Current collector for battery and battery using the same

Abstract

To provide a current collector for a battery which has excellent current collection characteristics and suppresses an excessive rise in battery temperature when an internal short circuit occurs.SOLUTION: The current collector 50 for a battery includes a first metal plating layer 10, a base material layer 20, and a second metal plating layer 30 in this order, the first metal plating layer 10 and the second metal plating layer 30 are respectively disposed in contact with the base material layer 20, the base material layer 20 includes a binder resin 21 and conductive particles 22, and when an average thickness of the base material layer 20 is defined as T0 [μ m] and an average diameter of the conductive particles 22 in a thickness direction is defined as D [μ m], D / T0 is 1.00 or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a current collector for a battery and a battery using the same. [Background technology]

[0002] As electronic devices such as mobile phones and laptops become smaller and lighter, there is a demand for higher capacity secondary batteries, which are the power sources for these devices. To meet this demand, lithium-ion batteries, which are capable of achieving high energy density, have become widespread. A lithium-ion battery includes a positive electrode, a negative electrode, a separator interposed between the positive and negative electrodes, and a nonaqueous electrolyte.

[0003] Generally, when a short circuit occurs inside a battery with a relatively low resistance, a large current flows at the short circuit point, accelerating the heat generation of the battery and leading to overheating. To avoid this phenomenon, various safety measures are taken in lithium-ion batteries, which have high energy density, not only from the viewpoint of manufacturing but also from the viewpoint of battery configuration. For example, separators are used that have a shutdown function that blocks pores and cuts off ionic current when an internal short circuit occurs. The shutdown function stops the flow of short-circuit current and stops heat generation. However, if the heat generated at the short circuit is large, the separator melts before the shutdown function can function, causing a meltdown that creates a large hole in the separator. If the meltdown causes a short circuit between the positive and negative electrodes, further overheating can occur, and in some cases the battery can catch fire or emit smoke, which is extremely dangerous.

[0004] Therefore, it has been proposed to form a porous film made of a heat-resistant resin such as aramid on the separator (Patent Document 1). Because heat-resistant resins such as aramid do not melt even at high temperatures, it is believed that the technology of Patent Document 1 will be highly capable of maintaining insulation between the positive and negative electrodes even in an overheated environment. However, in the conventional technology of Patent Document 1, although the porous membrane made of heat-resistant resin itself exhibits high heat resistance, if the membrane ruptures during a short circuit, it is easily dragged along by the melting or shrinkage of the underlying separator, which may cause the short circuit area to expand and lead to further overheating.

[0005] Therefore, a method has been proposed for suppressing current flow during a short circuit by forming a resistor layer made of a mixture of carbon powder and polyimide resin on the surface of the current collector (Patent Document 2). As mentioned above, overheating accelerates when the resistance value of the short-circuited area is low. Therefore, if the technology in Patent Document 2 is used, it is thought that overheating can be suppressed by increasing the resistance value even if an internal short circuit occurs.

[0006] However, in the technology of Patent Document 2, although the resistor layer increases the resistance value of the internal short-circuit part, thereby improving safety, forming a resistor layer necessary to ensure sufficient safety against short-circuits caused by large foreign objects such as nails results in excessively high electronic resistance at the interface between the active material particles and the current collector, degrading the load characteristics of the battery.

[0007] Patent Documents 3 and 4 propose a method of using a sheet of resin film such as PET or PP with metal plating layers formed on both sides as a current collector, with the aim of reducing the weight of the current collector without reducing its strength. With this current collector, heat generated during a short circuit causes the resin film of the current collector in the short-circuited area to melt, and the melted resin film interrupts the current, which is thought to prevent overheating. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 9-208736 [Patent Document 2] Japanese Patent Application Publication No. 10-199574 [Patent Document 3] Japanese Patent Application Publication No. 9-213338 [Patent Document 4] Japanese Patent Application Publication No. 9-283149 Summary of the Invention [Problem to be solved by the invention]

[0009] However, the technologies of Patent Documents 3 and 4 have the problem that current collection from the negative electrode depends on the metal plating layers formed on both sides of the resin film, which results in insufficient current collection at high currents and a decrease in the load characteristics of the battery.Furthermore, the technologies of Patent Documents 3 and 4 have the problem that if the metal plating layer on one side breaks, the metal plating layer on the broken surface can no longer function as a current collector.

[0010] An object of the present invention is to provide a current collector for a battery that has good current collecting properties and can suppress an excessive rise in battery temperature when an internal short circuit occurs. [Means for solving the problem]

[0011] The present invention provides the following [1] to

[10] . [1] A substrate having a first metal plating layer, a base layer, and a second metal plating layer in this order; the first metal plating layer and the second metal plating layer are disposed in contact with the base layer, the substrate layer contains a binder resin and conductive particles, A current collector for a battery, wherein when the average thickness of the base layer is defined as T0 [μm] and the average diameter of the conductive particles in the thickness direction is defined as D [μm], D / T0 is 1.00 or more. [2] The current collector for a battery according to [1], wherein T1 and T2 are each defined as an average thickness of the first metal plating layer and an average thickness of the second metal plating layer, respectively, and T1 and T2 are each less than 1.0 μm. [3] The current collector for a battery according to [1] or [2], wherein T0 / T1 and T0 / T2 are 0.003 or more and 0.200 or less, respectively, when the average thickness of the first metal plating layer is defined as T1 and the average thickness of the second metal plating layer is defined as T2. [4] The current collector for a battery according to any one of [1] to [3], wherein the conductive particles are contained in an amount of 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the binder resin. [5] The current collector for a battery according to any one of [1] to [4], wherein the conductive particles are substantially free of conductive particles having a diameter in the thickness direction of 1 / 2×T0 or less. [6] The current collector for a battery according to any one of [1] to [5], wherein the base layer has a single layer structure containing the binder resin and the conductive particles. [7] The current collector for a battery according to any one of [1] to [6], wherein the substrate layer has a Young's modulus at 23° C. of 200 MPa or more and 4500 MPa or less. [8] The current collector for a battery according to any one of [1] to [7], wherein the metal constituting the first metal plating layer and the second metal plating layer is Cu or Ni. [9] The battery current collector according to any one of [1] to [8], which is a current collector for a lithium ion battery.

[10] A battery comprising the battery current collector according to any one of [1] to [9]. [Effects of the Invention]

[0012] The current collector for a battery of the present invention and a battery using the same have good current collecting properties and can suppress an excessive rise in battery temperature when an internal short circuit occurs. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view showing one embodiment of a current collector for a battery of the present invention. [Figure 2] 1 is a cross-sectional view showing one embodiment of a lithium ion battery of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the battery current collector of the present invention and a battery using the same will be described.

[0015] [Battery current collectors] The battery current collector of the present invention is A first metal plating layer, a base layer, and a second metal plating layer in this order; the first metal plating layer and the second metal plating layer are disposed in contact with the base layer, the substrate layer contains a binder resin and conductive particles, When the average thickness of the base layer is defined as T0 [μm] and the average diameter of the conductive particles in the thickness direction is defined as D [μm], D / T0 is 1.00 or more.

[0016] FIG. 1 is a cross-sectional view showing one embodiment of the current collector for a battery of the present invention. 1 includes, in this order, a battery current collector 50, a first metal plating layer 10, a base layer 20, and a second metal plating layer 30. In FIG. 1, the first metal plating layer 10 and the second metal plating layer 30 are disposed in contact with the base layer 20. In FIG. 1, the base layer 20 includes a binder resin 21 and conductive particles 22.

[0017] <Base material layer> The substrate layer must contain a binder resin and conductive particles. Furthermore, when the average thickness of the base layer is defined as T0 [μm] and the average diameter of the conductive particles in the thickness direction is defined as D [μm], the base layer must have a D / T0 ratio of 1.00 or more.

[0018] The substrate layer preferably has a single layer structure containing the binder resin and the conductive particles.

[0019] <Binder resin> The substrate layer must contain a binder resin, which can prevent overheating when a short circuit occurs inside the battery. When a short circuit occurs due to a foreign object piercing an electrode, the short-circuited area generates heat, causing the binder resin in the short-circuited area to melt. This creates a void in the base layer where the binder resin has melted. This void is thought to interrupt the short-circuit current, preventing the battery from overheating.

[0020] The binder resin preferably has a melting point of 100°C or higher and 300°C or lower, preferably 120°C or higher and 280°C or lower, and more preferably 150°C or higher and 250°C or lower. By setting the melting point to 100°C or higher, it is possible to more easily stabilize the current collection characteristics under normal conditions when no short circuit has occurred. By setting the melting point to 300°C or lower, it is possible to more easily prevent the battery from overheating when a short circuit occurs inside the battery. In this specification, the melting point of the binder resin means the melting peak temperature (Tpm) according to JIS K7121: 1987. When the binder resin exhibits multiple melting peak temperatures (Tpm), it is preferable that the higher melting peak temperature (Tpm) is within the above range.

[0021] The binder resin is preferably a thermoplastic resin. Examples of thermoplastic resins include olefin resins such as polyethylene, polypropylene, polymethylpentene, ionomers, and various olefin-based thermoplastic elastomers; vinyl chloride resins such as polyvinyl chloride, polyvinylidene chloride, and vinyl chloride-vinyl acetate copolymers; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, ethylene glycol-terephthalic acid-isophthalic acid copolymers, and polyester-based thermoplastic elastomers; acrylic resins such as polymethyl (meth)acrylate, polyethyl (meth)acrylate, polybutyl (meth)acrylate, and methyl (meth)acrylate-butyl (meth)acrylate copolymers; polyamide resins typified by nylon 6 or nylon 66; cellulose resins such as cellulose triacetate, cellophane, and celluloid; styrene resins such as polystyrene, acrylonitrile-styrene copolymers, and acrylonitrile-butadiene-styrene copolymers (ABS); polyvinyl alcohol; ethylene-vinyl acetate copolymers; ethylene-vinyl alcohol copolymers; polycarbonate resins; polyarylate resins; polyimide resins; and polyurethane resins. These thermoplastic resins may be used alone or in combination of two or more.

[0022] The binder resin preferably has a functional group. By having the binder resin have a functional group, it is possible to improve the film-forming properties of the metal plating layer and the adhesion of the metal plating layer. Examples of the functional group include a carboxyl group and a hydroxyl group. Of these functional groups, a carboxyl group is preferred. The substrate layer may be subjected to a surface treatment to improve the film-forming property of the metal plating layer and the adhesion of the metal plating layer, such as a corona discharge treatment or a treatment using an excimer lamp.

[0023] <Conductive particles> The base layer must contain conductive particles. Furthermore, when the average thickness of the base layer is defined as T0 [μm] and the average diameter of the conductive particles in the thickness direction is defined as D [μm], the ratio D / T0 must be 1.00 or greater. By including conductive particles that satisfy these conditions, even when at least one of the first metal plating layer and the second metal plating layer is partially fractured, the first metal plating layer and the second metal plating layer can be electrically connected via the conductive particles. Therefore, even when the aforementioned fracture occurs, the current collector's properties can be maintained.

[0024] The ratio of D to T0 (D / T0) is preferably 1.01 or more, more preferably 1.03 or more, and even more preferably 1.05 or more. By making the ratio 1.01 or more, it is possible to more easily electrically connect the first metal plating layer and the second metal plating layer. The ratio of D to T0 (D / T0) is preferably 1.30 or less, more preferably 1.20 or less, and even more preferably 1.10 or less. By setting the ratio to 1.30 or less, it becomes easier to form the first metal plating layer and the second metal plating layer on the base layer.

[0025] The difference between D and T0 (D-T0) is preferably 0.1 μm or more, more preferably 0.2 μm or more, and even more preferably 0.3 μm or more. By making the difference 0.1 μm or more, it is possible to easily electrically connect the first metal plating layer and the second metal plating layer. The difference between D and T0 (D-T0) is preferably 1.0 μm or less, more preferably 0.5 μm or less, and even more preferably 0.3 μm or less. By keeping the difference 1.0 μm or less, it becomes easier to form the first metal plating layer and the second metal plating layer on the base layer.

[0026] The ranges of T0 and D are not particularly limited as long as the relationship D / T0 is 1.00 or more, but are preferably within the following ranges. T0, which indicates the average thickness of the base layer, is preferably 5 μm or more and 30 μm or less, more preferably 8 μm or more and 25 μm or less, and even more preferably 10 μm or more and 20 μm or less. By setting T0 to 5 μm or more, it is possible to more easily prevent the battery from overheating when a short circuit occurs inside the battery, and further, by setting T0 to 5 μm or more, it is possible to easily form the first metal plating layer and the second metal plating layer on the base layer. By setting T0 to 30 μm or less, it is possible to easily prevent the thickness of the battery from becoming excessively thick. D, which indicates the average diameter of the conductive particles in the thickness direction, is preferably selected so that (D-T0) falls within the above-mentioned range.

[0027] In this specification, the average thickness of the base layer, T0, is the average value of the thicknesses of the base layer at 30 randomly selected locations. The thicknesses at the 30 locations can be measured from cross-sectional photographs of the base layer taken with an SEM or the like.

[0028] In this specification, D, which indicates the average diameter of the conductive particles in the thickness direction, can be measured, for example, by the following procedures A1 and A2. A1: Take a cross-sectional photograph of the base layer using an SEM or similar. A2: The diameter of the conductive particles in the thickness direction shown in the cross-sectional photograph is measured. The average diameter of the conductive particles in the thickness direction of a total of 30 conductive particles is defined as D.

[0029] It is preferable that the base layer does not substantially contain conductive particles having a diameter in the thickness direction of 1 / 2×T0 or less, because conductive particles having a diameter in the thickness direction of 1 / 2×T0 or less do not substantially contribute to the electrical connection between the first metal plating layer and the second metal plating layer. "Substantially free" means that the content is 0.10% by mass or less, preferably 0.01% by mass or less, and more preferably 0% by mass, of the total solid content of the base layer.

[0030] Examples of conductive particles include metal particles, metal oxide particles, and coated particles having a conductive coating layer on the surface of a core particle. Among these, coated particles are preferred. Coated particles are preferred because they are less likely to precipitate in the composition that forms the base layer and because they facilitate weight reduction of the base layer. Examples of metals constituting the metal particles include Au, Ag, Cu, Al, Fe, Ni, Pd, Pt, Sn, etc. Examples of metal oxides constituting the metal oxide particles include tin oxide (SnO), antimony oxide (SbO), antimony tin oxide (ATO), indium tin oxide (ITO), aluminum zinc oxide (AZO), fluorinated tin oxide (FTO), zinc oxide (ZnO), etc. Examples of core particles for the coated particles include inorganic particles such as colloidal silica particles and silicon oxide particles, polymer particles such as fluororesin particles, acrylic resin particles and silicone resin particles, and organic-inorganic composite particles. Materials constituting the conductive coating layer include the above-mentioned metals or alloys thereof, and the above-mentioned metal oxides. The conductive coating layer can be formed by plating, vapor deposition, or the like.

[0031] The content of the conductive particles is preferably 1 part by mass or more and 20 parts by mass or less, more preferably 3 parts by mass or more and 15 parts by mass or less, and even more preferably 5 parts by mass or more and 10 parts by mass or less, relative to 100 parts by mass of the binder resin. By setting the content of the conductive particles to 1 part by mass or more, the resistance value of the battery current collector can be easily reduced. By setting the content of the conductive particles to 20 parts by mass or less, aggregation of the conductive particles can be easily suppressed, and the resistance value of the battery current collector can be easily reduced.

[0032] The substrate layer preferably has a Young's modulus at 23° C. of 200 MPa or more and 4500 MPa or less. By setting the Young's modulus of the base layer to 200 MPa or more, it becomes easier to form a metal plating layer on the base layer. When the Young's modulus of the base layer is less than 200 MPa, it is preferable to prepare a laminate having a Young's modulus of 200 MPa or more and 4500 MPa or less by laminating a carrier film to the base layer, then form a metal plating layer on the base layer of the laminate, and then peel off the carrier film. By setting the Young's modulus of the base layer to 4500 MPa or less, it becomes easier to produce the metal plating layer by roll-to-roll processing. In this specification, Young's modulus means the tensile modulus of elasticity according to JIS K7161-1:2014. The sample shape used for measuring Young's modulus was test piece type 2 as specified in JIS K7127:1999. The sample width was 10 mm and the sample length was 150 mm. The distance between the chucks of the testing machine was 100 mm, and the tensile speed was 200 mm / min.

[0033] <<Method for manufacturing base layer>> The substrate layer can be produced, for example, by the following method B1 or C1. B1: A base layer is formed by applying a base layer coating liquid containing a binder resin and conductive particles onto a first release substrate and drying it. Thereafter, the first release substrate is peeled off. C1: A composition containing a binder resin and conductive particles is extruded into a sheet by melt extrusion to form a substrate layer.

[0034] In the case of B1 above, a second release substrate may be provided on the opposite side of the base layer from the first release substrate. The first release substrate and the second release substrate are ultimately peeled off and used. By forming a laminate having the first release substrate, the base layer, and the second release substrate in this order, workability and handleability can be improved when forming the first metal plating layer and the second metal plating layer.

[0035] <Metal plating layer> The battery current collector of the present invention must have a first metal plating layer and a second metal plating layer, and the first metal plating layer and the second metal plating layer must be disposed in contact with the above-mentioned base layer. By including such a first metal plating layer and a second metal plating layer, the current collector can maintain its properties even when at least one of the first metal plating layer and the second metal plating layer is partially broken. Furthermore, by using a metal plating layer instead of a metal foil, the thickness of the battery current collector can be easily reduced.

[0036] When the average thickness of the first metal plating layer is defined as T1 and the average thickness of the second metal plating layer is defined as T2, it is preferable that T1 and T2 are each less than 1.0 μm. By making T1 and T2 each less than 1.0 μm, it becomes easier to reduce the thickness of the battery current collector. Each of T1 and T2 is more preferably 0.9 μm or less, and even more preferably 0.8 μm or less. If T1 and T2 are too thin, the current collection properties may be insufficient. Therefore, T1 and T2 are each preferably 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.5 μm or more.

[0037] Each of T0 / T1 and T0 / T2 is preferably 0.003 or more and 0.200 or less, more preferably 0.010 or more and 0.150 or less, and even more preferably 0.050 or more and 0.10 or less. The ratios T0 / T1 and T0 / T2 of 0.003 or more mean that the thickness of the base material layer is not too thin and / or the thickness of the metal plating layer is not too thick. Therefore, by making the ratios T0 / T1 and T0 / T2 0.003 or more, the thickness of the battery current collector can be made thin, and overheating of the battery can be more easily prevented when a short circuit occurs inside the battery. The fact that T0 / T1 and T0 / T2 are 0.200 or less means that the thickness of the base material layer is not too thick and / or the thickness of the metal plating layer is not too thin. Therefore, by setting T0 / T1 and T0 / T2 to 0.200 or less, the thickness of the battery current collector can be made thin while still easily exhibiting sufficient current collecting properties.

[0038] The first metal plating layer and the second metal plating layer may be dry-plated or wet-plated. Dry-plated layers can be formed by physical vapor deposition (PVD) methods such as vacuum deposition, sputtering, and ion plating; chemical vapor deposition (CVD) methods such as plasma-enhanced chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition; and wet-plated layers can be formed by electrolytic plating or electroless plating. Dry-plated layers are preferred because they are easily formed over the entire surface of the substrate layer, even if the substrate layer is wide. Furthermore, wet-plated layers contain phosphorus, an environmentally restricted substance, as an impurity, while dry-plated layers are less likely to contain phosphorus.

[0039] Examples of metals constituting the first metal plating layer and the second metal plating layer include Au, Ag, Cu, Al, Fe, Ni, Pd, Pt, Sn, etc. The above-mentioned metals may be a single metal containing only one kind of metal, or an alloy containing two or more kinds of metals. Among the above-mentioned metals, Cu or Ni is preferable. When the metal constituting the first metal plating layer and the second metal plating layer is Cu or Ni, the negative electrode current collector is useful. Among the above-mentioned metals, Al is also preferable. By using Al as the metal constituting the first metal plating layer and the second metal plating layer, the positive electrode current collector is useful. The metals constituting the first metal plating layer and the second metal plating layer may be the same type or different types, but are preferably the same type. The first metal plating layer and the second metal plating layer may each be formed as a single layer or as multiple layers, for example, the first metal plating layer and the second metal plating layer may each be a laminate of a Cu layer and a Ni layer.

[0040] <Resistance value> To improve the current collection characteristics, the current collector for a battery preferably has a resistance of 10.0 mΩ or less, more preferably 8.0 mΩ or less, and even more preferably 6.0 mΩ or less. There is no particular lower limit to the resistance of the current collector for a battery, but it is preferably 1.0 mΩ or more, and more preferably 2.0 mΩ or more. In this specification, the resistance value of a battery current collector means a value measured by a four-terminal method with one terminal placed on the first metal plating layer and the other terminal placed on the second metal plating layer.

[0041] The battery current collector of the present invention can be used as a current collector for various types of batteries, and is particularly preferably used as a current collector for lithium ion batteries.

[0042] [battery] The battery of the present invention includes the above-described battery current collector of the present invention. The battery may be of various types, with lithium ion batteries being particularly preferred.

[0043] An embodiment of a lithium ion battery will be described below.

[0044] Fig. 2 is a cross-sectional view that schematically shows the configuration of a lithium-ion battery 900. The lithium-ion battery 900 may be, for example, a cylindrical lithium-ion secondary battery as shown in Fig. 2. This lithium-ion secondary battery is equipped with a safety valve mechanism that releases gas to the outside of the battery when the pressure inside the battery increases due to an abnormality such as an internal short circuit. In the lithium-ion battery 900, an electrode group 104, in which a positive electrode 101 and a negative electrode 102 are wound with a separator 103 interposed therebetween, is housed together with a nonaqueous electrolyte in a battery case 107. Insulating plates 109 and 119 are disposed above and below the electrode group 104, and the positive electrode 101 is joined to a filter 112 via a positive electrode lead 105, and the negative electrode 102 is joined via a negative electrode lead 106 to the bottom of the battery case 107, which also serves as a negative electrode terminal.

[0045] The positive electrode 101 comprises a positive electrode current collector and a positive electrode active material layer supported thereon. The positive electrode active material layer may contain a binder, a conductive agent, etc. in addition to the positive electrode active material. The positive electrode 101 is produced, for example, by mixing a positive electrode mixture comprising the positive electrode active material and optional components with a liquid component to prepare a positive electrode mixture slurry, applying the resulting slurry to the positive electrode current collector, and drying it. The negative electrode 102 is also fabricated by, for example, mixing a negative electrode mixture containing a negative electrode active material and optional components with a liquid component to prepare a negative electrode mixture slurry, applying the resulting slurry to a negative electrode current collector, and drying it. When the negative electrode active material is an element capable of being alloyed with lithium, a silicon compound, a tin compound, or the like, the negative electrode active material layer may be formed by a gas phase method. Gas phase methods include chemical vapor deposition (CVD), vacuum deposition, and sputtering.

[0046] A lithium composite metal oxide can be used as the positive electrode active material of the lithium ion battery 900. For example, Li x CoO2, Li x NiO2, Li x MnO2, Li x Co y Ni 1-y O2 and Li x Co y M 1-y O zand the like (M=at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, and B). Here, x=0 to 1.2, y=0 to 0.9, and z=2.0 to 2.3. The value of x, which indicates the molar ratio of lithium, is the value immediately after preparation of the active material and increases or decreases during charge and discharge. Furthermore, a portion of these lithium-containing compounds may be substituted with a different element. The active material may be surface-treated with a metal oxide, lithium oxide, a conductive agent, or the like, or the surface may be hydrophobized. The positive electrode active material may be used alone or in combination of two or more types. Furthermore, the positive electrode active material layer may be formed by laminating two or more layers having different compositions.

[0047] Examples of the negative electrode active material for lithium ion batteries include metals, metal fibers, carbon materials, oxides, nitrides, tin compounds, silicon compounds, and various alloy materials. Examples of the carbon material include various natural graphites, coke, partially graphitized carbon, carbon fibers, spherical carbon, various artificial graphites, and amorphous carbon. Examples of the oxide include lithium titanate having a spinel crystal structure. A typical lithium titanate having a spinel crystal structure has the formula: Li4Ti5O 12 where the general formula is: Li x Ti 5-y M y O 12+z Lithium titanate represented by the formula (1) can also be used. Here, M is at least one element selected from the group consisting of vanadium, manganese, iron, cobalt, nickel, copper, zinc, aluminum, boron, magnesium, calcium, strontium, barium, zirconium, niobium, molybdenum, tungsten, bismuth, sodium, gallium, and rare earth elements, and x is the value of lithium titanate immediately after synthesis or in a fully discharged state, where 3≦x≦5, 0.005≦y≦1.5, and −1≦z≦1. Furthermore, simple substances such as silicon (Si) and tin (Sn), or silicon compounds such as alloys, compounds, and solid solutions, or tin compounds are preferred in terms of high capacity density. For example, silicon compounds include SiO x(0.05 < x < 1.95), or an alloy, compound, or solid solution in which at least one element selected from the group consisting of B, Mg, Ni, Ti, Mo, Co, Ca, Cr, Cu, Fe, Mn, Nb, Ta, V, W, Zn, C, N, and Sn replaces a part of Si in any of these can be used. As the tin compound, Ni2Sn4, Mg2Sn, SnO x (0 < x < 2), SnO2, SnSiO3, etc. can be applied. The negative electrode active material may be used alone or in combination of two or more. Also, two or more layers having different compositions may be laminated for the negative electrode active material layer.

[0048] As the binder for the positive electrode 101 or the negative electrode 102, for example, PVDF, PTFE, polyethylene, polypropylene, aramid resin, etc. can be used. Also, as the conductive agent to be included in the electrode, for example, graphites such as natural graphite and artificial graphite, carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, etc., conductive fibers such as carbon fibers and metal fibers, metal powders such as carbon fluoride and aluminum, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, organic conductive materials such as phenylene derivatives, etc. are used.

[0049] The mixing ratios of the positive electrode active material, the conductive agent, and the binder are desirably in the ranges of 80 to 97% by mass of the positive electrode active material, 1 to 20% by mass of the conductive agent, and 1 to 10% by mass of the binder, respectively. Also, the mixing ratios of the negative electrode active material and the binder are desirably in the ranges of 93 to 99% by mass of the negative electrode active material and 1 to 10% by mass of the binder, respectively. Also, when forming the negative electrode active material layer by the vapor phase method, the binder may not be included.

[0050] As the positive electrode current collector and / or the negative electrode current collector, the current collector for a battery of the present invention described above can be used. As the positive electrode current collector, a long porous conductive substrate or a non-porous conductive substrate may be used. Examples of materials used for the conductive substrate include stainless steel, Al, and Ti. It is more preferable to use Al for the positive electrode current collector, as this provides a current interruption effect during a short circuit and is lightweight. The thickness of the positive electrode current collector is not particularly limited, but is preferably 1 to 100 μm, and more preferably 5 to 20 μm. By setting the thickness of the positive electrode current collector within the above range, the electrode plate can be made lighter while maintaining its strength.

[0051] The separator 103 interposed between the positive electrode 101 and the negative electrode 102 is preferably a microporous thin film, woven fabric, or nonwoven fabric that has high ion permeability, a predetermined mechanical strength, and insulating properties. Polyolefins such as polypropylene and polyethylene are preferred as materials for the separator 103, as they have excellent durability and a shutdown function, thereby contributing to the safety of lithium-ion batteries. The thickness of the separator 103 is generally 10 to 300 μm, but is preferably 40 μm or less. A thickness of 15 to 30 μm is more preferred, with a thickness of 20 to 25 μm being even more preferred. The microporous film may be a single-layer membrane made of one material, or a composite or multilayer membrane made of one or more materials. The porosity of the separator 103 is preferably 30 to 70%. Here, the porosity refers to the volume ratio of pores to the separator volume. The porosity of the separator 103 is more preferably in the range of 35 to 60%.

[0052] As the non-aqueous electrolyte, a liquid, gel or solid (polymer solid electrolyte) substance can be used. A liquid nonaqueous electrolyte (nonaqueous electrolyte solution) is obtained by dissolving an electrolyte (e.g., a lithium salt) in a nonaqueous solvent. A gel nonaqueous electrolyte contains a nonaqueous electrolyte and a polymer material that holds the nonaqueous electrolyte. Suitable polymer materials include, for example, PVDF, polyacrylonitrile, polyethylene oxide, polyvinyl chloride, polyacrylate, and polyvinylidene fluoride hexafluoropropylene.

[0053] As the non-aqueous solvent for dissolving the electrolyte, known non-aqueous solvents can be used. The type of non-aqueous solvent is not particularly limited, but examples thereof include cyclic carbonates, chain carbonates, and cyclic carboxylic acid esters. Examples of cyclic carbonates include propylene carbonate (PC) and ethylene carbonate (EC). Examples of chain carbonates include diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC). Examples of cyclic carboxylic acid esters include γ-butyrolactone (GBL) and γ-valerolactone (GVL). One type of non-aqueous solvent may be used alone, or two or more types may be used in combination.

[0054] Examples of electrolytes dissolved in non-aqueous solvents include LiClO4, LiBF4, LiPF6, LiAlCl4, LiSbF6, LiSCN, LiCF3SO3, LiCF3CO2, LiAsF6, and LiB 10 Cl 10 The electrolyte may be used alone or in combination of two or more.

[0055] The non-aqueous electrolyte may contain an additive that decomposes on the negative electrode to form a coating with high lithium ion conductivity, thereby improving charge-discharge efficiency. Examples of additives with this function include vinylene carbonate (VC), 4-methylvinylene carbonate, and 4,5-dimethylvinylene carbonate. These may be used alone or in combination of two or more. Among these, at least one selected from the group consisting of vinylene carbonate, vinylethylene carbonate, and divinylethylene carbonate is preferred. The hydrogen atoms of the above compounds may be partially substituted with fluorine atoms. The amount of electrolyte dissolved in the non-aqueous solvent is preferably within the range of 0.5 to 2 mol / L.

[0056] Furthermore, the non-aqueous electrolyte may contain a known benzene derivative that decomposes during overcharge to form a coating on the electrode, thereby inactivating the battery. The benzene derivative preferably has a phenyl group and a cyclic compound group adjacent to the phenyl group. The cyclic compound group is preferably a phenyl group, a cyclic ether group, a cyclic ester group, a cycloalkyl group, a phenoxy group, or the like. Specific examples of the benzene derivative include cyclohexylbenzene, biphenyl, and diphenyl ether. These may be used alone or in combination of two or more. However, the content of the benzene derivative is preferably 10% by volume or less of the total non-aqueous solvent.

[0057] The filter 112 is connected to an inner cap 113, and a protrusion of the inner cap 113 is joined to a metal valve plate 114. Furthermore, the valve plate 114 is connected to a terminal plate 108 that also serves as a positive electrode terminal. The terminal plate 108, valve plate 114, inner cap 113, and filter 112 are integrated together to seal the opening of the battery case 107 via a gasket 111.

[0058] If an abnormality such as an internal short circuit occurs in the battery cell and the pressure inside the battery cell rises, the valve body 114 bulges toward the terminal plate 108, and the connection between the inner cap 113 and the valve body 114 comes apart, interrupting the current path. If the pressure inside the battery cell rises further, the valve body 114 breaks. As a result, gas generated inside the battery cell is discharged to the outside via the through-hole 112a in the filter 112, the through-hole 113a in the inner cap 113, the tear in the valve body 114, and the open part 108a in the terminal plate 108. [Explanation of symbols]

[0059] 10: First metal plating layer 20: Base material layer 21: Binder resin 22: Conductive particles 30: Second metal plating layer 50: Battery current collector 101: Positive electrode 102: Negative electrode 103: Separator 104: Electrode group 105: Positive lead 106: Negative electrode lead 107: Battery case 108:Terminal board 109: Insulating plate 110: Metal layer 111: Gasket 112: Filter 113: Inner cap 114: Valve body 119: Insulating plate 120: Negative electrode active material layer 900: Lithium-ion battery

Claims

1. a first metal plating layer, a base layer, and a second metal plating layer in this order; the first metal plating layer and the second metal plating layer are disposed in contact with the base layer, the substrate layer contains a binder resin and conductive particles, The average thickness of the substrate layer is T ０ [μm], and when the average diameter of the conductive particles in the thickness direction is defined as D [μm], D / T ０ A battery current collector, wherein

2. The average thickness of the first metal plating layer is T １ , the average thickness of the second metal plating layer is T ２ When defining １ and T ２ and each of the above is less than 1.0 μm.

3. The average thickness of the first metal plating layer is T １ , the average thickness of the second metal plating layer is T ２ When defining ０ / T １ , and T ０ / T ２ The battery current collector according to claim 1 , wherein each of these is 0.003 or more and 0.200 or less.

4. The current collector for a battery according to claim 1 , wherein the conductive particles are contained in an amount of 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the binder resin.

5. The conductive particles have a diameter in the thickness direction of 1 / 2×T ０ 2. The battery current collector according to claim 1, which is substantially free of the following conductive particles:

6. The battery current collector according to claim 1 , wherein the substrate layer has a single layer structure including the binder resin and the conductive particles.

7. 2. The current collector for a battery according to claim 1, wherein the substrate layer has a Young's modulus at 23°C of 200 MPa or more and 4500 MPa or less.

8. 2. The current collector for a battery according to claim 1, wherein the metal constituting the first metal plating layer and the second metal plating layer is Cu or Ni.

9. 10. The battery current collector according to claim 1, which is a current collector for a lithium ion battery.

10. A battery comprising the current collector for a battery according to any one of claims 1 to 9.

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