Zinc negative electrode mixture, zinc negative electrode, and zinc battery

Abstract

To provide a zinc negative electrode mixture capable of forming a zinc negative electrode that can obtain sufficiently uniform and good electronic conductivity throughout the electrode and can extend the battery life, and a zinc negative electrode and a battery formed using the same.SOLUTION: A zinc negative electrode mixture contains zinc particles, the zinc particles having a tap density of 3.8 g / mL or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a zinc negative electrode composite, a zinc negative electrode, and a zinc battery. More specifically, the present invention relates to a zinc negative electrode composite that can be suitably used for forming negative electrodes of batteries that can be used in many industrial fields, from portable devices to automobiles, and a zinc negative electrode and zinc battery formed using the same. [Background technology]

[0002] Anode composites contain anode active materials and are the materials that form the anode of a battery. Among them, zinc anode composites, which use zinc as the anode active material, have long been researched along with the widespread use of batteries. Batteries that use zinc in the anode include primary batteries, secondary batteries (storage batteries), and air batteries. 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.

[0003] On the other hand, in recent years, the development and improvement of batteries has become increasingly important in many industrial fields, from mobile devices to automobiles, and various new battery systems that are superior primarily in terms of battery performance and their application to secondary batteries have been developed and improved.

[0004] For example, with regard to zinc negative electrodes, a zinc negative electrode mixture containing zinc oxide has been disclosed, characterized in that the zinc oxide particles have a tap density of 0.77 g / mL or more (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-154260 Summary of the Invention [Problem to be solved by the invention]

[0006] Zinc batteries using zinc as the anode have the potential to be suitable for a variety of applications, due to the low cost of the zinc anode, the ability to use aqueous electrolytes, which are highly safe in these cases, and high energy density. However, zinc batteries using zinc as the anode still face challenges, such as achieving good electronic conductivity in the zinc anode, and the challenge of achieving excellent battery performance (charge-discharge cycle characteristics) during repeated charge-discharge cycles in secondary batteries. If these challenges can be resolved, zinc batteries could potentially be used in a wide range of industrial fields, from portable devices to automobiles, as long-life batteries that offer both economy, safety, and performance.

[0007] The present invention has been made in consideration of the above-mentioned current situation, and aims to provide a zinc negative electrode composite that can form a zinc negative electrode that can extend battery life, and a zinc negative electrode and battery formed using the same. [Means for solving the problem]

[0008] The present inventors have conducted extensive research into zinc batteries that can extend battery life. Focusing on zinc particles, the material for zinc anodes, the inventors discovered that forming a zinc anode using zinc particles with a very high tap density can achieve sufficiently uniform and excellent electronic conductivity throughout the electrode compared to conventional zinc anodes. In secondary batteries, local current concentration is suppressed, thereby suppressing local dendrite growth, resulting in excellent charge-discharge cycle characteristics and a longer battery life. Thus, the present inventors have conceived that the above-mentioned problems can be successfully solved by using a zinc anode composite containing zinc particles with a tap density of 3.8 g / mL or more, and have arrived at the present invention.

[0009] That is, the present invention (1) is a zinc negative electrode mixture containing zinc particles, the zinc particles having a tap density of 3.8 g / mL or more.

[0010] The present invention (2) is the zinc negative electrode mixture of the present invention (1), in which the zinc particles contain bismuth and indium.

[0011] The present invention (3) is the zinc negative electrode mixture of the present invention (1) or (2), wherein the zinc particles have a maximum particle size of 100 μm or less.

[0012] The present invention (4) is a zinc negative electrode made using the zinc negative electrode mixture of any one of the present inventions (1) to (3).

[0013] The present invention (5) is a zinc battery comprising the zinc negative electrode of the present invention (4).

[0014] The present invention (6) is the zinc battery of the present invention (5), further comprising an organic / inorganic separator.

[0015] The present invention (7) is the zinc battery of the present invention (6), in which the zinc negative electrode is wrapped in a bag-shaped organic / inorganic separator. [Effects of the Invention]

[0016] The zinc negative electrode mixture of the present invention has the above-mentioned composition, and can provide a zinc negative electrode that can obtain sufficiently uniform and good electronic conductivity throughout the electrode and can extend the battery life. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is an image diagram showing the state of the current collector during charging and discharging in the zinc negative electrode according to the present invention. [Figure 2] FIG. 2 is an image showing the state of the current collector during charging and discharging in a conventional zinc negative electrode. [Figure 3] FIG. 3 is a graph showing the discharge capacity / charge capacity (%) versus the number of cycles for each of the zinc batteries of Examples 1 to 3 and Comparative Examples 1 and 2. [Figure 4] FIG. 4 is a graph showing the discharge capacity / theoretical capacity (%) of the zinc batteries of Examples 1 and 2 when discharged after a 1-hour rest and when discharged after a 24-hour rest. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be described in detail below. It should be noted that a combination of two or more of the individual preferred configurations of the present invention described below is also a preferred embodiment of the present invention.

[0019] <Zinc negative electrode mixture> (zinc particles) The zinc negative electrode composite of the present invention contains zinc particles having a tap density of 3.8 g / mL or more. The zinc particles are composed of zinc particles and / or zinc alloy particles. The use of a zinc negative electrode formed from a zinc negative electrode composite containing such zinc particles can extend the life of a battery. The reasons for this are thought to be as follows.

[0020] That is, if the tap density of zinc particles contained in the zinc negative electrode composite is high, a layer with high density and many contact points between zinc particles can be easily formed on the current collector. Because the zinc particles also function as a conductive additive, good electronic conductivity is ensured within the zinc active material, and the electronic conductive network can be sufficiently maintained even during discharge. (For example, see Figure 1. In Figure 1, a layer with high density of zinc particles 2 can be formed on current collector 1, and the zinc particles 2 ensure electronic conductivity even during discharge.) This allows for sufficiently uniform and good electronic conductivity to be obtained throughout the electrode. In secondary batteries, local current concentration is suppressed, which suppresses local dendrite growth and improves charge-discharge cycle characteristics. On the other hand, if the tap density of the zinc particles contained in the zinc negative electrode composite is small, the density of the zinc particles will be high and a layer with many contact points between the zinc particles will not be able to be formed on the current collector, and good electronic conductivity will not be sufficiently ensured within the zinc active material, which may make it impossible to maintain an electronic conductive network during discharge (for example, see Figure 2. In Figure 2, the density of zinc particles 2 is high and a layer with many contact points between the zinc particles will not be able to be formed on current collector 1, and electronic conductivity due to zinc particles 2 is lost near current collector 1 during discharge).

[0021] Furthermore, if the tap density of the zinc particles contained in the zinc negative electrode mixture is high, a high-density active material layer can be formed on the current collector, which minimizes contact between the active material and the electrolyte in the active material layer when the battery is in a charged state. Furthermore, the gaps between the zinc particles (other conductive additives, binders, thickeners, etc. may be present between the particles) and between the zinc particles and the current collector are small, which prevents, for example, excessive penetration of water contained in the aqueous electrolyte into the current collector. As a result, it is believed that the above-mentioned problems can be alleviated and battery performance can be improved.

[0022] The tap density of the zinc particles is preferably 3.9 g / mL or more, more preferably 4 g / mL or more, and is preferably 20 g / mL or less, more preferably 15 g / mL or less, even more preferably 10 g / mL or less, even more preferably 8 g / mL or less, even more preferably 6 g / mL or less, even more preferably 5 g / mL or less, and particularly preferably 4.5 g / mL or less. The tap density is measured by the method described in the examples.

[0023] Particles having a tap density in the above range can be obtained, for example, by mixing zinc particles having different average particle sizes or aspect ratios, or by adjusting the content of metal elements such as bismuth and magnesium in the zinc alloy particles.

[0024] As described above, the zinc particles having a tap density of 3.8 g / mL or more are composed of zinc particles and / or zinc alloy particles. The metal element other than zinc contained in the zinc alloy particles is preferably at least one selected from the group consisting of bismuth, indium, aluminum, magnesium, iron, copper, lead, nickel, cobalt, and manganese. The zinc alloy particles more preferably contain bismuth or indium, and particularly preferably contain bismuth and indium.

[0025] This makes it possible to further suppress the side reaction of water decomposition and the accompanying generation of hydrogen gas that may occur when a water-containing electrolyte solution is used in a battery such as a secondary battery. The mass proportion of each of the metal elements other than zinc in the zinc alloy particles is preferably 50 ppm or more, more preferably 100 ppm or more, even more preferably 200 ppm or more, and particularly preferably 300 ppm or more, relative to the zinc alloy particles, and each mass proportion is preferably 10,000 ppm or less, more preferably 5,000 ppm or less, even more preferably 3,000 ppm or less, and particularly preferably 2,000 ppm or less, relative to the zinc alloy particles. The zinc alloy particles containing bismuth and indium may mean that the zinc particles contain zinc alloy particles containing bismuth and indium, or may contain zinc alloy particles containing bismuth and zinc alloy particles containing indium. The zinc particles may consist only of zinc alloy particles containing bismuth and indium, or may consist only of zinc alloy particles containing bismuth and zinc alloy particles containing indium.

[0026] In the zinc negative electrode composite of the present invention, the mass ratio of bismuth in the zinc alloy particles is preferably 50 ppm or more, more preferably 100 ppm or more, even more preferably 200 ppm or more, and particularly preferably 300 ppm or more, relative to the zinc alloy particles. The mass proportion of the bismuth relative to the zinc alloy particles is preferably 10,000 ppm or less, more preferably 5,000 ppm or less, even more preferably 3,000 ppm or less, and particularly preferably 2,000 ppm or less.

[0027] In the zinc negative electrode composite of the present invention, the mass ratio of indium in the zinc alloy particles is preferably 50 ppm or more, more preferably 100 ppm or more, even more preferably 200 ppm or more, and particularly preferably 300 ppm or more, relative to the zinc alloy particles. The mass proportion of indium relative to the zinc alloy particles is preferably 10,000 ppm or less, more preferably 5,000 ppm or less, even more preferably 3,000 ppm or less, and particularly preferably 2,000 ppm or less.

[0028] The mass ratio of bismuth to indium in the zinc alloy particles is preferably 1:10 to 10:1, more preferably 1:5 to 5:1, even more preferably 1:2 to 2:1, and particularly preferably 2:3 to 3:2. The mass proportion of bismuth, indium, etc. in the zinc alloy particles can be determined by ICP or by chemical analysis, and it is preferable to use the value determined by ICP.

[0029] The following describes the preferred mass ratio of metal elements other than zinc based on the zinc particles. The mass ratio of each of the metal elements other than zinc in the zinc particles is preferably 50 ppm or more, more preferably 100 ppm or more, even more preferably 200 ppm or more, and particularly preferably 300 ppm or more, relative to the zinc particles, and each mass ratio is preferably 10,000 ppm or less, more preferably 5,000 ppm or less, even more preferably 3,000 ppm or less, and particularly preferably 2,000 ppm or less, relative to the zinc particles.

[0030] In the zinc negative electrode composite of the present invention, the mass proportion of bismuth in the zinc particles is preferably 50 ppm or more, more preferably 100 ppm or more, even more preferably 200 ppm or more, and particularly preferably 300 ppm or more, relative to the zinc particles. The mass proportion of the bismuth relative to the zinc particles is preferably 10,000 ppm or less, more preferably 5,000 ppm or less, even more preferably 3,000 ppm or less, and particularly preferably 2,000 ppm or less.

[0031] In the zinc negative electrode composite of the present invention, the mass ratio of indium in the zinc particles is preferably 50 ppm or more, more preferably 100 ppm or more, even more preferably 200 ppm or more, and particularly preferably 300 ppm or more, relative to the zinc particles. The mass proportion of the indium relative to the zinc particles is preferably 10,000 ppm or less, more preferably 5,000 ppm or less, even more preferably 3,000 ppm or less, and particularly preferably 2,000 ppm or less.

[0032] The mass ratio of bismuth to indium in the zinc particles is preferably 1:10 to 10:1, more preferably 1:5 to 5:1, even more preferably 1:2 to 2:1, and particularly preferably 2:3 to 3:2. The mass proportion of bismuth, indium, etc. in the zinc particles can be determined by ICP or by chemical analysis, and it is preferable to use the value determined by ICP.

[0033] In addition, examples of the shape of zinc particles having a tap density of 3.8 g / mL or more include fine powder, powder, granules, fine particles, scales, fibers, granules, polyhedrons, rods, rectangular parallelepipeds, cylindrical shapes, and shapes containing curved surfaces. The above shape can be confirmed by SEM (scanning electron microscope).

[0034] The zinc particles having a tap density of 3.8 g / mL or more preferably have a maximum particle size of 100 μm or less, more preferably 75 μm or less. Such a small maximum particle size increases the specific surface area of ​​the zinc particles, thereby further improving the battery characteristics. The maximum particle size is preferably 20 μm or more. When the maximum particle size is 20 μm or more, self-discharge tends to be more easily suppressed. For the same reason, the maximum particle size is more preferably 25 μm or more, even more preferably 32 μm or more, even more preferably 38 μm or more, still more preferably 45 μm or more, even more preferably 53 μm or more, and particularly preferably 63 μm or more. Such a large maximum particle size reduces the specific surface area of ​​the zinc particles, making it possible to more effectively prevent self-discharge.

[0035] The maximum particle size of the zinc particles can be determined by subjecting a sample (zinc particles) to the following method, and determining the smallest mesh opening through which the entire sample passes as the maximum particle size of the sample. The sample (zinc particles) was sieved using JIS test sieves: 30 mesh (opening 500 μm), 36 mesh (opening 425 μm), 42 mesh (opening 355 μm), 50 mesh (opening 300 μm), 60 mesh (opening 250 μm), 70 mesh (opening 212 μm), 83 mesh (opening 180 μm), 93 mesh (opening 160 μm), 100 mesh (opening 150 μm), 119 mesh (opening 125 μm), 140 Sieving is performed using mesh (opening size 106 μm), 149 mesh (opening size 100 μm), 166 mesh (opening size 90 μm), 200 mesh (opening size 75 μm), 235 mesh (opening size 63 μm), 280 mesh (opening size 53 μm), 330 mesh (opening size 45 μm), 390 mesh (opening size 38 μm), 440 mesh (opening size 32 μm), 500 mesh (opening size 25 μm), and 635 mesh (opening size 20 μm). For example, if a sample (zinc particles) entirely passes through a 200 mesh (75 μm opening) sieve, but some particles do not pass through a 235 mesh (63 μm opening) sieve, the maximum particle size of the sample is considered to be 75 μm.

[0036] The zinc particles having a tap density of 3.8 g / mL or more have a specific surface area of ​​0.0001 m 2 / g or more. The specific surface area is more preferably 0.0003 m 2 / g or more, more preferably 0.0005m 2 / g or more. When the specific surface area of ​​zinc particles is large, the battery characteristics are further improved. 2 / g or less, and 0.5m 2 / g or less is more preferable. When the specific surface area of ​​the zinc particles is small in this way, the occurrence of self-discharge can be more sufficiently prevented. The specific surface area is the specific surface area measured by the BET method (BET specific surface area), and can be measured by the BET method using a commercially available specific surface area measuring device and nitrogen gas as an inert gas. Note that particles having a specific surface area in the above range can be produced, for example, by nanoparticleizing the particles or by selecting the preparation conditions during particle production to create irregularities on the particle surface.

[0037] The zinc particles having a tap density of 3.8 g / mL or more may have an aspect ratio (length / width) of 1 or more. The aspect ratio (length / width) is preferably 8 or less. The aspect ratio (length / width) is more preferably 5 or less, even more preferably 2 or less, and particularly preferably 1.5 or less. The aspect ratio (length / width) can be determined from the shape of the particles observed by SEM.

[0038] In the zinc negative electrode composite of the present invention, the proportion of the total amount of zinc particles having a tap density of 3.8 g / mL or more is preferably 0.1% by mass or more, more preferably 1% by mass or more, even more preferably 5% by mass or more, and particularly preferably 10% by mass or more, relative to 100% by mass of the solid content of the zinc negative electrode composite. Also, this proportion is preferably 99.9% by mass or less, more preferably 99% by mass or less, even more preferably 90% by mass or less, even more preferably 80% by mass or less, and particularly preferably 50% by mass or less.

[0039] The zinc negative electrode composite of the present invention may contain zinc particles having a tap density of 3.8 g / mL or more, and may also contain other components acting as active materials and / or other components acting as conductive additives. The proportion of the total amount of zinc particles having a tap density of 3.8 g / mL or more relative to the total amount (100 mass%) of components acting as active materials contained in the zinc negative electrode composite is preferably 5 mass% or more, more preferably 10 mass% or more, and even more preferably 20 mass% or more. By including zinc particles having a tap density of 3.8 g / mL or more within this range relative to the total amount of components acting as active materials, the effects of the present invention are further enhanced. The total amount of components acting as active materials contained in the zinc negative electrode composite may be zinc particles having a tap density of 3.8 g / mL or more.

[0040] (Active materials other than zinc particles) The other active material components include zinc-containing compounds other than zinc particles. Examples of such zinc-containing compounds include zinc oxide, conductive zinc oxide, zinc hydroxide, zinc halides such as zinc sulfide, tetrahydroxyzinc alkali metal salts, tetrahydroxyzinc alkaline earth metal salts, and zinc fluoride, zinc carboxylate compounds, zinc borate, zinc phosphate, zinc hydrogen phosphate, zinc silicate, zinc aluminate, carbonates, bicarbonates, nitrates, and sulfates; organic zinc compounds; and zinc compound salts. Among these, zinc oxide, conductive zinc oxide, zinc hydroxide, tetrahydroxyzinc alkali metal salts, tetrahydroxyzinc alkaline earth metal salts, zinc halides such as zinc fluoride, zinc carboxylate compounds, zinc borate, zinc phosphate, zinc silicate, zinc aluminate, and zinc carbonate are more preferred.

[0041] In the zinc negative electrode mixture of the present invention, the mass ratio (mass ratio) of zinc particles to zinc-containing compounds other than zinc particles is preferably 1:99 to 100:0, more preferably 2:98 to 80:20, even more preferably 3:97 to 50:50, and particularly preferably 5:95 to 35:65.

[0042] (Conductive additive) The zinc anode composite of the present invention may further contain a conductive additive other than zinc particles. Examples of such conductive additives include conductive carbon, conductive ceramic, metals (single or alloy) such as copper, brass, nickel, silver, bismuth, indium, lead, and tin, and oxides and hydroxides containing at least one of these metal elements (preferably oxides and hydroxides containing one of these metal elements as the main component [i.e., the metal elements with the largest amount of substance]). Examples of conductive carbon include graphite, glassy carbon, amorphous carbon, graphitizable carbon, non-graphitizable carbon, carbon nanofoam, activated carbon, graphene, nanographene, graphene nanoribbons, fullerenes, carbon black, carbon fiber, fibrous carbon, carbon nanotubes, carbon nanohorns, vulcan, ketjen black, and acetylene black. Among these, graphite, graphitizable carbon, non-graphitizable carbon, graphene, carbon black, carbon fiber, fibrous carbon, carbon nanotube, vulcan, ketjen black, and acetylene black are preferred.

[0043] When a conductive additive other than zinc particles is blended into the zinc negative electrode composite of the present invention, the blending amount of the conductive additive is preferably 0.001 to 99.9 mass% relative to 100 mass% of the solids content of the zinc negative electrode composite. Note that zinc particles and other active materials that also function as conductive additives are excluded from the calculation of the blending amount of the conductive additive. When the blending amount of the conductive additive is within this range, the zinc negative electrode formed from the zinc negative electrode composite exhibits better battery performance when used as the negative electrode of a battery.

[0044] (polymer) The zinc negative electrode mixture of the present invention preferably contains a polymer in addition to the above-mentioned active material and conductive additive. 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 typified by poly(meth)acrylate, polymaleate, polyitaconate, and polymethylene glutarate, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, and the like. Examples of suitable materials include halogen-containing polymers such as ethylene; epoxy resins; sulfonate-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-containing polymers such as polyethyleneimine; carbamate-containing polymers; carbamide-containing polymers; epoxy-containing polymers; heterocyclic and / or ionized heterocyclic 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 zinc anodes.

[0045] 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 chains, or as bonding sites with a crosslinker. These polymers may be used alone or in combination of two or more types. The polymer may be crosslinked.

[0046] The polymer preferably has a weight-average molecular weight of 200 to 7,000,000. This makes it possible to adjust the ionic conductivity, flexibility, etc. of the resulting zinc negative electrode. 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 weight average molecular weight converted into polystyrene by gel permeation chromatography (GPC) under the following conditions. Apparatus: Tosoh Corporation HCL-8220GPC Column: TSKgel Super AWM-H Eluent (LiBr·H2O, NMP containing phosphoric acid): 0.01 mol / L

[0047] The mass proportion of the polymer is preferably 0.1 to 30 mass% relative to 100 mass% of the solid content of the zinc negative electrode mixture of the present invention, more preferably 0.5 to 15 mass%, even more preferably 1 to 12 mass%, and particularly preferably 2 to 10 mass%.

[0048] (Other ingredients) The zinc negative electrode mixture of the present invention may contain, in addition to zinc particles, an active material, a conductive aid, and a polymer, and may further contain one or more other components other than these. The other components are not particularly limited, but examples thereof include alumina, silica, etc. The other components can function to assist ion conductivity, etc. In the zinc negative electrode mixture of the present invention, the mass proportion of other components is preferably 1 mass % or less, and more preferably 0.1 mass % or less, relative to 100 mass % of the active material.

[0049] The zinc negative electrode composite of the present invention can be prepared by mixing the above zinc particles with other active materials, conductive additives, polymers, and other components as needed. Mixing can be performed using a mixer, blender, kneader, bead mill, ready mill, ball mill, or the like. During mixing, an organic solvent such as water, methanol, ethanol, propanol, isopropanol, tetrahydrofuran, or N-methylpyrrolidone, or a mixture of water and an organic solvent, may be added. After mixing, the particles may be sieved to achieve a desired particle size. Mixing can be performed using either a wet method, in which a liquid component such as water or an organic solvent is added to the solid components, or a dry method, in which only the solid components are used without adding any liquid components. When mixing is performed using a wet method, the liquid components such as water or an organic solvent may be removed by drying after mixing. Mixing can also be performed using a combination of a wet method and a dry method.

[0050] <Zinc anode> The present invention also relates to a zinc negative electrode made using the zinc negative electrode mixture of the present invention. The zinc negative electrode usually comprises a current collector and an active material layer formed on the current collector using the zinc negative electrode mixture.

[0051] The zinc negative electrode can be prepared, for example, by the following method. The zinc negative electrode composite (mixture) of the present invention obtained by the above-mentioned method is kneaded with a solvent such as water or an organic solvent such as N-methylpyrrolidone using a kneader or the like. Next, the resulting slurry or paste mixture is applied to a current collector by coating, pressing, adhering, etc., so as to achieve as uniform a film thickness as possible.

[0052] Examples of the current collector include (electrolytic) copper foil, copper mesh (expanded metal), foamed copper, punched copper, copper alloys such as brass, brass foil, brass mesh (expanded metal), foamed brass, punched brass, nickel foil, corrosion-resistant nickel, nickel mesh (expanded metal), punched nickel, metallic zinc, corrosion-resistant metallic zinc, zinc foil, zinc mesh (expanded metal), (punched) steel plate, nonwoven fabrics imparted with conductivity; copper alloys such as (electrolytic) copper foil, copper mesh (expanded metal), foamed copper, punched copper, and brass, brass foil, brass mesh (expanded metal), foamed brass, punched brass, nickel foil, and corrosion-resistant nickel. Nickel, nickel mesh (expanded metal), punched nickel, metallic zinc, corrosion-resistant metallic zinc, zinc foil, zinc mesh (expanded metal), (punched) steel plate, non-woven fabric; (electrolytic) copper foil plated with Ni, Zn, Sn, Pb, Hg, Bi, In, Tl, brass, etc., copper mesh (expanded metal), foamed copper, punched copper, copper alloys such as brass, brass foil, brass mesh (expanded metal), foamed brass, punched brass, nickel foil, corrosion-resistant nickel, nickel mesh (expanded metal), punched nickel, metallic zinc, corrosion-resistant metallic zinc, zinc foil, zinc mesh (expanded metal), (punched) steel plate, non-woven fabric; silver; materials used as current collectors and containers in electrochemical elements.

[0053] The above-mentioned slurry or paste mixture may be coated or pressed onto one side of a current collector, or may be coated, pressed, or adhered onto both sides or the entire surface. After coating, the current collector is dried at 0 to 250°C. The drying temperature is more preferably 15 to 200°C. The drying time is preferably 4 to 48 hours. Drying may be performed by vacuum drying. After drying, the current collector is preferably pressed using a roll press or the like at a pressure of 0.01 to 20 tons. The pressing pressure is more preferably 0.1 to 15 tons. A zinc negative electrode (zinc composite electrode) having an active material layer obtained in this manner suppresses current concentration and water decomposition within the zinc negative electrode, particularly when used as a negative electrode for a secondary battery, thereby minimizing deterioration of the zinc negative electrode due to dendrite growth and the generation of hydrogen and oxygen.

[0054] The average thickness of the active material layer according to the present invention is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 30 μm or more, and particularly preferably 50 μm or more. The average thickness of the active material layer is, for example, preferably 5 mm or less, more preferably 2 mm or less, and even more preferably 1 mm or less. The average thickness of the zinc negative electrode of the present invention is preferably 10 μm to 10 mm, more preferably 50 μm to 5 mm, and even more preferably 100 μm to 2 mm. The average thickness can be calculated by measuring at any 10 points with a micrometer.

[0055] The zinc negative electrode of the present invention may be integrated with a separator, further comprising an organic / inorganic separator as described below. For example, a preferred embodiment of the present invention is one in which the zinc negative electrode of the present invention is wrapped in a bag-shaped organic / inorganic separator.

[0056] <Zinc battery> A zinc battery comprising the zinc negative electrode of the present invention also constitutes one aspect of the present invention. The battery of the present invention may further comprise a positive electrode and an aqueous electrolyte. The battery of the present invention may further comprise a separator. The separator is a component that separates the positive electrode and the negative electrode, retains the electrolyte, and ensures ionic conductivity between the positive electrode and the negative electrode. In the case of a secondary battery using a zinc negative electrode, the separator also functions to suppress deterioration of the zinc negative electrode active material and the formation of dendrites, moisten the positive and negative electrodes, and prevent liquid drying up.

[0057] (separator) The separator is not particularly limited, and examples thereof include nonwoven fabrics, filter paper, microporous membranes, etc. Materials constituting these 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, 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 or 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 separator (ion-conductive membrane) containing the polymer material and an inorganic compound. The inorganic compound in the organic-inorganic separator is preferably, for example, a metal oxide, hydroxide, sulfate, or layered double hydroxide. The inorganic compound is preferably in the form of particles. Separators such as organic / inorganic separators may further contain a binder such as a conjugated diene polymer, or may have a porous support (porous substrate) such as a nonwoven fabric, woven fabric, or microporous film made of a polyolefin polymer, etc. The separator may be one of these, or may be a combination of two or more of them, such as by laminating them.

[0058] As described above, the zinc battery of the present invention is preferably configured to include an organic / inorganic separator. In particular, it is more preferable that the zinc negative electrode is wrapped in a bag-shaped organic / inorganic separator. In other words, it is more preferable that the active material and / or active material layer in the zinc negative electrode is wrapped in a bag-shaped organic / inorganic separator.

[0059] The zinc negative electrode being wrapped in a bag-shaped organic / inorganic separator means that when a zinc battery is formed using the zinc negative electrode, at least a portion of the active material layer containing the active material is wrapped in a bag-shaped organic / inorganic separator so that the active material and the electrolyte do not come into direct contact with each other, i.e., the active material layer is contained in and wrapped by the bag-shaped organic / inorganic separator. Among these, when a zinc battery is formed using the zinc negative electrode, it is preferable that the active material layer containing the active material is wrapped in a bag-shaped organic / inorganic separator so that substantially all of the active material does not come into direct contact with the electrolyte. When a zinc battery is formed using the zinc negative electrode, the active material and the electrolyte interact via the organic / inorganic separator, allowing the battery to undergo an electrochemical reaction.

[0060] The active material being wrapped in a bag-shaped organic / inorganic separator means that each active material constituting a part or the whole of the active material layer is wrapped in a bag-shaped organic / inorganic separator. An active material layer in which an active material is wrapped in a bag-shaped organic / inorganic separator is formed, for example, by wrapping the active material to form the active material layer in a bag-shaped organic / inorganic separator in advance, and then using the active material wrapped in the bag-shaped organic / inorganic separator to form a layer. Here, the active material may be wrapped in an organic / inorganic separator that is bag-shaped and contains only the active material, or may be wrapped in an organic / inorganic separator that is bag-shaped and contains the active material and active material layer constituent materials other than the active material, such as a conductive aid or other additives.

[0061] The active material layer being wrapped in a bag-shaped organic / inorganic separator means that the active material layer formed on the electrode is partially or entirely wrapped in the organic / inorganic separator. The active material layer wrapped in a bag-shaped organic / inorganic separator is typically formed by forming an active material layer using an active material and, if necessary, active material layer constituent materials other than the active material, and then wrapping the active material layer in a bag-shaped organic / inorganic separator. In one preferred embodiment of the present invention, the entire active material layer formed on the zinc negative electrode is wrapped in a bag-shaped organic / inorganic separator. Furthermore, when the active material layer in the zinc negative electrode is divided into several units, each unit may be wrapped in a bag-shaped organic / inorganic separator. When the active material layer is wrapped in a bag-shaped organic / inorganic separator, it can also be said that each unit containing a certain amount of active material is wrapped in a bag-shaped organic / inorganic separator. The number of units may be two or more.

[0062] In addition, when the active material layer of the zinc negative electrode is wrapped in a bag-shaped organic / inorganic separator, when at least one surface of the active material layer constituting the zinc negative electrode is bonded to the current collector layer, it is sufficient that part or all of the remaining surface of the active material layer that is not bonded to the current collector is wrapped in a bag-shaped organic / inorganic separator, and it is preferable that all of the remaining surface is wrapped in a bag-shaped organic / inorganic separator. Furthermore, in terms of significantly exhibiting the effects of the present invention, it is more preferable that the active material layer has multiple surfaces facing the electrolyte and these multiple surfaces are wrapped in bag-shaped organic / inorganic separators.

[0063] (positive electrode) The positive electrode is formed using a positive electrode composite. The positive electrode composite is composed of a positive electrode active material. The positive electrode active material can be any material commonly used as a positive electrode active material for primary batteries or secondary batteries, and is not particularly limited. Examples of the positive electrode active material 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 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 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 be a nickel compound.

[0064] (electrolyte) The electrolyte is not particularly limited as long as it is one that is commonly used as an electrolyte for batteries. Examples include water-containing electrolytes and organic solvent-based electrolytes, with water-containing electrolytes being preferred. A water-containing electrolyte refers to an electrolyte that uses only water as the electrolyte raw material (aqueous electrolyte) or an electrolyte that uses a solution obtained by adding an organic solvent to water as the electrolyte raw material. Examples of the aqueous electrolyte 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. Although the electrolyte is not particularly limited, when using an aqueous electrolyte, a compound that generates hydroxide ions that are responsible for ionic conduction in the system is preferred. In particular, potassium hydroxide aqueous solution is preferred from the viewpoint of ionic conductivity. The aqueous electrolytes can be used alone or in combination. The water-containing electrolyte may also contain an organic solvent used in organic solvent-based electrolytes. Examples of the organic solvent 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, fluorine-containing polyethylene glycols, etc. One or more kinds of electrolytic solutions can be used.

[0065] The concentration of the electrolyte solution is preferably 0.01 to 20 mol / L. By using an electrolyte solution with such a concentration, good battery performance can be achieved. Furthermore, the concentration is more preferably 0.1 to 18 mol / L.

[0066] In a battery using the zinc negative electrode of the present invention, a water-containing electrolyte can be used as the electrolyte, resulting in a highly safe battery. Thus, a battery constructed using the zinc negative electrode, positive electrode, separator, and aqueous electrolyte of the present invention also constitutes one aspect of the present invention. The battery of the present invention may contain one or more of these essential components. Furthermore, it is particularly preferable that the battery of the present invention is a secondary battery, which can exhibit the effect of improving battery performance (charge-discharge cycle characteristics) during repeated charge and discharge. Even when the battery of the present invention is a primary battery, it can exhibit the effect of achieving sufficiently uniform and good electronic conductivity throughout the electrode, thereby extending the battery life.

[0067] The form of a battery using the zinc negative electrode of the present invention may be any of a primary battery, a rechargeable secondary battery, a mechanical charge (mechanical replacement of the zinc negative electrode), or a third electrode separate from the positive electrode composed of the zinc negative electrode of the present invention and the positive electrode active material as described above.

[0068] 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.

[0069] 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. [Example]

[0070] 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 mass" and "%" means "% by mass."

[0071] (Tap density measurement method) Weigh out 20 g of zinc particles. Gently place the weighed sample into a 10 ml measuring cylinder, ensuring that the surface of the sample is horizontal. Tap the 10 ml measuring cylinder containing the sample 700 times. After tapping, level the surface of the sample and read the volume on the scale of the 10 ml measuring cylinder. Tap density ρt = M (mass of zinc particles) / V (volume of zinc particles after tapping)

[0072] Example 1 A mixture of 22 parts by mass of powdered zinc particles (1) (tap density: 4.01 g / mL, maximum particle size: 63 μm, Bi content: 330 ppm, In content: 320 ppm), 48 parts by mass of zinc oxide (Mitsui Mining & Smelting Co., Ltd.), 5 parts by mass of polytetrafluoroethylene (Daikin Industries, Ltd.), 20 parts by mass of water, and 5 parts by mass of ethanol (99.5%, Wako Pure Chemical Industries, Ltd.) was kneaded to obtain a zinc negative electrode composite (1). The resulting zinc negative electrode composite (1) was hand-rolled into a 0.4 mm thick sheet, attached to both sides of a brass mesh current collector, pressed with a flat press, and dried to obtain a zinc electrode composite electrode (1) (thickness: 0.6 mm). A battery was fabricated using the zinc electrode composite electrode, a nickel electrode as the positive electrode, a nonwoven fabric and an organic / inorganic separator between the positive and negative electrodes, and an 8 M potassium hydroxide aqueous solution saturated with zinc oxide as the electrolyte, and a charge / discharge cycle test was performed. The current value is 8.3mA / cm 2 (Charge and discharge times: 1 hour each) As a result, a cycle life of more than 200 cycles was obtained.

[0073] (Examples 2 and 3, Comparative Examples 1 and 2) Zinc negative electrode composites (2) to (3), (c1) to (c2) were obtained in the same manner as in Example 1, except that 22 parts by mass of the powdered zinc particles shown in Table 1 were used instead of 22 parts by mass of the powdered zinc particles (1). Furthermore, zinc negative electrode composites obtained were used instead of the zinc negative electrode composite (1), and zinc electrode composite electrodes (2) to (3), (c1) to (c2) were obtained in the same manner as in Example 1. Instead of the zinc electrode composite electrode (1), the zinc electrode composite electrodes obtained in each Example and Comparative Example were used, and batteries were fabricated in the same manner as in Example 1, and a charge-discharge cycle test was performed. The results (cycle life) are shown in Table 2. Among the evaluation results of the zinc particles used in each of the Examples and Comparative Examples shown in Table 1, the tap density is a value measured by the above-mentioned (tap density measurement method). The maximum particle size, Bi content, and In content are based on the information sources of the following providers. Provided by: Grillo-Werke Aktiengesellschaft (Grillo-Werke GmbH) Source: CERTIFICATE OF ANALYSIS

[0074] [Table 1]

[0075] [Table 2]

[0076] FIG. 3 is a graph showing the discharge capacity / charge capacity (%) versus the number of cycles for each of the zinc batteries of Examples 1 to 3 and Comparative Examples 1 and 2. 4 is a graph showing the discharge capacity / theoretical capacity (%) of the zinc batteries of Examples 1 and 2 when discharged after a 1-hour rest and when discharged after a 24-hour rest, respectively. The discharge current value was 1 mA / cm 2 It was found that the zinc batteries of Example 1 and Example 2 sufficiently suppressed self-discharge, but the zinc battery of Example 1 suppressed self-discharge more than the zinc battery of Example 1. This is thought to be because the maximum particle size and surface area of ​​the zinc particles used were in more preferable ranges.

[0077] The results of the examples revealed the following. A zinc negative electrode was formed using a zinc negative electrode composite containing zinc particles with a tap density of 3.8 g / mL or higher. It was demonstrated that a storage battery constructed using this negative electrode exhibited excellent charge-discharge cycle characteristics, suppressing deterioration in battery performance even after repeated charge-discharge cycles. This is believed to be due to the zinc negative electrode being able to achieve sufficiently uniform and good electronic conductivity throughout the electrode, which in secondary batteries suppresses local current concentration and therefore local dendrite growth. Furthermore, in primary batteries, the ability to achieve sufficiently uniform and good electronic conductivity throughout the electrode is believed to extend battery life. [Explanation of symbols]

[0078] 1: Current collector 2: Zinc particles 3: Zinc oxide

Claims

1. A zinc negative electrode mixture containing zinc particles, The zinc particles have a tap density of 3.8 g / mL or more. A zinc negative electrode mixture characterized by:

2. The zinc particles contain bismuth and indium The zinc negative electrode mixture according to claim 1 .

3. The zinc particles have a maximum particle size of 100 μm or less.

3. The zinc negative electrode mixture according to claim 1 or 2.

4. The zinc negative electrode mixture according to claim 1 or 2 is used. A zinc negative electrode characterized by:

5. A zinc negative electrode according to claim 4. A zinc battery characterized by:

6. Further, organic / inorganic separators are included.

6. The zinc battery according to claim 5.

7. The zinc negative electrode is wrapped in a bag-shaped organic / inorganic separator.

7. The zinc battery according to claim 6.

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