit in which a plurality of batteries are stacked in this way may be accommodated in upper and lower cases (for example, metal cases) to form an assembled battery.
- the battery case is accommodated in the case by fastening the metal case with the fastening member. Therefore, the battery is pressurized in the stacking direction within the case. Due to such pressurization, in-plane pressure distribution is likely to occur in a large-sized battery, which imposes a burden on the electrode active material during charge and discharge and tends to deteriorate the battery life.
- the configuration of the present embodiment since the variation in the porosity in the positive electrode active material is small, it is considered that the current concentration due to the pressure distribution can be reduced.
- the nonaqueous electrolyte secondary battery of this embodiment maintains a discharge capacity even when used for a long period of time, and has good cycle characteristics.
- Vehicle applications such as electric vehicles, hybrid electric vehicles, fuel cell vehicles, and hybrid fuel cell vehicles require higher capacity, larger size, and longer life than electric and portable electronic devices. . Therefore, the nonaqueous electrolyte secondary battery can be suitably used as a vehicle power source, for example, a vehicle driving power source or an auxiliary power source.
- a battery or an assembled battery formed by combining a plurality of these batteries can be mounted on the vehicle.
- a plug-in hybrid electric vehicle having a long EV mileage or an electric vehicle having a long charging mileage can be formed by installing such a battery.
- a battery having a long life with excellent long-term reliability and output characteristics can be configured
- a plug-in hybrid electric vehicle having a long EV mileage or an electric vehicle having a long charging mileage can be formed by installing such a battery. it can.
- a hybrid car a fuel cell car, an electric car (four-wheeled vehicles (passenger cars, trucks, buses, commercial vehicles, light cars, etc.)
- the application is not limited to automobiles.
- it can be applied to various power sources for moving vehicles such as other vehicles, for example, trains, and power sources for mounting such as uninterruptible power supplies. It is also possible to use as.
- a preferred method for producing a non-aqueous electrolyte secondary battery according to the present invention includes a step of mixing a positive electrode active material, a binder, a solvent, and the like and kneading (hereinafter also simply referred to as a kneading step), and further adding a solvent. And then mixing, and after the slurry composition is coated on the positive electrode current collector, it is dried to obtain a positive electrode. Furthermore, it is preferable to perform press working after the drying step, and in this case, a hot pressing step is more preferable.
- a positive electrode active material, a binder, and other compounding components are placed in an appropriate solvent, and mixed and dispersed by a disperser to prepare a paste.
- the term “kneading” refers to kneading in a state where the solid content rate is higher than that of the final slurry for forming an active material layer. By kneading in such a high solid content state, a composition in which each material is uniformly dispersed can be obtained. By such uniform dispersion, the components are brought into close contact with each other, and the active material layer can be densified.
- the solvent used in the kneading step is not particularly limited.
- ketones such as acetone, aromatic hydrocarbon solvents such as toluene and xylene, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF) , Polar solvents such as dimethylacetamide (DMAc), dimethylsulfoxide (DMSO), tetrahydrofuran (THF), acetonitrile, and the like can be used. These may be used alone or in combination of two or more.
- the mixer used for mixing in the kneading step is not particularly limited, and examples thereof include a planetary mixer, a biaxial kneader, and a triaxial kneader.
- the order of addition to the mixer is not particularly limited, and after adding powder such as active material to the mixer, the solvent is added: powder such as active material and solvent are charged almost simultaneously. Either may be sufficient.
- the solid concentration in the kneading step is preferably 75 to 90% by weight in the mixture because a high tenacity can be applied.
- the variation in the porosity of the positive electrode active material layer is not particularly limited, but can be controlled by controlling the coating conditions of the positive electrode active material layer. Specifically, by increasing the dispersibility of the active material or the like in the slurry, the variation in porosity is reduced. For example, when the kneading time is increased, variation in porosity in the positive electrode active material layer can be reduced. A shorter kneading time is preferable in view of production efficiency. However, in this embodiment, it is necessary to reduce the variation to 6.0% or less, and for the purpose of improving the dispersibility of the active material or the like, it is preferable that the kneading time is long.
- the kneading time is preferably 100 minutes or more, more preferably more than 100 minutes, and more preferably 110 minutes or more.
- the upper limit of the kneading time is not particularly limited, but it is preferably 200 minutes or less in consideration of production efficiency and effect saturation.
- the temperature at which the kneading is carried out is preferably 15 to 40 ° C. from the viewpoint of coating properties.
- a solvent is added to obtain a slurry composition.
- the solvent the solvent used in the above kneading step can be used.
- the solid content concentration of the slurry composition is not particularly limited, but is preferably 45 to 65% by weight in view of ease of coating.
- the method for applying the positive electrode active material layer slurry composition to the positive electrode current collector is not particularly limited, but a thick coating layer can be formed, such as a die coat such as a slide die coat, a comma direct coat, or a comma reverse coat.
- a thick coating layer can be formed, such as a die coat such as a slide die coat, a comma direct coat, or a comma reverse coat.
- the method is suitable. However, depending on the coating weight, it may be applied by gravure coating or gravure reverse coating.
- the basis weight (one-side coating amount) when applying (applying) the slurry composition to the positive electrode current collector is not particularly limited, but is preferably 10.0 to 30.0 mg / kg from the viewpoint of increasing the capacity and reducing the weight. cm 2 , more preferably 13.0 to 25.0 mg / cm 2 .
- the active material layer can also be obtained by irradiating an electron beam or radiation to cause a crosslinking reaction of the binder. Application and drying may be repeated a plurality of times.
- the electrode drying temperature should normally be high to some extent in order to shorten the drying time. However, in this embodiment, it is necessary to reduce the variation to 6.0% or less, and it is important to control the drying temperature of the electrode low. Since the drying temperature of the electrode is low, it is difficult for convection in the slurry to occur, and it is possible to suppress the occurrence of partial convection and uneven pores.
- the drying temperature of the electrode is preferably 120 ° C. or lower, preferably 118 ° C. or lower, more preferably 115 ° C. or lower, and particularly preferably 110 ° C. or lower. Further, the drying time is appropriately set as the time required for completion of drying at the above temperature, and is, for example, 2 seconds to 1 hour.
- the density of the active material layer, the adhesion to the current collector, and the homogeneity can be improved by pressing the obtained positive electrode active material layer.
- the pressing is performed using, for example, a metal roll, an elastic roll, a heating roll (heat roll), a sheet press machine, or the like.
- the pressing temperature may be performed at room temperature or under heating conditions as long as the temperature is lower than the temperature for drying the coating film of the active material layer, but it is performed under heating conditions. It is preferable.
- the temperature during hot pressing is preferably 100 to 150 ° C., more preferably 110 to 140 ° C., and particularly preferably 115 to 130 ° C. .
- the one where press temperature is higher is the direction which the dispersion
- the positive electrode can be produced by such a process.
- the production of the negative electrode active material layer and the assembly of the battery can be produced by a conventionally known method.
- Example 1 Preparation of Electrolyte Solution A mixed solvent (30:30:40 (volume ratio)) of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) was used as a solvent. Further, 1.0M LiPF 6 was used as a lithium salt. Furthermore, 2.0% by weight of vinylene carbonate was added to 100% by weight of the total of the solvent and the lithium salt to prepare an electrolytic solution. Note that “1.0 M LiPF 6 ” means that the lithium salt (LiPF 6 ) concentration in the mixture of the mixed solvent and the lithium salt is 1.0 M.
- NMP N-methyl-2-pyrrolidone
- the density of the positive electrode active material layer is 2.9 g / cm 3
- the coating amount on one side of the positive electrode active material layer is 15.0 mg / cm 2
- the positive electrode active material A positive electrode having a layer thickness of 50 ⁇ m was produced.
- Negative Electrode 94% by weight of natural graphite (average particle size: 20 ⁇ m) as a negative electrode active material, 2% by weight of acetylene black as a conductive assistant, 3% by weight of styrene-butadiene rubber (SBR) as a binder, 1% by weight of carboxymethyl cellulose (CMC) % Solid content was prepared. An appropriate amount of ion-exchanged water as a slurry viscosity adjusting solvent was added to the solid content to prepare a negative electrode active material slurry composition.
- SBR styrene-butadiene rubber
- the negative electrode active material slurry composition was applied to both sides of a copper foil (10 ⁇ m) as a current collector, dried and pressed, and the density of the negative electrode active material layer was 1.4 g / cm 3 .
- a negative electrode having a coating amount of 7.3 mg / cm 2 was produced.
- Step of Completing Single Cell The positive electrode produced above was cut into a 200 mm ⁇ 204 mm rectangular shape, and the negative electrode was cut into a 205 ⁇ 209 mm rectangular shape (24 positive electrodes, 25 negative electrodes). This positive electrode and negative electrode were alternately laminated via a 210 ⁇ 214 mm separator (polypropylene microporous membrane, thickness 25 ⁇ m, porosity 55%) to produce a power generation element.
- a 210 ⁇ 214 mm separator polypropylene microporous membrane, thickness 25 ⁇ m, porosity 55%)
- a tab was welded to the resulting power generation element, and the battery was completed by sealing together with the electrolyte in an exterior made of an aluminum laminate film. Thereafter, the battery was sandwiched between a urethane rubber sheet (thickness 3 mm) larger than the electrode area and an Al plate (thickness 5 mm), and the battery was appropriately pressed from both sides in the stacking direction. Then, the battery thus obtained was charged for the first time over 5 hours (upper limit voltage 4.2 V), then aged at 45 ° C. for 5 days, degassed and discharged, The battery of the example was completed.
- the battery thus produced had a rated capacity (cell capacity) of 40 Ah, and the ratio of the positive electrode area to the rated capacity was 10.2 cm 2 / Ah. Moreover, when the ratio of the rated capacity to the pore volume of the positive electrode active material layer was determined for the obtained battery, it was 1.42 Ah / cc.
- the rated capacity of the battery was obtained as follows.
- the rated capacity is measured by the following procedures 1 and 2 at a temperature of 25 ° C. and a voltage range of 3.0 V to 4.15 V.
- Procedure 1 After reaching 4.15 V by constant current charging at 0.2 C, charge for 2.5 hours by constant voltage charging, and then rest for 10 seconds.
- Procedure 2 Stops for 10 seconds after reaching 3.0V by constant current discharge of 0.2C.
- Example 2 In the production of the positive electrode, the kneading time was 140 minutes, the drying temperature of the electrode was 109 ° C., the pressing temperature was 125 ° C., the density of the positive electrode active material layer was 3.2 g / cm 3 , and the coating amount on one side of the positive electrode active material layer 18.0 mg / cm 2 , the single-sided coating amount of the negative electrode active material layer was 8.8 mg / cm 2 , and the electrode size was as shown in Table 2. An electrolyte secondary battery was obtained.
- the rated capacity (cell capacity) of the battery was 50 Ah, and the value of the ratio of the positive electrode area to the rated capacity was 8.4 cm 2 / Ah. Moreover, when the ratio of the rated capacity to the pore volume of the positive electrode active material layer was determined for the obtained battery, it was 2.08 Ah / cc.
- Example 3 In the production of the positive electrode, the kneading time is 150 minutes, the drying temperature of the electrode is 108 ° C., the press temperature is 130 ° C., the density of the positive electrode active material layer is 3.3 g / cm 3 , and the coating amount on one side of the positive electrode active material layer was a 21.5mg / cm 2, 10.5mg / cm 2 on one side coated amount of the negative electrode active material layer, except that the electrode size was as described in Table 2, the non-aqueous in the same manner as in example 1 An electrolyte secondary battery was obtained.
- the rated capacity (cell capacity) of the battery was 60 Ah, and the value of the ratio of the positive electrode area to the rated capacity was 7.0 cm 2 / Ah. Moreover, when the ratio of the rated capacity to the pore volume of the positive electrode active material layer was determined for the obtained battery, it was 2.50 Ah / cc.
- Example 4 A non-aqueous electrolyte secondary battery was obtained in the same manner as in Example 1 except that the kneading time was 120 minutes, the electrode drying temperature was 120 ° C., and the press temperature was 120 ° C.
- the rated capacity (cell capacity) of the battery was 40 Ah, and the value of the ratio of the positive electrode area to the rated capacity was 10.2 cm 2 / Ah. Moreover, when the ratio of the rated capacity to the pore volume of the positive electrode active material layer was determined for the obtained battery, it was 1.42 Ah / cc.
- Example 5 A non-aqueous electrolyte secondary battery was obtained in the same manner as in Example 2 except that the kneading time was 130 minutes, the electrode drying temperature was 115 ° C., and the press temperature was 120 ° C. in the production of the positive electrode.
- the rated capacity (cell capacity) of the battery was 50 Ah, and the value of the ratio of the positive electrode area to the rated capacity was 8.4 cm 2 / Ah. Moreover, when the ratio of the rated capacity to the pore volume of the positive electrode active material layer was determined for the obtained battery, it was 2.08 Ah / cc.
- Example 6 A nonaqueous electrolyte secondary battery was obtained in the same manner as in Example 3 except that in the production of the positive electrode, the kneading time was 140 minutes, the drying temperature of the electrode was 110 ° C., and the press temperature was 125 ° C.
- the rated capacity (cell capacity) of the battery was 60 Ah, and the value of the ratio of the positive electrode area to the rated capacity was 7.0 cm 2 / Ah. Moreover, when the ratio of the rated capacity to the pore volume of the positive electrode active material layer was determined for the obtained battery, it was 2.50 Ah / cc.
- Example 7 A non-aqueous electrolyte secondary battery was obtained in the same manner as in Example 1, except that the kneading time was 110 minutes, the electrode drying temperature was 120 ° C., and the press temperature was 115 ° C.
- the rated capacity (cell capacity) of the battery was 40 Ah, and the value of the ratio of the positive electrode area to the rated capacity was 10.2 cm 2 / Ah. Moreover, when the ratio of the rated capacity to the pore volume of the positive electrode active material layer was determined for the obtained battery, it was 1.42 Ah / cc.
- Example 8 A non-aqueous electrolyte secondary battery was obtained in the same manner as in Example 2, except that the kneading time was 120 minutes, the electrode drying temperature was 118 ° C., and the press temperature was 115 ° C.
- the rated capacity (cell capacity) of the battery was 50 Ah, and the value of the ratio of the positive electrode area to the rated capacity was 8.4 cm 2 / Ah. Moreover, when the ratio of the rated capacity to the pore volume of the positive electrode active material layer was determined for the obtained battery, it was 2.08 Ah / cc.
- Example 9 A non-aqueous electrolyte secondary battery was obtained in the same manner as in Example 3 except that in the production of the positive electrode, the kneading time was 130 minutes, the electrode drying temperature was 115 ° C., and the press temperature was 120 ° C.
- the rated capacity (cell capacity) of the battery was 60 Ah, and the value of the ratio of the positive electrode area to the rated capacity was 7.0 cm 2 / Ah. Moreover, when the ratio of the rated capacity to the pore volume of the positive electrode active material layer was determined for the obtained battery, it was 2.50 Ah / cc.
- Example 10 A non-aqueous electrolyte secondary battery was obtained in the same manner as in Example 1, except that in the production of the positive electrode, the kneading time was 100 minutes, the electrode drying temperature was 120 ° C., and the press temperature was 115 ° C.
- the rated capacity (cell capacity) of the battery was 40 Ah, and the value of the ratio of the positive electrode area to the rated capacity was 10.2 cm 2 / Ah. Moreover, when the ratio of the rated capacity to the pore volume of the positive electrode active material layer was determined for the obtained battery, it was 1.42 Ah / cc.
- Example 11 A non-aqueous electrolyte secondary battery was obtained in the same manner as in Example 2, except that the kneading time was 100 minutes, the electrode drying temperature was 118 ° C., and the press temperature was 115 ° C.
- the rated capacity (cell capacity) of the battery was 50 Ah, and the value of the ratio of the positive electrode area to the rated capacity was 8.4 cm 2 / Ah. Moreover, when the ratio of the rated capacity to the pore volume of the positive electrode active material layer was determined for the obtained battery, it was 2.08 Ah / cc.
- Example 12 A non-aqueous electrolyte secondary battery was obtained in the same manner as in Example 3 except that in the production of the positive electrode, the kneading time was 110 minutes, the electrode drying temperature was 118 ° C., and the press temperature was 115 ° C.
- the rated capacity (cell capacity) of the battery was 60 Ah, and the value of the ratio of the positive electrode area to the rated capacity was 7.0 cm 2 / Ah. Moreover, when the ratio of the rated capacity to the pore volume of the positive electrode active material layer was determined for the obtained battery, it was 2.50 Ah / cc.
- Example 1 In producing the positive electrode, a nonaqueous electrolyte secondary battery was obtained in the same manner as in Example 1 except that the kneading time was 80 minutes, the drying temperature of the electrode was 120 ° C., and no heating was performed during pressing. .
- the rated capacity (cell capacity) of the battery was 40 Ah, and the value of the ratio of the positive electrode area to the rated capacity was 10.2 cm 2 / Ah. Moreover, when the ratio of the rated capacity to the pore volume of the positive electrode active material layer was determined for the obtained battery, it was 1.42 Ah / cc.
- Example 2 In the production of the positive electrode, a nonaqueous electrolyte secondary battery was obtained in the same manner as in Example 2 except that the kneading time was 90 minutes, the electrode drying temperature was 120 ° C., and no heating was performed during pressing. .
- the rated capacity (cell capacity) of the battery was 50 Ah, and the value of the ratio of the positive electrode area to the rated capacity was 8.4 cm 2 / Ah. Moreover, when the ratio of the rated capacity to the pore volume of the positive electrode active material layer was determined for the obtained battery, it was 2.08 Ah / cc.
- Example 3 In the production of the positive electrode, a nonaqueous electrolyte secondary battery was obtained in the same manner as in Example 3, except that the kneading time was 100 minutes, the drying temperature of the electrode was 120 ° C., and heating was not performed during pressing. .
- the rated capacity (cell capacity) of the battery was 60 Ah, and the value of the ratio of the positive electrode area to the rated capacity was 7.0 cm 2 / Ah. Moreover, when the ratio of the rated capacity to the pore volume of the positive electrode active material layer was determined for the obtained battery, it was 2.50 Ah / cc.
- the rated capacity (cell capacity) of the battery was 25 Ah, and the value of the ratio of the positive electrode area to the rated capacity was 14.3 cm 2 / Ah. Moreover, when the ratio of the rated capacity to the pore volume of the positive electrode active material layer was determined for the obtained battery, it was 2.08 Ah / cc.
- the rated capacity (cell capacity) of the battery was 35 Ah, and the value of the ratio of the positive electrode area to the rated capacity was 12.9 cm 2 / Ah. Moreover, when the ratio of the rated capacity to the pore volume of the positive electrode active material layer was determined for the obtained battery, it was 1.12 Ah / cc.
- the rated capacity (cell capacity) of the battery was 15 Ah, and the value of the ratio of the positive electrode area to the rated capacity was 3.3 cm 2 / Ah. Moreover, when the ratio of the rated capacity to the pore volume of the positive electrode active material layer was determined for the obtained battery, it was 2.08 Ah / cc.
- the current density with respect to the positive electrode was set to 2 mA / cm 2 , and the batteries produced in each Example and Comparative Example were charged to a cutoff voltage of 4.15 V to obtain an initial charge capacity, and after a pause of 1 hour, to a cutoff voltage of 3.0 V
- the capacity when discharged was defined as the initial discharge capacity.
- This charge / discharge cycle was repeated 500 times.
- the ratio of the discharge capacity at the 500th cycle to the initial discharge capacity was defined as the capacity maintenance rate (%), and the cycle durability was evaluated.
- Table 2 below shows the electrode size, the number of layers, the positive electrode weight, the positive electrode density, the negative electrode weight, and the negative electrode density of each Example and Comparative Example.
- the nonaqueous electrolyte secondary batteries of the examples are excellent in cycle characteristics. Further, when the ratio of the capacity to the pore volume of the positive electrode active material layer is 2.20 Ah / cc or more by comparing Example 9 with Example 12, the variation in the porosity of the positive electrode active material layer is 5 It can be seen that by setting the ratio to 0.0% or less, the cycle characteristics are remarkably improved. In addition, it can be seen that the non-aqueous electrolyte secondary batteries of Examples 1 to 6 in which the variation in the porosity of the positive electrode active material layer is 4.0% or less are particularly excellent in cycle characteristics.
- Comparative Example 4 having a small rated capacity
- Comparative Example 5 having a small rated capacity with respect to the pore volume of the positive electrode active material layer
- Comparative Example 6 having a small cell area
- the capacity retention rate was maintained even when the variation exceeded 6.0%. It can be seen that, in a battery having a high capacity, a high capacity density, and a large area, the cycle characteristics are remarkably improved by setting the variation to 6.0% or less.
- Lithium ion secondary battery 11 negative electrode current collector, 12 positive electrode current collector, 13 negative electrode active material layer, 15 positive electrode active material layer, 17 separator, 19 cell layer, 21 power generation elements, 25 negative current collector, 27 positive current collector, 29 Battery exterior material.
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Abstract
Description
図1は、本発明の電池の一実施形態である扁平積層型電池の概要を模式的に表した断面概略図である。積層型とすることで、電池をコンパクトにかつ高容量化することができる。なお、本明細書においては、図1に示す扁平積層型の双極型でないリチウムイオン二次電池を例に挙げて詳細に説明する。
図1は、扁平積層型の双極型ではない非水電解質リチウムイオン二次電池(以下、単に「積層型電池」ともいう)の基本構成を模式的に表した断面概略図である。図1に示すように、本実施形態の積層型電池10は、実際に充放電反応が進行する扁平略矩形の発電要素21が、外装体である電池外装材29の内部に封止された構造を有する。ここで、発電要素21は、正極と、セパレータ17と、負極とを積層した構成を有している。なお、セパレータ17は、非水電解質(例えば、液体電解質)を内蔵している。正極は、正極集電体12の両面に正極活物質層15が配置された構造を有する。負極は、負極集電体11の両面に負極活物質層13が配置された構造を有する。具体的には、1つの正極活物質層15とこれに隣接する負極活物質層13とが、セパレータ17を介して対向するようにして、負極、電解質層および正極がこの順に積層されている。これにより、隣接する正極、電解質層および負極は、1つの単電池層19を構成する。したがって、図1に示す積層型電池10は、単電池層19が複数積層されることで、電気的に並列接続されてなる構成を有するとも言える。
正極は、正極集電体と、正極集電体の表面に形成された正極活物質を含む正極活物質層とを有するものである。
正極集電体を構成する材料に特に制限はないが、好適には金属が用いられる。具体的には、金属としては、アルミニウム、ニッケル、鉄、ステンレス、チタン、銅、その他合金等などが挙げられる。これらのほか、ニッケルとアルミニウムとのクラッド材、銅とアルミニウムとのクラッド材、またはこれらの金属の組み合わせのめっき材などが好ましく用いられうる。また、金属表面にアルミニウムが被覆されてなる箔であってもよい。なかでも、電子伝導性や電池作動電位の観点からは、アルミニウム、ステンレス、銅が好ましい。
正極活物質層15は、正極活物質を含み、必要に応じて、バインダー;導電助剤、電解質(ポリマーマトリックス、イオン伝導性ポリマー、電解液など)、およびイオン伝導性を高めるためのリチウム塩などのその他の添加剤をさらに含む。
正極活物質としては、例えば、LiMn2O4、LiCoO2、LiNiO2、Li(Ni-Mn-Co)O2およびこれらの遷移金属の一部が他の元素により置換されたもの等のリチウム-遷移金属複合酸化物、リチウム-遷移金属リン酸化合物、リチウム-遷移金属硫酸化合物などが挙げられる。好ましくは、容量、出力特性の観点から、リチウム-遷移金属複合酸化物が、正極活物質として用いられる。場合によっては、2種以上の正極活物質が併用されてもよい。
正極活物質層に用いられるバインダーとしては、特に限定されないが、例えば、ポリエチレン、ポリプロピレン、ポリエチレンテレフタレート(PET)、ポリエーテルニトリル、ポリアクリロニトリル、ポリイミド、ポリアミド、セルロース、カルボキシメチルセルロース(CMC)およびその塩、エチレン-酢酸ビニル共重合体、ポリ塩化ビニル、スチレン・ブタジエンゴム(SBR)、イソプレンゴム、ブタジエンゴム、エチレン・プロピレンゴム、エチレン・プロピレン・ジエン共重合体、スチレン・ブタジエン・スチレンブロック共重合体およびその水素添加物、スチレン・イソプレン・スチレンブロック共重合体およびその水素添加物などの熱可塑性高分子、ポリフッ化ビニリデン(PVdF)、ポリテトラフルオロエチレン(PTFE)、テトラフルオロエチレン・ヘキサフルオロプロピレン共重合体(FEP)、テトラフルオロエチレン・パーフルオロアルキルビニルエーテル共重合体(PFA)、エチレン・テトラフルオロエチレン共重合体(ETFE)、ポリクロロトリフルオロエチレン(PCTFE)、エチレン・クロロトリフルオロエチレン共重合体(ECTFE)、ポリフッ化ビニル(PVF)等のフッ素樹脂、ビニリデンフルオライド-ヘキサフルオロプロピレン系フッ素ゴム(VDF-HFP系フッ素ゴム)、ビニリデンフルオライド-ヘキサフルオロプロピレン-テトラフルオロエチレン系フッ素ゴム(VDF-HFP-TFE系フッ素ゴム)、ビニリデンフルオライド-ペンタフルオロプロピレン系フッ素ゴム(VDF-PFP系フッ素ゴム)、ビニリデンフルオライド-ペンタフルオロプロピレン-テトラフルオロエチレン系フッ素ゴム(VDF-PFP-TFE系フッ素ゴム)、ビニリデンフルオライド-パーフルオロメチルビニルエーテル-テトラフルオロエチレン系フッ素ゴム(VDF-PFMVE-TFE系フッ素ゴム)、ビニリデンフルオライド-クロロトリフルオロエチレン系フッ素ゴム(VDF-CTFE系フッ素ゴム)等のビニリデンフルオライド系フッ素ゴム、エポキシ樹脂等が挙げられる。これらのバインダーは、単独で用いてもよいし、2種以上を併用してもよい。
導電助剤とは、正極活物質層または負極活物質層の導電性を向上させるために配合される添加物をいう。導電助剤としては、ケッチェンブラック、アセチレンブラック等のカーボンブラック、グラファイト、炭素繊維などの炭素材料が挙げられる。活物質層が導電助剤を含むと、活物質層の内部における電子ネットワークが効果的に形成され、電池の出力特性の向上に寄与しうる。
第一実施形態では、正極活物質層における空孔率のばらつきが6.0%以下である。
負極は、負極集電体と、負極集電体の表面に形成された負極活物質層とを有するものである。
負極活物質層は負極活物質を含み、必要に応じて、導電助剤、バインダー、電解質(ポリマーマトリックス、イオン伝導性ポリマー、電解液など)、イオン伝導性を高めるためのリチウム塩などのその他の添加剤をさらに含む。導電助剤、バインダー、電解質(ポリマーマトリックス、イオン伝導性ポリマー、電解液など)、イオン伝導性を高めるためのリチウム塩などのその他の添加剤については、上記正極活物質層の欄で述べたものと同様である。
セパレータは、電解質を保持して正極と負極との間のリチウムイオン伝導性を確保する機能、および正極と負極との間の隔壁としての機能を有する。
集電板(25、27)を構成する材料は、特に制限されず、リチウムイオン二次電池用の集電板として従来用いられている公知の高導電性材料が用いられうる。集電板の構成材料としては、例えば、アルミニウム、銅、チタン、ニッケル、ステンレス鋼(SUS)、これらの合金等の金属材料が好ましい。軽量、耐食性、高導電性の観点から、より好ましくはアルミニウム、銅であり、特に好ましくはアルミニウムである。なお、正極集電板27と負極集電板25とでは、同一の材料が用いられてもよいし、異なる材料が用いられてもよい。
また、図示は省略するが、集電体11と集電板(25、27)との間を正極リードや負極リードを介して電気的に接続してもよい。正極および負極リードの構成材料としては、公知のリチウムイオン二次電池において用いられる材料が同様に採用されうる。なお、外装から取り出された部分は、周辺機器や配線などに接触して漏電したりして製品(例えば、自動車部品、特に電子機器等)に影響を与えないように、耐熱絶縁性の熱収縮チューブなどにより被覆することが好ましい。
電池外装材(電池外装体)29としては、公知の金属缶ケースを用いることができるほか、発電要素を覆うことができる、アルミニウムを含むラミネートフィルムを用いた袋状のケースが用いられうる。該ラミネートフィルムには、例えば、PP、アルミニウム、ナイロンをこの順に積層してなる3層構造のラミネートフィルム等を用いることができるが、これらに何ら制限されるものではない。高出力化や冷却性能に優れ、EV、HEV用の大型機器用電池に好適に利用することができるという観点から、ラミネートフィルムが望ましく、軽量化の観点からアルミニウムラミネートフィルムがより好ましい。
第一実施形態において、正極活物質層の空孔体積に対する定格容量の比は1.40Ah/cc以上である。正極活物質層の空孔体積に対する容量の比は、正極活物質層の高容量密度化を示す指標である。ここで、正極活物質層の活物質密度を示すg/ccでは、正極活物質自体の密度が考慮される必要がある。例えば、活物質の密度の小さい材料では、同じ容積中に同程度の活物質が充填されても、活物質の密度の大きい材料よりも、正極活物質層の密度が小さくなるため、密度が小さいのか、正極活物質の重量が小さいのかが把握できない。そのため、本明細書では、空孔体積あたりの容量を規定し、容量密度の高さの指標としている。さらに、空孔体積あたりの容量とすることで、どれだけ隙間なく正極活物質が充填されているかという密度の指標となる。
一般的な電気自動車では、電池格納スペースが170L程度である。このスペースにセルおよび充放電制御機器等の補機を格納するため、通常セルの格納スペース効率は50%程度となる。この空間へのセルの積載効率が電気自動車の航続距離を支配する因子となる。単セルのサイズが小さくなると上記積載効率が損なわれるため、航続距離を確保できなくなる。
組電池は、電池を複数個接続して構成した物である。詳しくは少なくとも2つ以上用いて、直列化あるいは並列化あるいはその両方で構成されるものである。直列、並列化することで容量および電圧を自由に調節することが可能になる。
本実施形態の非水電解質二次電池は、長期使用しても放電容量が維持され、サイクル特性が良好である。電気自動車やハイブリッド電気自動車や燃料電池車やハイブリッド燃料電池自動車などの車両用途においては、電気・携帯電子機器用途と比較して、高容量、大型化が求められるとともに、長寿命化が必要となる。したがって、上記非水電解質二次電池は、車両用の電源として、例えば、車両駆動用電源や補助電源に好適に利用することができる。
次に本発明の非水電解質二次電池の製造方法について、その一例を説明するが、本発明は、かかる例のみに限定されるものではない。
1.電解液の作製
エチレンカーボネート(EC)、エチルメチルカーボネート(EMC)、ジエチルカーボネート(DEC)の混合溶媒(30:30:40(体積比))を溶媒とした。また1.0MのLiPF6をリチウム塩とした。さらに上記溶媒と上記リチウム塩との合計100重量%に対して2.0重量%のビニレンカーボネートを添加して電解液を作製した。なお、「1.0MのLiPF6」とは、当該混合溶媒およびリチウム塩の混合物におけるリチウム塩(LiPF6)濃度が1.0Mであるという意味である。
正極活物質としてLiNi1/3Mn1/3Co1/3O2(平均粒子径:15μm)90重量%、導電助剤としてアセチレンブラック 5重量%、およびバインダーとしてPVdF 5重量%からなる固形分を用意した。この固形分に対し、スラリー粘度調整溶媒であるN-メチル-2-ピロリドン(NMP)を適量添加して、固形分濃度を80重量%とし、プラネタリーミキサーにより固練りを130分実施した。さらにスラリー粘度調整溶媒であるN-メチル-2-ピロリドン(NMP)を適量添加し、正極スラリー組成物を作製した(固形分55重量%)。次に、正極スラリー組成物を、集電体であるアルミニウム箔(厚み20μm)の両面にダイコーターにより塗布した。塗布直後の電極乾燥温度は115℃とした。その後、ヒートロールプレスにより120℃(ロール温度)でホットプレスを行い、正極活物質層の密度2.9g/cm3、正極活物質層の片面塗工量15.0mg/cm2、正極活物質層の厚さ50μmの正極を作製した。
負極活物質として天然黒鉛(平均粒子径:20μm)94重量%、導電助剤としてアセチレンブラック2重量%およびバインダーとしてスチレン-ブタジエンゴム(SBR) 3重量%、カルボキシメチルセルロース(CMC) 1重量%からなる固形分を用意した。この固形分に対し、スラリー粘度調整溶媒であるイオン交換水を適量添加して、負極活物質スラリー組成物を作製した。次に、負極活物質スラリー組成物を、集電体である銅箔(10μm)の両面に塗布し、乾燥・プレスを行って、負極活物質層の密度は、1.4g/cm3、片面塗工量7.3mg/cm2の負極を作製した。
上記で作製した正極を200mm×204mmの長方形状に切断し、負極を205×209mmの長方形状に切断した(正極24枚、負極25枚)。この正極と負極とを210×214mmのセパレータ(ポリプロピレン製の微多孔膜、厚さ25μm、空隙率55%)を介して交互に積層して発電要素を作製した。
定格容量は、温度25℃、3.0Vから4.15Vの電圧範囲で、次の手順1~2によって測定される。
正極の作製において、固練り時間を140分、電極の乾燥温度を109℃、プレス温度を125℃とし、正極活物質層の密度を3.2g/cm3、正極活物質層の片面塗工量を18.0mg/cm2、負極活物質層の片面塗工量を8.8mg/cm2とし、電極サイズを表2に記載のようにしたこと以外は、実施例1と同様にして非水電解質二次電池を得た。
正極の作製において、固練り時間を150分、電極の乾燥温度を108℃、プレス温度を130℃とし、正極活物質層の密度を3.3g/cm3、正極活物質層の片面塗工量を21.5mg/cm2、負極活物質層の片面塗工量を10.5mg/cm2とし、電極サイズを表2に記載のようにしたこと以外は、実施例1と同様にして非水電解質二次電池を得た。
正極の作製において、固練り時間を120分、電極の乾燥温度を120℃、プレス温度を120℃としたこと以外は、実施例1と同様にして非水電解質二次電池を得た。
正極の作製において、固練り時間を130分、電極の乾燥温度を115℃、プレス温度を120℃としたこと以外は、実施例2と同様にして非水電解質二次電池を得た。
正極の作製において、固練り時間を140分、電極の乾燥温度を110℃、プレス温度を125℃としたこと以外は、実施例3と同様にして非水電解質二次電池を得た。
正極の作製において、固練り時間を110分、電極の乾燥温度を120℃、プレス温度を115℃としたこと以外は、実施例1と同様にして非水電解質二次電池を得た。
正極の作製において、固練り時間を120分、電極の乾燥温度を118℃、プレス温度を115℃としたこと以外は、実施例2と同様にして非水電解質二次電池を得た。
正極の作製において、固練り時間を130分、電極の乾燥温度を115℃、プレス温度を120℃としたこと以外は、実施例3と同様にして非水電解質二次電池を得た。
正極の作製において、固練り時間を100分、電極の乾燥温度を120℃、プレス温度を115℃としたこと以外は、実施例1と同様にして非水電解質二次電池を得た。
正極の作製において、固練り時間を100分、電極の乾燥温度を118℃、プレス温度を115℃としたこと以外は、実施例2と同様にして非水電解質二次電池を得た。
正極の作製において、固練り時間を110分、電極の乾燥温度を118℃、プレス温度を115℃としたこと以外は、実施例3と同様にして非水電解質二次電池を得た。
正極の作製において、固練り時間を80分、電極の乾燥温度を120℃とし、プレスの際に加熱を行わなかったこと以外は、実施例1と同様にして非水電解質二次電池を得た。
正極の作製において、固練り時間を90分、電極の乾燥温度を120℃とし、プレスの際に加熱を行わなかったこと以外は、実施例2と同様にして非水電解質二次電池を得た。
正極の作製において、固練り時間を100分、電極の乾燥温度を120℃とし、プレスの際に加熱を行わなかったこと以外は、実施例3と同様にして非水電解質二次電池を得た。
正極活物質層の密度を3.2g/cm3、正極活物質層の片面塗工量を10.2mg/cm2、負極活物質層の片面塗工量を5.3mg/cm2とし、電極サイズを表2に記載のようにしたこと以外は、比較例2と同様にして非水電解質二次電池を得た。
正極の作製において、固練り時間を70分、電極の乾燥温度を120℃とし、プレスの際に加熱を行わなかったこと、正極活物質層の密度を2.7g/cm3、正極活物質層の片面塗工量を11.8mg/cm2、負極活物質層の片面塗工量を5.6mg/cm2とし、電極サイズを表2に記載のようにした以外は、実施例1と同様にして非水電解質二次電池を得た。
正極活物質層の密度を3.2g/cm3、正極活物質層の片面塗工量を26mg/cm2、負極活物質層の片面塗工量を12.7mg/cm2とし、電極サイズを表2に記載のようにしたこと以外は、比較例2と同様にして非水電解質二次電池を得た。
正極に対する電流密度を2mA/cm2として、各実施例および比較例で作製した電池をカットオフ電圧4.15Vまで充電して初期充電容量とし、1時間の休止後、カットオフ電圧3.0Vまで放電したときの容量を初期放電容量とした。この充放電サイクルを500回繰返した。初期放電容量に対する500サイクル目の放電容量の割合を容量維持率(%)とし、サイクル耐久性として評価した。
11 負極集電体、
12 正極集電体、
13 負極活物質層、
15 正極活物質層、
17 セパレータ、
19 単電池層、
21 発電要素、
25 負極集電板、
27 正極集電板、
29 電池外装材。
Claims (5)
- 正極集電体の表面に正極活物質を含む正極活物質層が形成されてなる正極と、
負極集電体の表面に負極活物質を含む負極活物質層が形成されてなる負極と、
セパレータと、
を含む発電要素を有し、
正極活物質層の空孔体積に対する定格容量の比が1.40Ah/cc以上であり、定格容量に対する電池面積の比が4.0cm2/Ah以上であり、かつ、定格容量が30Ah以上である、非水電解質二次電池であって、
正極活物質層における空孔率のばらつきが6.0%以下である、非水電解質二次電池。 - 前記正極活物質層の空孔体積に対する定格容量の比が2.20Ah/cc以上で、前記正極活物質層における空孔率のばらつきが5.0%以下である、請求項1に記載の非水電解質二次電池。
- 前記正極活物質層における空孔率のばらつきが4.0%以下である、請求項1または2に記載の非水電解質二次電池。
- 前記正極活物質がLiaNibMncCodMxO2(但し、式中、a、b、c、d、xは、0.9≦a≦1.2、0<b<1、0<c≦0.5、0<d≦0.5、0≦x≦0.3を満たす。MはTi、Zr、Nb、W、P、Al、Mg、V、Ca、SrおよびCrから選ばれる少なくとも1種類である)で表される組成を有するリチウム複合酸化物である、請求項1~3のいずれか1項に記載の非水電解質二次電池。
- 扁平型非水電解質二次電池である、請求項1~4のいずれか1項に記載の非水電解質二次電池。
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EP16904629.9A EP3471190B1 (en) | 2016-06-08 | 2016-06-08 | Nonaqueous electrolyte secondary battery |
PCT/JP2016/067136 WO2017212594A1 (ja) | 2016-06-08 | 2016-06-08 | 非水電解質二次電池 |
US16/308,024 US20190355969A1 (en) | 2016-06-08 | 2016-06-08 | Non-Aqueous Electrolyte Secondary Battery |
KR1020187035545A KR102036038B1 (ko) | 2016-06-08 | 2016-06-08 | 비수전해질 이차 전지 |
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