Negative electrode for zinc battery, method for producing same, zinc battery, and negative electrode

Abstract

The invention relates to a negative electrode for a zinc battery, the zinc battery, a method for manufacturing the negative electrode for the zinc battery, and a negative electrode material for the zinc battery. The negative electrode for a zinc cell has a negative electrode mixture containing zinc oxide, and the ratio (I002 / I101) of the peak intensity (I002) derived from the (002) plane of zinc oxide to the peak intensity (I101) derived from the (101) plane of zinc oxide in the X-ray diffraction pattern of the negative electrode mixture is 0.4 or more.

Description

Technical Field

[0001] This invention relates to a negative electrode for zinc batteries, a zinc battery, a method for manufacturing a negative electrode for zinc batteries, and a negative electrode material for zinc batteries. Background Technology

[0002] As zinc batteries, known types include nickel-zinc batteries, zinc-air batteries, and silver-zinc batteries. For example, a nickel-zinc secondary battery, a type of nickel-zinc battery, replaces the hydrogen storage alloy negative electrode of a nickel-metal hydride secondary battery with a negative electrode containing zinc or zinc compounds. Zinc is a resource-rich, inexpensive material with low environmental impact. Furthermore, nickel-zinc secondary batteries have advantages such as a high open-circuit voltage of up to 1.8V, high theoretical energy density, and high power. Due to these characteristics, the development of nickel-zinc secondary batteries has been promoted in recent years to make them a replacement for lead-acid batteries and to expand their applications to energy storage or automotive applications.

[0003] For this type of zinc battery, improved discharge characteristics are required; for example, it is required to have high output characteristics (discharge characteristics under high output) that can cope with increased load.

[0004] In contrast, Patent Document 1 discloses a method for manufacturing a negative electrode for zinc batteries using a negative electrode mixture containing zinc oxide particles with an average particle size of 0.28 μm or less. Patent Document 2 discloses a method for manufacturing a negative electrode for zinc batteries using a negative electrode mixture containing zinc oxide particles with an average particle size of less than 0.60 μm. Thus, it has been studied that using zinc oxide particles with relatively small average particle sizes increases the specific surface area and improves the utilization rate of the active material.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2020-087703

[0008] Patent Document 2: Japanese Patent Application Publication No. 2019-133769

[0009] The problem the invention aims to solve

[0010] However, the batteries manufactured using zinc oxide particles, as disclosed in Patent Documents 1 and 2, do not have ideal discharge characteristics at high output.

[0011] Furthermore, in the preparation of the negative electrode, a slurry is prepared by mixing negative electrode active materials such as zinc oxide particles, other components, and water, and then coating the slurry onto a current collector. However, for zinc oxide particles with relatively small average particle sizes, as disclosed in Patent Documents 1 and 2, a large amount of water is required due to their large specific surface area, resulting in low manufacturability. Summary of the Invention

[0012] The present invention was made in view of the above circumstances, and its object is to provide a zinc battery negative electrode with good manufacturability and which can improve the discharge characteristics of the battery, a zinc battery, a method for manufacturing a zinc battery negative electrode, and a zinc battery negative electrode material.

[0013] Solution to the problem

[0014] This invention relates to the following: a negative electrode for zinc batteries, a zinc battery, a method for manufacturing a negative electrode for zinc batteries, and a negative electrode material for zinc batteries.

[0015] [1] A negative electrode for a zinc battery, comprising a negative electrode compound containing zinc oxide, wherein in the X-ray diffraction pattern of the negative electrode compound, the peak intensity (I) from the (002) plane of zinc oxide is... 002 ) relative to the peak intensity (I) from the (101) plane of zinc oxide 101 The ratio of (I) 002 / I 101 The value is above 0.4.

[0016] [2] The negative electrode for a zinc battery as described in [1], wherein the zinc oxide comprises zinc oxide particles.

[0017] The median diameter of the zinc oxide particles is greater than 3 μm and less than 20 μm.

[0018] [3] The negative electrode for zinc batteries as described in [2], wherein the negative electrode mixture further comprises second zinc oxide particles with a median diameter of less than 2 μm.

[0019] [4] The negative electrode for zinc batteries as described in [3], wherein the content of the zinc oxide particles relative to the total amount of the zinc oxide particles and the second zinc oxide particles in the negative electrode mixture is 50% by mass or more.

[0020] [5] A negative electrode for a zinc battery as described in any one of [1] to [4], wherein the negative electrode for a zinc battery further comprises a current collector for retaining the negative electrode mixture, the current collector being a non-porous current collector.

[0021] [6] A zinc battery having a positive electrode, a negative electrode and an alkaline electrolyte, wherein the negative electrode is a zinc battery negative electrode as described in any one of [1] to [5].

[0022] [7] The zinc battery as described in [6], wherein the zinc battery is a nickel-zinc secondary battery.

[0023] [8] A method for manufacturing a negative electrode for a zinc battery, comprising: a step of preparing zinc oxide particles, wherein the peak intensity (I) of the (002) plane in the X-ray diffraction pattern of the zinc oxide particles is... 002 Peak intensity (I) relative to the (101) plane 101 The ratio of (I)002 / I 101 The concentration of zinc oxide particles is 0.5 or higher; and the process of preparing a negative electrode mixture using the zinc oxide particles.

[0024] [9] The method for manufacturing a negative electrode for a zinc battery as described in [8], wherein the median diameter of the zinc oxide particles is 3 μm or more and 20 μm or less.

[0025]

[10] The method for manufacturing a negative electrode for a zinc battery as described in [9], wherein, in the step of preparing the negative electrode mixture, the negative electrode mixture comprises the zinc oxide particles and a second zinc oxide particle with a median diameter of less than 2 μm.

[0026]

[11] The method for manufacturing a negative electrode for a zinc battery as described in

[10] , wherein the content of the zinc oxide particles relative to the total amount of the zinc oxide particles and the second zinc oxide particles in the negative electrode mixture is 50% by mass or more.

[0027]

[12] A negative electrode material for zinc batteries, comprising zinc oxide particles, wherein the peak intensity (I) of the (002) plane in the X-ray diffraction pattern of the zinc oxide particles is... 002 Peak intensity (I) relative to the (101) plane 101 The ratio of (I) 002 / I 101 The value is above 0.5.

[0028] Invention Effects

[0029] According to the present invention, a zinc battery negative electrode, a zinc battery, a method for manufacturing a zinc battery negative electrode, and a zinc battery negative electrode material are provided that have good manufacturability and can improve the discharge characteristics of the battery. Attached Figure Description

[0030] Figure 1 This is a perspective view showing a partial cross-section of a nickel-zinc secondary battery according to one embodiment of the present invention.

[0031] Figure 2 These are X-ray diffraction patterns of the zinc oxide powder used in the examples and comparative examples.

[0032] Figure 3 These are the results of particle size distribution measurements of the zinc oxide powder used in the examples and comparative examples.

[0033] Figure 4 The X-ray diffraction patterns are those of the negative electrodes recovered from the batteries of the examples and comparative examples. Detailed Implementation

[0034] To improve manufacturability, the inventors attempted to increase the particle size of the zinc oxide particles. Generally, zinc oxide particles are produced by melting and vaporizing metallic zinc, followed by oxidation in air. Therefore, the resulting zinc oxide particles have a relatively small particle size, typically less than 1 μm.

[0035] In contrast, the inventors have discovered that by sintering zinc oxide powder at a temperature above 1000°C and then pulverizing it to the desired size, zinc oxide particles with relatively large particle sizes can be obtained. Furthermore, although the zinc oxide particles obtained by this method have large particle sizes and small specific surface areas, the discharge characteristics of the battery can still be improved; specifically, the voltage drop of the battery when a load is applied during discharge can be reduced, thereby improving the discharge characteristics at high output.

[0036] Furthermore, the zinc oxide particles obtained in this manner differ from those obtained by previous methods. Their characteristic peak intensity along the c-axis in the powder X-ray diffraction pattern increases, indicating a highly ordered and anisotropic structure along the c-axis. In other words, it can be inferred that during the post-sintering pulverization process, phenomena such as the growth of zinc oxide crystal particles, the generation of oxygen vacancies, and deformation of the crystal structure occur, thus causing the increase in characteristic intensity along the c-axis in the powder X-ray diffraction pattern.

[0037] Furthermore, although the specific surface area of ​​the zinc oxide particles mentioned above is relatively small, the reason why they can improve the discharge characteristics of the battery is still unclear. However, it can be speculated that as the anisotropy of the zinc oxide particles increases, the proportion of highly reactive crystal faces increases, thus expanding the reaction area and thereby improving reactivity.

[0038] That is, in this invention, zinc oxide particles can be used as electrode materials for batteries, preferably as negative electrode materials for zinc batteries, and more preferably as negative electrode active materials for zinc batteries. In the X-ray diffraction pattern of these zinc oxide particles, the peak intensity (I) of the (002) plane is... 002 Peak intensity (I) relative to the (101) plane 101 The ratio of peak intensity ratio (I) 002 / I 101 The peak intensity ratio (I) of zinc oxide particles or negative electrode mixtures containing zinc oxide particles in a negative electrode obtained using this negative electrode material is 0.5 or higher. 002 / I 101 The value is above 0.4.

[0039] The embodiments of the present invention will now be described in detail. However, the present invention is not limited to the embodiments described below, and various modifications can be made within the scope of its spirit.

[0040] 1. Negative electrode for zinc batteries

[0041] The negative electrode for a zinc battery in this embodiment (hereinafter, simply referred to as "negative electrode") has a negative electrode mixture. The negative electrode mixture is preferably held by a current collector. That is, the negative electrode in this embodiment preferably comprises a current collector and a negative electrode mixture. The negative electrode may or may not undergo activation treatment.

[0042] 1-1. current collector

[0043] The current collector can be either non-porous or porous. A non-porous current collector is one that does not have pores, at least in the portion holding the negative electrode binder; for example, a non-porous foil. A porous current collector can be a mesh, sponge, fibrous, or felt-like porous metal body, a perforated metal plate, or a steel mesh. The material of the current collector can be any metallic material that is conductive and stable even at the reaction potential of the negative electrode. Examples of such materials include copper, copper alloys (e.g., brass), and iron, with copper being preferred.

[0044] The current collector is preferably a non-porous current collector, more preferably a non-porous foil. Because the zinc oxide particles mentioned above have a relatively large particle size, voids easily form between them. Therefore, compared to conventional zinc oxide particles, the filling density of the negative electrode mixture is prone to decrease; furthermore, under low pressing strength, a decrease in mechanical strength or shedding of the active material is also likely to occur. Using a non-porous current collector allows for uniform pressing, thus reducing the likelihood of active material shedding and further improving the filling density.

[0045] The surface of the current collector can be plated with a metal layer. The metal used to form the coating is preferably a metal whose hydrogen overpotential is higher than that of the metal contained in the bulk of the current collector, and more preferably a metal whose hydrogen overpotential is higher than that of copper (e.g., tin).

[0046] 1-2. Negative electrode mixture

[0047] The negative electrode agent is retained in the current collector, for example, in a layered form. The negative electrode agent contains zinc oxide. Zinc oxide, for example, can function as a negative electrode active material. Moreover, in the X-ray diffraction pattern of the negative electrode agent in the negative electrode, the peak intensity (I) of the (002) plane is... 002 ) relative to the peak intensity (I) from the (101) plane of zinc oxide 101 The ratio of peak intensity ratio (I) 002 / I 101 The value is above 0.4.

[0048] If the peak intensity ratio of the negative electrode agent is (I 002 / I 101A peak intensity ratio (Ic) of 0.4 or higher can improve both the manufacturability of the negative electrode mixture and the discharge characteristics of the battery. Specifically, using zinc oxide particles with high c-axis characteristic peak intensity as raw materials can improve the reactivity of zinc oxide particles and thus enhance the discharge characteristics of the zinc battery. Furthermore, the smaller specific surface area of ​​zinc oxide particles allows for reduced water content during slurry preparation, thereby improving the manufacturability of the negative electrode mixture. On the other hand, from the perspective of reducing manufacturing costs or suppressing the decline in discharge characteristics caused by increased pulverization load, a peak intensity ratio (Ic) of the negative electrode mixture is crucial. 002 / I 101 The preferred value is 1 or less.

[0049] In the X-ray diffraction pattern, the peak position of the (002) plane appears in the range of 2θ = 33.5 to 35.0 degrees. The peak position of the (101) plane appears in the range of 2θ = 35.5 to 37.0 degrees.

[0050] X-ray diffraction (XRD) determination of the negative electrode mixture can be performed through the following steps.

[0051] First, a 2cm x 2cm piece of the negative electrode was cut as the test sample. X-ray diffraction analysis was performed on the test sample using an X-ray diffraction apparatus (e.g., a MiniFlex 600 manufactured by Rigaku Corporation). The measurement conditions are as follows.

[0052] (Measurement conditions)

[0053] X-rays: Cu-Kα rays

[0054] Tube voltage: 40kV

[0055] Tube current: 15mA

[0056] Scanning range: 20°~100°

[0057] Step width: 0.02°

[0058] Scanning speed: 5° / min.

[0059] Based on the above measurement conditions, the crystal structure of zinc oxide powder can be analyzed using X-ray analysis software PDXL2 (e.g., Rigaku Corporation PDXL).

[0060] Peak intensity ratio of negative electrode compound (I) 002 / I 101 The concentration of zinc oxide particles used in the preparation of the negative electrode mixture can be adjusted by the type and composition of these particles. For example, in the preparation of the negative electrode mixture, the concentration of zinc oxide particles used as the negative electrode active material in a certain proportion can be adjusted by the ratio of their peak intensity in the X-ray diffraction pattern (I0). 002 / I 101Zinc oxide particles with a peak intensity ratio of 0.5 or higher can increase the peak intensity ratio (I0.5) of the negative electrode compound. 002 / I 101 Adjust to the above range.

[0061] Peak intensity ratio (I) in X-ray diffraction pattern 002 / I 101 Zinc oxide particles with a peak intensity ratio of 0.5 or higher can be obtained by pulverizing sintered zinc oxide powder. Therefore, the aforementioned peak intensity ratio of zinc oxide particles used to prepare the negative electrode additive can be adjusted by the pulverization load (e.g., pulverization intensity and pulverization time) during the preparation of the zinc oxide particles. For example, by appropriately reducing the pulverization load, the peak intensity ratio (I0.5) of the zinc oxide particles will decrease. 002 / I 101 It is easy to increase appropriately.

[0062] The morphology of zinc oxide in the negative electrode depends on whether activation treatment is performed and the degree of charge / discharge, for example, it can be in particulate form. That is, the negative electrode mixture can contain zinc oxide particles.

[0063] The median diameter of the zinc oxide particles is not particularly limited, but is preferably 3.0 μm or more, more preferably 10 μm or more. If the median diameter of the zinc oxide particles is 3.0 μm or more, the grinding intensity during the preparation of the zinc oxide particles can be further reduced, thereby further reducing the decrease in crystallinity. Furthermore, since the specific surface area of ​​the zinc oxide particles is moderately reduced, the water content can be reduced during slurry preparation, thereby further improving manufacturability. Additionally, from the viewpoint of reducing the unevenness of the negative electrode surface and making the negative electrode easier to mix with negative electrode additives such as bismuth oxide and indium oxide, thereby better suppressing self-discharge, the median diameter of the zinc oxide particles is preferably 20 μm or less.

[0064] It should be noted that the median diameter refers to the median diameter corresponding to a cumulative mass of 50%. The median diameter of zinc oxide particles can be obtained using a particle size distribution measuring device and by laser diffraction / scattering.

[0065] The median diameter of zinc oxide particles can be adjusted by the grinding load (such as grinding intensity and grinding time). For example, if the grinding intensity is reduced or the grinding time is shortened, the median diameter of zinc oxide particles is more likely to increase.

[0066] The shape of the zinc oxide particles is not particularly limited; they can be irregular or spherical. From the viewpoint of increasing the packing density of the active material, spherical particles are preferred.

[0067] The content of zinc oxide particles in the negative electrode mixture is not particularly limited, but preferably, for example, it is 40% by mass or more relative to the total mass of the negative electrode active material. If the above-mentioned content of zinc oxide particles is 40% by mass or more, the reactivity of zinc oxide particles can be further improved, thereby further improving the discharge characteristics of the battery. From the same point of view, the content of zinc oxide particles in the negative electrode mixture relative to the total mass of the negative electrode active material is more preferably 50% by mass or more and 90% by mass or less.

[0068] 1-2-2. Second zinc oxide particles

[0069] The negative electrode mixture may further include zinc oxide particles with a particle size different from the zinc oxide particles described above. For example, the negative electrode mixture may further include second zinc oxide particles with a median diameter smaller than the zinc oxide particles described above. The median diameter of the second zinc oxide particles is preferably 2 μm or less, more preferably 0.5 μm or more and 2 μm or less. By further including second zinc oxide particles with a median diameter of 2 μm or less, the filling density of the negative electrode mixture can be further increased, thereby further increasing the energy density of the battery.

[0070] The second zinc oxide particles differ from the zinc oxide particles mentioned above and can be zinc oxide particles prepared by conventional methods.

[0071] The content ratio of zinc oxide particles and second zinc oxide particles in the negative electrode mixture is not particularly limited. For example, relative to the total content of zinc oxide particles and second zinc oxide particles in the negative electrode mixture, the content of zinc oxide particles is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more. If the above-mentioned content of zinc oxide particles is 50% by mass or more, the peak intensity ratio (I0.05) in the X-ray diffraction pattern of the negative electrode mixture can be improved. 002 / I 101 The larger the content of zinc oxide particles, the better the discharge characteristics of the battery. On the other hand, the content of zinc oxide particles is preferably 90% by mass or less, more preferably 80% by mass or less. If the content of zinc oxide particles is 90% by mass or less, it is easier to fill the gaps between the larger zinc oxide particles with smaller second zinc oxide particles, thereby further increasing the filling density of the negative electrode active material and further increasing the energy density of the battery.

[0072] The total amount of zinc oxide particles and second zinc oxide particles in the negative electrode mixture is not specifically limited. For example, when these zinc oxide particles are included as negative electrode active materials, preferably, the total amount of zinc oxide particles and second zinc oxide particles is 50% by mass or more, and more preferably 70% by mass or more, relative to the total mass of the negative electrode active materials. Furthermore, the upper limit of the total amount of zinc oxide particles and second zinc oxide particles relative to the total mass of the negative electrode active materials in the negative electrode mixture is not specifically limited, but it can generally be set to 90% by mass or less.

[0073] 1-2-3. Other ingredients

[0074] The negative electrode mixture may also contain other negative electrode active materials besides zinc oxide, negative electrode additives, and binders, as needed.

[0075] Other negative electrode active materials include at least one of zinc, zinc alloys, and zinc-containing compounds. Besides zinc, other metals constituting zinc alloys may include bismuth, aluminum, and indium. Examples of zinc-containing compounds include zinc hydroxide, zinc sulfide, zinc tetrahydroxy ion salts, zinc halides, zinc carboxylic acid compounds such as zinc acetate, zinc tartrate, and zinc oxalate, magnesium zincate, calcium zincate, barium zincate, zinc borate, zinc silicate, zinc aluminate, zinc fluoride, zinc carbonate, zinc bicarbonate, zinc nitrate, and zinc sulfate. Preferably, other negative electrode active materials include zinc (metallic zinc). Metallic zinc can serve as both a discharge storage material and a conductive material.

[0076] Other negative electrode active materials may be in powder form. For example, when using zinc or zinc alloys, the median diameter of other negative electrode active materials can be set to 10 μm or more and 1000 μm or less. When using zinc-containing compounds, it can be set to 0.1 μm or more and 100 μm or less. The median diameter can be determined using the same method as described above.

[0077] The content of the negative electrode active material in the negative electrode mixture can be set to be, for example, 75% or more by mass relative to the total mass of the negative electrode mixture, preferably 90% or more and 95% or less by mass.

[0078] Negative electrode additives can be components that reduce the dissolution of the negative electrode active material into the electrolyte. Examples of such negative electrode additives include bismuth oxide, bismuth hydroxide, indium oxide, indium hydroxide, potassium oxalate, and their hydrates. For example, if potassium oxalate and its hydrate dissolve in the electrolyte, they dissociate into oxalate ions. Consequently, the zinc ions dissolved in the electrolyte form a poorly soluble salt with the oxalate ions, covering the surface of the negative electrode active material, thus reducing the contact between the metallic zinc of the negative electrode active material and the electrolyte.

[0079] When the negative electrode mixture contains a negative electrode additive, the content of the negative electrode additive in the negative electrode mixture, for example, relative to the total mass of the negative electrode mixture, can be set to 1% or more and 20% or less by mass, preferably 3% or more and 10% or less by mass.

[0080] The binder serves the following functions: it binds the negative electrode active material and the negative electrode additive together, and simultaneously binds the negative electrode active material and the negative electrode additive to the negative electrode current collector. Examples of binders include: hydroxypropyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, sodium polyacrylate, polyimide, polyamide-imide, polyamide, styrene-butadiene rubber, polyethylene oxide, polytetrafluoroethylene, polyvinylidene fluoride, perfluoroalkoxy fluororesins, and tetrafluoroethylene-hexafluoropropylene copolymers. Among these, styrene-butadiene rubber is preferred due to its high bonding effect and alkali resistance.

[0081] When the negative electrode mixture contains a binder, the amount of binder in the negative electrode mixture is only required to allow the negative electrode mixture to bond sufficiently with the negative electrode current collector. For example, relative to the total mass of the negative electrode mixture, it can be set to 1% or more and 5% or less by mass, preferably 1% or more and 3% or less by mass.

[0082] 1-2-4.Physical properties

[0083] (Particle size distribution of the entire particle group including zinc oxide)

[0084] In the case where the negative electrode mixture contains, for example, zinc oxide particles with a median diameter of 3 μm or more and second zinc oxide particles with a median diameter of 2 μm or less, preferably, in the particle size distribution of the entire particle group containing zinc oxide, including the zinc oxide particles and the second zinc oxide particles, a first peak exists in the range of particle size of 3 μm or more (preferably 3 μm or more and 20 μm or less), and a second peak exists in the range of particle size of 2 μm or less (see below). Figure 3 ).

[0085] Particle size distribution can be determined using the Mastersizer 3000 laser diffraction particle size analyzer from Malvern Panalytical: zinc oxide particles are added to pure water to reach a specified concentration, and then the particle size is determined by ultrasonic dispersion and stirring.

[0086] 1-3. Manufacturing method of negative electrode

[0087] The negative electrode of this embodiment can be manufactured by any method. For example, the negative electrode of this embodiment can be manufactured by the following steps: 1) preparing the above-mentioned peak intensity ratio (I 002 / I 101 The process includes: 1) the process of preparing zinc oxide particles with a particle size of 0.5 or higher; and 2) the process of preparing a negative electrode mixture containing the prepared zinc oxide particles.

[0088] 1) Process for preparing zinc oxide particles

[0089] First, prepare the peak intensity ratio (I) mentioned above. 002 / I 101 Zinc oxide particles with a peak intensity of 0.5 or higher. The peak intensity ratio of zinc oxide particles can be determined using the same method as the X-ray diffraction method described above, except when using an aggregate of zinc oxide particles (zinc oxide powder) used to prepare the negative electrode mixture as the test sample.

[0090] Zinc oxide particles can be either commercially available or prepared. In the case of prepared zinc oxide particles, they can be obtained, for example, by pulverizing existing zinc oxide powder after calcining it into a sintered body. The particles obtained in this way are also called calcined zinc white. As mentioned above, the peak intensity ratio of the zinc oxide particles in the raw material stage can be adjusted by the pulverization load (pulverization intensity and pulverization time) during zinc oxide preparation.

[0091] The calcination temperature can be any temperature that can produce a sintered body, for example, it can be set to above 1000℃, preferably 1100℃~1150℃.

[0092] The pulverization of the sintered body can be carried out by any method. Pulverization can be performed under conditions (pulverization intensity, pulverization time) that yield the desired particle size. By doing so, zinc oxide particles with the aforementioned median diameter can be obtained.

[0093] 2) The process of preparing the negative electrode mixture

[0094] Next, a negative electrode mixture containing the prepared zinc oxide particles is prepared.

[0095] Specifically, the prepared zinc oxide particles are mixed and kneaded with (as needed) the above-mentioned second zinc oxide particles or other negative electrode active materials, negative electrode additives, binders, water or solvents to prepare a negative electrode slurry.

[0096] For example, a negative electrode slurry can be prepared by mixing zinc oxide particles with a median diameter of 3 μm or more and 20 μm or less with second zinc oxide particles with a median diameter of 2 μm or less. The mixing ratio of the zinc oxide particles with a median diameter of 3 μm or more and 20 μm or less and the second zinc oxide particles can be the same as the content ratio of zinc oxide particles to second zinc oxide particles in the negative electrode slurry described above. Thus, a negative electrode slurry containing zinc oxide particles with a median diameter of 3 μm or more and 20 μm or less and second zinc oxide particles with a median diameter of 1 μm or less can be obtained. A more preferred range for the median diameter of the zinc oxide particles and the second zinc oxide particles during the preparation of the negative electrode slurry, and the method for determining them, are the same as described above. Furthermore, the particle size distribution of the entire particle group containing zinc oxide is the same as described above.

[0097] In addition, the ratio of the peak intensity of the (002) plane to the peak intensity of the (101) plane in the X-ray diffraction pattern of the second zinc oxide particles during the preparation of the negative electrode slurry (I 002 / I 101 For example, it is preferable to be less than 0.5, more preferably 0.3 or more and less than 0.5. The amount of each component used to prepare the negative electrode mixture slurry is also set in such a way that the content of each component in the negative electrode mixture is within the above-mentioned range.

[0098] Furthermore, after the obtained negative electrode slurry is coated onto the current collector and dried, it is pressed as needed, thereby preparing a negative electrode mixture (e.g., a negative electrode mixture layer).

[0099] 2. Zinc battery

[0100] 2-1. Structure

[0101] A zinc battery according to one embodiment of the present invention will be described. In this embodiment, a nickel-zinc secondary battery will be described as an example of a zinc battery.

[0102] Figure 1 This is a perspective view showing a partial cross-section of the nickel-zinc secondary battery 10 of this embodiment. A portion of the wound body 16 is not shown in this view.

[0103] like Figure 1 As shown, the nickel-zinc secondary battery 10 is, for example, a cylindrical battery of FA size, having an outer can 12, a sealing body 14, a winding body 16 (electrode assembly), an electrolyte (not shown), an upper insulating component 18, and a lower insulating component 20.

[0104] The outer can 12 is a container that houses the wound body 16. In this embodiment, it is a bottomed cylindrical container with an open top. The outer can 12 is conductive, and its bottom wall 12A functions as the negative terminal. The material constituting the outer can 12 can be any material that is conductive and resistant to corrosion from the electrolyte or the electrochemical reactions inside the battery, typically including metals such as iron and steel.

[0105] The sealing body 14 is fixed to the opening of the outer can 12 through the insulating gasket 22, and functions as a positive terminal while sealing the outer can 12. The sealing body 14 includes a cover plate 24, a valve body 26, and a positive terminal 28.

[0106] The cover plate 24 is a conductive, circular plate-shaped component with a central through-hole 24A. The insulating gasket 22 has an annular shape surrounding the cover plate 24 and is sandwiched between the outer can 12 and the sealing body 14. The cover plate 24 and the insulating gasket 22 work together to airtightly seal the opening of the outer can 12.

[0107] The valve body 26 is a rubber component and is disposed on the outer surface of the cover plate 24 in a manner that blocks the through hole 24A.

[0108] The positive terminal 28 is a metal, flanged, cylindrical component that is electrically connected to the outer surface of the cover plate 24. The positive terminal 28 presses against the cover plate 24 to engage the valve body 26. Additionally, the positive terminal 28 has a vent (not shown).

[0109] Furthermore, during normal operation, the through-hole 24A is airtightly sealed by the valve body 26. On the other hand, when gas is generated inside the outer canister 12, and its internal pressure increases, the valve body 26 is compressed by the internal pressure, opening the through-hole 24A. As a result, the gas is discharged from the outer canister 12 to the outside through the through-hole 24A and the vent hole (not shown) of the positive terminal 28. In other words, the through-hole 24A, the valve body 26, and the positive terminal 28 form a safety valve for the battery.

[0110] The wound body 16 includes a positive electrode 30, a negative electrode 32, and a separator 34. That is, the wound body 16 is formed by winding a structure consisting of a stacked separator 34, a positive electrode 30, a separator 34, and a negative electrode 32 with the negative electrode 32 on the outside.

[0111] A negative electrode 32 is disposed on the outermost circumferential surface of the wound body 16, and the negative electrode 32 is in contact with the inner wall surface of the outer can 12. That is, the negative electrode 32 is electrically connected to the outer can 12, which serves as the negative terminal.

[0112] On the other hand, a positive lead 36 is connected to the positive electrode 30 of the wound body 16. The positive lead 36 is connected to the cover plate 24. Thus, the positive electrode 30 and the positive terminal 28 are electrically connected to each other via the positive lead 36 and the cover plate 24.

[0113] An upper insulating component 18 is disposed between the wound body 16 and the cover plate 24. Thus, the negative electrode 32 of the wound body 16 does not contact the sealing body 14. Furthermore, the upper insulating component 18 has a slit 18A for the positive electrode lead 36 to pass through.

[0114] The lower insulating component 20 is disposed between the bottom of the winding body 16 and the outer can 12. As a result, the positive electrode 30 of the winding body 16 does not come into contact with the inner wall surface of the outer can 12.

[0115] An alkaline electrolyte (not shown) is sealed inside an outer container 12. The alkaline electrolyte is an aqueous solution containing an alkali metal hydroxide. Examples of alkali metal hydroxides include potassium hydroxide, sodium hydroxide, and lithium hydroxide. Potassium hydroxide and lithium hydroxide are preferred. There may be one alkali metal hydroxide or a combination of two or more.

[0116] The concentration of alkali metal hydroxide in the alkaline electrolyte is not particularly limited, but is preferably 25% by mass or more and 45% by mass or less (5.0N or more and 8.0N or less). If the concentration of alkali metal hydroxide in the alkaline electrolyte is 25% by mass or more, the ionic conductivity can be further improved. If the concentration of alkali metal hydroxide in the alkaline electrolyte is 45% by mass or less, the dissolution of zinc oxide from the negative electrode can be further reduced.

[0117] Furthermore, zinc compounds such as zinc oxide and zinc hydroxide can be further dissolved in the alkaline electrolyte. This is done to further suppress the dissolution of zinc or zinc oxide from the negative electrode into the electrolyte. For example, the alkaline electrolyte is preferably an electrolyte prepared by dissolving zinc oxide to a saturated concentration. That is, the concentration of zinc ions in the alkaline electrolyte, converted from zinc oxide, is preferably 4% by mass or more. The concentration of zinc ions in the alkaline electrolyte can be determined by inductively coupled plasma optical emission spectrometry (ICP-OES).

[0118] Next, the components that make up the winding body 16 will be described.

[0119] (1) Positive electrode

[0120] Positive electrode 30 contains a positive electrode current collector and a positive electrode additive.

[0121] The positive electrode current collector can be, for example, a metal foil, a mesh, a sponge, a fiber, or a felt-like porous metal body, or a perforated metal plate or steel mesh. The material of the positive electrode current collector can be any metallic material that is stable even at the reaction potential of the positive electrode, such as nickel or stainless steel, with nickel being preferred. That is, the positive electrode current collector can be nickel foam, a nickel-plated mesh, sponge, or fibrous metal body.

[0122] The positive electrode mixture remains on the positive electrode current collector and contains the positive electrode active material.

[0123] (Positive electrode active material)

[0124] The positive electrode active material contains particles containing nickel hydroxide. Nickel hydroxide can be dissolved in at least one of cobalt (Co), zinc (Zn), and cadmium (Cd). The amount of the dissolved metal element in the nickel hydroxide particles relative to the total mass of the particles can be set to 5% to 10% by mass.

[0125] In addition, the particles containing nickel hydroxide can also be composite particles, which comprise: a matrix particle containing nickel hydroxide and a coating layer containing a cobalt compound doped with an alkali metal. The amount of cobalt (Co) in the composite particle relative to the total mass of the composite particle can be set to 2% to 5% by mass.

[0126] The coating layer is configured to coat at least a portion of the surface of the matrix particles. Preferably, the coating layer contains a cobalt compound doped with an alkali metal. Examples of alkali metals include sodium (Na), lithium (Li), etc. They can be one or more. The cobalt compound is preferably a trivalent or higher-valence cobalt compound such as cobalt oxyhydroxide (CoOOH). Thus, the high-valence cobalt compound incorporating an alkali metal into the crystal has high electrical conductivity.

[0127] The presence or absence of a coating layer can be confirmed by preparing a cross-sectional sample containing nickel hydroxide particles using a cross-section polishing machine and observing its cross-section using a scanning electron microscope (SEM).

[0128] The median diameter of the aforementioned particles is not particularly limited, but is preferably 10 μm to 20 μm. That is, if the median diameter of the particles is within this range, the specific surface area of ​​the particles is increased, thereby further improving the utilization rate of the positive electrode active material. It should be noted that the median diameter can be measured using the same method as described above.

[0129] The content of the positive electrode active material in the positive electrode mixture relative to the total mass of the positive electrode mixture can be set to, for example, 80% by mass or more and 100% by mass or less, preferably 90% by mass or more and 100% by mass or less. It should be noted that the total mass of the positive electrode mixture refers to the total mass of the positive electrode mixture in the dry state (the total mass of the solid components of the positive electrode mixture).

[0130] (Other ingredients)

[0131] The positive electrode mixture may be further supplemented with positive electrode additives or binders as needed.

[0132] Examples of positive electrode additives include: yttrium oxide; cobalt compounds such as cobalt oxide, metallic cobalt, and cobalt hydroxide; zinc compounds such as metallic zinc, zinc oxide, and zinc hydroxide; rare earth compounds such as erbium oxide; and niobium oxide. For example, zinc compounds such as zinc oxide or zinc hydroxide can be added to inhibit the expansion of the positive electrode additive. The content of zinc compounds relative to the total mass of the positive electrode active material can be set at 0.1% to 5% by mass.

[0133] The binder serves the following functions: it binds the positive electrode active material and the positive electrode additive together, and simultaneously binds the positive electrode active material and the positive electrode additive to the positive electrode current collector. Examples of binders include hydrophilic or hydrophobic polymers, such as hydroxypropyl cellulose or carboxymethyl cellulose (CMC), sodium polyacrylate, and fluorinated polymers (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.).

[0134] (2) Negative electrode

[0135] The negative electrode 32 can be the negative electrode described above.

[0136] (3) Diaphragm

[0137] As described above, the separator 34 is disposed between the positive electrode 30 and the negative electrode 32 (reference). Figure 1 The diaphragm 34 can be a non-woven fabric or a microporous membrane.

[0138] There are no particular limitations on the materials used for nonwoven fabrics and microporous membranes; they can be polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyphenylene sulfide, and polyamides, etc. Among these, polyolefins are preferred from the viewpoint of mechanical strength or shutdown properties, and polypropylene is more preferred.

[0139] Nonwoven fabrics and microporous membranes can be endowed with hydrophilic functional groups through hydrophilization treatments. For example, nonwoven fabrics and microporous membranes can be materials endowed with sulfonation groups through sulfonation treatment by impregnation in acids containing sulfate groups, such as sulfuric acid or fuming sulfuric acid. As a result, alkaline electrolytes can more easily wet the nonwoven fabrics or microporous membranes.

[0140] The diaphragm 34 may be a single type or a combination of two or more types. For example, as the diaphragm 34, a laminate of nonwoven fabric and hydrophilically treated microporous membrane may be used.

[0141] 2-2. Manufacturing Method

[0142] The aforementioned nickel-zinc secondary battery can be manufactured by any method. For example, the aforementioned nickel-zinc secondary battery can be manufactured by the following steps: 1) a step of preparing a positive electrode and a negative electrode; and 2) a step of obtaining a nickel-zinc secondary battery using the prepared positive electrode and negative electrode.

[0143] Regarding process 1)

[0144] First, prepare the positive and negative electrodes. The negative electrode can be prepared using the method described above. The positive electrode can be prepared using the same method as the negative electrode.

[0145] Regarding process 2)

[0146] Next, using the prepared positive and negative electrodes, a nickel-zinc secondary battery was prepared.

[0147] Specifically, a wound body is prepared by winding the prepared positive electrode 30 and negative electrode 32 in a state where they are stacked with a separator 34 in between (e.g., a laminate of nonwoven fabric and microporous membrane). A positive electrode lead 36 is welded to one end of the positive electrode 30 in the longitudinal direction. Then, for example, after stacking the separator 34, positive electrode 30, separator 34, and negative electrode 32 in sequence, the wound body 16 is obtained by winding along the longitudinal direction with the negative electrode 32 facing outward.

[0148] The obtained winding body 16 is placed inside the outer packaging can 12, and after the electrolyte is injected, the opening of the outer packaging can 12 is sealed with the sealing body 14.

[0149] After being left to stand for a certain period of time, the material is activated by charging under specified conditions. The activation conditions can be adjusted according to the properties of the electrode active materials (positive electrode active material and negative electrode active material). In this embodiment, for example, the material can be charged to its nominal capacity at a constant current and constant voltage of 1.9V and then discharged to 1.3V, and this cycle can be performed 5 times. Thus, a nickel-zinc secondary battery 10 can be obtained.

[0150] 3. Variations

[0151] It should be noted that in the above embodiments, a nickel-zinc secondary battery was described as an example of a zinc battery, but the present invention is not limited to the above embodiments. For example, the zinc battery can be a zinc-air battery with an air electrode as the positive electrode (e.g., an air-zinc secondary battery), or a silver-zinc battery with a silver oxide electrode as the positive electrode (e.g., a silver-zinc secondary battery). In addition, the nickel-zinc secondary battery is not limited to a cylindrical nickel-zinc secondary battery, but can also be a square or stacked nickel-metal hydride secondary battery.

[0152] [Example]

[0153] The present invention will be described in detail based on the embodiments, but the present invention is not limited to these embodiments.

[0154] 1. Preparation and determination of zinc oxide powder

[0155] 1-1. Preparation of Zinc Oxide Powder

[0156] <Preparation of Zinc Oxide Powder A>

[0157] High-purity metallic zinc is melted and vaporized, then oxidized in air. This yields high-purity zinc oxide powder A with a median diameter of 0.75 μm, meeting the first standard of JIS K 1410-1995.

[0158] <Preparation of Zinc Oxide Powder B>

[0159] Zinc oxide powder prepared using the same method as zinc oxide powder A was calcined at 1100℃~1150℃ to obtain a sintered body of zinc oxide powder. This sintered body was then pulverized to obtain zinc oxide powder B with a median diameter of 4.4 μm.

[0160] <Preparation of Zinc Oxide Powder C>

[0161] In addition to changing the pulverization method of the sintered body to adjust the pulverization intensity, zinc oxide powder C with a median diameter of 12.0 μm was obtained in the same manner as zinc oxide powder B.

[0162] 1-2. Measurement

[0163] The median diameter, specific surface area, and X-ray diffraction patterns of zinc oxide powders A to C were determined using the following methods.

[0164] 1-2-1. Median diameter

[0165] Using a particle size distribution measuring device, the median diameter, which is the cumulative 50% based on mass, was determined by laser diffraction / scattering.

[0166] 1-2-2. Specific surface area

[0167] Specific surface area was determined using the BET method via nitrogen adsorption, according to ASTM-D6556.

[0168] 1-2-3. X-ray diffraction (XRD) measurement

[0169] Zinc oxide powders A through C were subjected to powder X-ray diffraction (PXRD) analysis to determine their crystal structures. The MiniFlex 600 (Rigaku Corporation) was used as the measuring apparatus, and the PDXL (Rigaku Corporation) software was used for PXRD analysis. The measurement conditions are as follows.

[0170] (Measurement conditions)

[0171] X-rays: Cu-Kα rays

[0172] Tube voltage: 40kV

[0173] Tube current: 15mA

[0174] Scanning range: 20°~100°

[0175] Step width: 0.02°

[0176] Scanning speed: 5° / min.

[0177] 1-2-4. Particle size distribution determination (XRD)

[0178] The particle size distribution of zinc oxide powder A, zinc oxide powder B, zinc oxide powder C, a mixture of zinc oxide powder A and zinc oxide powder B (A / B = 50 / 50 mass ratio), and a mixture of zinc oxide powder A and zinc oxide powder C (A / C = 50 / 50 mass ratio) were determined by the following methods.

[0179] Specifically, using a Mastersizer 3000 laser diffraction particle size analyzer from Malvern Panalytical, zinc oxide particles were added to pure water to reach a specified concentration, and then the particle size distribution was determined by ultrasonic dispersion and stirring.

[0180] 1-2-5. Measurement Results

[0181] The determination results of zinc oxide powders A to C are shown in Table 1. Additionally, the X-ray diffraction patterns of zinc oxide powders A to C are shown in... Figure 2 As shown. Figure 2 The X-ray diffraction patterns of zinc oxide powder A, zinc oxide powder B, and zinc oxide powder C are shown in the image, from bottom to top. Additionally, the particle size distribution of the zinc oxide powder is as follows: Figure 3 As shown.

[0182] [Table 1]

[0183]

[0184] like Figure 2 As shown, the X-ray diffraction pattern of zinc oxide powder A is highly consistent with the literature values. In contrast, for zinc oxide powders B and C, the peak intensities of 002, 102, and 103, which contain more c-axis information, are relatively stronger than the literature values. That is to say, the peak intensity of zinc oxide powder A is higher than that of (I02, 102, and 103). 002 / I 101 The peak intensity ratio (I) of zinc oxide powders B and C is less than 0.5, which corresponds to the peak intensity ratio of B and C. 002 / I 101 The value is relatively high, reaching above 0.5.

[0185] Furthermore, compared to zinc oxide powders A and C, zinc oxide powder B exhibits a broader peak. This indicates the presence of oxygen vacancies, crystal structure deformation, and anisotropy caused by the stress applied during pulverization.

[0186] In addition, such as Figure 3 As shown, the mixture of zinc oxide powder A and zinc oxide powder B, as well as the mixture of zinc oxide powder A and zinc oxide powder C, all have a first peak (from zinc oxide powder B and C) in the range of particle size greater than 3 μm and less than 20 μm, and a second peak (from zinc oxide powder A) in the range of particle size less than 2 μm.

[0187] 2. Preparation, measurement, and evaluation of the negative electrode

[0188] 2-1. Preparation of the negative electrode

[0189] <Preparation of Negative Electrode 1>

[0190] The negative electrode slurry was prepared by mixing 80 parts by weight of zinc oxide powder B, 20 parts by weight of zinc oxide powder A, 25 parts by weight of metallic zinc powder (the total amount of zinc oxide powder B, zinc oxide powder A and metallic zinc powder relative to the solid component of the negative electrode slurry (total mass of the negative electrode slurry) is 91.7 by weight), bismuth oxide powder, potassium oxalate monohydrate, thickener, water and styrene-butadiene rubber according to the specified amounts.

[0191] The obtained negative electrode slurry was coated onto a tin-plated, non-porous copper foil and dried. It was then pressed using a pressing roller and cut into specified sizes. This yielded a capacity of 25 mAh / cm² per unit area. 2 The negative electrode.

[0192] <Preparation of Negative Electrode 2>

[0193] Except for changing zinc oxide powder B to zinc oxide powder C, negative electrode 2 is prepared in the same way as negative electrode 1.

[0194] <Preparation of Negative Electrode 3 and Negative Electrode 4>

[0195] Except for changing the contents of zinc oxide powder C and zinc oxide powder A to those shown in Table 2, negative electrodes 3 and 4 were prepared in the same manner as negative electrode 2. It should be noted that the capacity per unit area is 23.6 mAh / cm². 2 .

[0196] <Preparation of Negative Electrode 5>

[0197] The negative electrode 5 was prepared in the same manner as negative electrode 2, except that zinc oxide powder A was omitted and the content of zinc oxide powder C was changed to 100 parts by mass. It should be noted that the capacity per unit area is 23.6 mAh / cm². 2 .

[0198] <Preparation of Negative Electrode 6>

[0199] Except that zinc oxide powder B was not added and the content of zinc oxide powder A was changed to 100 parts by mass, negative electrode 6 was prepared in the same manner as negative electrode 1.

[0200] 2-2. Measurement and Evaluation

[0201] 2-2-1. X-ray diffraction (XRD) measurement

[0202] X-ray diffraction measurements were performed on the obtained negative electrodes 1 to 6. It should be noted that, except that the prepared negative electrodes were cut into 2cm x 2cm pieces and used as the test samples, the X-ray diffraction measurements were performed using the same methods and conditions as described above.

[0203] 2-2-2. Manufacturability

[0204] The manufacturability of the preparation of the negative electrode mixture slurry is evaluated according to the following criteria.

[0205] ○: Even when the water content of the slurry is below 80% relative to the total amount of zinc oxide particles (and secondary zinc oxide particles), the slurry exhibits good stability, fluidity, and drying speed.

[0206] ×: When the water content of the slurry is below 80% relative to the amount of zinc oxide particles (and the total amount of secondary zinc oxide particles), the stability, fluidity, and drying speed of the slurry are all poor.

[0207] The measurement results are as follows Figure 2 As shown.

[0208] [Table 2]

[0209]

[0210] As shown in Table 2, it can be seen that the peak intensity ratio (I) of the negative electrode 6 using only zinc oxide powder A is... 002 / I 101 The peak intensity ratio (I) is less than 0.5, compared to the peak intensity ratio (I) of negative electrodes using zinc oxide powder B or C from 1 to 5. 002 / I 101 The X-ray diffraction (XRD) value is relatively high, above 0.4. These results indicate that the XRD pattern of the negative electrode roughly corresponds to the XRD pattern of the zinc oxide powder used, maintaining the crystal structure.

[0211] In addition, the negative electrode mixtures using zinc oxide powder B or C (negative electrode mixtures 1 to 5) require less water to prepare the slurry compared to the negative electrode mixtures without zinc oxide powder B and C (negative electrode mixture 6), indicating that the manufacturability is also good.

[0212] 3. Preparation and evaluation of zinc batteries

[0213] 3-1. Preparation of Zinc Batteries

[0214] [Preparation of Zinc Battery 1]

[0215] <Preparation of the positive electrode>

[0216] (1) Preparation of positive electrode active material particles

[0217] Positive electrode active material particles were prepared by reaction crystallization.

[0218] Specifically, an aqueous solution is prepared by mixing nickel sulfate, zinc sulfate, and cobalt sulfate, and then ammonium ions are added to prepare an ammonia complex. The pH, reaction temperature, and ammonium ion concentration are adjusted to specified conditions, and an aqueous solution of sodium hydroxide is added to allow for a continuous reaction and slow crystal growth. This yields nickel hydroxide matrix particles with zinc and cobalt dissolved in them.

[0219] The obtained matrix particles were placed in an ammonia solution, and while adjusting the pH, a cobalt sulfate solution was added to precipitate cobalt hydroxide on the surface of the matrix particles. The precipitated cobalt hydroxide was then chemically oxidized by spraying a sodium hydroxide solution onto the particles under an oxygen-containing atmosphere and followed by heating, converting the precipitated cobalt hydroxide into cobalt hydroxide (a conductive cobalt compound).

[0220] Thus, positive electrode active material particles with a coating layer containing sodium-introduced cobalt hydroxyl oxide on the surface of the matrix particles are obtained.

[0221] (2) Preparation of the positive electrode

[0222] The positive electrode active material powder (comprising the positive electrode active material particles prepared above, with a mass ratio of 97.1% relative to the solid component of the positive electrode mixture slurry (total mass of the positive electrode mixture)), 1 part by mass of zinc oxide powder, cobalt hydroxide powder, yttrium oxide powder, niobium oxide powder, thickener, PTFE, and water are mixed according to the specified amounts to prepare the positive electrode mixture slurry.

[0223] The obtained positive electrode slurry was filled into nickel foam, dried, pressed, and cut to specified dimensions. This resulted in a capacity of 13.4 mAh / cm². 2 The positive pole.

[0224] <Preparation of Electrolyte>

[0225] An electrolyte was prepared by dissolving 4% by mass of zinc oxide in an aqueous solution containing 6 mol / L potassium hydroxide and 0.5 mol / L lithium hydroxide (potassium hydroxide 25.81% by mass, lithium oxide 0.92% by mass, totaling 26.73% by mass).

[0226] <Battery Manufacturing>

[0227] The prepared positive electrode, the prepared negative electrode 1, and a diaphragm assembly consisting of a nonwoven fabric diaphragm and a hydrophilically treated polypropylene microporous membrane are wound together to obtain an electrode assembly. Specifically, materials sequentially layered with the diaphragm assembly / positive electrode / diaphragm assembly / negative electrode are wound to obtain an electrode assembly with the negative electrode disposed on the outermost circumferential surface. This assembly is then inserted into a tin-plated outer can.

[0228] Then, 5.738g of the electrolyte prepared above was injected to prepare a cylindrical nickel-zinc secondary battery with a nominal capacity of 2000mAh.

[0229] The obtained battery was charged to its nominal capacity under a constant current and constant voltage of 1.9V and then discharged to 1.3V. This cycle was repeated 5 times for activation treatment.

[0230] [Preparation of Zinc Batteries 2-6]

[0231] Except for changing the type of negative electrode to that shown in Table 3, zinc batteries 2 to 6 are prepared in the same manner as zinc battery 1.

[0232] 3-2. Evaluation

[0233] 3-2-1. Cold Start Current Test (CCA Test)

[0234] The obtained zinc battery was subjected to CCA testing.

[0235] Specifically, first, the zinc battery 1 is charged at 25°C for 24 hours at a constant current constant voltage (CCCV) rate of 0.5C with a maximum voltage of 1.9V. Then, after a 24-hour pause, it is discharged at -18°C for 30 seconds at a constant current (CC) current with a CCA current. It should be noted that the highest current value that zinc battery 1 can achieve according to the standard is defined as the CCA current.

[0236] (CCA Test Conditions)

[0237] Charging: CCCV_1.9V_0.5C_24h

[0238] Pause: 24h

[0239] Discharge: CCA current

[0240] Discharge time: 30 seconds

[0241] Temperature: Tested at 25°C only during the charging phase; subsequently at -18°C.

[0242] Furthermore, the voltage of the zinc battery was measured after a 30-second discharge. If it remained at 0.9V after a 30-second discharge, it was considered to have met the standard.

[0243] 3-2-2. X-ray diffraction determination of the negative electrode recovered from the battery

[0244] After activation and CCA testing, the battery was discharged to 1.3V, and the negative electrode was removed. The removed negative electrode was washed with deionized water, and samples were taken from any location other than the unreacted portions at the beginning and end of the winding for X-ray diffraction. During sampling, any portion of the negative electrode other than the aforementioned unreacted portions was cut into 2cm x 2cm pieces to serve as the sample. X-ray diffraction was performed under the same conditions and methods as the X-ray diffraction determination of the negative electrode described above.

[0245] 3-2-3. Evaluation Results

[0246] The evaluation results of zinc batteries 1–6 are shown in Table 3. Additionally, the X-ray diffraction patterns of the recovered negative electrodes from zinc batteries 1, 2, and 6 are shown in Table 3. Figure 4 As shown.

[0247] [Table 3]

[0248]

[0249] As shown in Table 3, it can be seen that in zinc battery 6 (Comparative Example 1), the voltage after 30 seconds in the CCA test at -18°C is lower than the standard. In contrast, the voltage after 30 seconds in zinc batteries 1 and 2 (Examples) exceeds the standard by 0.9V. Thus, compared with the above-mentioned peak intensity ratio (I... 002 / I 101 Compared to zinc batteries with a negative electrode less than 0.4, the peak intensity ratio (I) of XRD derived from zinc oxide is significantly higher. 002 / I 101 In zinc batteries 1 and 2, which have a negative electrode with a particle size of 0.4 or higher, although they use more zinc oxide particles with larger particle size and smaller specific surface area in their negative electrodes, they exhibit good discharge characteristics in CCA tests.

[0250] Therefore, it can be inferred that when using the above peak intensity ratio (I) 002 / I 101 When the negative electrode has a specific surface area of ​​0.4 or higher, the improved discharge performance due to the increased reactivity is better than the decreased discharge performance due to the reduced specific surface area.

[0251] In addition, such as Figure 4 As shown, the peak intensity ratio (I) of the XRD of the negative electrode recovered from the battery after CCA testing 002 / I 101 The cathode is the same as the cathode before it was made into a battery. Therefore, it can be concluded that the anisotropic zinc oxide particles used as the cathode are stable and maintain their crystal structure after the battery is made.

[0252] Specifically, in the X-ray diffraction patterns of the negative electrodes recovered from zinc batteries 1 and 2, an increase in peak intensity from the (002) plane of zinc oxide was observed compared to the negative electrode recovered from zinc battery 6. This trend is the same as that observed in the negative electrodes before they were used to make the battery.

[0253] In particular, in the X-ray diffraction measurement of the negative electrode recovered from the zinc battery 1, the peak intensity ratio of the peak intensity from the (002) plane located near 34° to the peak intensity from the (101) plane located near 36° with the strongest intensity is 0.62. It can be seen that the peak intensity ratio is above 0.4, which is the same as the state of the negative electrode before the battery was made.

[0254] Industrial applicability

[0255] According to the present invention, a zinc battery anode material with good manufacturability and improved discharge characteristics, a zinc battery anode, a zinc battery, and a method for manufacturing the zinc battery anode are provided.

[0256] This application claims priority to Japanese Patent Application No. 2024-185830, filed on October 22, 2024. The contents of that application, including its description and drawings, are incorporated herein by reference in their entirety.

Claims

1. A negative electrode for a zinc battery, characterized in that, It contains a negative electrode compound containing zinc oxide. In the X-ray diffraction pattern of the negative electrode compound, the peak intensity I from the (002) plane of zinc oxide is... 002 The peak intensity I relative to the (101) plane of zinc oxide 101 The ratio of I 002 / I 101 It is above 0.

4.

2. The negative electrode for a zinc battery as described in claim 1, wherein, The zinc oxide comprises zinc oxide particles. The median diameter of the zinc oxide particles is greater than 3 μm and less than 20 μm.

3. The negative electrode for a zinc battery as described in claim 2, wherein, The negative electrode mixture also contains second zinc oxide particles with a median diameter of less than 2 μm.

4. The negative electrode for a zinc battery as described in claim 3, wherein, The zinc oxide particles contain at least 50% by mass relative to the total amount of zinc oxide particles and the second zinc oxide particles in the negative electrode mixture.

5. The negative electrode for a zinc battery as described in claim 1, wherein, The negative electrode for the zinc battery also has a current collector to retain the negative electrode binder. The current collector is a non-porous current collector.

6. A zinc battery, characterized in that, It has a positive electrode, a negative electrode, and an alkaline electrolyte. The negative electrode is the negative electrode for a zinc battery as described in claim 1.

7. The zinc battery as described in claim 6, wherein, The zinc battery is a nickel-zinc secondary battery.

8. A method for manufacturing a negative electrode for a zinc battery, characterized in that, include: The process of preparing zinc oxide particles as follows, in the X-ray diffraction pattern of the zinc oxide particles, the peak intensity I of the (002) plane. 002 Peak intensity I relative to the (101) plane 101 The ratio of I 002 / I 101 0.5 or higher; and The process of preparing a negative electrode mixture containing the zinc oxide particles.

9. The method for manufacturing a negative electrode for a zinc battery as described in claim 8, wherein, The median diameter of the zinc oxide particles is greater than 3 μm and less than 20 μm.

10. The method for manufacturing a negative electrode for a zinc battery as described in claim 9, wherein, In the process of preparing the negative electrode mixture, The negative electrode mixture contains the zinc oxide particles and a second zinc oxide particle with a median diameter of less than 2 μm.

11. The method for manufacturing a negative electrode for a zinc battery as described in claim 10, wherein, The zinc oxide particles contain at least 50% by mass relative to the total amount of zinc oxide particles and the second zinc oxide particles in the negative electrode mixture.

12. A negative electrode material for zinc batteries, characterized in that, The zinc oxide particles contained herein have the following X-ray diffraction pattern, in which the peak intensity I of the (002) plane is... 002 Peak intensity I relative to the (101) plane 101 The ratio of I 002 / I 101 It is above 0.5.

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