Battery

Abstract

Provided is a battery in which a positive electrode (100) has a first positive electrode active material layer (122) containing a positive electrode active material represented by the general formula LixNiyCozM1-y-zO2 (0.80 ≤ y ≤ 0.93, and M is a metal element including at least one of the elements Mn and Al). The length of the first positive electrode active material layer (122) in the lengthwise direction thereof is 300-740 mm.

Description

[Technical field]

[0001] The present invention relates to a battery. [Background technology]

[0002] In recent years, non-aqueous electrolyte batteries such as lithium ion secondary batteries have been developed. The battery includes a positive electrode, a negative electrode, and a separator. The positive electrode includes a positive electrode current collector and a positive electrode active material layer. The negative electrode includes a negative electrode current collector and a negative electrode active material layer. The separator separates the positive electrode and the negative electrode from each other.

[0003] Patent Document 1 describes an example of a lithium ion secondary battery in which a positive electrode and a negative electrode are laminated. In this battery, the positive electrode active material layer contains a lithium nickel-based composite oxide having a layered crystal structure in which the composition ratio of nickel to the total of nickel, cobalt, and manganese is 0.4. The length of the positive electrode in the longitudinal direction is 250 mm. In addition, the ratio of output to capacity of the battery is less than 25 W / Wh.

[0004] Patent Document 2 describes an example of a lithium ion secondary battery in which a positive electrode and a negative electrode are stacked. In this battery, the positive electrode active material contains a lithium nickel-based composite oxide having a layered crystal structure in which the composition ratio of nickel to the total of nickel, cobalt, and manganese is 0.8.

[0005] Patent Document 3 describes an example of a lithium ion secondary battery in which a positive electrode, a negative electrode, and a separator are wound together. In this battery, the positive electrode active material contains a lithium nickel-based composite oxide having a layered structure in which the composition ratio of nickel to the total of nickel, cobalt, and aluminum elements is 0.8. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2017-33827 A [Patent Document 2] International Publication No. 2015 / 156399 [Patent Document 3] JP 2017-63041 A Summary of the Invention [Problem to be solved by the invention]

[0007] In batteries such as lithium ion secondary batteries, it is desirable for the capacity and output to be high. The inventors of the present invention have conducted research and found that the capacity and output of a battery are related to the longitudinal length of the positive electrode active material layer. However, Patent Documents 1 to 3 do not describe the relationship between the longitudinal length of the positive electrode active material layer and the capacity and output of the battery.

[0008] One object of the present invention is to provide a battery having a high capacity and high power output. Other objects of the present invention will become apparent from the description of this specification. [Means for solving the problem]

[0009] One aspect of the present invention is A positive electrode is provided, The positive electrode is represented by the general formula Li x Ni y Co z M 1-y-z A positive electrode active material layer including a positive electrode active material represented by the formula: O2 (0.80≦y≦0.93, M is a metal element including at least one element of Mn and Al), In the battery, the length in the longitudinal direction of the positive electrode active material layer is 300 mm or more and 740 mm or less. Effect of the Invention

[0010] According to the above aspect of the present invention, a battery with high capacity and high output can be provided. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a plan view of a battery according to an embodiment. [Diagram 2] 2 is a cross-sectional view along the line AA′ of FIG. 1. [Diagram 3] FIG. 2 is a plan view of a positive electrode according to the embodiment. [Figure 4] 1 is a graph showing an example of the relationship between the longitudinal length of a positive electrode active material layer, the battery capacity, and the battery output in a case where the battery has 16 layers of positive electrodes. [Diagram 5] 1 is a graph showing an example of the relationship between the longitudinal length of a positive electrode active material layer, the battery capacity, and the battery output in a case where the battery has 23 layers of positive electrodes. [Figure 6] 1 is a graph showing an example of the relationship between the longitudinal length of a positive electrode active material layer, the battery capacity, and the battery output in a case where the battery has 31 layers of positive electrodes. [Figure 7] 1 is a graph showing an example of the relationship between the longitudinal length of a positive electrode active material layer, the battery capacity, and the battery output in a case where the battery has 42 layers of positive electrodes. [Figure 8] 1 is a graph showing an example of the relationship between the longitudinal length of a positive electrode active material layer, the battery capacity, and the battery output in a case where the battery has 50 layers of positive electrodes. [Figure 9] 1 is a graph showing an example of the relationship between the longitudinal length of a positive electrode active material layer, the battery capacity, and the battery output in a case where the battery has 54 layers of positive electrodes. [Figure 10] 1 is a graph showing an example of the relationship between the longitudinal length of the positive electrode active material layer and the ratio of output to capacity of the battery when the laminate has 16, 23, 31, 42, 50 and 54 layers of positive electrodes. [Figure 11] 1 is a graph showing an example of the relationship between the longitudinal length of the positive electrode active material layer and the cell temperature rise of the battery when the laminate has 16, 23, 31, 42, 50 and 54 positive electrode layers. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same components are given the same reference numerals, and the description will be omitted as appropriate.

[0013] Fig. 1 is a plan view of a battery 10 according to an embodiment. Fig. 2 is a cross-sectional view taken along line AA' in Fig. 1. Fig. 3 is a plan view of a positive electrode 100 according to an embodiment.

[0014] In FIG. 1 to FIG. 3, the first direction X indicates the length direction of the battery 10. The positive direction of the first direction X, which is the direction indicated by the arrow indicating the first direction X, is the direction from the positive electrode lead 130 to the negative electrode lead 230 described later. The negative direction of the first direction X, which is the opposite direction to the direction indicated by the arrow indicating the first direction X, is the direction from the negative electrode lead 230 to the positive electrode lead 130. The second direction Y intersects with the first direction X, specifically, is perpendicular to it, and indicates the width direction of the battery 10. The third direction Z intersects with both the first direction X and the second direction Y, specifically, is perpendicular to it, and indicates the thickness direction of the battery 10. In addition, in FIG. 1 and FIG. 3, the white circle with a black dot indicating the third direction Z indicates that the direction from the back of the paper to the front is the positive direction of the third direction Z, and the direction from the front of the paper to the back is the negative direction of the third direction Z. In Figure 2, the white circle with an X indicating the second direction Y indicates that the direction from the front of the paper to the back is the positive direction of the second direction Y, and the direction from the back of the paper to the front is the negative direction of the second direction Y.

[0015] In this embodiment, the battery 10 is arranged so that the thickness direction of the battery 10, i.e., the third direction Z, is parallel to the vertical direction. The positive direction of the third direction Z, which is the direction indicated by the arrow indicating the third direction Z, is the upward direction in the vertical direction. On the other hand, the negative direction of the third direction Z, which is the opposite direction to the direction indicated by the arrow indicating the third direction Z, is the downward direction in the vertical direction.

[0016] The battery 10 will be described with reference to Fig. 1. In this embodiment, the battery 10 is a lithium ion secondary battery.

[0017] The battery 10 includes a positive electrode lead 130 , a negative electrode lead 230 , and an exterior material 400 .

[0018] The positive electrode lead 130 is electrically connected to a positive electrode 100 shown in Fig. 2, which will be described later. The positive electrode lead 130 is made of, for example, aluminum or an aluminum alloy.

[0019] The negative electrode lead 230 is electrically connected to the negative electrode 200 shown in Fig. 2, which will be described later. The negative electrode lead 230 is made of, for example, copper or a copper alloy, or a nickel-plated copper or copper alloy.

[0020] The exterior material 400 has a rectangular shape having four sides. In this embodiment, the positive electrode lead 130 is provided on a side of the exterior material 400 located on the negative side in the first direction X, and the negative electrode lead 230 is provided on a side of the exterior material 400 located on the positive side in the first direction X. However, the positive electrode lead 130 and the negative electrode lead 230 may be provided on a common side of the exterior material 400 (for example, a side located on the positive or negative side in the first direction X).

[0021] The exterior material 400 accommodates the laminate 20 shown in FIG. 2, which will be described later, together with an electrolyte solution (not shown).

[0022] The exterior material 400 includes, for example, a heat-sealable resin layer and a barrier layer, and is, for example, a laminated film including a heat-sealable resin layer and a barrier layer.

[0023] The resin material forming the thermally adhesive resin layer is, for example, polyethylene (PE), polypropylene, etc. The thickness of the thermally adhesive resin layer is, for example, 20 μm or more and 200 μm or less.

[0024] The barrier layer has a barrier property such as preventing leakage of an electrolyte or intrusion of moisture from the outside, and is a barrier layer formed of a metal such as stainless steel (SUS) foil, aluminum foil, aluminum alloy foil, copper foil, titanium foil, etc. The thickness of the barrier layer is, for example, 10 μm or more and 100 μm or less.

[0025] The thermally adhesive resin layer of the laminated film may be one layer or two or more layers.Similarly, the barrier layer of the laminated film may be one layer or two or more layers.

[0026] The electrolyte is, for example, a non-aqueous electrolyte that contains, for example, a lithium salt and a solvent that dissolves the lithium salt.

[0027] Lithium salts include, for example, LiClO4, LiBF4, LiBF6, LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiB 10 Cl 10 , LiAlCl4, LiCl, LiBr, LiB(C2H5)4, CF3SO3Li, CH3SO3Li, LiC4F9SO3, Li(CF3SO2)2N, Li(C2F5SO2)2N, lithium carboxylates of lower fatty acids, etc.

[0028] Examples of the solvent that dissolves the lithium salt include carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), and vinylene carbonate (VC); lactones such as γ-butyrolactone and γ-valerolactone; ethers such as trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, tetrahydrofuran, and 2-methyltetrahydrofuran; and dimethyl sulfoxide. sulfoxides such as 1,3-dioxolane, 4-methyl-1,3-dioxolane, and the like; nitrogen-containing solvents such as acetonitrile, nitromethane, formamide, dimethylformamide, and the like; organic acid esters such as methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate, and the like; phosphoric acid triesters and diglymes; triglymes; sulfolanes such as sulfolane and methylsulfolane; oxazolidinones such as 3-methyl-2-oxazolidinone, and the like; sultones such as 1,3-propane sultone, 1,4-butane sultone, naphtha sultone, and the like. These substances may be used alone or in combination.

[0029] The laminate 20 will be described with reference to FIG.

[0030] The laminate 20 has a plurality of positive electrodes 100, a plurality of negative electrodes 200, and a separator 300. The plurality of positive electrodes 100 and the plurality of negative electrodes 200 are alternately arranged in the third direction Z. The total number of the plurality of positive electrodes 100 can be, for example, 16 or more and 54 or less. The total number of the plurality of negative electrodes 200 may be, for example, one more than the total number of the positive electrodes 100. The separator 300 separates the positive electrodes 100 and the negative electrodes 200 adjacent to each other in the third direction Z. In one example, the separator 300 extends in a zigzag manner so as to pass between the adjacent positive electrodes 100 and the negative electrodes 200 while folding back along the second direction Y. Alternatively, each of the plurality of separators 300 may be located between the adjacent positive electrodes 100 and the negative electrodes 200. The laminate 20 may have only one positive electrode 100 and only one negative electrode 200.

[0031] The following describes in detail the positive electrode 100. The positive electrode 100 has a positive electrode current collector 110, a first positive electrode active material layer 122, and a second positive electrode active material layer .

[0032] The first positive electrode active material layer 122 is located on the upper surface of the positive electrode current collector 110. The second positive electrode active material layer 124 is located on the lower surface of the positive electrode current collector 110.

[0033] The end of the positive electrode current collector 110 on the negative side in the first direction X is connected to the positive electrode lead 130 shown in FIG.

[0034] The positive electrode current collector 110 is formed of, for example, aluminum, stainless steel, nickel, titanium, or an alloy thereof. The positive electrode current collector 110 has a shape of, for example, a foil, a flat plate, or a mesh. The positive electrode current collector 110 has a thickness of, for example, 1 μm or more and 50 μm or less.

[0035] The first positive electrode active material layer 122 contains a positive electrode active material, a binder resin, and a conductive assistant. Details of the first positive electrode active material layer 122 are as follows. The following details of the first positive electrode active material layer 122 also apply to the second positive electrode active material layer 124 unless otherwise specified.

[0036] The positive electrode active material is represented by the general formula Li x Ni y Co z M 1-y-z O2 (0.80 ≤ y ≤ 0.93, where M is a metal element containing at least one of the elements Mn and Al). When the composition ratio y is within the above range, it is possible to reduce the cost and increase the capacity per unit weight, and it is possible to stabilize the crystal structure of the positive electrode active material. Further, when the composition ratio y is within the above range, it is possible to suppress a decrease in thermal stability in the charged state as compared with the case where the composition ratio y is greater than the above range. In the general formula, x satisfies 1 ≤ x ≤ 1.2, and y and z are positive numbers satisfying y + z < 1. Since it becomes difficult to synthesize a single-phase composite oxide as the proportion of manganese increases, it is desirable that 1 - y - z ≤ 0.4. Further, since the cost increases and the capacity decreases as the proportion of cobalt increases, it is desirable that z < y and z < 1 - y - z. In order to obtain a high-capacity battery, it is particularly preferable that y > 1 - y - z and y > z. The positive electrode active material is, for example, a lithium nickel-based composite oxide such as a lithium nickel cobalt manganese composite oxide having a layered crystal structure represented by the above general formula.

[0037] The first positive electrode active material layer 122 contains, for example, 90% by weight or more and 99% by weight or less of the positive electrode active material with respect to 100% by weight of the total weight of the first positive electrode active material layer 122.

[0038] The total coating amount of the first positive electrode active material layer 122 and the second positive electrode active material layer 124 is, for example, 25 mg / cm 2 or more and 50 mg / cm 2 or less.

[0039] Examples of the binder resin contained in the first positive electrode active material layer 122 include thermoplastic polymers such as polyethylene, polypropylene, polyethylene terephthalate (PET), polyether nitrile, polyacrylonitrile, polyimide, polyamide, cellulose, carboxymethyl cellulose (CMC), 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, styrene-isoprene-styrene block copolymer and its hydrogenated product, etc.; polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polychloroethylene, etc. Fluorine resins such as polyvinyl fluoride (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinyl fluoride (PVF), etc.; vinylidene fluoride-based fluororubbers such as vinylidene fluoride-hexafluoropropylene-based fluororubber (VDF-HFP-based fluororubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-HFP-TFE-based fluororubber), vinylidene fluoride-pentafluoropropylene-based fluororubber (VDF-PFP-TFE-based fluororubber), vinylidene fluoride-perfluoromethylvinyl ether-tetrafluoroethylene-based fluororubber (VDF-PFMVE-TFE-based fluororubber), vinylidene fluoride-chlorotrifluoroethylene-based fluororubber (VDF-CTFE-based fluororubber), etc.; epoxy resins, etc. Among these, polyvinylidene fluoride (PVdF), polyimide, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polypropylene, polytetrafluoroethylene (PTFE), polyacrylonitrile, and polyamide are more preferable.These preferred binder resins have excellent heat resistance, and further have a very wide potential window and are stable at both the positive electrode potential and the negative electrode potential, making them suitable for use in the active material layer. These binder resins may be used alone or in combination of two or more.

[0040] It is possible to appropriately determine the amount of binder resin contained in the first positive electrode active material layer 122. The first positive electrode active material layer 122 contains, for example, 0.1 wt % to 10.0 wt % of the binder resin with respect to the total weight of the first positive electrode active material layer 122 being 100 wt %.

[0041] The conductive assistant contained in the first positive electrode active material layer 122 is, for example, carbon black, Ketjen black, acetylene black, natural graphite, artificial graphite, carbon nanotubes, carbon nanofibers, carbon nanohorns, and other carbon fibers. The graphite is, for example, flake graphite or spherical graphite. These substances may be used alone or in combination.

[0042] It is possible to appropriately determine the amount of the conductive assistant contained in the first positive electrode active material layer 122. The first positive electrode active material layer 122 contains, for example, 0.1 wt % to 8.0 wt % of the conductive assistant with respect to the total weight of the first positive electrode active material layer 122 being 100 wt %.

[0043] The first positive electrode active material layer 122 may appropriately contain a pH adjuster (e.g., oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, or fumaric acid) for neutralizing an alkaline component contained in the positive electrode active material for reasons such as preventing gelation of the slurry.

[0044] The length L of the first positive electrode active material layer 122 in the longitudinal direction is within a predetermined range, as described below. When the length L of the first positive electrode active material layer 122 in the longitudinal direction is within the predetermined range, the battery 10 can achieve high capacity and high output.

[0045] The length W of the first positive electrode active material layer 122 in the short side direction is not less than 70 mm and not more than 120 mm.

[0046] It is possible to appropriately determine the thickness of the first positive electrode active material layer 122. The thickness of the first positive electrode active material layer 122 is, for example, not less than 35 μm and not more than 65 μm.

[0047] The negative electrode 200 will be described in detail below. The negative electrode 200 has a negative electrode current collector 210, a first negative electrode active material layer 222, and a second negative electrode active material layer 224.

[0048] The first negative electrode active material layer 222 is located on the upper surface of the negative electrode current collector 210. The second negative electrode active material layer 224 is located on the lower surface of the negative electrode current collector 210.

[0049] The end of the negative electrode current collector 210 on the positive side in the first direction X is connected to the negative electrode lead 230 shown in FIG.

[0050] The negative electrode current collector 210 is formed of, for example, copper, stainless steel, nickel, titanium, or an alloy thereof. The shape of the negative electrode current collector 210 is, for example, a foil, a flat plate, or a mesh. The thickness of the negative electrode current collector 210 in the third direction Z (third direction Z) is, for example, 1 μm or more and 50 μm or less.

[0051] The first negative electrode active material layer 222 contains a negative electrode active material and a binder resin. The first negative electrode active material layer 222 may further contain a conductive assistant, if necessary. Details of the first negative electrode active material layer 222 are as follows. The following details of the first negative electrode active material layer 222 also apply to the second negative electrode active material layer 224 unless otherwise specified.

[0052] Examples of the negative electrode active material include, but are not limited to, metals such as Si and Sn; metal oxides such as TiO, Ti2O3, TiO2, SiO2, SiO, and SnO2; and Li4Ti5O 12Preferred examples of the negative electrode active material include composite oxides of lithium and transition metals such as Li7MnN, Li-Pb alloys, Li-Al alloys, Li, carbon powder, graphite (natural graphite, artificial graphite), carbon black, activated carbon, carbon fiber, coke, soft carbon, hard carbon, and other carbon materials. Among these, by using an element that alloys with lithium, it is possible to obtain a battery with a high capacity and excellent output characteristics having a high energy density compared to conventional carbon materials. These negative electrode active materials may be used alone or in combination of two or more. The above-mentioned elements that alloy with lithium are not limited to the following, but specifically include Si, Ge, Sn, Pb, Al, In, Zn, H, Ca, Sr, Ba, Ru, Rh, Ir, Pd, Pt, Ag, Au, Cd, Hg, Ga, Tl, C, N, Sb, Bi, O, S, Se, Te, Cl, and the like.

[0053] The first negative electrode active material layer 222 contains, for example, 90% by weight to 99% by weight of the negative electrode active material, with the total weight of the first negative electrode active material layer 222 being 100% by weight.

[0054] The total weight of the first negative electrode active material layer 222 and the second negative electrode active material layer 224 is, for example, 12 mg / cm 2 More than 28mg / cm 2 The following is the result.

[0055] When an organic solvent is used as a solvent for obtaining the slurry, the binder resin contained in the first negative electrode active material layer 222 can be, for example, the binder resin exemplified as the binder resin contained in the first positive electrode active material layer 122. When water is used as a solvent for obtaining the slurry, the binder resin contained in the first negative electrode active material layer 222 can be, for example, a styrene-based polymer (styrene-butadiene rubber, styrene-vinyl acetate copolymer, styrene-acrylic copolymer, etc.), acrylonitrile-butadiene rubber, methyl methacrylate-butadiene rubber, (meth)acrylic polymer (polyethyl acrylate, polyethyl methacrylate, polypropyl acrylate, polymethyl methacrylate (methyl methacrylate rubber), polypropyl methacrylate, polyisopropyl acrylate, polyisopropyl methacrylate, polybutyl acrylate, polybutyl acrylate, etc.), or the like. poly(ethyl methacrylate), polyhexyl acrylate, polyhexyl methacrylate, polyethylhexyl acrylate, polyethylhexyl methacrylate, polylauryl acrylate, polylauryl methacrylate, etc.), polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene copolymer, polybutadiene, butyl rubber, fluororubber, polyethylene oxide, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene-propylene-diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, polyester resin, phenolic resin, epoxy resin;Polyvinyl alcohol (average polymerization degree is preferably 200 to 4000, more preferably 1000 to 3000, and saponification degree is preferably 80 mol % or more, more preferably 90 mol % or more) and modified products thereof (1 to 80 mol % saponification product of vinyl acetate units of copolymer of ethylene / vinyl acetate = 2 / 98 to 30 / 70 molar ratio, 1 to 50 mol % partial acetalization product of polyvinyl alcohol, etc.), starch and modified products thereof (oxidized starch, phosphated starch, cationic starch, etc.), cellulose derivatives (carboxymethylcellulose (CMC), methylcellulose, hydroxypropylcellulose, hydroxyethylcellulose, and salts thereof, etc.), polyvinylpyrrolidone, polya The binder may be a water-soluble polymer such as acrylic acid (salt), polyethylene glycol, (meth)acrylamide and / or (meth)acrylate copolymer [(meth)acrylamide polymer, (meth)acrylamide-(meth)acrylate copolymer, (meth)acrylate alkyl (carbon number 1 to 4) ester-(meth)acrylate copolymer, etc.], styrene-maleate copolymer, Mannich modified polyacrylamide, formalin condensation resin (urea-formalin resin, melamine-formalin resin, etc.), polyamide polyamine or dialkylamine-epichlorohydrin copolymer, polyethyleneimine, casein, soybean protein, synthetic protein, and mannangalactan derivative. These aqueous binder resins may be in the form of an emulsion. These aqueous binders may be used alone or in combination of two or more.;

[0056] It is possible to appropriately determine the amount of binder resin contained in the first negative electrode active material layer 222. The first negative electrode active material layer 222 contains, for example, 0.1 wt % to 10.0 wt % of binder resin with respect to the total weight of the first negative electrode active material layer 222 being 100 wt %.

[0057] The length of the first negative electrode active material layer 222 in the longitudinal direction can be determined appropriately according to the length L of the first positive electrode active material layer 122 in the longitudinal direction.

[0058] The length of the first negative electrode active material layer 222 in the short side direction can be determined appropriately depending on the length W of the first positive electrode active material layer 122 in the short side direction.

[0059] It is possible to appropriately determine the thickness of the first negative electrode active material layer 222. The thickness of the first negative electrode active material layer 222 is, for example, not less than 40 μm and not more than 75 μm.

[0060] The separator 300 will now be described in detail.

[0061] The separator 300 has a function of electrically insulating the positive electrode 100 and the negative electrode 200 and allowing ions (for example, lithium ions) to pass therethrough. The separator 300 can be, for example, a porous separator.

[0062] The shape of the separator 300 can be appropriately determined depending on the shape of the positive electrode 100 or the negative electrode 200, and can be, for example, rectangular.

[0063] The substrate 310 includes a porous resin layer containing polyolefin as a main component. Specifically, the porous resin layer includes 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more of polyolefin relative to 100% by weight of the total weight of the porous resin layer, and may include 100% by weight of polyolefin relative to 100% by weight of the total weight of the porous resin layer. The porous resin layer may be a single layer, or may be two or more layers. Examples of polyolefin include polypropylene and polyethylene.

[0064] The thickness of the separator 300 (in the third direction Z) can be appropriately determined, and can be set to, for example, not less than 8.0 μm and not more than 45.0 μm. EXAMPLES

[0065] FIG. 4 is a graph showing an example of the relationship between the longitudinal length of the positive electrode active material layer, the capacity of the battery, and the output of the battery when the battery has 16 layers of positive electrodes. FIG. 5 is a graph showing an example of the relationship between the longitudinal length of the positive electrode active material layer, the capacity of the battery, and the output of the battery when the battery has 23 layers of positive electrodes. FIG. 6 is a graph showing an example of the relationship between the longitudinal length of the positive electrode active material layer, the capacity of the battery, and the output of the battery when the battery has 31 layers of positive electrodes. FIG. 7 is a graph showing an example of the relationship between the longitudinal length of the positive electrode active material layer, the capacity of the battery, and the output of the battery when the battery has 42 layers of positive electrodes. FIG. 8 is a graph showing an example of the relationship between the longitudinal length of the positive electrode active material layer, the capacity of the battery, and the output of the battery when the battery has 50 layers of positive electrodes. FIG. 9 is a graph showing an example of the relationship between the longitudinal length of the positive electrode active material layer, the battery capacity, and the battery output when the battery has 54 layers of positive electrodes.

[0066] 4 to 9, the horizontal axis of the graph represents the longitudinal length of the positive electrode active material layer (unit: mm), the vertical axis on the left side of the graph represents the battery capacity (unit: Wh), and the vertical axis on the right side of the graph represents the battery output (unit: W).

[0067] In FIG. 4 to FIG. 9, the battery was manufactured as follows.

[0068] (Preparation of positive electrode active material) Sodium hydroxide and ammonia were continuously added to an aqueous solution (1.0 mol / L) in which nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved so that the pH was 11.0, and a metal composite hydroxide in which nickel, cobalt, and manganese were dissolved in a molar ratio of 80:10:10 was produced by coprecipitation. This metal composite oxide and lithium hydroxide were weighed so that the ratio of the total number of moles of metals other than Li (Ni, Co, Mn) to the number of moles of Li was 1:1, and then thoroughly mixed, heated at a heating rate of 5°C / min, pre-baked at 700°C for 2 hours in an oxygen atmosphere, heated at a heating rate of 3°C / min, baked at 750°C for 10 hours, and cooled to room temperature to obtain an NMC composite oxide as a lithium nickel cobalt manganese composite oxide.

[0069] (Preparation of positive electrode plate) The positive electrode active material obtained as described above was mixed with 97% by weight of carbon nanotubes as a conductive assistant, 1.2% by weight of polyvinylidene fluoride (PVdF) as a binder resin, and an appropriate amount of N-methyl-2-pyrrolidone (NMP) as a slurry viscosity adjusting solvent to prepare a positive electrode active material slurry. This positive electrode active material slurry was applied to both sides of an aluminum foil as a positive electrode current collector and dried. Thereafter, a pressing process was performed to prepare a positive electrode plate, and the weight of the positive electrode active material layer on both sides of the positive electrode plate was 32.1 mg / cm. 2 It was made so that

[0070] (Preparation of negative electrode plate) Graphite powder and SiO powder were used as the negative electrode active material. These powders were mixed uniformly with binder resins, styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC), in a ratio of graphite:SiO:SBR:CMC=94:3:2:1, and added to a solvent, NMP, to prepare a negative electrode active material slurry. This negative electrode active material slurry was applied to both sides of a copper foil, which was a negative electrode current collector, and dried. Thereafter, a pressing process was performed to make a negative electrode plate, so that the weight of the negative electrode active material layer of the negative electrode plate was 19.8 mg / cm. 2 It was made so that

[0071] (Battery Construction) A part of the positive electrode plate prepared as described above was cut out to obtain a positive electrode. As the positive electrode, 12 types of positive electrodes with different longitudinal directions of the positive electrode active material layer were prepared as plotted in the graphs of Figs. 4 to 9. For these positive electrodes, the length in the short-side direction of the positive electrode active material layer was 88 mm in each case. In addition, a part of the negative electrode plate prepared as described above was cut out to obtain a negative electrode. As the negative electrode, 12 types of negative electrodes were prepared for each of the above-mentioned 12 types of positive electrodes, in which the longitudinal direction of the negative electrode active material layer was 102% of the longitudinal direction of the positive electrode active material layer. For these negative electrodes, the length in the short-side direction of the negative electrode active material layer was 90 mm in each case. A laminate was prepared by alternately stacking a predetermined number of layers of positive electrodes and a predetermined number of layers of negative electrodes with a separator interposed therebetween. In Figs. 4, 5, 6, 7, 8, and 9, the total number of positive electrodes was 16, 23, 31, 42, 50, and 54, respectively. 4 to 9, the total number of negative electrodes was set to be greater than the total number of positive electrodes by 1. This stack was housed in a laminate film, which was an exterior material, and an electrolyte was injected to fabricate a battery.

[0072] 4 to 9, the capacity of the battery 10 was measured as follows: First, the battery was charged at 1 / 3 C to a charging voltage of 4.2 V under constant current-constant voltage (CC-CV) conditions at 25° C. Then, the battery was discharged to 2.5 V at 1 / 3 C under constant current conditions, and the capacity was measured.

[0073] In Figs. 4 to 9, the output of the battery 10 was measured as follows. First, the battery was charged at 1 / 3 C to a charging voltage of 4.2 V under constant current-constant voltage (CC-CV) conditions at 25°C. Then, the battery was discharged at 1 C for 30 minutes under constant current conditions to adjust the charge depth to 50%. Then, the battery was discharged at 1 C for 10 seconds. The voltage immediately before the battery was discharged at 1 C for 10 seconds after adjusting the charge depth to 50% was set to V1 (unit: V). The voltage after the battery was discharged at 1 C for 10 seconds was set to V2 (unit: V). The difference between the voltages V1 and V2 was set to ΔV (unit: V1). This difference ΔV was divided by the discharged current value to calculate the direct current resistance DCR (unit: Ω). The maximum current value (unit: A) was calculated as (V1-3.0) / DCR=I, and the product of this maximum current value I and the voltage of 3.0 V was set to the output.

[0074] 4 to 9, the capacity of the battery increases in proportion to the longitudinal length of the positive electrode active material layer, and the proportionality constant is constant regardless of the number of positive electrodes.

[0075] 4 to 9, the battery output is a concave function when the longitudinal length of the positive electrode active material layer is in the range of about 200 mm to 1000 mm, with the battery output having a maximum value when the longitudinal length of the positive electrode active material layer is in the range of 400 mm to 600 mm. The maximum value of the battery output and the longitudinal length of the positive electrode active material layer at which the battery output has a maximum value vary depending on the number of positive electrodes.

[0076] In each of the graphs in Figures 4 to 9, when the longitudinal length of the positive electrode active material layer is 300 mm or more and 740 mm or less, the battery output is approximately 80% or more of the maximum value of the battery output. Also, when the longitudinal length of the positive electrode active material layer is 390 mm or more and 640 mm or less, the battery output is approximately 90% or more of the maximum value of the battery output. Therefore, from the viewpoint of high capacity and high output of the battery, the longitudinal length of the positive electrode active material layer can be 300 mm or more and 740 mm or less, preferably 390 mm or more and 640 mm or less.

[0077] FIG. 10 is a graph showing an example of the relationship between the longitudinal length of the positive electrode active material layer and the ratio of output to capacity of the battery when the laminate has 16, 23, 31, 42, 50, and 54 positive electrode layers.

[0078] 10, the horizontal axis of the graph represents the longitudinal length (unit: mm) of the positive electrode active material layer, and the vertical axis of the graph represents the ratio (unit: W / Wh) of the output (unit: W) to the capacity (unit: Wh) of the battery.

[0079] As shown in FIG. 10, when the number of positive electrodes is 23 or more and 54 or less, the ratio of the output to the capacity of the battery is approximately 3 W / Wh or more and 17 W / Wh or less when the longitudinal length of the positive electrode active material layer is 300 mm or more and 740 mm or less. When the ratio of the output to the capacity of the battery is less than 3 W / Wh, the resistance of the battery is too high, so that the battery cannot follow the load characteristics when used as a vehicle battery. From the viewpoint of the resistance of the battery, the number of positive electrodes can be 23 or more, preferably 31 or more. In addition, when the ratio of the output to the capacity of the battery is greater than 17 W / Wh, the capacity per area of ​​the battery may be insufficient. From the viewpoint of the capacity per area of ​​the battery, the number of positive electrodes can be 54 or less, preferably 50 or less.

[0080] FIG. 11 is a graph showing an example of the relationship between the longitudinal length of the positive electrode active material layer and the cell temperature rise of the battery when the laminate has 16, 23, 31, 42, 50, and 54 positive electrode layers.

[0081] 11, the horizontal axis of the graph represents the longitudinal length (unit: mm) of the positive electrode active material layer, and the vertical axis of the graph represents the cell temperature rise (unit: K) of the battery.

[0082] In Figure 11, the cell temperature rise of the battery was measured as follows. First, the battery was charged at 25°C under constant current-constant voltage (CC-CV) conditions from 1 / 3 C to a charging voltage of 4.2 V. Then, under constant current conditions, the maximum cell temperature was measured when the battery was continuously discharged to 2.5 V at 6 C. The difference between this maximum cell temperature and the cell temperature after charging and before continuous discharge was taken as the cell temperature rise.

[0083] As shown in Fig. 11, when the number of positive electrodes is 23 or more and 54 or less, the cell temperature rise of the battery is about 230K or less when the longitudinal length of the positive electrode active material layer is 300mm or more and 740mm or less. If the cell temperature rise exceeds 230K, the risk of battery ignition increases rapidly. From the viewpoint of reducing the risk of battery ignition, the number of positive electrodes 100 can be 23 or more, preferably 31 or more.

[0084] Although the embodiment and examples of the present invention have been described above with reference to the drawings, these are merely examples of the present invention, and various configurations other than those described above can also be adopted.

[0085] This application claims priority based on Japanese Patent Application No. 2021-019627, filed on February 10, 2021, the disclosure of which is incorporated herein in its entirety. [Explanation of symbols]

[0086] 10 batteries 20 Laminate 100 Positive electrode 110 Positive electrode current collector 122 First positive electrode active material layer 124 Second positive electrode active material layer 130 Positive lead 200 Negative electrode 210 Negative electrode current collector 222 First negative electrode active material layer 224 Second negative electrode active material layer 230 Negative lead 300 Separator 310 Base material 400 Exterior Materials X 1st direction Y Second direction Z 3rd direction

Claims

1. A positive electrode is provided, The positive electrode is a compound represented by the general formula Li ｘ Ni ｙ Co ｚ M １－ｙ－ｚ O ２ (1≦x≦1.2) (0.80≦y≦0.93, M is a metal element including at least one element of Mn and Al), The length of the positive electrode active material layer in the longitudinal direction is 300 mm or more and 740 mm or less, A battery comprising 16 or more and 54 or less of the positive electrodes.

2. The battery according to claim 1, A battery comprising 23 or more and 54 or less of the positive electrodes.

3. The battery according to claim 1 or 2, The battery, wherein the length of the positive electrode active material layer in the short side direction is 70 nm or more and 120 nm or less.

4. The battery according to any one of claims 1 to 3, The positive electrode active material layer comprises a lithium nickel cobalt manganese composite oxide having a layered crystal structure represented by the general formula.

5. The battery according to any one of claims 1 to 4, The positive electrode active material layer contains 90% by weight or more of the positive electrode active material, with respect to 100% by weight of a total weight of the positive electrode active material layer.

6. The battery according to any one of claims 1 to 5, The weight of the positive electrode active material layer is 25 mg / cm ２ 50mg / cm or more ２ Below is the battery.

7. The battery according to any one of claims 1 to 6, A battery comprising a plurality of the positive electrodes and a plurality of the negative electrodes stacked alternately.

Images