Zinc electrode

Abstract

The present invention provides a method for prolonging the life of a battery including a zinc electrode, and also improving the weight energy density thereof. The present invention is a zinc electrode which comprises: a current collector including a resin fiber and a conductive layer covering the surface of the resin fiber; and a zinc-containing substance as an active material. Further, the present invention is a battery including the zinc electrode.

Description

Zinc electrode

[0001] The present invention relates to a zinc electrode, and more particularly to a zinc electrode used in a battery and a battery comprising the zinc electrode.

[0002] In recent years, the importance of batteries has rapidly increased in many industries, from small portable devices to large applications such as automobiles, and various new battery systems have been developed and improved, with advantages mainly in terms of capacity, weight energy density, and rechargeability.

[0003] Many technological developments have been made regarding the electrodes used in such batteries, and from the viewpoint of improving the above-mentioned performance of mainly nickel electrodes, battery electrodes in which the surface of a porous material such as a fiber is coated with a metal have been disclosed (see, for example, Patent Documents 1 to 11).

[0004] In addition, zinc anodes, which use zinc-containing substances as the anode active material, have long been researched as batteries have become more widespread. In particular, air-zinc primary batteries, manganese-zinc primary batteries, and silver-zinc primary batteries have been put to practical use and are widely used around the world.

[0005] Japanese Patent No. 3386805, Japanese Patent Laid-Open No. 3-130393, Japanese Patent Laid-Open No. 3-130395, Japanese Patent Laid-Open No. 3-130394, Japanese Patent Laid-Open No. 61-208756, Japanese Patent Laid-Open No. 2007-234484, Japanese Patent Laid-Open No. 2008-66145, Japanese Patent Laid-Open No. 2008-305698, Japanese Patent Laid-Open No. 2008-71533, Japanese Patent Laid-Open No. 2008-159497, Japanese Patent Laid-Open No. 2009-140676

[0006] However, zinc electrodes have issues specific to zinc electrodes, such as the dissolution and precipitation reaction of zinc-containing substances occurring near the active material layer, and repeated charging and discharging over a long period of time can cause the battery reaction to become uneven, or the uneven reaction can cause additives such as conductive additives to become unevenly distributed and lose their effectiveness, resulting in a shorter lifespan.

[0007] The present invention has been made in view of the above-mentioned current situation, and aims to provide a method for extending the life of a battery comprising a zinc electrode and improving the weight energy density.

[0008] The present inventors have investigated various methods for extending the life of zinc batteries and have focused on making the current collector fibrous. They have found that if a current collector including resin fibers and a conductive layer covering the surface of the resin fibers and a zinc electrode including a zinc-containing material as an active material are used, the impregnation of the electrolyte can be improved even in a thick film, making the battery reaction uniform and stable, thereby extending the life of the zinc battery and improving the weight energy density. They have conceived a brilliant solution to the above problems and have arrived at the present invention.

[0009] That is, the present invention (1) is a current collector including resin fibers and a conductive layer covering the surface thereof, and a zinc electrode including a zinc-containing substance as an active material.

[0010] The present invention (2) is the zinc electrode of the present invention (1), wherein the conductive layer contains a metal and / or a metal oxide.

[0011] The present invention (3) is the zinc electrode of the present invention (2), wherein the metal and / or metal oxide contains at least one metal element selected from the group consisting of zinc, tin, bismuth, indium, lead, cadmium, gold, copper, and silver.

[0012] The present invention (4) is a zinc electrode in any combination with any of the present inventions (1) to (3), in which the conductive layer includes an outermost layer containing at least one metal selected from the group consisting of zinc, tin, bismuth, indium, lead, and cadmium and / or a metal oxide thereof.

[0013] The present invention (5) is a zinc electrode in any combination with any of the present inventions (1) to (4), wherein the conductive layer includes an outermost layer and an intermediate layer between the outermost layer and the resin fiber, and the intermediate layer includes at least one metal selected from the group consisting of gold, copper, silver, and tin and / or a metal oxide thereof.

[0014] The present invention (6) is a zinc electrode in any combination with any of the present inventions (1) to (5), in which the conductive layer contains a metal.

[0015] The present invention (7) is a zinc electrode in any combination with any of the present inventions (1) to (6), in which the average thickness of the conductive layer is 0.1 to 40 μm.

[0016] The present invention (8) is a zinc electrode in any combination with any of the present inventions (1) to (7), wherein the current collector is a porous current collector and the zinc electrode contains a zinc-containing substance as an active material in the pores of the porous current collector.

[0017] The present invention (9) is a battery comprising the zinc electrode of any one of the present inventions (1) to (8).

[0018] The zinc electrode of the present invention has the above-mentioned structure, and can prolong the life of a battery comprising the zinc electrode and improve the weight energy density.

[0019] FIG. 1 is a graph showing charge-discharge curves at the 100th cycle for the battery of the example and the battery of the comparative example.

[0020] The present invention will be described in detail below. Note that a combination of two or more of the individual preferred embodiments of the present invention described below is also a preferred embodiment of the present invention.

[0021] <Zinc Electrode> The zinc electrode of the present invention comprises a current collector including resin fibers and a conductive layer covering the surface of the resin fibers, and a zinc-containing substance as an active material.

[0022] The current collector includes a resin fiber (core material) and a conductive layer covering the surface of the resin fiber. The conductive layer may completely cover the resin fiber, but may not completely cover the resin fiber, and the resin fiber may be partially exposed.

[0023] [Conductive Layer] The conductive layer has an electrical conductivity of 1×10 ６ The electrical conductivity is 5×10 S / m or more. ６ The electrical resistance is preferably S / m or more. The electrical resistance is obtained by measuring the electrical resistance in the thickness direction of the conductive layer using a tester.

[0024] The conductive material may be any material that allows the conductive layer to exhibit the above-mentioned specific electrical conductivity, and may be, for example, one or more of metals such as zinc, tin, bismuth, indium, lead, cadmium, gold, copper, brass, silver, and tin; metal compounds such as metal oxides; conductive carbon; conductive ceramics; and conductive polymers.

[0025] Among these, it is preferable to use a metal and / or a metal oxide (more preferably, a metal) as the conductive material. That is, it is preferable that the conductive layer contains a metal and / or a metal oxide, and more preferably a metal layer made of a metal, a metal oxide layer made of a metal oxide, or a laminate of a metal layer and / or a metal oxide layer. Among these, from the viewpoint of improving electronic conductivity, it is even more preferable that the conductive layer contains a metal, and it is particularly preferable that the conductive layer is a metal layer made of a metal or a laminate thereof. In this specification, when simply referring to a metal, the metal means a metal element or an alloy. Note that the metal oxide is not particularly limited as long as the conductive layer exhibits the above-mentioned specific electrical conductivity, but from the viewpoint of improving electronic conductivity, indium tin oxide (ITO) and the like are suitable. Furthermore, the metal oxide is a low-valent metal oxide (e.g., Cu), which is formed by forming a conductive layer made of an easily oxidizable metal (e.g., a metal with a high ionization tendency such as zinc or tin, or copper, silver, etc.) and then oxidizing the surface or the entire conductive layer with oxygen in the outside air. ２ O, Ag ２ O, SnO, etc.).

[0026] The metal and / or metal oxide is not particularly limited as long as it has the above-mentioned electrical conductivity, but it is preferable that it contains at least one metal element selected from the group consisting of zinc, tin, bismuth, indium, lead, cadmium, gold, copper, and silver.

[0027] The conductive layer preferably includes a surface layer containing at least one metal and / or metal oxide thereof selected from the group consisting of zinc, tin, bismuth, indium, lead, and cadmium, and more preferably includes a surface layer containing at least one metal and / or metal oxide thereof selected from the group consisting of zinc, tin, bismuth, indium, lead, and cadmium. From the viewpoint of achieving better electronic conductivity, the conductive layer further preferably includes a surface layer containing at least one metal selected from the group consisting of zinc, tin, bismuth, indium, lead, and cadmium, and particularly preferably includes a surface layer containing at least one metal selected from the group consisting of zinc, tin, bismuth, indium, lead, and cadmium. These metals have high hydrogen overvoltages, and can form a mixed potential with the zinc-containing material, which is the active material, to sufficiently suppress hydrogen generation, thereby further suppressing self-discharge of the zinc-containing material. As the metal element constituting the metal or metal oxide of the outermost surface layer, zinc, tin, bismuth, and indium are more preferred from the viewpoint of increasing safety. Furthermore, zinc, tin, bismuth, lead, and cadmium are more preferred from the viewpoint of further reducing costs. From both of these viewpoints, zinc, tin, and bismuth are particularly preferred. Furthermore, it is preferable that the outermost surface layer of the conductive layer does not contain nickel, iron, or steel (SUS). It is even more preferable that the outermost surface layer of the conductive layer does not contain copper. Since these metals have low hydrogen overvoltage, not using these metals in the outermost surface layer can sufficiently suppress the formation of a mixed potential between these metals and the zinc-containing material, which is the active material, thereby preventing hydrogen generation and further suppressing self-discharge of the zinc-containing material. Note that when the conductive layer is a single layer, the conductive layer itself becomes the outermost surface layer.

[0028] The conductive layer includes an outermost layer and an intermediate layer between the outermost layer and the resin fiber. The intermediate layer preferably contains at least one metal and / or metal oxide thereof selected from the group consisting of gold, copper, silver, and tin. More preferably, the intermediate layer is a metal layer made of at least one metal selected from the group consisting of gold, copper, silver, and tin, a metal oxide layer made of the metal oxide, or a laminate made of the metal layer and / or the metal oxide layer (a laminate of the metal layers, a laminate of the metal oxide layers, or a laminate of the metal layer and the metal oxide layer). The intermediate layer further preferably contains at least one metal selected from the group consisting of gold, copper, silver, and tin. A metal layer made of at least one metal selected from the group consisting of gold, copper, silver, and tin is particularly preferred. This improves the electronic conductivity of the conductive layer. Copper and tin are more preferred as metal elements constituting the metal or metal oxide of the intermediate layer from the viewpoint of cost reduction. Furthermore, gold, copper, and silver are more preferred from the viewpoint of electronic conductivity. From both of these perspectives, copper is particularly preferred.

[0029] In addition, when a metal with low hydrogen overvoltage, such as gold, copper, cobalt, or iron, is used in the conductive layer, it is preferable to further laminate a metal with high hydrogen overvoltage, such as zinc, tin, bismuth, indium, lead, or cadmium, on the surface in order to suppress self-discharge of the zinc-containing material. It is particularly preferable that the intermediate layer of the conductive layer contains copper, and the outermost layer contains zinc and / or tin. Zinc and tin are easier to plate using copper as a base material than resin fibers, which is advantageous in terms of manufacturing. When the outermost layer is zinc, the zinc in the outermost layer is not in a particulate form like zinc active materials, so its function as an active material is limited.

[0030] When the conductive layer includes an outermost layer and an intermediate layer between the outermost layer and the resin fiber, the outermost layer may completely cover the intermediate layer, or may not completely cover the intermediate layer, leaving part of the intermediate layer exposed. However, when the conductive layer is formed by laminating a metal with a high hydrogen overvoltage on the surface of a metal with a low hydrogen overvoltage, it is particularly preferable that the outermost layer substantially completely cover the intermediate layer.

[0031] When the conductive layer is formed by laminating multiple layers, the compositions and thicknesses of the layers may be the same or different. The outermost layer is usually only one layer, but the intermediate layer may be one or more layers. When the intermediate layer is made up of multiple layers, each layer may or may not completely cover the layer or resin fiber below it.

[0032] The total content of metal and metal oxide (more preferably, the content of metal) in the conductive layer is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. It is particularly preferable that the conductive layer consists essentially of metal or metal and metal oxide, and most preferably consists essentially of metal.

[0033] The average thickness of the conductive layer is preferably 0.1 μm or more. The average thickness of the conductive layer is preferably 40 μm or less. For example, the average thickness of the conductive layer is preferably 0.1 to 40 μm. When the average thickness of the conductive layer is 0.1 μm or more, the electronic conductivity is superior. When the average thickness of the conductive layer is 40 μm or less, the occurrence of cracks can be more sufficiently prevented. The average thickness is more preferably 0.2 μm or more. The average thickness is more preferably 35 μm or less. For example, the average thickness is more preferably 0.2 to 35 μm. In this specification, the average thickness is measured by observing the cross section of the current collector with an electron microscope and calculating the simple average of the thicknesses at any 10 points on the conductive layer. Specifically, it can be calculated as follows. 1) The current collector (porous body) is cut in the thickness direction, and the resulting cross section is observed with a scanning electron microscope. 10 cross-sectional images are randomly selected in the thickness direction of the fiber on which the conductive layer is formed. 2) Next, the thickness of the conductive layer is measured at 10 randomly selected locations in each of the 10 selected cross-sectional images, and the simple average of the 10 measurements is used as the thickness of the conductive layer in each cross-sectional image. 3) The thicknesses of the conductive layer in each cross-sectional image are simply averaged, and the resulting value is used as the average thickness of the conductive layer in the current collector. The method for cutting the current collector (porous body) in the thickness direction is not particularly limited, but includes mechanical cutting with a razor or further ion milling the cross section obtained after mechanical cutting. A JEOL Ltd. razor (T5332 TEFLON (registered trademark) COATED) can be used as the razor. The scanning electron microscope is not particularly limited, but for example, a TM3000 Miniscope manufactured by Hitachi Technologies, Ltd. can be used. When multiple conductive layers are present, such as an intermediate layer and an outermost layer, the thickness of each layer can be measured in the same manner. The average thickness of the conductive layer of the current collector in a zinc electrode can also be determined in the same manner.

[0034] In the conductive layer, the ratio of the average thickness of the outermost layer to the average thickness of the intermediate layer can be, for example, 1:100 to 100:1, preferably 1:40 to 40:1, more preferably 1:20 to 20:1, even more preferably 1:10 to 10:1, still more preferably 1:5 to 5:1, still more preferably 1:2 to 5:1, still more preferably 1:1 to 4:1, and particularly preferably 4:3 to 3:1.

[0035] The mass proportion of the conductive layer is preferably 0.5% by mass or more, more preferably 1% by mass or more, even more preferably 3% by mass or more, and particularly preferably 5% by mass or more, based on 100% by mass of the zinc electrode of the present invention. The mass proportion of the conductive layer is preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less, based on 100% by mass of the zinc electrode of the present invention. For example, the mass proportion of the conductive layer is preferably 0.5 to 40% by mass, more preferably 1 to 35% by mass, even more preferably 3 to 30% by mass, and particularly preferably 5 to 30% by mass, based on 100% by mass of the zinc electrode of the present invention.

[0036] The mass proportion of the conductive layer can be determined by combining ICP optical emission spectroscopy with, as needed, EDX analysis (energy dispersive X-ray analysis) such as SEM-EDX analysis or TEM-EDX analysis. When ICP optical emission spectroscopy is employed, it is preferable to use a solution obtained by acid decomposing a predetermined amount of zinc electrode (for example, using a microwave decomposition device) as the measurement sample. For example, an ICPE-9000 manufactured by Shimadzu Corporation can be used as the ICP optical emission spectroscopy device, and an ETHOS One manufactured by Milestone General can be used as the microwave decomposition device.

[0037] [Resin Fiber] Examples of the resin fiber include hydrocarbon moiety-containing polymers such as polyethylene and polypropylene, polytetrafluoroethylene moiety-containing polymers, polyvinylidene fluoride moiety-containing polymers, cellulose-based polymers such as cellulose, fibrillated cellulose, viscose rayon, cellulose acetate, hydroxyalkyl cellulose, and carboxymethyl cellulose, polyvinyl alcohol-based polymers such as polyvinyl alcohol and partially acetalized polyvinyl alcohol (for example, vinylon), aromatic ring moiety-containing polymers such as cellophane, polystyrene, and polyphenylene sulfide, polyacrylonitrile moiety-containing polymers, polyacrylamide moiety-containing polymers, polyvinyl halide moiety-containing polymers, nylon, and the like. Examples of suitable fibers include polyamide moiety-containing polymers such as propylene, polyimide moiety-containing polymers, ester moiety-containing polymers, poly(meth)acrylic acid moiety-containing polymers, poly(meth)acrylate moiety-containing polymers, hydroxyl group-containing polymers such as polyisoprenol and poly(meth)allyl alcohol, carbonate group-containing polymers such as polycarbonate, ester group-containing polymers such as polyester, carbamate or carbamide group-containing polymers such as polyurethane, agar, gel compounds, organic-inorganic hybrid (composite) compounds, ion-exchange polymers, cyclized polymers, sulfonate-containing polymers, quaternary ammonium salt-containing polymers, quaternary phosphonium salt-containing polymers, and ether group-containing polymers. Among these, hydrocarbon moiety-containing polymers such as polypropylene, polyvinyl alcohol-based polymers, aromatic ring-containing polymers, and polyamide moiety-containing polymers are more preferred due to their chemical stability. These fibers may be used alone or in combination of two or more. The use of resin fibers can make the zinc electrode flexible, which is thought to contribute to preventing cracks and other defects in the zinc electrode. The resin fibers may be an insulating material that does not substantially conduct electricity.

[0038] The resin fibers may be hydrophilized by adding a surfactant, sulfonating with chemicals such as fuming sulfuric acid or chlorosulfonic acid, fluorinating, or grafting, or by corona discharge or plasma discharge. When the resin fiber is a hydrocarbon moiety-containing polymer, it is preferably hydrophilized. Examples of the resin fibers include nonwoven fabrics, woven fabrics, meshes, and felts, with nonwoven fabrics and meshes being preferred.

[0039] The resin fiber has a density of 0.01 g / cm ３ It is preferable that the concentration is 0.03 g / cm or more. ３ More preferably, it is 0.05 g / cm or more. ３ More preferably, it is 0.1 g / cm or more. ３ The upper limit of the density is not particularly limited, but is preferably 1 g / cm ３ It is preferable that the density is 0.7 g / cm or less. ３ More preferably, it is 0.5 g / cm or less. ３ For example, the density is 0.01 to 1 g / cm ３ is preferably 0.03 to 0.7 g / cm ３ More preferably, it is 0.05 to 0.5 g / cm ３ More preferably, it is 0.1 to 0.5 g / cm ３ The density is particularly preferably 1 / 2 or 1 / 4. The density is calculated by measuring the mass and the volume of the resin fiber, including the surface irregularities and the internal space, and dividing the mass by the volume.

[0040] The average fiber diameter of the resin fiber is not particularly limited, but is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more. The average fiber diameter is preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less. The average fiber diameter is preferably 1 to 200 μm, more preferably 5 to 150 μm, and even more preferably 10 to 100 μm. The resin fiber is cut in the thickness direction, and the resulting cross section is observed with a scanning electron microscope. Ten cross-sectional images in the thickness direction of each fiber constituting the resin fiber are arbitrarily selected, and the major diameters at the ten selected locations are measured. The simple average of the ten measured values ​​is calculated, and this value can be used as the average fiber diameter of the resin fiber. The major diameter refers to the length of the longest line segment connecting two outer peripheries in the cross-sectional image in the thickness direction. The method for cutting the resin fibers in the thickness direction is not particularly limited, but may include mechanical cutting with a razor or further ion milling the cross section obtained after mechanical cutting. The razor may be a razor (T5332 TEFLON (registered trademark) COATED) manufactured by JEOL Ltd. The scanning electron microscope may be, but is not particularly limited, a TM3000 Miniscope manufactured by Hitachi Technologies, Ltd. The average fiber diameter of the resin fibers in the current collector and the average fiber diameter of the resin fibers constituting the current collector in the zinc electrode may also be determined by the same method.

[0041] The average thickness of the resin fiber is not particularly limited, but is preferably 25 μm or more, more preferably 30 μm or more, even more preferably 40 μm or more, and particularly preferably 50 μm or more. The average thickness is preferably 10 mm or less, more preferably 1000 μm or less, even more preferably 500 μm or less, and particularly preferably 200 μm or less. The average thickness is preferably 25 to 10,000 μm, more preferably 30 to 1000 μm, even more preferably 40 to 500 μm, and particularly preferably 50 to 200 μm. The average thickness of the resin fiber can be measured using a micrometer, and the simple average of the thicknesses measured at any 10 locations can be used as the average thickness of the resin fiber.

[0042] The mass proportion of the resin fibers is not particularly limited, but is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, based on 100% by mass of the zinc electrode of the present invention. Furthermore, the mass proportion is preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less. For example, the mass proportion is preferably 1 to 40% by mass, more preferably 3 to 35% by mass, and even more preferably 5 to 30% by mass. The mass proportion of the resin fibers can be determined as follows: The content (mass%) of the conductive layer in the current collector is determined by ICP atomic emission spectroscopy of the current collector, and the remainder is taken as the content (mass%) of the resin fibers in the current collector. The mass ratio X of the resin fiber content to the conductive layer content (resin fiber content / conductive layer content) is then determined. The content Y (mass%) of the conductive layer in the zinc electrode is determined by ICP atomic emission spectroscopy of the zinc electrode, and Z (mass%) obtained by the following formula can be used to determine the mass proportion of the resin fibers in the zinc electrode. Z=Y×X The measurement sample preparation method, ICP optical emission spectrometer, and microwave decomposition device to be used can preferably be the same as those for the mass ratio of the conductive layer in the zinc electrode described above.

[0043] The current collector is usually a porous current collector. By using a porous current collector, the current collector can be made to have ion conductivity in the direction through which it penetrates (thickness direction or current direction). In addition, the current collector can be made lighter.

[0044] The current collector has a density of 0.01 g / cm ３ More than 0.03 g / cm ３ More preferably, 0.05 g / cm ３ More preferably, 0.1 g / cm ３ More preferably, it is 0.3 g / cm or more. ３ It is more preferable that the value is 0.5 g / cm or more. ３ It is even more preferable that the concentration is 1 g / cm or more. ３ The upper limit of the density is not particularly limited, but is preferably 10 g / cm ３ Preferably, it is 7 g / cm or less. ３ More preferably, it is 5 g / cm or less. ３ For example, the density is 0.01 to 10 g / cm ３ is preferably 0.03 to 7 g / cm ３ More preferably, it is 0.05 to 5 g / cm ３ More preferably, it is 0.1 to 5 g / cm ３ More preferably, it is 0.3 to 5 g / cm ３ It is more preferable that the density is 0.5 to 5 g / cm ３ It is even more preferable that the density is 1 to 5 g / cm ３ It is particularly preferable that the density is 100% or less. The density is calculated by measuring the mass and the volume of the resin fiber, including the surface irregularities and internal spaces, and dividing the mass by the volume. For example, the current collector (porous body) is cut into a specific size (for example, 40 mm x 40 mm) in the surface direction to obtain a rectangular parallelepiped (the thickness of which remains the same as that of the porous body), and the weight of the obtained rectangular parallelepiped is weighed. The value obtained by the following formula can be used as the density of the current collector (porous body). Density [g / cm ３ ] = (mass of rectangular parallelepiped [g]) / (volume of rectangular parallelepiped [cm ３In the above formula, the volume of the rectangular parallelepiped is calculated from the length, width, and thickness of the rectangular parallelepiped, and the thickness of the rectangular parallelepiped is measured at 10 points using a micrometer and the average value is used.

[0045] (Active Material) The zinc electrode of the present invention contains a zinc-containing material as an active material. The zinc electrode of the present invention preferably contains a zinc-containing material as an active material in the pores of the porous current collector. By arranging the active material three-dimensionally in the zinc electrode in this manner, a uniform reaction is possible, resulting in good performance. The zinc-containing material may be metallic zinc (elemental zinc), a zinc-containing alloy, or a compound containing zinc as a constituent element (hereinafter also referred to as a zinc-containing compound). The elemental zinc may also function as a conductive additive, but it also functions as an active material by undergoing an oxidation-reduction reaction during battery use. In this specification, elemental zinc, as well as the zinc-containing alloy and zinc-containing compound described below, are referred to as active materials and are distinguished from conductive additives.

[0046] The zinc-containing alloy may be a zinc alloy used in (alkaline) dry batteries or air batteries, such as an alloy of zinc with at least one selected from the group consisting of magnesium, lithium, manganese, aluminum, bismuth, and indium. The zinc-containing compound may be any active material, such as zinc oxide (e.g., Type 1 / Type 2 / Type 3 as defined in JIS K1410 (2006)), zinc hydroxide, zinc sulfide, zinc tetrahydroxyzinc alkali metal salts, zinc tetrahydroxyzinc alkaline earth metal salts, zinc chloride, and other zinc halide compounds, zinc carboxylate compounds such as zinc acetate, zinc borate, zinc phosphate, zinc hydrogen phosphate, zinc silicate, zinc aluminate, basic zinc carbonate, zinc carbonate, zinc nitrate, and zinc sulfate; complex oxides of zinc and other metal elements; and metal oxides that form a solid solution with zinc. One or more of these compounds may be used. Among the zinc-containing compounds, the zinc compounds are preferred, with zinc oxide being more preferred.

[0047] The active material is usually in a particulate form, and preferably has an average particle diameter of 1 nm or more. It is more preferably 10 nm or more, even more preferably 50 nm or more, and particularly preferably 100 nm or more. The average particle diameter is preferably 500 μm or less. It is more preferably 400 μm or less, even more preferably 200 μm or less, and particularly preferably 100 μm or less. For example, the average particle diameter is preferably 1 nm to 500 μm. It is more preferably 10 nm to 400 μm, even more preferably 50 nm to 200 μm, and particularly preferably 100 nm to 100 μm. In this specification, the average particle diameter refers to the average particle diameter in a volume-based particle size distribution obtained by particle size distribution measurement using dynamic light scattering. In the measurement, the active material particles are diluted with a dispersion medium (ion-exchanged water containing 0.2% sodium hexametaphosphate) to prepare a measurement sample. As a particle size distribution measuring device using the dynamic light scattering method, for example, a concentrated particle size analyzer FPAR-1000AS manufactured by Otsuka Electronics Co., Ltd. can be used.

[0048] The active material may have an aspect ratio (length / width) of 1 or greater. The aspect ratio (length / width) is preferably 10 or less. The aspect ratio (length / width) is more preferably 8 or less, even more preferably 5 or less, even more preferably 4 or less, even more preferably 2 or less, and particularly preferably 1.5 or less. For example, the aspect ratio (length / width) is preferably 1 to 10. More preferably, it is 1 to 8, even more preferably 1 to 5, even more preferably 1 to 4, even more preferably 1 to 2, and particularly preferably 1 to 1.5. The aspect ratio (length / width) can be determined from the shape of particles observed with an SEM. That is, the active material is observed with an SEM (scanning electron microscope), and the major and minor axes of 10 randomly selected particles in the SEM image are measured to determine the major axis / minor axis ratio. The simple average of the major axis / minor axis ratios can be used as the aspect ratio of the active material. Here, the major axis refers to the length of the longest line segment (A) among the line segments connecting two points on the periphery of each particle image, and the minor axis refers to the distance (length of the line segment) between two intersections of the periphery and a line that passes through the midpoint of the longest line segment (A) and is perpendicular to the line segment (A).

[0049] In the zinc electrode of the present invention, the mass ratio of zinc elemental substance to zinc-containing substance other than zinc elemental substance is preferably 1:99 to 100:0, more preferably 2:98 to 80:20, even more preferably 3:97 to 50:50, still more preferably 5:95 to 35:65, and particularly preferably 8:92 to 25:75.

[0050] The mass proportion of the active material is preferably 50% by mass or more, based on 100% by mass of the total of the active material and polymer (solid content) contained in the zinc electrode of the present invention. The mass proportion of the active material is preferably 99.9% by mass or less. For example, the mass proportion of the active material is preferably 50 to 99.9% by mass. When the mass proportion of the active material is within this range, the zinc electrode will have a sufficient battery capacity. The mass proportion of the active material is more preferably 55% by mass or more, and even more preferably 60% by mass or more. The mass proportion of the active material is more preferably 99.5% by mass or less, and even more preferably 99% by mass or less. For example, the mass proportion of the active material is more preferably 55 to 99.5% by mass, and even more preferably 60 to 99% by mass. The polymer refers to a polymer that the zinc electrode of the present invention may contain in addition to the current collector and active material described above, as described below. The mass ratio of the current collector to the active material is preferably 1:9 to 5:4, more preferably 1:7 to 1:1, and even more preferably 1:5 to 4:5.

[0051] (Polymer) The zinc electrode of the present invention preferably contains a polymer in addition to the current collector and active material described above. Examples of the polymer include hydrocarbon moiety-containing polymers such as polyethylene and polypropylene, aromatic group-containing polymers such as polystyrene, ether group-containing polymers such as alkylene glycol, hydroxyl group-containing polymers such as polyvinyl alcohol and poly(α-hydroxymethyl acrylate), amide bond-containing polymers such as polyamide, nylon, polyacrylamide, polyvinylpyrrolidone, and N-substituted polyacrylamide, imide bond-containing polymers such as polymaleimide, carboxyl group-containing polymers such as poly(meth)acrylic acid, polymaleic acid, polyitaconic acid, and polymethylene glutaric acid, carboxylate-containing polymers such as poly(meth)acrylate, polymaleate, polyitaconate, and polymethylene glutarate, polyvinyl chloride, polyvinylidene fluoride, and polytetrafluoroethylene. Examples of suitable polymers include halogen-containing polymers such as ethylene; epoxy resins; sulfonate moiety-containing polymers; quaternary ammonium salt- or quaternary phosphonium salt-containing polymers; ion-exchange polymers used in cation and anion exchange membranes; conjugated diene polymers such as styrene-butadiene polymers; sugars such as cellulose, cellulose acetate, hydroxyalkyl cellulose (e.g., hydroxyethyl cellulose), carboxymethyl cellulose, chitin, chitosan, and alginic acid (salts); amino group-containing polymers such as polyethyleneimine; carbamate group moiety-containing polymers; carbamide group moiety-containing polymers; epoxy group moiety-containing polymers; heterocyclic and / or ionized heterocyclic moiety-containing polymers; polymer alloys; heteroatom-containing polymers; and low-molecular-weight surfactants. These polymers function as binders for the active material and can prevent cracking in the zinc electrode. From the viewpoint of excellent binding properties, the polymer is preferably a carboxyl group-containing polymer, a carboxylate-containing polymer, or a conjugated diene-based polymer, more preferably a carboxylate-containing polymer or a conjugated diene-based polymer, and particularly preferably a conjugated diene-based polymer. It is also preferable to use two or more of these preferred polymers in combination.

[0052] Polymers can be obtained from monomers corresponding to their constituent units by radical polymerization, radical (alternating) copolymerization, anionic polymerization, anionic (alternating) copolymerization, cationic polymerization, cationic (alternating) copolymerization, graft polymerization, graft (alternating) copolymerization, living polymerization, living (alternating) copolymerization, dispersion polymerization, emulsion polymerization, suspension polymerization, ring-opening polymerization, cyclopolymerization, polymerization by light, ultraviolet light, or electron beam irradiation, metathesis polymerization, electrolytic polymerization, etc. When these polymers have functional groups, they may be present in the main chain and / or side chain, or as bonding sites with a crosslinking agent. These polymers may be used alone or in combination of two or more. The above polymers may be crosslinked.

[0053] The weight-average molecular weight of the polymer is preferably 200 or more. Furthermore, the weight-average molecular weight is preferably 7,000,000 or less. For example, the weight-average molecular weight is preferably 200 to 7,000,000. This allows for adjustment of the ionic conductivity, flexibility, and other properties of the resulting zinc electrode. The weight-average molecular weight of the polymer is more preferably 1,000 or more, and even more preferably 5,000 or more. Furthermore, the weight-average molecular weight of the polymer is more preferably 2,000,000 or less, and even more preferably 800,000 or less. For example, the weight-average molecular weight of the polymer is more preferably 1,000 to 2,000,000, and even more preferably 5,000 to 800,000. The weight-average molecular weight can be measured as a polystyrene-equivalent weight-average molecular weight by gel permeation chromatography (GPC) under the following conditions: Apparatus: Tosoh Corporation HCL-8220 GPC Column: TSKgel Super AWM-H Eluent (LiBr·H ２ O, NMP containing phosphoric acid): 0.01 mol / L

[0054] The mass proportion of the polymer is preferably 0.1% by mass or more, based on 100% by mass of the total active material and polymer (solid content) contained in the zinc electrode. The mass proportion of the polymer is more preferably 0.3% by mass or more, even more preferably 0.5% by mass or more, and particularly preferably 1% by mass or more. The mass proportion of the polymer is preferably 30% by mass or less, based on 100% by mass of the total active material and polymer (solid content) contained in the zinc electrode. The mass proportion of the polymer is more preferably 15% by mass or less, even more preferably 10% by mass or less, and particularly preferably 5% by mass or less. For example, the mass proportion of the polymer is preferably 0.1 to 30% by mass, based on 100% by mass of the total active material and polymer (solid content) contained in the zinc electrode. The mass proportion of the polymer is more preferably 0.3 to 15% by mass, even more preferably 0.5 to 10% by mass, and particularly preferably 1 to 5% by mass.

[0055] The zinc electrode of the present invention may contain a single element or a compound containing such an element as a constituent element to suppress the water decomposition side reaction that may occur when a water-containing electrolyte is used in a battery such as a secondary battery made using the zinc electrode. Examples of specific elements include Al, B, Ba, Bi, Br, C, Ca, Cd, Ce, Cl, Cu, Eu, F, Ga, Hg, In, La, Mg, Mn, N, Nb, Nd, Ni, P, Pb, S, Sb, Sc, Si, Sm, Sn, Sr, Ti, Tl, Y, and Zr.

[0056] When a conductive additive is used in the zinc electrode of the present invention, the mass proportion of the conductive additive can be 0.0001 mass% or more relative to 100 mass% of the active material in the zinc electrode. Preferably, it is 0.0005 mass% or more, and more preferably, it is 0.001 mass% or more. Furthermore, the mass proportion of the conductive additive can be 80 mass% or less relative to 100 mass% of the active material in the zinc electrode. Preferably, it is 60 mass% or less, and more preferably, it is 40 mass% or less. For example, the mass proportion of the conductive additive can be 0.0001 to 80 mass% relative to 100 mass% of the active material in the zinc electrode. Preferably, it is 0.0005 to 60 mass%, and more preferably, it is 0.001 to 40 mass%.

[0057] (Other Components) The zinc electrode of the present invention may contain, in addition to the current collector and active material, a polymer, a conductive additive, etc., and may further contain one or more other components. The other components are not particularly limited, but examples include alumina, silica, etc. The other components can function to assist ion conductivity, etc. In the electrode precursor of the present invention, the mass proportion of the other components is preferably 1 mass% or less, more preferably 0.1 mass% or less, relative to 100 mass% of the active material.

[0058] The zinc electrode of the present invention preferably has an average thickness of 25 μm or more, more preferably 30 μm or more, even more preferably 40 μm or more, and particularly preferably 50 μm or more. The zinc electrode of the present invention is relatively lightweight even as a thick film, and is capable of uniform reaction. The average thickness of the zinc electrode is preferably 10 mm or less. For example, the average thickness of the zinc electrode is preferably 25 μm to 10 mm, more preferably 30 μm to 10 mm, even more preferably 40 μm to 10 mm, and particularly preferably 50 μm to 10 mm. The average thickness of the zinc electrode of the present invention can be calculated by measuring the thickness at any 10 locations using a micrometer or the like and calculating the simple average value.

[0059] The zinc electrode of the present invention is preferably obtained by impregnating a current collector comprising resin fibers and a conductive layer covering the surface thereof with a composition containing a zinc active material and a polymer. This allows for the production of an electrode containing a zinc-containing material as an active material within the pores of the porous current collector. The zinc electrode of the present invention can be obtained, for example, by contacting and impregnating the current collector with a slurry or paste-like composition (hereinafter also referred to as a slurry or the like) containing the active material and a polymer according to the present invention. If the composition contains volatile components such as a solvent, it may be further dried. For example, after contacting and impregnating the current collector with the composition, the zinc electrode can be obtained by drying, if necessary, to evaporate some or all of the volatile components, such as the solvent, contained in the composition. Furthermore, rolling may be performed as necessary. When producing the zinc electrode of the present invention, reducing voids by rolling can further suppress the occurrence of cracks due to voids. Furthermore, the film thickness can be made uniform, increasing the electrode density and volumetric capacity density. Impregnation and rolling may be repeated two or more times.

[0060] The zinc electrode of the present invention may be formed by applying the above composition to a current collector, pressing, adhering, piezoelectrically applying, rolling, stretching, melting, or the like.

[0061] <Zinc Battery> The present invention also relates to a battery comprising the zinc electrode of the present invention. As described above, the battery of the present invention comprises the zinc electrode of the present invention, and therefore can be driven sufficiently, has a long life, and is very excellent in weight energy density.

[0062] When the zinc electrode described above is used as the negative electrode of the zinc battery of the present invention, the positive electrode active material can be any material commonly used as a positive electrode active material for primary or secondary batteries, and is not particularly limited. Examples include, but are not limited to, oxygen (when oxygen is the positive electrode active material, the positive electrode becomes an air electrode composed of a perovskite-type compound capable of reducing oxygen or oxidizing water, a cobalt-containing compound, an iron-containing compound, a copper-containing compound, a manganese-containing compound, a platinum-containing compound, or the like), nickel oxyhydroxide, nickel hydroxide, nickel hydroxide, cobalt-containing nickel hydroxide, and other nickel compounds, and silver oxide. Among these, for example, a nickel compound is preferred as the positive electrode active material. Furthermore, when a zinc electrode is used as the negative electrode of the zinc battery of the present invention, the positive electrode may also include a current collector including resin fibers and a conductive layer covering the surface thereof, as well as an active material, which is also a preferred embodiment of the present invention. Furthermore, the form of a battery using the zinc electrode of the present invention as a negative electrode may be any of a primary battery, a chargeable and dischargeable secondary battery, a battery using mechanical charging (mechanical replacement of the zinc negative electrode), a battery using a third electrode other than a positive electrode composed of the negative electrode of the present invention and the positive electrode active material as described above, and the like.

[0063] The electrolyte used in the battery of the present invention can be any commonly used battery electrolyte, and is not particularly limited. Examples include, for example, organic solvent-based electrolytes, aqueous electrolytes, and solid electrolytes. Examples of organic solvent-based electrolytes include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, dimethoxymethane, diethoxymethane, dimethoxyethane, tetrahydrofuran, methyltetrahydrofuran, diethoxyethane, dimethyl sulfoxide, sulfolane, acetonitrile, benzonitrile, ionic liquids, fluorine-containing carbonates, fluorine-containing ethers, polyethylene glycols, and fluorine-containing polyethylene glycols. These may be used alone or in combination of two or more. Examples of aqueous electrolytes include potassium hydroxide aqueous solution, sodium hydroxide aqueous solution, lithium hydroxide aqueous solution, zinc sulfate aqueous solution, zinc nitrate aqueous solution, zinc phosphate aqueous solution, and zinc acetate aqueous solution. Among these, alkaline electrolytes such as potassium hydroxide aqueous solution, sodium hydroxide aqueous solution, and lithium hydroxide aqueous solution are preferred. The aqueous electrolyte solution may be used alone or in combination of two or more kinds. The aqueous electrolyte solution may contain the organic solvent-based electrolyte solution.

[0064] The battery of the present invention may further include a separator. The separator may be any material that separates the positive electrode and the negative electrode, retains the electrolyte, and ensures ionic conductivity between the positive electrode and the negative electrode. There are no particular limitations on the separator, and examples thereof include nonwoven fabrics, filter paper, and microporous membranes. Examples of materials that can be used for these include hydrocarbon moiety-containing polymers such as polyethylene and polypropylene, polytetrafluoroethylene moiety-containing polymers, polyvinylidene fluoride moiety-containing polymers, cellulose, fibrillated cellulose, viscose rayon, cellulose acetate, hydroxyalkyl cellulose, and carboxymethyl cellulose, polyvinyl alcohol-based polymers such as polyvinyl alcohol and partially acetalized polyvinyl alcohol, aromatic ring moiety-containing polymers such as cellophane and polystyrene, polyacrylonitrile moiety-containing polymers, polyacrylamide moiety-containing polymers, polyvinyl halide moiety-containing polymers, and polyamides such as nylon. Examples of suitable polymer materials include hydroxyl group-containing polymers such as polyisoprenol and poly(meth)allyl alcohol, carbonate group-containing polymers such as polycarbonate, ester group-containing polymers such as polyester, carbamate and carbamide group-containing polymers such as polyurethane, agar, gel compounds, ion-exchange polymers, cyclized polymers, sulfonate-containing polymers, quaternary ammonium salt-containing polymers, quaternary phosphonium salt polymers, cyclic hydrocarbon group-containing polymers, and ether group-containing polymers. The separator may be an ion-conductive inorganic membrane such as a layered double hydroxide such as hydrotalcite, or an organic-inorganic composite membrane (ion-conductive membrane) containing the above polymer material and an inorganic compound. The separator may be one of these materials, or a combination of two or more of these materials, such as by lamination.

[0065] The battery of the present invention can be obtained by a known method, for example, by stacking a separator and a positive electrode on a negative electrode, inserting the stack into a battery cell of an appropriate size, and introducing an electrolyte solution into the battery cell.

[0066] The battery of the present invention has a long life and an excellent weight energy density, and can be suitably used in a wide range of applications from small portable devices to large applications such as automobiles.

[0067] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" means "parts by weight" and "%" means "% by mass."

[0068] (Average particle size of active material) The average particle size of the active material (zinc metal) used in each example was determined as follows: The active material was added to and mixed with a dispersion medium (ion-exchanged water containing 0.2% sodium hexametaphosphate) to prepare a measurement sample, and the volume-based particle size distribution was measured using a concentrated particle size analyzer FPAR-1000AS manufactured by Otsuka Electronics Co., Ltd., and the 50% particle size was taken as the average particle size of the active material.

[0069] (Aspect Ratio of Active Material) The aspect ratio of the active material (zinc metal) used in each example was determined as follows. The active material was observed under a scanning electron microscope, and the major and minor axes of 10 randomly selected particles in the electron microscope image were measured to determine the major / minor axis ratio. The simple average of the obtained major / minor axis ratios of the 10 particles was used as the aspect ratio of the active material. The major axis is the length of the longest line segment (A) among the line segments connecting two points on the periphery of each particle image, and the minor axis is the distance (length of the line segment) between the two intersections of the periphery and a line passing through the midpoint of the longest line segment (A) and perpendicular to the line segment (A).

[0070] (Average fiber diameter of resin fiber) The resin fiber used in each example was cut in the thickness direction with a razor (T5332 TEFLON (registered trademark) COATED) manufactured by JEOL Ltd., and the obtained cross section was observed with a scanning electron microscope. 10 cross sections in the thickness direction of each fiber constituting the resin fiber were randomly selected, and the major axis at the selected 10 locations was measured. The simple average of the 10 measured values ​​was calculated, and the obtained value was used as the average fiber diameter of the resin fiber. The major axis was the length of the longest line segment connecting two points on the periphery of the cross section in the thickness direction. The scanning electron microscope used was a TM3000 Miniscope manufactured by Hitachi Technologies, Ltd.

[0071] (Average Thickness of Resin Fiber) The average thickness of the resin fiber used in each example was measured at 10 locations using a micrometer, and the simple average value was taken as the average thickness of the resin fiber.

[0072] (Average Thickness of Conductive Layer (Plating Layer)) The current collector (porous body) obtained in each Example was cut in the thickness direction with a razor (T5332 TEFLON (registered trademark) COATED) manufactured by JEOL Ltd., and the resulting cross section was observed with a scanning electron microscope. Ten cross-sectional images in the thickness direction of the fiber on which the conductive layer (plating layer) was formed were randomly selected. The thickness of the conductive layer was then measured at ten randomly selected locations in each of the ten selected cross-sectional images, and the simple average of the ten measurements was used as the thickness of the conductive layer in each cross-sectional image. The thicknesses of the conductive layer in each cross-sectional image thus obtained (a total of 10) were simply averaged, and the resulting value was used as the average thickness of the conductive layer (plating layer) in the current collector. A TM3000 Miniscope manufactured by Hitachi Technologies, Ltd. was used as the scanning electron microscope. When multiple conductive layers were present, such as an intermediate layer and an outermost layer, the thickness was determined for each layer in the same manner.

[0073] (Density of Current Collector (Porous Body)) The current collector (porous body) obtained in each example was cut in the plane direction to a specific size (for example, 40 mm × 40 mm) to obtain a rectangular parallelepiped (the thickness of which was the same as that of the current collector). The weight of the obtained rectangular parallelepiped was measured, and the value obtained by the following formula was taken as the density of the current collector. Density [g / cm ３] = (mass of rectangular parallelepiped [g]) / (volume of rectangular parallelepiped [cm ３ The volume of the rectangular parallelepiped in the above formula is a value obtained by calculation using the length, width, and thickness of the rectangular parallelepiped, and the thickness of the rectangular parallelepiped is a simple average value of thicknesses measured at 10 points using a micrometer.

[0074] (Average Thickness of Zinc Negative Electrode) The average thickness of the zinc negative electrode obtained in each example was measured at 10 locations using a micrometer, and the simple average value was taken as the average thickness of the zinc negative electrode.

[0075] (Comparative Example 1) Zinc metal (average particle size 75 μm), styrene butadiene rubber, and sodium polyacrylate were mixed and stirred in a mass ratio of 98:1:1 to obtain a coating material (c1). The obtained coating material (c1) was impregnated into a brass mesh prepared as a current collector, and then dried and rolled to obtain a zinc negative electrode (c1). The average thickness of the obtained zinc negative electrode (c1) was 140 μm.

[0076] (Example 1) Zinc metal (average particle size 75 μm), styrene butadiene rubber, and sodium polyacrylate were mixed and stirred in a mass ratio of 98:1:1 to obtain a coating material (1). A nylon resin mesh was plated with Cu and Sn in this order as a current collector, to obtain a porous body (1) in which the nylon resin surface was covered with a Cu-plated layer (intermediate layer) and a Sn-plated layer (outermost layer). The porous body (1) was impregnated with the coating material (1), followed by drying and rolling to obtain a zinc negative electrode (1). The obtained zinc negative electrode (1) had an average thickness of 140 μm.

[0077] (Example 2) Zinc oxide (average particle size 1 μm), polytetrafluoroethylene, and sodium polyacrylate were mixed and stirred in a mass ratio of 95:4:1 to obtain a paint (2). The zinc negative electrode (1) obtained in Example 1 was impregnated with the paint (2), dried, and rolled to obtain a zinc negative electrode (2). The average thickness of the zinc negative electrode was 250 μm. The weight energy density was calculated for each zinc negative electrode obtained in each Example and Comparative Example. The results are shown in Tables 1 and 2. The weight energy density was calculated as follows. (Method of calculating weight energy density) The weight energy density of the zinc negative electrode obtained in each Example and Comparative Example was calculated using the following formula. D = Wa x (Wb / 100) x tc / Wc D: weight energy density (mAh / g) Wa: mass (g) of active material contained per unit volume of zinc negative electrode Wb: zinc (Zn) content (mass %) in the active material Wc: mass (g) per unit volume of zinc negative electrode tc: theoretical capacity of zinc (Zn) 820 (mAh / g)

[0078] (Comparative Example 2) A charge-discharge cycle test was carried out using the zinc negative electrode (c1) obtained in Comparative Example 1, a carbon electrode as a positive electrode, and a nonwoven fabric and an anion conductor disposed between the positive and negative electrodes, and an 8M potassium hydroxide aqueous solution saturated with zinc oxide as an electrolyte. The current value was 1 mA / cm. ２ (Charge / discharge voltage: 1.35 V, discharge voltage: 0.35 V) As a result, a cycle life of 1000 cycles or more was obtained.

[0079] (Example 3) A charge-discharge cycle test was carried out in the same manner as in Comparative Example 2, except that the zinc negative electrode (c1) obtained in Example 1 was used instead of the zinc negative electrode (1). As a result, a cycle life of 1,000 cycles or more was obtained.

[0080] The charge-discharge curves at the 100th cycle in Example 3 and Comparative Example 2 are shown in Figure 1. It was confirmed that the use of a zinc negative electrode using a porous body in which the surface of nylon resin fiber was covered with a Cu plating layer (intermediate layer) and a Sn plating layer (outermost layer) as the current collector provided the same battery operation as when a brass mesh current collector was used.

[0081] (Example 4) A paint (4) was obtained by mixing and stirring zinc metal (average particle size 75 μm, aspect ratio 3.0), styrene butadiene rubber, and sodium polyacrylate in a mass ratio of 95:3:2 using water as a solvent. As a current collector, a mesh (average thickness 160 μm) made of polypropylene resin fibers (average fiber diameter 87 μm) was plated with Cu and Sn in this order to obtain a porous body (4) in which the surface of the polypropylene resin fibers was covered with a Cu-plated layer (intermediate layer, average thickness 5 μm) and a Sn-plated layer (outermost layer, average thickness 15 μm). The density of the obtained porous body (4) was 0.48 g / cm ３ The coating material (4) was impregnated into the porous body (4), followed by drying and rolling to obtain a zinc negative electrode (4). The average thickness of the obtained zinc negative electrode (4) was 210 μm. In the zinc negative electrode (4), the mass proportion of the conductive layer was 8.8 mass%, and the mass proportion of the resin fiber was 9.5 mass%.

[0082] The mass proportion of the conductive layer and the mass proportion of the resin fiber in the zinc negative electrode (4) obtained in Example 4 were determined by ICP atomic emission spectrometry. Specific details are as follows. (Mass Proportion of Conductive Layer in Zinc Negative Electrode (4)) A predetermined amount of the zinc electrode (4) was acid-decomposed using a microwave decomposition device (ETHOS One manufactured by Milestone General), and the resulting solution was used as a measurement sample. Using this measurement sample, quantitative analysis of Sn and Cu was performed using an ICP atomic emission spectrometry analyzer, and the mass proportion of the conductive layer in the zinc negative electrode (4) was determined from the obtained Sn and Cu contents. As the ICP atomic emission spectrometry analyzer, an ICPE-9000 manufactured by Shimadzu Corporation was used. (Mass Proportion of Resin Fiber in Zinc Negative Electrode (4)) First, the total content (mass%) of Sn and Cu in the porous body (4) obtained in Example 4 was determined by ICP atomic emission spectroscopy. This was defined as the content of the conductive layer, and the remainder was defined as the content (mass%) of the resin fiber in the porous body (4). The mass ratio X of the resin fiber content to the conductive layer content (resin fiber content / conductive layer content) was determined. Next, the content Y (mass%) of the conductive layer in the zinc electrode (4) was determined by ICP atomic emission spectroscopy. Using the obtained X and Y, Z (mass%) obtained by the following formula was defined as the mass proportion of the resin fiber in the zinc electrode. Z = Y x X The method for preparing the measurement sample, the microwave decomposition device used, and the ICP atomic emission spectroscopy device were the same as those used for the mass proportion of the conductive layer in the zinc negative electrode (4).

[0083] (Example 5) A zinc negative electrode (5) was obtained in the same manner as in Example 4, except that a nonwoven fabric (average thickness 90 μm) made of polypropylene resin fiber / high-density polyethylene resin fiber (average fiber diameter 35 μm) and polypropylene ultrafine fiber (average fiber diameter 14 μm) that had been hydrophilized with fluorine gas was used instead of the mesh made of polypropylene resin fiber (average fiber diameter 87 μm) in Example 4, the average thickness of the Cu plating layer (intermediate layer) was set to 3 μm, the average thickness of the Sn plating layer (outermost layer) was set to 4 μm, and the amount of paint (4) was changed. The average thickness of the obtained zinc negative electrode (5) was 140 μm.

[0084] (Example 6) A zinc negative electrode (6) was obtained in the same manner as in Example 4, except that a nonwoven fabric (average thickness 90 μm) made of polypropylene resin fiber / polyethylene resin fiber (average fiber diameter 18 μm) was used instead of the mesh made of polypropylene resin fiber (average fiber diameter 87 μm), the average thickness of the Cu plating layer (intermediate layer) was set to 3 μm, the average thickness of the Sn plating layer (outermost layer) was set to 6 μm, and the amount of paint (4) was changed. The average thickness of the obtained zinc negative electrode (6) was 140 μm.

[0085] (Example 7) A zinc negative electrode (7) was obtained in the same manner as in Example 4, except that a nonwoven fabric (average thickness 90 μm) made of vinylon resin fiber (average fiber diameter 10 μm) was used instead of the mesh made of polypropylene resin fiber (average fiber diameter 87 μm), the average thickness of the Cu plating layer (intermediate layer) was set to 4 μm, the average thickness of the Sn plating layer (outermost layer) was set to 10 μm, and the amount of paint (4) was changed. The average thickness of the obtained zinc negative electrode (7) was 140 μm.

[0086] (Example 8) A zinc negative electrode (8) was obtained in the same manner as in Example 4, except that a mesh (average thickness 100 μm) made of polyphenylene sulfide resin fiber (average fiber diameter 55 μm) was used instead of the mesh made of polypropylene resin fiber (average fiber diameter 87 μm), the average thickness of the Cu plating layer (intermediate layer) was set to 7 μm, the average thickness of the Sn plating layer (outermost layer) was set to 20 μm, and the amount of paint (4) was changed. The average thickness of the zinc negative electrode (8) was 150 μm.

[0087]

[0088] The zinc negative electrodes obtained in Examples 4 to 8 were subjected to the charge-discharge cycle test described in Comparative Example 2, and all of them had a cycle life of 1,000 cycles or more. It was confirmed that even when zinc negative electrodes using porous bodies in which the surfaces of various resin fibers were covered with a Cu-plated layer (intermediate layer) and a Sn-plated layer (outermost layer) as current collectors were used, a life of 1,000 cycles or more was achieved, similar to the case in which a brass mesh current collector was used.

Claims

1. A current collector including a resin fiber and a conductive layer covering the surface thereof, and containing a zinc-containing substance as an active material, the conductive layer includes a outermost surface layer and an intermediate layer between the outermost surface layer and the resin fiber, the outermost surface layer contains a metal containing tin and / or a metal oxide thereof, the intermediate layer contains a metal containing copper and / or a metal oxide thereof, and the zinc electrode is characterized in that.

2. The zinc electrode according to Claim 1, wherein the ratio of the average thickness of the outermost surface layer to the average thickness of the intermediate layer is 1:1 to 4:

1.

3. The zinc electrode according to Claim 1 or 2, wherein the ratio of the average thickness of the outermost surface layer to the average thickness of the intermediate layer is 4:3 to 3:

1.

4. The zinc electrode according to Claim 1 or 2, wherein the conductive layer contains a metal.

5. The zinc electrode according to Claim 1 or 2, wherein the average thickness of the conductive layer is 0.1 to 40 μm.

6. The current collector is a porous current collector, The zinc electrode according to Claim 1 or 2, wherein the zinc-containing substance is contained as an active material in the pores of the porous current collector.

7. A battery comprising the zinc electrode according to Claim 1 or 2.