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

[Technical Field]

[0001] This invention relates to a zinc electrode. More specifically, to a zinc electrode used in a battery, and to a battery comprising the zinc electrode. [Background technology]

[0002] In recent years, the importance of batteries has rapidly increased in many industries, from small portable devices to large-scale applications such as automobiles. As a result, various new battery systems are being developed and improved, primarily those that offer advantages in terms of capacity, gravimetric energy density, and rechargeability.

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

[0004] Furthermore, zinc anodes, which use zinc-containing materials as the negative electrode active material, have been studied for a long time alongside the spread of batteries. In particular, air-zinc primary batteries, manganese-zinc primary batteries, and silver-zinc primary batteries have been put into practical use and are widely used around the world. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 3386805 [Patent Document 2] Japanese Patent Application Publication No. 3-130393 [Patent Document 3] Japanese Patent Application Publication No. 3-130395 [Patent Document 4] Japanese Patent Application Publication No. 3-130394 [Patent Document 5] Japanese Patent Application Publication No. 61-208756 [Patent Document 6] Japanese Patent Publication No. 2007-234484 [Patent Document 7] Japanese Patent Application Laid-Open No. 2008-66145 [Patent Document 8] Japanese Patent Application Laid-Open No. 2008-305698 [Patent Document 9] Japanese Patent Application Laid-Open No. 2008-71533 [Patent Document 10] Japanese Patent Application Laid-Open No. 2008-159497 [Patent Document 11] Japanese Patent Application Laid-Open No. 2009-140676 [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] However, in the zinc electrode, where a dissolution and deposition reaction of a zinc-containing substance occurs near the active material layer, when charge and discharge are repeated over a long period, in the process, the battery reaction becomes non-uniform, or additives such as conductive aids are unevenly distributed due to the non-uniformity of the reaction, resulting in the loss of the effect, and there are problems peculiar to the zinc electrode such as shortening of the life. <​​​​​​​​​​​​​​​

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

[0011] The present invention (3) is a zinc electrode of the present invention (2) wherein the above metal and / or metal oxide comprises at least one metallic 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 of the present inventions (1) to (3), wherein the conductive layer comprises a surface layer containing at least one metal and / or a metal oxide selected from the group consisting of zinc, tin, bismuth, indium, lead, and cadmium.

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

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

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

[0016] The present invention (8) is a zinc electrode in any combination of the present invention (1) to (7) wherein the current collector is a porous current collector, and the zinc electrode is a zinc electrode in any combination of the present invention (1) to (7) wherein 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 a zinc electrode according to any of the present inventions (1) to (8). [Effects of the Invention]

[0018] The zinc electrode of the present invention has the above-described configuration and can extend the lifespan of a battery containing the zinc electrode, as well as improve the gravimetric energy density. [Brief explanation of the drawing]

[0019] [Figure 1] Figure 1 is a graph showing the charge-discharge curves at 100 cycles for the battery in the example and the battery in the comparative example. [Modes for carrying out the invention]

[0020] The present invention will be described in detail below. Furthermore, combinations of two or more of the individual preferred embodiments of the present invention described below are also preferred embodiments 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 its surface, and a zinc-containing substance as an active material.

[0022] (Current collector) The current collector described above includes a resin fiber (core material) and a conductive layer covering its surface. The conductive layer may completely cover the resin fiber, but it does not have to completely cover it, and a portion of the resin fiber may be exposed.

[0023] [Conductive layer] The above conductive layer has an electrical conductivity of 1 × 10⁻⁶ at 0°C. 6 This refers to a layer made of a conductive material with an electrical conductivity of S / m or higher. The electrical conductivity is 5 × 10 6 It is preferable that the ratio is S / m or higher. The above electrical resistance is obtained by measuring the electrical resistance in the thickness direction of the conductive layer using a tester.

[0024] As for the conductive material, any conductive layer that exhibits the above-mentioned specific electrical conductivity is acceptable. For example, one or more of the following can be used: metals such as zinc, tin, bismuth, indium, lead, cadmium, gold, copper, brass, silver, metal compounds such as metal oxides, conductive carbon, conductive ceramics, conductive polymers, etc.

[0025] In particular, it is preferable to use a metal and / or metal oxide (more preferably a metal) as the conductive material. That is, it is preferable that the conductive layer contains a metal and / or 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. In particular, from the viewpoint of achieving better electronic conductivity, it is even more preferable that the conductive layer contains a metal, and especially preferable a metal layer made of a metal or a laminate thereof. In this specification, when simply referred to as "metal," it means a metal in its elemental form or an alloy thereof. 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 achieving superior electronic conductivity, indium tin oxide (ITO) and the like are preferred. Furthermore, the metal oxide may be a low-valence metal oxide (e.g., Cu2O, Ag2O, SnO, etc.) formed by oxidizing the surface or the entire conductive layer by oxygen in the ambient air after forming a conductive layer made of an easily oxidizable metal (e.g., metals with high ionization tendencies such as zinc and tin, or copper, silver, etc.).

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

[0027] The conductive layer preferably includes a top surface layer comprising at least one metal and / or a metal oxide selected from the group consisting of zinc, tin, bismuth, indium, lead, and cadmium, and more preferably includes a top surface layer comprising at least one metal and / or a metal oxide selected from the group consisting of zinc, tin, bismuth, indium, lead, and cadmium. From the viewpoint of improving electronic conductivity, the conductive layer is even more preferably comprising a top surface layer comprising at least one metal selected from the group consisting of zinc, tin, bismuth, indium, lead, and cadmium, and particularly preferably comprises a top surface layer comprising at least one metal selected from the group consisting of zinc, tin, bismuth, indium, lead, and cadmium. These metals can sufficiently suppress the generation of hydrogen by forming a hybrid potential with the zinc-containing active material when the hydrogen overpotential is high, and can further suppress the self-discharge of the zinc-containing material. From the viewpoint of increasing safety, zinc, tin, bismuth, and indium are more preferred as the metal elements constituting the outermost layer of metal or metal oxide. From the viewpoint of reducing costs, zinc, tin, bismuth, lead, and cadmium are more preferred. From both of these viewpoints, zinc, tin, and bismuth are particularly preferred. Furthermore, it is preferable that the conductive layer does not contain nickel, iron, or steel (SUS) in its outermost layer. It is even more preferable that the conductive layer does not contain copper in its outermost layer. Since these metals have low hydrogen overpotential, by not using these metals in the outermost layer, it is possible to sufficiently suppress the generation of hydrogen by forming a hybrid potential with the zinc-containing material, which is the active material, and to further suppress the self-discharge of the zinc-containing material. Furthermore, if there is only one conductive layer, that conductive layer itself becomes the outermost layer.

[0028] Furthermore, the conductive layer includes an outermost layer and an intermediate layer between the outermost layer and the resin fibers. The intermediate layer preferably contains at least one metal selected from the group consisting of gold, copper, silver, and tin, and / or a metal oxide thereof. It is more preferable that 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 a metal oxide thereof, or a laminate made of the metal layer and / or the metal oxide layer (a laminate of the metal layer, a laminate of the metal oxide layer, or a laminate of the metal layer and the metal oxide layer). It is even more preferable that the intermediate layer contains at least one metal selected from the group consisting of gold, copper, silver, and tin, and it is particularly preferable that the intermediate layer is a metal layer made of at least one metal selected from the group consisting of gold, copper, silver, and tin. This results in superior electronic conductivity of the conductive layer. From the viewpoint of cost reduction, copper and tin are more preferable as the metal elements constituting the intermediate layer metal or metal oxide. Furthermore, from the viewpoint of electronic conductivity, gold, copper, and silver are more preferable. From both of these viewpoints, copper is particularly preferable.

[0029] Furthermore, when using metals with low hydrogen overpotential, such as gold, copper, cobalt, or iron, in the conductive layer described above, it is preferable to further laminate metals with high hydrogen overpotential, such as zinc, tin, bismuth, indium, lead, or cadmium, on its surface to suppress the self-discharge of the zinc-containing material. In particular, it is more preferable that the conductive layer contains copper as an intermediate layer and zinc and / or tin as the outermost layer. In addition, zinc and tin are easier to plate using copper as a base material than resin fibers, which is advantageous from a manufacturing standpoint. When the outermost layer is zinc, the zinc in the outermost layer is not in granular form like zinc active material, 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 fibers, the outermost layer may completely cover the intermediate layer, or it may not completely cover it, leaving a portion of the intermediate layer exposed. However, when the conductive layer is formed by laminating a metal with a high hydrogen overpotential onto the surface of a metal with a low hydrogen overpotential, it is particularly preferable that the outermost layer substantially completely covers the intermediate layer.

[0031] If the conductive layer described above is formed by laminating multiple layers, the composition and thickness of each layer may be the same or different. Furthermore, while the outermost layer is usually only one layer, the intermediate layer may consist of one or more layers. If the intermediate layer consists of multiple layers, each layer may or may not completely cover the layer or resin fiber below it.

[0032] In the conductive layer described above, the total content of metal and metal oxide (more preferably, the content of metal) is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. Furthermore, it is particularly preferable that the conductive layer is substantially composed of metal, or metal and metal oxide, and most preferably substantially composed of metal.

[0033] The average thickness of the conductive layer is preferably 0.1 μm or more. Furthermore, 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. An average thickness of 0.1 μm or more results in superior electronic conductivity. Furthermore, an average thickness of 40 μm or less provides more effective crack prevention. Moreover, an average thickness of 0.2 μm or more is more preferable. Furthermore, an average thickness of 35 μm or less is more preferable. For example, an average thickness of 0.2 to 35 μm is more preferable. In this specification, the average thickness is measured by observing the cross-section of the current collector with an electron microscope and determining the simple average of the thicknesses of any 10 points on the conductive layer. Specifically, it can be calculated as follows. 1) Cut the current collector (porous material) in the thickness direction, observe the resulting cross-section with a scanning electron microscope, and arbitrarily select 10 locations in the fiber thickness direction where the conductive layer is formed. 2) Next, in each of the 10 selected cross-sectional images, the thickness of the conductive layer is measured at 10 arbitrary locations, and the simple average of the 10 obtained measurements is taken as the thickness of the conductive layer in each cross-sectional image. 3) Based on the above, the thickness of the conductive layer in each cross-sectional image is simply averaged, and the resulting value is taken as the average thickness of the conductive layer in the current collector. The method for cutting the current collector (porous material) in the thickness direction is not particularly limited, but methods such as mechanically cutting with a razor or further ion milling the cross-section obtained after mechanical cutting can be employed. As for the razor, a razor manufactured by JEOL Ltd. (T5332 TEFLON® COATED) can be used. While there are no particular limitations on the scanning electron microscope, for example, the TM3000 Miniscope manufactured by Hitachi Technologies, Ltd. can be used. Even when there are multiple conductive layers, such as an intermediate layer and an outermost layer, measurements can be taken for each layer in the same manner. The average thickness of the conductive layer of the current collector in a zinc electrode can be determined using a similar method.

[0034] In the conductive layer described above, 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, even more preferably 1:5 to 5:1, even more preferably 1:2 to 5:1, even more preferably 1:1 to 4:1, and particularly preferably 4:3 to 3:1.

[0035] The mass percentage of the conductive layer described above 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 percentage of the conductive layer described above 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 percentage 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 ratio of the conductive layer can be determined by combining ICP emission spectroscopy and, if necessary, EDX analysis (energy-dispersive X-ray analysis) such as SEM-EDX analysis and TEM-EDX analysis. When using ICP emission spectroscopy, it is preferable to use a solution obtained by acid decomposition (for example, using a microwave decomposition device) of a predetermined amount of zinc electrode as the measurement sample. For example, the ICPE-9000 manufactured by Shimadzu Corporation can be used as the ICP emission spectroscopy device, and the ETHOS One manufactured by Milestone General can be used as the microwave decomposition device.

[0037] [Resin fiber] Examples of the above resin fibers include hydrocarbon-containing polymers such as polyethylene and polypropylene, polytetrafluoroethylene-containing polymers, polyvinylidene fluoride-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 (e.g., vinylon), aromatic ring-containing polymers such as cellophane, polystyrene, and polyphenylene sulfide, polyacrylonitrile-containing polymers, polyacrylamide-containing polymers, polyhalogenated vinyl-containing polymers, and nylon. Examples of fibers include polyamide-containing polymers such as ron, polyimide-containing polymers, ester-containing polymers, poly(meth)acrylic acid-containing polymers, poly(meth)acrylic acid-containing polymers, hydroxyl-containing polymers such as polyisoprenol and poly(meth)allyl alcohol, carbonate-containing polymers such as polycarbonate, ester-containing polymers such as polyester, carbamate and carbamide-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-containing polymers. Among these, hydrocarbon-containing polymers such as polypropylene, polyvinyl alcohol-based polymers, aromatic ring-containing polymers, and polyamide-containing polymers are more preferred due to their chemical stability. These fibers may be used individually or in combination of two or more types. By using resin fibers, the zinc electrode can be made flexible, which is thought to contribute to preventing the occurrence of cracks in the zinc electrode. Furthermore, the above-mentioned resin fibers may be insulating materials that are substantially non-conductive to electricity.

[0038] As the resin fiber, those hydrophilically treated by a method of imparting a surfactant, sulfonation with chemicals such as fuming sulfuric acid and chlorosulfonic acid, methods such as fluorination and grafting treatment, or a method by corona discharge or plasma discharge may be used. When the resin fiber is a hydrocarbon site-containing polymer, it is preferably hydrophilically treated. Examples of the resin fiber include non-woven fabric, woven fabric, mesh, felt, etc., and among them, non-woven fabric and mesh are preferable.

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

[0040] The average fiber diameter of the above resin fibers 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. A resin fiber can be cut in the thickness direction, and the resulting cross-section can be observed with a scanning electron microscope. Ten cross-sectional images in the thickness direction of each fiber constituting the resin fiber can be arbitrarily selected. The major axis at the selected ten locations can be measured, and the simple average of the ten measured values ​​can be calculated. The resulting value can be considered the average fiber diameter of the resin fiber. The major axis refers to the length of the longest line segment connecting two points on the outer circumference in the cross-sectional image in the thickness direction. There are no particular limitations on the method for cutting the resin fibers in the thickness direction, but methods such as mechanically cutting with a razor or further ion milling the surface obtained after mechanical cutting can be employed. As for the razor, a razor manufactured by JEOL Ltd. (T5332 TEFLON® COATED) can be used. While there are no particular limitations on the scanning electron microscope, for example, the TM3000 Miniscope manufactured by Hitachi Technologies, Ltd. can be used. 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 can be determined using the same method.

[0041] The average thickness of the above resin fibers 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 above resin fibers can be measured using a micrometer, and the thickness can be measured at any 10 locations, with the simple average value being adopted as the average thickness of the resin fibers.

[0042] The mass percentage of the above resin fibers is not particularly limited, but for example, it is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, in 100% by mass of the zinc electrode of the present invention. Furthermore, the mass percentage 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 percentage 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 ratio of the above resin fibers can be determined as follows. The content (mass%) of the conductive layer in the current collector is determined by ICP emission spectroscopy, and the remainder is taken as the content (mass%) of 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 calculated. By ICP emission spectroscopy of the zinc electrode, the content Y (mass%) of the conductive layer in the zinc electrode can be determined, and the Z (mass%) obtained by the following formula can be used as the mass ratio of resin fibers in the zinc electrode. Z = Y × X Furthermore, the same methods used for preparing the measurement sample, as well as the ICP emission spectrometer and microwave resolution device used, can preferably be the same as those used in the case of the mass ratio of the conductive layer in the zinc electrode described above.

[0043] The current collector described above is typically a porous current collector. By using a porous current collector, it is possible to create a current collector that is ionically conductive in the direction of penetration (thickness direction or current direction). In addition, the current collector can be made lighter.

[0044] The above current collector has a density of 0.01 g / cm³. 3 The above is preferable, and 0.03 g / cm³ 3 The above is more preferable, 0.05 g / cm³ 3 The above is even more preferable, 0.1 g / cm³ 3 It is even more preferable that the above is true, and 0.3 g / cm³ 3 It is even more preferable that the above is true, specifically 0.5 g / cm³. 3 It is even more preferable that the concentration be 1 g / cm³ or higher. 3 It is especially preferable that the above conditions are met. The density mentioned above does not have a particularly limited upper limit, but is 10 g / cm³. 3 Preferably, it is 7 g / cm³ 3 More preferably, it is 5 g / cm³. 3 The following is even more preferable: For example, the above densities range from 0.01 to 10 g / cm³. 3 Preferably, the concentration is 0.03 to 7 g / cm³. 3 It is more preferable that the concentration be 0.05 to 5 g / cm³. 3 It is even more preferable that the concentration be 0.1 to 5 g / cm³. 3 It is even more preferable that the concentration be 0.3 to 5 g / cm³. 3 It is even more preferable that the concentration be 0.5-5 g / cm³. 3 It is even more preferable that the concentration be 1-5 g / cm³. 3 It is particularly preferable that this be the case. The density mentioned above is calculated by measuring the mass and volume of the resin fiber, including surface irregularities and internal space, and then dividing the mass by the volume. For example, a current collector (porous material) can be cut in the planar direction to obtain a rectangular parallelepiped (with the thickness remaining the thickness of the porous material), and the weight of the obtained rectangular parallelepiped can be measured. The value obtained by the following formula can then be considered the density of the current collector (porous material). Density [g / cm 3 ] = (mass of the rectangular prism [g]) / (volume of the rectangular prism [cm³]) 3 ]) In the above formula, the volume of the rectangular prism should be calculated using its length, width, and thickness. The thickness of the rectangular prism can be measured at 10 points using a micrometer, and the average value should be used.

[0045] (active material) The zinc electrode of the present invention contains a zinc-containing substance as an active material. In the present invention, it is preferable that the zinc electrode contains a zinc-containing material as an active material within the pores of the porous current collector. By arranging the active material three-dimensionally within the zinc electrode in this way, a uniform reaction becomes possible, and good performance can be obtained. The zinc-containing substance may be metallic zinc (elementary zinc), an alloy containing zinc, or a compound containing zinc as a constituent element (hereinafter also referred to as a zinc-containing compound). The elemental zinc described above may function as a conductive additive, but it also functions as an active material through oxidation-reduction reactions during the use of the battery. In this specification, elemental zinc, as well as alloys and zinc-containing compounds described later, are referred to as active materials and are distinguished from conductive additives.

[0046] The zinc-containing alloy mentioned above may be a zinc alloy used in (alkaline) dry cell batteries or air batteries, and examples include an alloy of zinc with at least one element selected from the group consisting of magnesium, lithium, manganese, aluminum, bismuth, and indium. The zinc-containing compound mentioned above can be any compound that can be used as an active material. Examples include zinc oxide (e.g., types 1 / 2 / 3 as specified in JIS K1410 (2006)), zinc halogen compounds such as zinc hydroxide, zinc sulfide, tetrahydroxyzinc alkali metal salts, tetrahydroxyzinc alkaline earth metal salts, and zinc chloride, zinc carboxylate compounds such as zinc acetate, zinc compounds such as 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 solid-solve zinc. One or more of these can be used. Among zinc-containing compounds, the above-mentioned zinc compound is preferred, and zinc oxide is more preferred.

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

[0048] The above-mentioned active material only needs to have an aspect ratio (vertical / horizontal) of 1 or more. Furthermore, it is preferable that the aspect ratio (vertical / horizontal) is 10 or less. More preferably, the aspect ratio (vertical / horizontal) is 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, it is preferable that the aspect ratio (vertical / horizontal) is 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 above aspect ratio (vertical / horizontal) can be determined from the shape of the particles observed by SEM. In other words, the active material can be observed using a scanning electron microscope (SEM), and the major and minor axes can be measured for 10 arbitrarily selected particles in the SEM image. The major / minor axis ratio can then be determined, and the simple average of the major / minor axis ratio can be adopted 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 outer perimeter in the image of each individual particle, and the minor axis refers to the distance (length of the line segment) between the two intersection points of the line that passes through the midpoint of the longest line segment (A) and is perpendicular to line segment (A), and the outer perimeter.

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

[0050] The mass percentage of the active material is preferably 50% by mass or more, based on 100% by mass of the total active material and polymer (solid content) contained in the zinc electrode of the present invention. Furthermore, the mass percentage of the active material is preferably 99.9% by mass or less. For example, the mass percentage of the active material is preferably 50 to 99.9% by mass. When the proportion of the active material is within this range, the zinc electrode becomes more sufficient in terms of battery capacity. The mass percentage of the active material is more preferably 55% by mass or more, and even more preferably 60% by mass or more. Furthermore, the mass percentage 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 percentage of the active material is more preferably 55 to 99.5% by mass, and even more preferably 60 to 99% by mass. The polymer referred to hereby means a polymer that may be included in the zinc electrode of the present invention, in addition to the current collector and active material described above, as will be described later. Furthermore, 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 above polymers include hydrocarbon-containing polymers such as polyethylene and polypropylene; aromatic-containing polymers such as polystyrene; ether-containing polymers such as alkylene glycol; hydroxyl-containing polymers such as polyvinyl alcohol and poly(α-hydroxymethylacrylate); amide-containing polymers such as polyamide, nylon, polyacrylamide, polyvinylpyrrolidone, and N-substituted polyacrylamide; imide-containing polymers such as polymaleimide; carboxyl-containing polymers such as poly(meth)acrylic acid, polymaleic acid, polyitaconic acid, and polymethylene glutaric acid; carboxylate-containing polymers represented by poly(meth)acrylic acid, polymaleic acid, polyitaconic acid, and polymethylene glutaric acid; polyvinyl chloride, polyvinylidene fluoride, and polytetrafluoroethylene Examples of polymers include halogen-containing polymers such as ethylene; epoxy resins; polymers containing sulfonate moieties; polymers containing quaternary ammonium salts or quaternary phosphonium salts; ion-exchange polymers used in cation-anion exchange membranes, etc.; conjugated diene polymers such as styrene-butadiene polymers; sugars such as cellulose, cellulose acetate, hydroxyalkylcellulose (e.g., hydroxyethylcellulose), carboxymethylcellulose, chitin, chitosan, and alginic acid (salt); amino group-containing polymers such as polyethyleneimine; polymers containing carbamate group moieties; polymers containing carbamide group moieties; polymers containing epoxy group moieties; polymers containing heterocyclic and / or ionized heterocyclic moieties; polymer alloys; heteroatom-containing polymers; and low molecular weight surfactants. One or more of these can be used. These polymers act as binders for the active material and can prevent crack formation in the zinc electrode. From the viewpoint of excellent binding properties, the above polymers are preferably carboxyl group-containing polymers, carboxylate-containing polymers, and conjugated diene polymers, more preferably carboxylate-containing polymers and conjugated diene polymers, and particularly preferably conjugated diene polymers. 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, alternating radical copolymerization, anionic polymerization, alternating anionic copolymerization, cationic polymerization, alternating cationic copolymerization, graft polymerization, alternating graft copolymerization, living polymerization, alternating living copolymerization, dispersion polymerization, emulsion polymerization, suspension polymerization, ring-opening polymerization, cyclization polymerization, polymerization by light, ultraviolet light or electron beam irradiation, metathesis polymerization, electrolytic polymerization, etc. If these polymers have functional groups, they may be present in the main chain and / or side chains, or they may exist as bonding sites with crosslinking agents. One type of polymer may be used, or two or more types may be used. The above polymer may be crosslinked.

[0053] The above polymer preferably has a weight-average molecular weight of 200 or more. Furthermore, it is preferable that the weight-average molecular weight be 7,000,000 or less. For example, the weight-average molecular weight is preferably between 200 and 7,000,000. This allows for adjustment of the ionic conductivity and flexibility 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 above weight-average molecular weight can be measured as the weight-average molecular weight converted to polystyrene by gel permeation chromatography (GPC) under the following conditions. Equipment: HCL-8220GPC manufactured by Tosoh Corporation Column: TSKgel Super AWM-H Eluent (LiBr·H2O, NMP containing phosphoric acid): 0.01 mol / L

[0054] The mass percentage of the above polymer is preferably 0.1% by mass or more, relative to 100% by mass of the total active material and polymer (solid content) contained in the zinc electrode. More preferably, the mass percentage of the polymer is 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 percentage of the above polymer is preferably 30% by mass or less, relative to the total mass of the active material and polymer (solid content) contained in the zinc electrode (100% by mass). More preferably, the mass percentage of the polymer is 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 percentage of the polymer is preferably 0.1 to 30% by mass with respect to 100% by mass of the total active material and polymer (solid content) contained in the zinc electrode. More preferably, the mass percentage of the polymer is 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 elemental elements or compounds composed of these elements in order to suppress the decomposition side reaction of water that may occur when a water-containing electrolyte is used in a battery such as a secondary battery made using the electrode. 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, Zr, etc.

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

[0057] (Other ingredients) 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. Other components are not particularly limited, but examples include alumina and silica. These other components can function to assist in ionic conductivity, among other things. In the electrode precursor of the present invention, the mass ratio of other components is preferably 1% by mass or less, and more preferably 0.1% by mass or less, relative to 100% by 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 allows for a uniform reaction. Furthermore, the average thickness of the zinc electrode is preferably 10 mm or less. For example, the zinc electrode preferably has an average thickness of 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 this invention can be determined by measuring the thickness at any 10 locations using a micrometer or the like and taking the simple average value.

[0059] The zinc electrode of the present invention is preferably obtained by impregnating a current collector, which includes resin fibers and a conductive layer covering its surface, with a composition containing zinc active material and a polymer. This makes it possible to suitably obtain an electrode in which a zinc-containing material is included as an active material in the pores of a porous current collector. The zinc electrode of the present invention is obtained, for example, by contacting and impregnating the current collector with a slurry-like or paste-like composition (hereinafter also referred to as slurry-like, etc.) containing the active material and polymer according to the present invention. If the composition contains volatile components such as a solvent, it may be dried further. For example, after contacting and impregnating the current collector with the composition, the zinc electrode can be obtained by drying the composition to evaporate some or all of the volatile components such as the solvent, as needed. Rolling may also be performed as needed. When obtaining the zinc electrode of the present invention, reducing the voids by rolling can further suppress the occurrence of cracks caused by the voids. In addition, the film thickness can be made uniform, increasing the electrode density and raising the volumetric capacity density. Furthermore, the impregnation and rolling process may be repeated two or more times.

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

[0061] <Zinc battery> The present invention is also a battery comprising the zinc electrode of the present invention as described above. As described above, the battery of the present invention, by being composed of the zinc electrode of the present invention, can operate sufficiently, has a long lifespan, and has excellent gravimetric 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 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 and oxidizing water, a cobalt-containing compound, an iron-containing compound, a copper-containing compound, a manganese-containing compound, a platinum-containing compound, etc.), nickel compounds such as nickel oxyhydroxide, nickel hydroxide, and cobalt-containing nickel hydroxide, and silver oxide. Among these, for example, it is preferable that the positive electrode active material is a nickel compound. 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 comprising resin fibers and a conductive layer covering its surface, as well as an active material, and this is also one of the preferred embodiments of the present invention. Furthermore, the battery using the zinc electrode of the present invention as the negative electrode may take any form, including a primary battery, a rechargeable secondary battery, the use of mechanical charge (mechanical replacement of the zinc negative electrode), or the use of a third electrode separate from the positive electrode, which is composed of the negative electrode of the present invention and the positive electrode active material described above.

[0063] The electrolyte used in the battery of the present invention can be any electrolyte commonly used in batteries, and is not particularly limited. Examples include 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. One or more of these can be used. Examples of aqueous electrolytes include aqueous potassium hydroxide solution, aqueous sodium hydroxide solution, aqueous lithium hydroxide solution, aqueous zinc sulfate solution, aqueous zinc nitrate solution, aqueous zinc phosphate solution, aqueous zinc acetate solution, and the like. Among these, alkaline electrolytes such as aqueous potassium hydroxide solution, aqueous sodium hydroxide solution, and aqueous lithium hydroxide solution are preferred. The above-mentioned aqueous electrolyte can be used individually or in combination of two or more types. The aqueous electrolyte may also contain the above-mentioned organic solvent-based electrolyte.

[0064] The battery of the present invention may also use a separator. The separator can be any member that separates the positive electrode and the negative electrode, holds the electrolyte, and ensures ion conductivity between the positive and negative electrodes. There are no particular restrictions on the separator, but examples include nonwoven fabrics, filter paper, and microporous membranes. Examples of materials constituting these include hydrocarbon-containing polymers such as polyethylene and polypropylene, polytetrafluoroethylene-containing polymers, polyvinylidene fluoride-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, aromatic ring-containing polymers such as cellophane and polystyrene, polyacrylonitrile-containing polymers, polyacrylamide-containing polymers, polyhalogenated vinyl polymers, and polyamides such as nylon. Examples of polymer materials include polymers containing hydroxyl groups, polymers containing polyimide groups, polymers containing ester groups, polymers containing poly(meth)acrylic acid groups, polymers containing poly(meth)acrylic acid groups, polymers containing hydroxyl groups such as polyisoprennol and poly(meth)allyl alcohol, polymers containing carbonate groups such as polycarbonate, polymers containing ester groups such as polyester, polymers containing carbamate or carbamide groups such as polyurethane, agar, gel compounds, ion-exchange polymers, cyclized polymers, sulfonate-containing polymers, polymers containing quaternary ammonium salts, polymers containing quaternary phosphonium salts, polymers containing cyclic hydrocarbon groups, and polymers containing ether groups. The separator may be an inorganic film having ion conductivity, such as a layered double hydroxide like hydrotalcite, or an organic-inorganic composite film (ion-conducting film) containing the above polymer material and an inorganic compound. The separator may be one of these types, or two or more types may be combined by laminating or other means.

[0065] The battery of the present invention can be obtained using known methods. For example, a separator and a positive electrode can be placed on top of the negative electrode, inserted into a battery cell of an appropriate size, and an electrolyte solution can be introduced into the battery cell to produce a battery.

[0066] The battery of the present invention has a long lifespan and excellent gravimetric energy density, making it suitable for a wide range of applications, from small portable devices to large-scale applications such as automobiles. [Examples]

[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 "mass%".

[0068] (Average particle size of the 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 a dispersion medium (0.2% sodium hexametaphosphate-containing ion-exchanged water) and mixed to form the measurement sample. The volume-based particle size distribution was measured using an Otsuka Electronics Co., Ltd. concentrated particle size analyzer FPAR-1000AS, and the 50% particle size was taken as the average particle diameter of the active material.

[0069] (Aspect ratio of the active material) The aspect ratio of the active material (zinc metal) used in each example was determined as follows. The active material was observed using a scanning electron microscope, and the major and minor axes were measured for 10 arbitrarily selected particles in the electron microscope image. The major / minor axis ratio was determined, and the simple average of the obtained major / minor axis ratios for the 10 particles was defined as the aspect ratio of the active material. The major axis refers to the length of the longest line segment (A) among the line segments connecting two points on the outer perimeter in each particle image, while the minor axis refers to the distance (length of the line segment) between the two intersection points of the line that passes through the midpoint of the longest line segment (A) and is perpendicular to line segment (A), and the outer perimeter.

[0070] (Average fiber diameter of resin fibers) The resin fibers used in each example were cut in the thickness direction with a JEOL Ltd. razor (T5332 TEFLON® COATED), and the resulting cross-sections were observed with a scanning electron microscope. Ten locations were arbitrarily selected in the thickness direction of the cross-sectional image of each fiber constituting the resin fiber, and the major axis was measured at the selected ten locations. The simple average of the ten measured values ​​was calculated, and the resulting value was taken as the average fiber diameter of the resin fiber. As the major axis, the length of the longest line segment connecting two points on the outer circumference of the cross-sectional image in the thickness direction was adopted. The scanning electron microscope used was a Hitachi Technologies Ltd. TM3000 Miniscope.

[0071] (Average thickness of resin fibers) The average thickness of the resin fibers used in each example was determined by measuring the thickness at 10 points using a micrometer and taking the simple average of these measurements.

[0072] (Average thickness of the conductive layer (plating layer)) The current collector (porous material) obtained in each embodiment was cut in the thickness direction with a razor blade manufactured by JEOL Ltd. (T5332 TEFLON® COATED), and the resulting cross-section was observed with a scanning electron microscope. Ten cross-sectional images in the fiber thickness direction where the conductive layer (plating layer) was formed were arbitrarily selected. Next, the thickness of the conductive layer was measured at 10 arbitrarily selected locations in each of the 10 selected cross-sectional images, and the simple average of the 10 obtained measurements was taken as the thickness of the conductive layer in each cross-sectional image. The thickness of the conductive layer in each of the 10 cross-sectional images obtained in this way was then simply averaged, and the resulting value was taken 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. The same procedure was followed for each layer, even when multiple conductive layers existed, such as an intermediate layer and a surface layer.

[0073] (Density of the current collector (porous material)) The current collector (porous material) obtained in each embodiment was cut in the planar direction to a specific size (for example, 40 mm x 40 mm) to obtain a rectangular parallelepiped (with the same thickness as the current collector). The weight of the obtained rectangular parallelepiped was measured, and the value obtained by the following formula was defined as the density of the current collector. Density [g / cm 3 ] = (mass of the rectangular prism [g]) / (volume of the rectangular prism [cm³]) 3 ]) The volume of the rectangular prism in the above formula is a value obtained by calculation using the length, width, and thickness of the rectangular prism, and the thickness of the rectangular prism is the simple average value obtained by measuring the thickness at 10 points using a micrometer.

[0074] (Average thickness of the zinc negative electrode) The average thickness of the zinc negative electrode obtained in each example was determined by measuring the thickness at 10 points using a micrometer and taking the simple average of these measurements.

[0075] (Comparative Example 1) A coating (c1) was obtained by mixing zinc metal (average particle size 75 μm), styrene-butadiene rubber, and sodium polyacrylate in a mass ratio of 98:1:1 and stirring. The obtained coating (c1) was impregnated into a brass mesh prepared as a current collector, then dried and rolled to obtain a zinc anode (c1). The average thickness of the obtained zinc anode (c1) was 140 μm.

[0076] (Example 1) A paint (1) was obtained by mixing zinc metal (average particle size 75 μm), styrene-butadiene rubber, and sodium polyacrylate in a mass ratio of 98:1:1 and stirring. As a current collector, a porous body (1) was obtained in which a mesh made of nylon resin was plated with Cu and Sn in that order, and the surface of the nylon resin was covered with a Cu plating layer (intermediate layer) and a Sn plating layer (outermost layer). A zinc anode (1) was obtained by impregnating a porous body (1) with paint (1), drying it, and rolling it. The average thickness of the obtained zinc anode (1) was 140 μm.

[0077] (Example 2) Paint (2) was obtained by mixing zinc oxide (average particle size 1 μm), polytetrafluoroethylene, and sodium polyacrylate in a mass ratio of 95:4:1 and stirring. A zinc anode (2) was obtained by impregnating the zinc anode (1) obtained in Example 1 with paint (2), drying it, and rolling it. The average thickness of the zinc anode was 250 μm. The gravimetric energy density was calculated for the zinc anodes obtained in each example and comparative example. The results are shown in Tables 1 and 2. The gravitational energy density was calculated as follows: (Method for calculating gravitational energy density) The gravimetric energy density of the zinc anode obtained in each example and comparative example was calculated using the following formula. D = Wa × (Wb / 100) × tc / Wc D: Gravimetric energy density (mAh / g) Wa: Mass of active material per unit volume of zinc negative electrode (g) Wb: Zinc (Zn) content in the active material (mass %) Wc: Mass per unit volume of zinc negative electrode (g) tc: Theoretical capacity of zinc (Zn) 820 (mAh / g) [Table 1]

[0078] (Comparative Example 2) A charge-discharge cycle test was performed using the zinc negative electrode (c1) obtained in Comparative Example 1, a carbon electrode as the positive electrode, a nonwoven fabric and an anion conductor placed between the positive and negative electrodes, and an 8M potassium hydroxide aqueous solution saturated with zinc oxide as the electrolyte. The current value was 1 mA / cm². 2 (Charge / discharge voltage 1.35V, discharge voltage 0.35V) was used. As a result, a cycle life of over 1000 cycles was obtained.

[0079] (Example 3) In Comparative Example 2, a charge-discharge cycle test was performed in the same manner as in Comparative Example 2, except that the zinc anode (1) obtained in Example 1 was used instead of the zinc anode (c1). As a result, a cycle life of more than 1000 cycles was obtained.

[0080] Figure 1 shows the charge-discharge curves at 100 cycles for Example 3 and Comparative Example 2. It was confirmed that even when using a zinc negative electrode with a porous material in which the surface of nylon resin fibers is covered with a Cu plating layer (intermediate layer) and a Sn plating layer (outermost layer) as the current collector, the battery operation was similar to that when using a brass mesh current collector.

[0081] (Example 4) Paint (4) was obtained by mixing 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 and stirring. 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 that order to obtain a porous body (4) in which the surface of the polypropylene resin fibers was covered with a Cu plating layer (intermediate layer, average thickness 5 μm) and a Sn plating layer (outermost layer, average thickness 15 μm). The density of the resulting porous material (4) is 0.48 g / cm³. 3 That was the case. A zinc anode (4) was obtained by impregnating the porous body (4) with paint (4), drying it, and rolling it. The average thickness of the obtained zinc anode (4) was 210 μm. In the zinc negative electrode (4), the mass percentage of the conductive layer was 8.8% by mass, and the mass percentage of the resin fibers was 9.5% by mass.

[0082] The mass ratio of the conductive layer and the mass ratio of the resin fibers in the zinc negative electrode (4) obtained in Example 4 were determined by ICP emission spectroscopy. Specifically, they are as follows: (Mass ratio of the conductive layer in the zinc negative electrode (4)) A predetermined amount of zinc electrode (4) was acid-decomposed using a microwave decomposition device (ETHOS One, manufactured by Milestone General), and the resulting solution was used as the measurement sample. Using the sample, quantitative analysis of Sn and Cu was performed using an ICP emission spectrometer, and the mass ratio of the conductive layer in the zinc negative electrode (4) was determined from the obtained Sn and Cu content. The ICP emission spectrometer used was the ICPE-9000 manufactured by Shimadzu Corporation. (Mass ratio of resin fibers in the 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 emission spectroscopy, and this was taken as the content of the conductive layer. The remainder was taken as the content (mass%) of resin fibers in the porous body (4), and the mass ratio X of the resin fiber content to the conductive layer content (resin fiber content / conductive layer content) was calculated. Next, the content Y (mass %) of the conductive layer in the zinc electrode (4) was determined by ICP emission spectroscopy. Using the obtained X and Y values, the mass percentage of resin fibers in the zinc electrode was determined by the following formula, Z (mass%). Z = Y × X The method for preparing the measurement sample, the microwave resolution apparatus used, and the ICP emission spectrometer were the same as in the case of the mass ratio of the conductive layer in the zinc negative electrode (4).

[0083] (Example 5) In Example 4, instead of a mesh made of polypropylene resin fibers (average fiber diameter 87 μm), a nonwoven fabric (average thickness 90 μm) made of polypropylene resin fibers / high-density polyethylene resin fibers (average fiber diameter 35 μm) and polypropylene ultrafine fibers (average fiber diameter 14 μm), which had been hydrophilized with fluorine gas, was used. 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. In addition, the process was the same as in Example 4 to obtain a zinc anode (5). The average thickness of the obtained zinc anode (5) was 140 μm.

[0084] (Example 6) In Example 4, instead of a mesh made of polypropylene resin fibers (average fiber diameter 87 μm), a nonwoven fabric made of polypropylene resin fibers / polyethylene resin fibers (average fiber diameter 18 μm) (average thickness 90 μm) was used, 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. Except for these changes, a zinc anode (6) was obtained in the same manner as in Example 4. The average thickness of the obtained zinc anode (6) was 140 μm.

[0085] (Example 7) In Example 4, a nonwoven fabric made of vinylon resin fibers (average fiber diameter 10 μm) with an average thickness of 90 μm was used instead of a mesh made of polypropylene resin fibers (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. Otherwise, a zinc anode (7) was obtained in the same manner as in Example 4. The average thickness of the obtained zinc anode (7) was 140 μm.

[0086] (Example 8) In Example 4, instead of using a mesh made of polypropylene resin fibers (average fiber diameter 87 μm), a mesh made of polyphenylene sulfide resin fibers (average fiber diameter 55 μm) (average thickness 100 μm) was used. 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. In addition, the zinc anode (8) was obtained in the same manner as in Example 4. The average thickness of the zinc anode (8) was 150 μm.

[0087] [Table 2]

[0088] The charge-discharge cycle tests described in Comparative Example 2 were performed using the zinc anodes obtained in Examples 4 to 8, and in all cases, the cycle life was 1000 cycles or more. It was confirmed that even when using a zinc anode with a porous material in which the surface of various resin fibers is covered with a Cu plating layer (intermediate layer) and a Sn plating layer (outermost layer) as the current collector, the life was 1000 cycles or more, similar to the case when using a brass mesh current collector.

Claims

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

2. The zinc electrode according to claim 1, wherein the ratio of the average thickness of the outermost 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 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, characterized in that the conductive layer contains a metal.

5. The zinc electrode according to claim 1 or 2, characterized in that 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, characterized in that the zinc electrode contains a zinc-containing substance as an active material within the pores of the porous current collector.

7. A battery characterized by comprising a zinc electrode as described in claim 1 or 2.

Images