Zinc negative electrode material, zinc negative electrode and nickel-zinc battery

Abstract

The invention provides a zinc negative electrode material, a zinc negative electrode and a nickel-zinc battery in order to solve the problem that an oxidation film generated by a negative electrode of a nickel-zinc battery in the prior art hinders electron conduction and influences electrochemical performance. The zinc negative electrode material comprises a negative electrode active material, the negative electrode active material comprises a zinc composite material, the zinc composite material has a core-shell structure, the core-shell structure comprises an inner core, a middle layer and a shell layer, the inner core is zinc powder, the middle layer coats the inner core, and the shell layer coats the middle layer. According to the zinc negative electrode material provided by the invention, the surface of the inner core zinc powder is coated with the middle layer, so that the effect of protecting the zinc powder is achieved, corrosion to the zinc powder is slowed down, and the basic performance of the zinc powder is maintained; besides, the surface of the middle layer is coated with the shell layer, the property of the surface of the zinc powder can be changed, meanwhile, the shell layer can cover hydrogen evolution reaction active sites on the surface of the middle layer, the shell layer can adjust the reduction potential of the zinc powder, the overall hydrogen evolution overpotential on the surface of the zinc powder is increased, the hydrogen evolution side reaction is reduced, and the stability of the electrochemical performance of the battery is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrode and battery manufacturing, and particularly relates to a zinc negative electrode material, a zinc negative electrode and a nickel-zinc battery. Background Art

[0002] In the nickel-zinc battery system, zinc is a relatively active metal. Even in the internal environment of the battery, zinc is prone to react with oxygen in the surrounding environment or some oxidizing substances contained in the battery electrolyte, and then an oxide film is formed on the surface of the zinc powder. For example, the common reaction of zinc with oxygen will generate zinc oxide (ZnO). If this naturally formed oxide film is not controlled, its thickness may continue to increase. And the relatively thick oxide film has many disadvantages. From an electrochemical perspective, during the charge and discharge process of the nickel-zinc battery, the zinc powder serves as the negative electrode material and needs to participate in the transfer of electrons and the interaction with ions in the electrolyte to achieve the functions of electrical energy storage and release of the battery. However, the too thick oxide film will hinder the conduction of electrons, making it difficult for electrons to smoothly pass through the oxide film from the inside of the zinc powder to the external circuit. At the same time, it will also affect the effective contact and reaction between the ions in the electrolyte and the zinc powder, thereby greatly reducing the electrochemical activity of the zinc powder and resulting in a decline in the charge and discharge performance of the battery. Situations such as a decrease in the battery capacity, unstable discharge voltage, and low charge and discharge efficiency may occur. Summary of the Invention

[0003] Aiming at the problem that the oxide film generated on the negative electrode of the nickel-zinc battery in the prior art hinders electron conduction and affects the electrochemical performance, a zinc negative electrode material, a zinc negative electrode and a nickel-zinc battery are provided.

[0004] The technical solutions adopted by the present invention to solve the above technical problems are as follows: On the one hand, the present invention provides a zinc negative electrode material, including a negative electrode active material, the negative electrode active material includes a zinc composite material, the zinc composite material has a core-shell structure, the core-shell structure includes an inner core, an intermediate layer and an outer shell layer, the inner core is zinc powder, the intermediate layer is coated outside the inner core, and the outer shell layer is coated outside the intermediate layer; The intermediate layer includes a first material, and the first material includes one of calcium oxide, magnesium oxide, aluminum oxide, cerium oxide and silicon oxide; The outer shell layer includes a second material, and the second material includes one or more of carbon black, polytetrafluoroethylene, graphene and naphthol. Optionally, the thickness of the intermediate layer is 1-15 μm.

[0005] Optionally, the thickness of the outer shell layer is 1-15 μm.

[0006] Optionally, the molar ratio of the zinc powder, the first material and the second material is 96-99:0.5-3:0.5-2.

[0007] Optionally, the particle size of the zinc powder is 80 mesh - 400 mesh.

[0008] Optionally, in the zinc powder, the zinc content is 90 - 96%.

[0009] Optionally, the morphology of the zinc powder includes one or more of spherical, flaky, rod-shaped, and other irregular shapes.

[0010] Optionally, the specific surface area of the zinc powder is 80 - 590 m 2 / g, and the bulk density of the zinc powder is 5.5 - 7.50 g / mL.

[0011] Optionally, the negative electrode active material further includes a zinc alloy, and the zinc alloy includes one or more of zinc-aluminum alloy, zinc-magnesium alloy, zinc-copper alloy, and zinc-titanium alloy. Optionally, the zinc content in the zinc alloy is 62% - 98%.

[0012] Optionally, the negative electrode active material further includes a surfactant, and the surfactant includes one or more of sodium dodecyl sulfate, cetyltrimethylammonium bromide, docosyl betaine, and polyvinylpyrrolidone.

[0013] Optionally, the negative electrode active material further includes In2O3, Bi2O3, and Al2O3; In the negative electrode active material, the added mass of In2O3 is 0.5% - 1%, the added mass of Bi2O3 is 3% - 5%, and the added mass of Al2O3 is 1% - 3%.

[0014] Optionally, the negative electrode active material further includes zinc oxide, and the mass ratio of the zinc powder to the zinc oxide is 1:4 - 1:2.

[0015] On the other hand, the present invention provides a zinc negative electrode, including a current collector and a negative electrode material layer, the negative electrode material layer is disposed on the current collector, and the negative electrode material layer includes the zinc negative electrode material as described above.

[0016] Optionally, the negative electrode material layer further includes a conductive agent, a thickening agent, and a binder; In the negative electrode active material of the negative electrode material layer, the added mass of the conductive agent is 1% - 1.5%; the added mass of the thickening agent is 0.2% - 0.5%, and the added mass of the binder is 2% - 3%.

[0017] On the other hand, the present invention provides a nickel-zinc battery, including a positive electrode, a separator, an electrolyte, and the zinc negative electrode as described above.

[0018] The beneficial effects of the present invention are as follows: The zinc negative electrode material provided by the present invention includes a composite material with a core-shell structure, in which zinc powder is used as the inner core and is coated with an intermediate layer made of a first material. Coating the intermediate layer on the surface of the zinc powder can avoid direct contact between the zinc powder and the external environment, play a role in protecting the zinc powder, slow down the corrosion of the zinc powder, so that the zinc powder can maintain a relatively good state and maintain its basic performance. In addition, an outer shell layer made of a second material is coated on the surface of the intermediate layer. The coating of the outer shell layer is beneficial to changing the physical and chemical properties of the zinc powder surface. On the one hand, the outer shell layer can cover the hydrogen evolution reaction active sites that may exist on the surface of the intermediate layer. On the other hand, the outer shell layer can adjust the reduction potential of the zinc powder, increasing the overall hydrogen evolution overpotential on the zinc powder surface, thereby reducing the occurrence of hydrogen evolution side reactions and ensuring the stability of the battery's electrochemical performance. Detailed implementation manners

[0019] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0020] The present invention provides a zinc negative electrode material, including a negative electrode active material. The negative electrode active material includes a zinc composite material. The zinc composite material has a core-shell structure. The core-shell structure includes an inner core, an intermediate layer and an outer shell layer. The inner core is zinc powder, the intermediate layer is coated outside the inner core, and the outer shell layer is coated outside the intermediate layer; The intermediate layer includes a first material, and the first material includes one of calcium oxide, magnesium oxide, aluminum oxide, cerium oxide and silicon oxide; The outer shell layer includes a second material, and the second material includes one or more of carbon black, polytetrafluoroethylene, graphene and naphthol.

[0021] Specifically, the zinc negative electrode material provided by the present invention includes a composite material with a core-shell structure, in which zinc powder is used as the inner core and is coated with an intermediate layer made of a first material. Coating the intermediate layer on the surface of the zinc powder can avoid direct contact between the zinc powder and the external environment, play a role in protecting the zinc powder, slow down the corrosion of the zinc powder, so that the zinc powder can maintain a relatively good state and maintain its basic performance. In addition, an outer shell layer made of a second material is coated on the surface of the intermediate layer. The coating of the outer shell layer is beneficial to changing the physical and chemical properties of the zinc powder surface. On the one hand, the outer shell layer can cover the hydrogen evolution reaction active sites that may exist on the surface of the intermediate layer. On the other hand, the outer shell layer can adjust the reduction potential of the zinc powder, increasing the overall hydrogen evolution overpotential on the zinc powder surface, thereby reducing the occurrence of hydrogen evolution side reactions and ensuring the stability of the battery's electrochemical performance.

[0022] Specifically, after the outer shell layer coats the intermediate layer, it can also prevent the intermediate layer from falling off due to the scouring of the electrolyte and mechanical wear during battery use, extend the service life of the battery, and improve the overall performance and reliability of the battery. In summary, by treating the zinc powder in the nickel-zinc battery, the performance of the zinc powder in the battery is optimized, the occurrence of side reactions is reduced, and the overall performance and use safety of the battery are improved.

[0023] In some embodiments, the thickness of the intermediate layer is 1-15 μm.

[0024] It should be noted that as the negative electrode material, zinc powder needs to participate in the transfer of electrons and the interaction with ions in the electrolyte to achieve the functions of electrical energy storage and release in the battery. However, an intermediate layer that is too thick will hinder the conduction of electrons, making it difficult for electrons to pass through the intermediate layer from inside the zinc powder to the external circuit smoothly. At the same time, it will also affect the effective contact and reaction between the ions in the electrolyte and the zinc powder, thus greatly reducing the electrochemical activity of the zinc powder and resulting in a decline in the charge and discharge performance of the battery. A thinner intermediate layer is difficult to provide enough buffer space to cope with the volume expansion and contraction of the zinc powder.

[0025] Regarding the related problems existing in the above-mentioned too-thick intermediate layer, through previous verification by the inventor, when the coating thickness of the intermediate layer on the surface of the zinc powder is in the range of 1-15 μm, electrons can relatively smoothly pass through the intermediate layer from inside the zinc powder to the external circuit, and at the same time play a role in slowing down the natural oxidation rate of the zinc powder; in summary, controlling the thickness of the intermediate layer within a suitable range can not only ensure its sufficient ability to block the erosion of external oxidizing substances, but also not hinder the normal electrochemical activity of the zinc powder due to being too thick, enabling the zinc powder to continuously and stably participate in the charge and discharge process in the battery and maintaining good battery performance.

[0026] Specifically, the thickness of the intermediate layer can be 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 13 μm or 15 μm.

[0027] In some embodiments, the thickness of the outer shell layer is 1-15 μm.

[0028] Specifically, setting the outer shell layer is beneficial to reducing the occurrence of hydrogen evolution side reactions. When the thickness of the outer shell layer is 1-15 μm, it can cover the hydrogen evolution reaction active sites on the surface of the intermediate layer, and for materials with good barrier properties such as carbon black and polytetrafluoroethylene, it can also form a continuous protection at the microscopic level, reducing the contact between the electrolyte and the active sites, thereby playing an inhibitory role in the hydrogen evolution side reaction.

[0029] Specifically, the thickness of the outer shell layer can be 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 13 μm or 15 μm.

[0030] In some embodiments, the molar ratio of the zinc powder, the first material, and the second material is 96 - 99:0.5 - 3:0.5 - 2.

[0031] In some embodiments, the particle size of the zinc powder is 80 mesh - 400 mesh.

[0032] It should be noted that the particle size of zinc powder affects the electrochemical reaction and corrosion rate. Zinc powders with different particle sizes may exhibit different deposition morphologies and dendrite growth tendencies during the charge - discharge cycle; in the electrochemical reaction, a smaller particle size of zinc powder can increase the specific surface area and improve the active surface area of the electrochemical reaction. However, zinc powder with a small particle size is prone to self - corrosion in alkaline electrolytes, resulting in a decrease in the Coulombic efficiency of the battery. A larger particle size of zinc powder is relatively more stable in air, but due to its smaller specific surface area, its chemical reaction activity is relatively low.

[0033] Specifically, in this application, a surfactant is used to regulate the crystal form of the zinc powder to achieve the corresponding effect; in this application, the particle size of the zinc powder is set in the range of 80 mesh - 400 mesh. After optimizing the particle size of the zinc powder, it is further coated with the intermediate layer and the outer shell layer, which is beneficial to further stabilizing the surface state of the zinc powder, making the transmission of electrons and ions more smooth during the charge - discharge process of the battery, thereby improving the charge - discharge efficiency of the battery. In some embodiments, in the zinc powder, the content of zinc is 90% - 96%.

[0034] A suitable zinc content makes the physical and chemical properties of the zinc powder surface relatively uniform, which is beneficial for the outer shell layer to better cover the hydrogen evolution reaction active sites that may exist on the surface of the intermediate layer; if the zinc content is too high or too low, the distribution and properties of the active sites on the zinc powder surface may change, resulting in the outer shell layer being difficult to completely cover or having a poor covering effect. The inventors verified through experiments in the early stage that a zinc content of 90% - 96% can ensure that the outer shell layer plays the best covering role and reduces the occurrence of hydrogen evolution reactions. It is speculated that the reason may be that the zinc content in this range can enable the outer shell layer to more effectively adjust the reduction potential of the zinc powder, increasing the overall hydrogen evolution over - potential on the zinc powder surface, thereby more effectively reducing the hydrogen evolution side reaction and ensuring the stability of the battery's electrochemical performance.

[0035] In some embodiments, the morphology of the zinc powder includes one or more of spherical, flaky, rod - shaped, and other irregular shapes.

[0036] The morphology of zinc powder will affect its packing density, conductivity, and reaction activity.

[0037] Specifically, due to its regular spherical structure, the spherical zinc powder can achieve close packing and obtain a high packing density; the flaky zinc powder fills some voids by overlapping flakes; the rod-shaped zinc powder intersperses between the spherical and flaky zinc powders to further reduce voids; although the irregular-shaped zinc powder has an irregular shape, it can also fill some remaining tiny voids.

[0038] The spherical zinc powder provides stable and uniformly distributed reaction sites, which is conducive to controlling the reaction rate. The high specific surface area of the flaky zinc powder can contribute more highly active reaction sites. Therefore, the spherical zinc powder and the flaky zinc powder have a higher packing density and a uniform current distribution, which can reduce the growth of zinc dendrites. In some embodiments, the specific surface area of the zinc powder is 80 - 590 m 2 / g, and the packing density of the zinc powder is 5.5 - 7.50 g / mL.

[0039] The specific surface area in the range of 80 - 590 m² / g means that the zinc powder has a large number of surface atoms and abundant active sites, which can provide more sites for the electrochemical reaction during the charge and discharge process of the battery, making the ion exchange between the zinc powder and the electrolyte more sufficient, accelerating the reaction rate, and thus improving the charge and discharge performance of the battery; in addition, the larger specific surface area increases the contact area between the zinc powder and the intermediate layer, which is beneficial for the intermediate layer to coat more tightly and uniformly on the surface of the zinc powder. The intermediate layer can better adhere to the zinc powder, enhancing the interaction between the two, thereby improving the protection effect of the intermediate layer on the zinc powder and more effectively avoiding the direct contact between the zinc powder and the external environment, further slowing down the corrosion rate of the zinc powder.

[0040] In some embodiments, the negative electrode active material further includes a zinc alloy, and the zinc alloy includes one or more of a zinc-aluminum alloy, a zinc-magnesium alloy, a zinc-copper alloy, and a zinc-titanium alloy. Specifically, adding alloyed zinc to the negative electrode active material can improve its corrosion resistance and cycle stability, and at the same time, the zinc alloy can effectively alleviate the growth of dendrites.

[0041] In some embodiments, the zinc content in the zinc alloy is 62% - 98%.

[0042] Specifically, the zinc content in the zinc alloy can be 62%, 70%, 80%, 90%, or 98%.

[0043] In some embodiments, the negative electrode active material further includes a surfactant, and the surfactant includes one or more of sodium dodecyl sulfate, cetyltrimethylammonium bromide, docosyl betaine, and polyvinylpyrrolidone.

[0044] In some embodiments, the negative electrode active material further includes In2O3, Bi2O3, and Al2O3; In the negative electrode active material, the added mass of In2O3 is 0.5% - 1%, the added mass of Bi2O3 is 3% - 5%, and the added mass of Al2O3 is 1% - 3%.

[0045] Specifically, In2O3 mainly plays roles such as improving electrical conductivity and enhancing cycle stability in the battery negative electrode, thereby significantly improving battery performance; specifically, when In2O3 is added to the negative electrode material, it can effectively reduce the internal resistance of the battery, thereby improving the charge and discharge efficiency of the battery, and further significantly improving the overall electrical conductivity of the electrode material. In addition, the structural stability of In2O3 enables it to maintain a high capacity after multiple charge and discharge cycles. By compounding with other negative electrode materials such as graphite or silicon, In2O3 helps to mitigate the structural damage caused by volume changes during charge and discharge of these materials, thereby improving the cycle stability of the battery; Bi2O3 (bismuth oxide) plays roles of improving electrochemical performance, inhibiting dendrite formation, and enhancing cycle life in the negative electrode active material of nickel-zinc batteries; specifically, Bi2O3 has a high theoretical capacity as an electrode material because bismuth can undergo reversible reactions with metals such as lithium and sodium to form alloys, thereby storing a large amount of energy. In addition, in secondary batteries such as nickel-zinc batteries, Bi2O3 can effectively inhibit the formation of dendrites, thereby improving the safety and cycle stability of the battery. By compounding with carbon or zinc materials, Bi2O3 can alleviate the volume expansion problem during charge and discharge and improve the cycle stability of the electrode material; specifically, Al2O3 plays roles of inhibiting dendrite growth, improving electrochemical performance, and enhancing life in the nickel-zinc battery negative electrode. Al2O3 helps to maintain the activity and specific surface area of the zinc electrode during cycling, disrupt the close packing of zinc oxide, and increase the reactive surface area of zinc oxide, enabling zinc oxide to maintain high electrochemical activity during cycling. In some embodiments, the negative electrode active material further includes zinc oxide, and the mass ratio of the zinc powder to the zinc oxide is 1:4 - 1:2.

[0046] Another embodiment of the present invention provides a zinc negative electrode, including a current collector and a negative electrode material layer. The negative electrode material layer is disposed on the current collector, and the negative electrode material layer includes the above-mentioned zinc negative electrode material.

[0047] In some embodiments, the negative electrode material layer includes a conductive agent, a thickening agent, and a binder; In the negative electrode active material of the negative electrode material layer, the added mass of the conductive agent is 1% - 1.5%; the added mass of the thickening agent is 0.2% - 0.5%, and the added mass of the binder is 2% - 3%.

[0048] Specifically, the thickening agent includes styrene-butadiene rubber and polytetrafluoroethylene, and styrene-butadiene rubber (SBR): polytetrafluoroethylene (PTFE) = 3:7; The thickener includes sodium polyacrylate, sodium carboxymethyl cellulose and polyvinyl alcohol, and the mass ratio of sodium polyacrylate (PAANa): sodium carboxymethyl cellulose (CMC): polyvinyl alcohol (PVA) is 1:7:2; Specifically, the conductive agent includes one or more of nickel powder, nickel carbonyl powder, cobalt oxide, graphene, graphite, acetylene black and carbon powder.

[0049] Another embodiment of the present invention provides a nickel-zinc battery, which includes a positive electrode, a separator, an electrolyte and the zinc negative electrode described above.

[0050] Specifically, the separator is disposed between the positive electrode and the zinc negative electrode to form an electrode core, and then the electrode core is assembled with a battery case and filled with electrolyte to obtain a nickel-zinc battery; In the zinc negative electrode material of the nickel-zinc battery described in the present application, an intermediate layer made of a first material is used for coating. Coating the intermediate layer on the surface of the zinc powder can avoid direct contact between the zinc powder and the external environment, play a role in protecting the zinc powder, slow down the corrosion of the zinc powder, so that the zinc powder can maintain a relatively good state and maintain its basic performance; in addition, an outer shell layer made of a second material is coated on the surface of the intermediate layer. The coating of the outer shell layer is beneficial to changing the physical and chemical properties of the surface of the zinc powder. On the one hand, the outer shell layer can cover the hydrogen evolution reaction active sites that may exist on the surface of the intermediate layer. On the other hand, the outer shell layer can adjust the reduction potential of the zinc powder, increase the overall hydrogen evolution overpotential on the surface of the zinc powder, thereby reducing the occurrence of hydrogen evolution side reactions and ensuring the stability of the electrochemical performance of the battery.

[0051] The positive electrode includes a positive electrode current collector and a positive electrode active material layer. The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material is selected from one or more of Ni(OH)2 (nickel hydroxide), ZnO, CoO (cobalt oxide), Ni powder, Y2O3 (yttrium trioxide) and Yb2O3 (ytterbium trioxide).

[0052] The positive electrode active material layer further includes a positive electrode binder and a positive electrode conductive agent, and the positive electrode active material, the positive electrode binder and the positive electrode conductive agent are blended to obtain the positive electrode active material layer.

[0053] The positive electrode binder may be at least one of thermoplastic resins such as polyvinylidene fluoride, copolymers of vinylidene fluoride, polytetrafluoroethylene, copolymers of vinylidene fluoride - hexafluoropropylene, copolymers of tetrafluoroethylene - hexafluoropropylene, copolymers of tetrafluoroethylene - perfluoroalkyl vinyl ether, copolymers of ethylene - tetrafluoroethylene, copolymers of vinylidene fluoride - tetrafluoroethylene, copolymers of vinylidene fluoride - trifluoroethylene, copolymers of vinylidene fluoride - trichloroethylene, copolymers of vinylidene fluoride - fluoroethylene, copolymers of vinylidene fluoride - hexafluoropropylene - tetrafluoroethylene, thermoplastic polyimide, polyethylene, and polypropylene; acrylic resins, carboxymethyl cellulose, and styrene - butadiene rubber.

[0054] The positive electrode conductive agent may be at least one of conductive carbon black, conductive carbon spheres, conductive graphite, conductive carbon fibers, carbon nanotubes, graphene, or reduced graphene oxide.

[0055] The separator may be an existing conventional separator, which may be a ceramic separator, a polymer separator, a non - woven fabric, an inorganic - organic composite separator, etc., including but not limited to single - layer PP (polypropylene), single - layer PE (polyethylene), double - layer PP / PE, double - layer PP / PP, and triple - layer PP / PE / PP separators. double - layer PP / PE, double - layer PP / PP, and triple - layer PP / PE / PP separators. The following further illustrates the present invention through examples.

[0056] Example 1

[0057] This example is used to illustrate a zinc negative electrode material, a zinc negative electrode, and a nickel - zinc battery disclosed by the present invention, including the following operating steps: Pretreatment of zinc powder: Take zinc powder treated with sodium dodecyl sulfate (SDS) to obtain spherical zinc powder with a mesh size of 300. Preparation of core - shell structured zinc composite material: Take a solvent and calcium oxide and blend them evenly to obtain an intermediate layer slurry containing 2% calcium oxide. Take a solvent and graphene and blend them evenly to obtain an outer shell layer slurry containing 1% graphene. Coat the intermediate layer slurry on the surface of the inner core zinc powder to obtain a material with the inner core of zinc powder coated with an intermediate layer. The thickness of the intermediate layer formed by the intermediate layer slurry is 5 μm. Then coat the outer shell layer slurry on the surface of the intermediate layer to obtain a core - shell structured zinc composite material. The thickness of the outer shell layer formed by the outer shell layer slurry is 5 μm. The zinc content in the zinc powder is 96%. The molar ratio of the zinc powder, the first material, and the second material is 97:2:1. Preparation of zinc negative electrode: ​After mixing 1% conductive agent and 0.3% thickening agent, add 1% In2O3, 4% Bi2O3, 3% Al2O3, and 1.3% zinc-magnesium alloy. Stir for 30 minutes until well mixed, then add 67% ZnO and 20% zinc composite material. Stir for 20 minutes, and then add 2.4% binder and mix again to obtain the negative electrode paste. Coat the negative electrode paste onto the inclined drawn tin-coated copper mesh current collector, and then perform roll pressing, softening, and cutting to obtain the zinc negative electrode.

[0058] Prepare the positive electrode: Mix Ni(OH)2, ZnO, CoO, Ni powder, Ca(OH)2, Y2O3, Yb2O3, graphite, CMC, and PTFE in a weight ratio of 80:1:3:2:1:2:2:1:5:0.5. After stirring evenly, coat it on the positive electrode current collector, and then perform roll pressing, softening, and cutting to obtain the nickel positive electrode.

[0059] Prepare the electrolyte: Take 80% KOH (5 mol / L), 2% ZnO (0.5 mol / L), 10% silica sol, and 3% disodium hydrogen phosphate, with the remainder being water, and mix them to obtain the electrolyte.

[0060] Stack the positive electrode, separator, and zinc negative electrode in sequence, with the separator placed in the middle of the positive and negative electrodes to prepare the battery cell. Place the battery cell in an outer packaging bag for drying, inject the above electrolyte, and then perform operations such as vacuum packaging, standing, forming, and shaping to obtain the nickel-zinc battery.

[0061] Example 2 This example is used to illustrate a zinc negative electrode material, zinc negative electrode, and nickel-zinc battery disclosed in the present invention. It includes most of the operations in Example 1, and the differences are as follows: When preparing the outer shell layer paste, the second material is selected from naphthol.

[0062] Example 3 This example is used to illustrate a zinc negative electrode material, zinc negative electrode, and nickel-zinc battery disclosed in the present invention. It includes most of the operations in Example 1, and the differences are as follows: The thickness of the intermediate layer is 2 μm; The thickness of the outer shell layer is 2 μm.

[0063] Example 4 This example is used to illustrate a zinc negative electrode material, zinc negative electrode, and nickel-zinc battery disclosed in the present invention. It includes most of the operations in Example 1, and the differences are as follows: The thickness of the intermediate layer is 13 μm; The thickness of the outer shell layer is 13 μm.

[0064] Example 5 This example is used to illustrate a zinc negative electrode material, zinc negative electrode and nickel-zinc battery disclosed by the present invention. It includes most of the operations in Example 1, and the differences are as follows: The thickness of the intermediate layer is 2 μm; The thickness of the outer shell layer is 13 μm.

[0065] Example 6 This example is used to illustrate a zinc negative electrode material, zinc negative electrode and nickel-zinc battery disclosed by the present invention. It includes most of the operations in Example 1, and the differences are as follows: In the pretreatment of zinc powder, sodium dodecyl sulfate (SDS) is used for treatment to obtain spherical zinc powder with 100 meshes.

[0066] Example 7 This example is used to illustrate a zinc negative electrode material, zinc negative electrode and nickel-zinc battery disclosed by the present invention. It includes most of the operations in Example 1, and the differences are as follows: In the pretreatment of zinc powder, sodium dodecyl sulfate (SDS) is used for treatment to obtain spherical zinc powder with 400 meshes.

[0067] Example 8 This example is used to illustrate a zinc negative electrode material, zinc negative electrode and nickel-zinc battery disclosed by the present invention. It includes most of the operations in Example 1, and the differences are as follows: In the pretreatment of zinc powder, cetyltrimethylammonium bromide (CATB) is used for treatment to obtain rod-shaped zinc powder with 300 meshes.

[0068] Example 9 This example is used to illustrate a zinc negative electrode material, zinc negative electrode and nickel-zinc battery disclosed by the present invention. It includes most of the operations in Example 1, and the differences are as follows: In the pretreatment of zinc powder, polyvinylpyrrolidone (PVP) is used for treatment to obtain zinc powder with an irregular polyhedral morphology of 300 meshes.

[0069] Example 10 This example is used to illustrate a zinc negative electrode material, zinc negative electrode and nickel-zinc battery disclosed by the present invention. It includes most of the operations in Example 1, and the differences are as follows: In the pretreatment of zinc powder, sodium dodecyl sulfate (SDS) is used for treatment to obtain flaky zinc powder with 300 meshes.

[0070] Example 11 This example is used to illustrate a zinc negative electrode material, zinc negative electrode and nickel-zinc battery disclosed by the present invention. It includes most of the operations in Example 1, and the differences are as follows: The zinc content in the core zinc powder is 90%.

[0071] Example 12 This example is used to illustrate a zinc negative electrode material, a zinc negative electrode and a nickel-zinc battery disclosed by the present invention, including most of the operations in Example 1, and the differences are as follows: The molar ratio of the zinc powder, the first material and the second material is 96:3:1.

[0072] Example 13 This example is used to illustrate a zinc negative electrode material, a zinc negative electrode and a nickel-zinc battery disclosed by the present invention, including most of the operations in Example 1, and the differences are as follows: The molar ratio of the zinc powder, the first material and the second material is 99:0.5:0.5.

[0073] Comparative Example 1 This comparative example is used to comparatively illustrate a zinc negative electrode material, a zinc negative electrode and a nickel-zinc battery disclosed by the present invention, including most of the operations in Example 1, and the differences are as follows: No intermediate layer coating is performed on the surface of the zinc powder.

[0074] Comparative Example 2 This comparative example is used to comparatively illustrate a zinc negative electrode material, a zinc negative electrode and a nickel-zinc battery disclosed by the present invention, including most of the operations in Example 1, and the differences are as follows: No outer layer coating is performed on the surface of the zinc powder.

[0075] Comparative Example 3 This comparative example is used to comparatively illustrate a zinc negative electrode material, a zinc negative electrode and a nickel-zinc battery disclosed by the present invention, including most of the operations in Example 1, and the differences are as follows: No intermediate layer and outer layer coatings are performed on the zinc powder.

[0076] Performance Test The following performance tests are carried out on Examples 1-13 and Comparative Examples 1-3 prepared above: Battery test method: (1) The life test conditions are charging at 1C to 1.9V and discharging at 1C to 1.3V. Repeat the charge and discharge until the battery capacity is reduced to 60% of the first charge, and record the number of charge and discharge cycles; (2) The storage performance test environment is 60°C for 28 days; The storage performance capacity test conditions are discharging at 0.2C to 1.3V, charging at 0.2C to 1.9V, and leaving it to stand for 10 min, and repeating the above steps three times.

[0077] The obtained test results are filled into Table 1.

[0078] Table 1 As can be seen from the test results in Table 1, the overall test results of Examples 1-13 are better than those of Comparative Examples 1-3. For the zinc negative electrodes in Examples 1-13, during the preparation process, the zinc negative electrode material includes a zinc composite material with a core-shell structure, and the intermediate layer is coated on the surface of the zinc powder, avoiding the direct contact between the zinc powder and the external environment, enabling the zinc powder to maintain the integrity of its structure during the charge and discharge process of the battery, thereby improving the cycle stability of the battery. Through the action of the outer shell layer, the core-shell structure effectively inhibits the hydrogen evolution reaction, maintains the relative stability of the chemical environment inside the battery, and ensures the stability of the electrochemical performance of the battery. Therefore, the zinc composite material with a core-shell structure applied in Examples 1-13 is beneficial to improving the storage and cycle performance of nickel-zinc batteries; Compared with Example 1, in Example 3, the coating thicknesses of both the intermediate layer and the outer shell layer of the core-shell structure zinc composite material are 2 μm, and in Example 4, the coating thicknesses of both the intermediate layer and the outer shell layer of the core-shell structure zinc composite material are 13 μm. Compared with Example 1, the test data of Example 3 are slightly lower, and those of Example 4 are the second. Compared with Example 1 and Example 3, the coating thicknesses of the intermediate layer and the outer shell layer in Example 4 are relatively thick. However, an overly thick intermediate layer will hinder the conduction of electrons and reduce the electrochemical activity of the zinc powder. When the outer shell layer is too thick, the diffusion path of zinc ions in the electrode material will become significantly longer, resulting in a decrease in the charge and discharge rate of the battery. Therefore, an overly thick intermediate layer and outer shell layer affect the storage and cycle performance of the battery; in Example 5, the coating thickness of the intermediate layer is 2 μm, and the coating thickness of the outer shell layer is 13 μm, which is also not conducive to the improvement of electrical performance; Compared with Example 1, in Example 6, the test effect is relatively low, and in Example 7, the test effect is slightly higher than that in Example 1. The reason is that the particle size of the zinc powder in Example 6 is relatively small, and it is easy to undergo self-corrosion in the alkaline electrolyte, resulting in a decrease in the Coulomb efficiency of the battery; Compared with Example 1, in Examples 8-10, the test results of Example 10 are similar to those of Example 1, while the test results of Examples 8 and 9 are relatively low. The reason is that in Example 1, the morphology of the zinc powder is spherical, and in Example 10, the morphology of the zinc powder is flaky. Spherical zinc powder provides stable and uniformly distributed reaction sites, which is conducive to controlling the reaction rate. The high specific surface area of flaky zinc powder can contribute more highly active reaction sites. Therefore, spherical zinc powder and flaky zinc powder have higher packing densities and uniform current distributions, which can reduce the growth of zinc dendrites and improve the electrochemical performance of the battery; Compared with Example 1, the overall test performance of Example 11 is slightly lower than that of Example 1. The reason is that the zinc content in the inner core zinc powder in Example 11 is lower than that in Example 1. Therefore, the performance of Example 11 in improving the hydrogen evolution side reaction is slightly worse than that of Example 11, and thus the overall performance of the detected battery is relatively poor compared with Example 1; From the test results of Example 1, Example 12, and Example 13, it can be seen that the overall test performance of Example 1 is the best, followed by Example 12, and Example 13 is relatively poor. It is speculated that the reason is that the proportion of zinc powder in Example 13 is large, while the proportion of the first and second materials is low, which may lead to insufficient protection of the zinc powder by the outer shell layer and the intermediate layer, and the ability to inhibit the hydrogen evolution side reaction decreases. In contrast, the proportion of the first and second materials in Example 1 is relatively high. Therefore, its protection of the zinc powder and the effect of inhibiting hydrogen evolution can be relatively good, and then a battery with excellent overall performance is obtained. In Comparative Examples 1-3, since the core-shell structure of the intermediate layer and the outer shell layer is not included in the preparation of the zinc negative electrode in Comparative Example 3, the electrochemical performance of the battery cannot be improved.

[0079] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A zinc negative electrode material, characterized in that, It includes a negative electrode active material, the negative electrode active material includes a zinc composite material, the zinc composite material has a core-shell structure, the core-shell structure includes a core, an intermediate layer, and an outer shell layer, the core is zinc powder, the intermediate layer is coated outside the core, and the outer shell layer is coated outside the intermediate layer; The intermediate layer includes a first material, and the first material includes one of calcium oxide, magnesium oxide, aluminum oxide, cerium oxide, and silicon oxide; The outer shell layer includes a second material, and the second material includes one or more of carbon black, polytetrafluoroethylene, graphene, and naphthol.

2. The zinc negative electrode material according to claim 1, wherein The thickness of the intermediate layer is 1-15 μm.

3. The zinc negative electrode material according to claim 1, characterized in that, The thickness of the outer shell layer is 1-15 μm.

4. The zinc negative electrode material according to claim 1, wherein, The molar ratio of the zinc powder, the first material, and the second material is 96-99:0.5-3:0.5-2.

5. A zinc negative electrode material according to claim 1, characterized in that The particle size of the zinc powder is 80 mesh - 400 mesh.

6. A zinc negative electrode material according to claim 1, characterized in that In the zinc powder, the content of zinc is 90% - 96%.

7. A zinc negative electrode material according to claim 1, characterized in that, The morphology of the zinc powder includes one or more of spherical, flaky, rod-shaped, and other irregular shapes.

8. The zinc negative electrode material according to claim 1, characterized in that, The specific surface area of the zinc powder is 80 - 590 m 2 / g, and the bulk density of the zinc powder is 5.5 - 7.50 g / mL.

9. The zinc negative electrode material according to claim 1, characterized in that The negative electrode active material further includes a zinc alloy, and the zinc alloy includes one or more of zinc-aluminum alloy, zinc-magnesium alloy, zinc-copper alloy, and zinc-titanium alloy.

10. The zinc negative electrode material according to claim 9, characterized in that, The zinc content in the zinc alloy is 62% - 98%.

11. A zinc negative electrode material according to claim 1, characterized in that, The negative electrode active material further includes a surfactant, and the surfactant includes one or more of sodium dodecyl sulfate, cetyltrimethylammonium bromide, docosyl betaine, and polyvinylpyrrolidone.

12. A zinc negative electrode material according to claim 1, characterized in that, The negative electrode active material further includes In2O3, Bi2O3, and Al2O3; In the negative electrode active material, the added mass of In2O3 is 0.5% - 1%, the added mass of Bi2O3 is 3% - 5%, and the added mass of Al2O3 is 1% - 3%.

13. A zinc negative electrode material according to claim 1, characterized in that, The negative electrode active material includes zinc oxide, and the mass ratio of the zinc powder to the zinc oxide is 1:4 - 1:

2.

14. A zinc negative electrode, characterized in that, It includes a current collector and a negative electrode material layer, the negative electrode material layer is disposed on the current collector, and the negative electrode material layer includes the zinc negative electrode material according to any one of claims 1-13.

15. A zinc negative electrode according to claim 14, wherein, The negative electrode material layer further includes a conductive agent, a thickening agent, and a binder; In the negative electrode active material of the negative electrode material layer, the added mass of the conductive agent is 1% - 1.5%; the added mass of the thickening agent is 0.2% - 0.5%, and the added mass of the binder is 2% - 3%.

16. A nickel-zinc battery, characterized in that, It includes a positive electrode, a separator, an electrolyte, and the zinc negative electrode according to claim 14 or 15.

Images