Zinc negative electrode, preparation method and nickel-zinc battery

Abstract

In order to solve the problems that in the prior art, a zinc negative electrode is prone to corrosion and zinc dendrite growth in the charging and discharging process, the zinc negative electrode comprises a negative electrode base material, a negative electrode active layer and a composite coating, the composite coating comprises a first coating and a second coating, the negative electrode active layer is arranged on the surface of the negative electrode base material, and the second coating is arranged on the surface of the negative electrode base material. The second coating is arranged on one surface, deviating from the negative substrate, of the negative active layer; the first coating is arranged on one surface, deviating from the negative active layer, of the second coating; the first coating comprises a first material, the second coating comprises a second material, the first material comprises an amide polymer and / or an amide non-polymer, and the second material comprises one or more of an ionic liquid material, a zinc phosphate material and a cerium oxide material. The surface of the zinc negative electrode is coated with the composite coating, so that multiple protection on the zinc negative electrode is formed, contact between zinc and electrolyte is effectively reduced, corrosion reaction and zinc dendrite growth are inhibited, and the cycle performance and safety of the nickel-zinc battery are improved.

Description

Technical Field

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

[0002] Nickel-zinc batteries have broad application prospects in the fields of energy storage and consumer electronics due to their high energy density, environmental friendliness and safety. However, the zinc negative electrode is prone to corrosion and zinc dendrite growth during the charging and discharging process, resulting in shortened battery life, capacity decay and safety hazards. Existing solutions mainly focus on adjusting the electrolyte composition or using additives, but the effect is limited and cannot fundamentally solve the zinc corrosion problem. Therefore, it is particularly important to develop a negative electrode protection technology that effectively slows down zinc corrosion. Summary of the invention

[0003] Aiming at the problem that zinc negative electrode in the prior art is prone to corrosion and zinc dendrite growth during the charge and discharge process, a zinc negative electrode, a preparation method and a nickel-zinc battery are provided.

[0004] The technical solution adopted by the present invention to solve the above technical problems is as follows: In one aspect, the present invention provides a zinc negative electrode, comprising a negative electrode substrate, a negative electrode active layer and a composite coating, wherein the composite coating comprises a first coating and a second coating, wherein the negative electrode active layer is disposed on the surface of the negative electrode substrate, the second coating is disposed on a side of the negative electrode active layer away from the negative electrode substrate, and the first coating is disposed on a side of the second coating away from the negative electrode active layer; The first coating layer includes a first material, and the second coating layer includes a second material. The first material includes an amide polymer and / or an amide non-polymer, and the second material includes one or more of an ionic liquid material, a zinc phosphate material, and a cerium oxide material.

[0005] Optionally, the amide non-polymer includes one or more of stearic acid amide, erucic acid amide, benzamide and hydroxybenzamide.

[0006] Optionally, the amide polymer includes one or more of the following structural unit formulas: [-OC(CH 2 ) 4 -CO-NH-(CH 2 ) 6 NH-] n 、[-OC(CH 2 ) 8 -CO-NH-(CH 2 ) 10 NH-] n 、 [-NH(CH 2 ) 6-CO-NH-(C 6 H 4 )CO-] n ; The value of n is 5-10.

[0007] Optionally, the amide polymer includes one or more of polyamide 66, polyamide 610 and polyamide 6T.

[0008] Optionally, the ionic liquid material includes an ionic liquid, and the ionic liquid includes one or more of N-butylpyridinium tetrafluoroborate, tetraethylammonium chloride, tetrabutylphosphine chloride, and 1-butyl-3-methylimidazolium hexafluorophosphate.

[0009] Optionally, in the slurry used to form the first coating layer, the mass percentage of the first material is 0.1-2%; In the slurry used to form the second coating layer, the mass percentage of the second material is 0.1-2%.

[0010] Optionally, the coating thickness of the first coating on the surface of the zinc negative electrode is 2-10 μm; The coating thickness of the second coating on the surface of the zinc negative electrode is 2-10 μm.

[0011] Optionally, the negative electrode active layer includes a negative electrode active material, a conductive agent, a thickener, a dispersant and a binder; In the negative electrode active layer, the mass percentage of the negative electrode active material is 95.1%-97.5%, the mass percentage of the conductive agent is 1%-2%, the mass percentage of the thickener is 0.2%-0.4%, the mass percentage of the dispersant is 1%-2%, and the mass percentage of the binder is 0.3%-0.5%.

[0012] In another aspect, the present invention provides a method for preparing the zinc negative electrode, comprising the following operations: Taking a first material and a first solvent, mixing them to obtain a first coating slurry; Take a second material and a second solvent, mix them to obtain a second coating slurry; Taking a negative electrode substrate, coating the negative electrode active slurry on the surface of the negative electrode substrate to obtain a prefabricated negative electrode; The slurry of the second material is coated on the surface of the prefabricated negative electrode, and then the slurry of the first material is coated on the surface of the slurry of the second material to obtain a zinc negative electrode.

[0013] Optionally, the coating method of the slurry of the first coating layer and the slurry of the second coating layer on the surface of the prefabricated negative electrode includes one or more of dipping, brushing, spraying and spin coating.

[0014] Optionally, the mass ratio of the first solvent to the total mass of the first material is 10:1-8:1; The mass ratio of the second solvent to the total mass of the second material is 10:1-8:1.

[0015] On the other hand, the present invention provides a nickel-zinc battery, comprising a positive electrode, a separator, an electrolyte, and the zinc negative electrode or the zinc negative electrode prepared by the zinc negative electrode preparation method.

[0016] The beneficial effects of the present invention are: The zinc negative electrode provided by the present invention has a composite coating coated on the surface of the zinc negative electrode, and the composite coating includes a first coating and a second coating. The polar amide functional groups of the first material amide polymer and / or amide non-polymer in the first coating form a dense protective layer on the surface of the zinc negative electrode, thereby reducing the direct contact between the electrolyte and the zinc negative electrode, thereby reducing the corrosion rate of zinc during the charging and discharging process, extending the cycle life of the battery, and significantly improving the current efficiency of the zinc negative electrode, and effectively inhibiting the formation of dendrites; because the amide polymer and / or amide non-polymer in the first material will cause wear due to long-term circulation or external mechanical damage, affecting the protective effect of the coating, and thus affecting the performance of the nickel-zinc battery, based on the above factors, the composite coating provided by the present application also includes a second coating, and the second material in the second coating can repair the zinc negative electrode area exposed due to wear on the zinc negative electrode, thereby repairing the gap caused by wear of the first coating, and playing a barrier role; that is, the present invention forms multiple protections for the zinc negative electrode through the operation of coating the composite coating on the surface of the zinc negative electrode, effectively reducing the contact between zinc and the electrolyte, inhibiting corrosion reactions and zinc dendrite growth, and thus improving the cycle performance and safety of the nickel-zinc battery. DETAILED DESCRIPTION

[0017] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the 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.

[0018] The present invention provides a zinc negative electrode, comprising a negative electrode substrate, a negative electrode active layer and a composite coating, wherein the composite coating comprises a first coating and a second coating, wherein the negative electrode active layer is arranged on the surface of the negative electrode substrate, the second coating is arranged on a side of the negative electrode active layer away from the negative electrode substrate, and the first coating is arranged on a side of the second coating away from the negative electrode active layer; The first coating layer includes a first material, and the second coating layer includes a second material. The first material includes an amide polymer and / or an amide non-polymer, and the second material includes one or more of an ionic liquid material, a zinc phosphate material, and a cerium oxide material.

[0019] The zinc negative electrode provided by the present invention has a composite coating coated on the surface of the zinc negative electrode, and the composite coating includes a first coating and a second coating. The polar amide functional groups of the first material amide polymer and / or amide non-polymer in the first coating form a dense protective layer on the surface of the zinc negative electrode, thereby reducing the direct contact between the electrolyte and the zinc negative electrode, thereby reducing the corrosion rate of zinc during the charging and discharging process, extending the cycle life of the battery, and significantly improving the current efficiency of the zinc negative electrode, and effectively inhibiting the formation of dendrites; because the amide polymer and / or amide non-polymer in the first material will cause wear due to long-term circulation or external mechanical damage, affecting the protective effect of the coating, and thus affecting the performance of the nickel-zinc battery, based on the above factors, the composite coating provided by the present application also includes a second coating, and the second material in the second coating can repair the zinc negative electrode area exposed due to wear on the zinc negative electrode, thereby repairing the gap caused by wear of the first coating, and playing a barrier role; that is, the present invention forms multiple protections for the zinc negative electrode through the operation of coating the composite coating on the surface of the zinc negative electrode, effectively reducing the contact between zinc and the electrolyte, inhibiting corrosion reactions and zinc dendrite growth, and thus improving the cycle performance and safety of the nickel-zinc battery.

[0020] Specifically, the second material includes one or more of an ionic liquid material, a zinc phosphate material, and a cerium oxide material; The ionic liquid material is added to the nickel-zinc battery with self-repairing properties, which can automatically heal cracks during operation and maintain the integrity of the electrode. The ionic liquid has excellent chemical stability and corrosion resistance and is suitable for long-term working environments. The zinc phosphate material, in a nickel-zinc battery, when the coating is damaged, the zinc phosphate can react with the exposed zinc electrode to generate new zinc phosphate deposits, automatically repairing the wear gaps in the coating caused by long-term circulation or external mechanical damage, and the zinc phosphate material has long-term stable self-repairing properties in an electrolyte environment; In a nickel-zinc battery, when the coating of the cerium oxide material is damaged, cerium ions are redeposited in the damaged area through a dissolution-redeposition process to form a new protective layer. The cerium base in the cerium oxide material can interact with the zinc electrode to generate a dense cerium oxide film to protect zinc from corrosion.

[0021] In some embodiments, the amide non-polymer includes one or more of stearic acid amide, erucic acid amide, benzamide, and hydroxybenzamide.

[0022] In some embodiments, the amide polymer includes one or more of the following structural unit formulas: [-OC(CH 2 ) 4 -CO-NH-(CH 2 )6 NH-] n 、[-OC(CH 2 ) 8 -CO-NH-(CH 2 ) 10 NH-] n 、 [-NH(CH 2 ) 6 -CO-NH-(C 6 H 4 )CO-] n ; The value of n is 5-10.

[0023] Specifically, having the The polymer molecular chain of the structural unit contains abundant amide bonds, and in the electrolyte environment where the zinc negative electrode is located, the polymer molecules can be attached to the surface of the zinc negative electrode by physical adsorption or chemical adsorption, and the nitrogen atoms in the amide bonds can interact with the active sites on the zinc surface, so that they are preferentially adsorbed on the surface of the zinc electrode, and then spread on the surface to form a continuous protective film, which can effectively block the corrosive components in the electrolyte from directly contacting the zinc negative electrode, thereby inhibiting hydrogen evolution corrosion caused by water, oxidative corrosion involving oxygen, and chemical corrosion caused by acidic electrolytes; With structural unit formula The polymer has a longer molecular chain and better flexibility. When a protective film is formed on the surface of the zinc negative electrode, its coverage integrity and density are relatively good, which in turn has a stronger barrier effect on the corrosive components in the electrolyte and can more effectively prevent water, oxygen and other substances that may cause zinc corrosion from contacting the zinc negative electrode; For the structural unit formula The introduction of benzene rings into the polymer structure increases the rigidity of the molecular chain. After being adsorbed on the surface of the zinc negative electrode to form a protective film, the protective film has better stability and shape retention ability due to its rigid structure, and is not easily destroyed by factors such as the flow of electrolyte and volume changes during battery charging and discharging.

[0024] In some embodiments, the amide polymer includes one or more of polyamide 66, polyamide 610, and polyamide 6T.

[0025] In some embodiments, the ionic liquid material includes an ionic liquid including one or more of N-butylpyridinium tetrafluoroborate, tetraethylammonium chloride, tetrabutylphosphine chloride, and 1-butyl-3-methylimidazolium hexafluorophosphate.

[0026] In some embodiments, in the first coating layer, in the slurry used to form the first coating layer, the mass percentage of the first material is 0.1-2%; In the slurry used to form the second coating layer, the mass percentage of the second material is 0.1-2%.

[0027] In some embodiments, the coating thickness of the first coating on the surface of the zinc negative electrode is 2-10 μm; The coating thickness of the second coating on the surface of the zinc negative electrode is 2-10 μm.

[0028] Specifically, when the first coating and the second coating are covered on the surface of the zinc negative electrode with a thickness of 2-10μm, they can act as a barrier layer to effectively prevent some corrosive components in the electrolyte from directly contacting the zinc negative electrode. The thickness range of 2-10μm is relatively suitable, which can not only ensure that the coating completely covers the surface of the zinc negative electrode, but also help maintain the good density of the coating itself. If the coating is too thin, there may be pores or incomplete coverage, making it easy for corrosive components to contact the zinc negative electrode through the gaps in the coating, thereby causing corrosion; if the coating is too thick, on the one hand, it may increase costs and process difficulties, and on the other hand, it may cause cracking and peeling of the coating due to internal stress and other problems, affecting its barrier effect.

[0029] The coating thickness of the first coating on the surface of the zinc negative electrode can be 2μm, 3μm, 5μm, 7μm, or 10μm; the coating thickness of the second coating on the surface of the zinc negative electrode can be 2μm, 3μm, 5μm, 7μm, or 10μm.

[0030] In some embodiments, the negative electrode active layer includes a negative electrode active material, a conductive agent, a thickener, a dispersant, and a binder; In the negative electrode active layer, the mass percentage of the negative electrode active material is 95.1%-97.5%, the mass percentage of the conductive agent is 1%-2%, the mass percentage of the thickener is 0.2%-0.4%, the mass percentage of the dispersant is 1%-2%, and the mass percentage of the binder is 0.3%-0.5%.

[0031] Another embodiment of the present invention provides a method for preparing the zinc negative electrode, comprising the following operations: After mixing the conductive agent, thickener, dispersant and binder, add the negative electrode active material and mix well to obtain the negative electrode active slurry; Taking a first material and a first solvent, mixing them to obtain a slurry of the first material; Taking a second material and a second solvent, mixing them to obtain a slurry of the second material; Taking a negative electrode substrate, coating the negative electrode active slurry on the surface of the negative electrode substrate to obtain a prefabricated negative electrode; The slurry of the second material is coated on the surface of the prefabricated negative electrode, and then the slurry of the first material is coated on the surface of the slurry of the second material to obtain a zinc negative electrode.

[0032] Specifically, the conductive agent includes one or more of nickel powder, carbonyl nickel powder, cobalt oxide, graphene, graphite, acetylene black and carbon powder; the thickener includes carboxymethyl cellulose (CMC); the dispersant includes any one of sodium polyacrylate (PAANa), potassium polyacrylate (PAAK), polyacrylamide (PAM) and polyacrylic acid (PAA); selecting a polymer with high ionic conductivity as a dispersant can reduce the internal resistance of the negative electrode, increase the conductivity, and improve the storage and life of the battery. In a preferred embodiment, the dispersant is selected from polyacrylic acid; the binder includes styrene-butadiene rubber (SBR) and polytetrafluoroethylene (PTFE).

[0033] In some embodiments, the coating method of the slurry of the first coating layer and the slurry of the second coating layer on the surface of the prefabricated negative electrode includes one or more of dipping, brushing, spraying and spin coating.

[0034] Specifically, in the operation of applying the composite coating by the dip coating method, the zinc electrode is immersed in the slurry of the second coating, taken out after being fully wetted, allowed to dry in the air or heated in an oven, and then wetted or coated with the slurry of the first coating, thereby forming a uniform composite coating on the surface of the prefabricated negative electrode.

[0035] Specifically, in the operation of applying the composite coating by the brush coating method, the slurry of the second coating layer and the slurry of the first coating layer are respectively brushed evenly on the surface of the prefabricated negative electrode, and then dried.

[0036] Specifically, in the operation of applying the composite coating by the spraying method, the slurry of the second coating and the slurry of the first coating are respectively loaded into the spraying equipment, sprayed evenly on the surface of the prefabricated negative electrode, and then dried.

[0037] Specifically, in the operation of applying the composite coating by the spin coating method, the electrode is rotated at high speed and the centrifugal force is used to evenly distribute the composite coating slurry on the surface of the prefabricated negative electrode. The coating thickness can be adjusted by controlling the rotation speed and the solution concentration.

[0038] In some embodiments, the mass ratio of the first solvent of the composite coating slurry to the total mass of the first material is 10:1-8:1; The mass ratio of the second solvent to the total mass of the second material is 10:1-8:1.

[0039] Specifically, the first material and the second material cooperate with the first solvent and the second solvent respectively, which helps to improve the stability of the coating. The appropriate amount of solvent can make the materials in the coating disperse better, form a stable structure after the coating dries, and reduce the possibility of cracking and peeling of the coating due to factors such as internal stress. The stable coating can continue to play its role in blocking corrosion and regulating zinc ion transmission during multiple charge and discharge processes of the zinc negative electrode, maintain a good electrochemical environment on the surface of the zinc negative electrode, and reduce the corrosion and dendrite growth problems of the zinc negative electrode caused by coating failure.

[0040] Another embodiment of the present invention provides a nickel-zinc battery, comprising a positive electrode, a separator, an electrolyte, and the zinc negative electrode or the zinc negative electrode prepared by the zinc negative electrode preparation method.

[0041] The diaphragm is placed between the positive electrode and the negative electrode to form a battery core, and then the battery core is assembled and injected with liquid with a battery shell to obtain a nickel-zinc battery.

[0042] The nickel-zinc battery provided by the present invention comprises the zinc negative electrode, wherein a composite coating is coated on the surface of the zinc negative electrode, wherein the composite coating comprises a first coating and a second coating, wherein the polar amide functional groups of the first material amide polymer and / or amide non-polymer in the first coating form a dense protective layer on the surface of the zinc negative electrode, thereby reducing the direct contact between the electrolyte and the zinc negative electrode, thereby reducing the corrosion rate of zinc during the charge and discharge process, extending the cycle life of the battery, thereby significantly improving the current efficiency of the zinc negative electrode, and effectively inhibiting the formation of dendrites; since the amide polymer and / or amide non-polymer in the first material Wear caused by long-term circulation or external mechanical damage affects the protective effect of the coating, and thus affects the performance of the nickel-zinc battery. Based on the above factors, the composite coating provided in the present application also includes a second coating. The second material in the second coating can repair the zinc negative electrode area exposed due to wear on the zinc negative electrode, and then repair the gap caused by wear of the first coating, thereby playing a barrier role; that is, the present invention forms multiple protections for the zinc negative electrode by coating the composite coating on the surface of the zinc negative electrode, effectively reduces the contact between zinc and the electrolyte, inhibits corrosion reactions and zinc dendrite growth, and thus improves the cycle performance and safety of the nickel-zinc battery.

[0043] The positive electrode comprises a positive electrode current collector and a positive electrode active layer, wherein the positive electrode active layer comprises a positive electrode active material, and the positive electrode active material is selected from Ni(OH) 2 (nickel hydroxide), ZnO, CoO (cobalt oxide), Ni powder, Y 2 O 3 (yttrium trioxide) and Yb 2 O 3 (ytterbium trioxide) or more.

[0044] The positive electrode active layer further includes a positive electrode binder and a positive electrode conductor. The positive electrode active material, the positive electrode binder and the positive electrode conductor are mixed to obtain the positive electrode active layer.

[0045] The positive electrode binder can be polyvinylidene fluoride, a copolymer of vinylidene fluoride, polytetrafluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene, a copolymer of tetrafluoroethylene-hexafluoropropylene, a copolymer of tetrafluoroethylene-perfluoroalkyl vinyl ether, a copolymer of ethylene-tetrafluoroethylene, a copolymer of vinylidene fluoride-tetrafluoroethylene, a copolymer of vinylidene fluoride-trifluoroethylene, a copolymer of vinylidene fluoride-trichloroethylene, a copolymer of vinylidene fluoride-fluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, a thermoplastic resin such as thermoplastic polyimide, polyethylene and polypropylene; at least one of acrylic resin, carboxymethyl cellulose and styrene butadiene rubber.

[0046] The positive electrode conductive agent may be at least one of conductive carbon black, conductive carbon balls, conductive graphite, conductive carbon fibers, carbon nanotubes, graphene, or reduced graphene oxide.

[0047] The diaphragm can be an existing conventional diaphragm, which can be a ceramic diaphragm, a polymer diaphragm, a non-woven fabric, a non-woven Organic-organic composite membranes, 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 diaphragms.

[0048] The present invention is further described below by way of examples.

[0049] Example 1 This embodiment is used to illustrate the zinc negative electrode, preparation method and nickel-zinc battery disclosed in the present invention, and includes the following steps: Preparation of negative electrode: (1) Mix 1.5% conductive agent, 0.32% thickener, and 1.5% dispersant, then add 0.05% In 2 O 3 、2.75%Bi 2 O 3 、4% Al 2 O 3 , stirred for 30 min, 1.5% Ca(OH) 2 , stirring for 30 min, after mixing, adding 61% ZnO and 27% Zn in portions, after mixing, adding 0.38% binder to obtain negative electrode slurry; The negative electrode slurry is coated on the obliquely drawn tinned copper mesh current collector, and the prefabricated negative electrode of the nickel-zinc battery is obtained by rolling, softening and cutting. Anhydrous ethanol is mixed with polyamide 6T to obtain a slurry of the first coating layer, and anhydrous ethanol is mixed with a zinc phosphate material to obtain a slurry of the second coating layer, wherein the mass ratio of polyamide 6T to zinc phosphate material is 1:1; The second coating slurry is coated on the surface of the prefabricated negative electrode by spin coating, and then the first coating slurry is coated on the surface of the second coating slurry, wherein the coating thickness of the first coating slurry and the second coating slurry is 5 μm, and a zinc negative electrode is obtained after drying.

[0050] Preparation of positive electrode: 85% Ni(OH) 2 , 1.5%ZnO, 3%CoO, 2%Ni powder, 2%Ca(OH) 2 , 1%Y 2 O 3 、1%Yb 2 O 3 , 3% graphite, 1.5% CMC, and 1% PTFE are mixed, stirred evenly, coated on the positive electrode current collector, and then rolled, softened, and cut to obtain the positive electrode.

[0051] Prepare electrolyte: The electrolyte of this embodiment has a composition of 24% KOH, 3% NaOH, 1% LiOH, 1% disodium hydrogen phosphate, 1% boraxite, 1% zinc oxide, 0.5% ammonium chloride, 0.2% lithium fluoride, and the rest is water.

[0052] Preparation of nickel-zinc battery: The positive electrode, the separator and the negative electrode are stacked in order so that the separator is between the positive and negative electrodes to prepare a battery cell. The battery cell is dried in an outer packaging bag, injected with the above-mentioned electrolyte, and subjected to vacuum packaging, standing, forming, shaping and other processes to obtain a nickel-zinc battery.

[0053] Example 2 This example is used to illustrate the zinc negative electrode, preparation method and nickel-zinc battery disclosed in the present invention, and includes most of the operations in Example 1, except that: In the preparation of the first coating layer, the first material is selected from polyamide 610, and in the preparation of the second coating layer, the second material is selected from cerium oxide material.

[0054] Example 3 This example is used to illustrate the zinc negative electrode, preparation method and nickel-zinc battery disclosed in the present invention, and includes most of the operations in Example 1, except that: In the preparation of the first coating, the first material is selected from polyamide 66, and in the preparation of the second coating, the second material is selected from N-butylpyridinium tetrafluoroborate.

[0055] Example 4 This example is used to illustrate the zinc negative electrode, preparation method and nickel-zinc battery disclosed in the present invention, and includes most of the operations in Example 1, except that: In the preparation of the first coating, the first material is selected from benzamide.

[0056] Example 5 This example is used to illustrate the zinc negative electrode, preparation method and nickel-zinc battery disclosed in the present invention, and includes most of the operations in Example 1, except that: In the preparation of the first coating, the first material is selected from erucamide.

[0057] Example 6 This example is used to illustrate the zinc negative electrode, preparation method and nickel-zinc battery disclosed in the present invention, and includes most of the operations in Example 1, except that: In the preparation of the first coating, the first material is selected from benzamide and polyamide 6T, and the mass ratio of benzamide to polyamide 6T is 1:1.

[0058] Example 7 This example is used to illustrate the zinc negative electrode, preparation method and nickel-zinc battery disclosed in the present invention, and includes most of the operations in Example 1, except that: In the preparation of the second coating, the second material is selected from tetraethylammonium chloride and cerium oxide material, and the mass ratio of the tetraethylammonium chloride to the cerium oxide material is 1:1.

[0059] Example 8 This example is used to illustrate the zinc negative electrode, preparation method and nickel-zinc battery disclosed in the present invention, and includes most of the operations in Example 1, except that: In the preparation of the second coating, the second material is selected from tetrabutylphosphine chloride and cerium oxide material, and the mass ratio of the tetrabutylphosphine chloride to the cerium oxide material is 1:1.

[0060] Example 9 This example is used to illustrate the zinc negative electrode, preparation method and nickel-zinc battery disclosed in the present invention, and includes most of the operations in Example 1, except that: The coating thickness of the first coating layer and the second coating layer is 3 μm.

[0061] Example 10 This example is used to illustrate the zinc negative electrode, preparation method and nickel-zinc battery disclosed in the present invention, and includes most of the operations in Example 1, except that: The coating thickness of the first coating layer and the second coating layer is 8 μm.

[0062] Comparative Example 1 This comparative example is used to compare and illustrate the zinc negative electrode, preparation method and nickel-zinc battery disclosed in the present invention, including most of the operations in Example 1, except that: The second coating layer is not included and the material in the first coating layer is an amide-based non-polymer (erucamide).

[0063] Comparative Example 2 This comparative example is used to compare and illustrate the zinc negative electrode, preparation method and nickel-zinc battery disclosed in the present invention, including most of the operations in Example 1, except that: The second coating layer is not included and the material in the first coating layer is an amide-based non-polymer (hydroxybenzamide).

[0064] Comparative Example 3 This comparative example is used to compare and illustrate the zinc negative electrode, preparation method and nickel-zinc battery disclosed in the present invention, including most of the operations in Example 1, except that: The second coating was not included and the material in the first coating was polyamide 66.

[0065] Comparative Example 4 This comparative example is used to compare and illustrate the zinc negative electrode, preparation method and nickel-zinc battery disclosed in the present invention, including most of the operations in Example 1, except that: Does not include first coat.

[0066] Comparative Example 5 This comparative example is used to compare and illustrate the zinc negative electrode, preparation method and nickel-zinc battery disclosed in the present invention, including most of the operations in Example 2, except that: Does not include first coat.

[0067] Performance Testing The relevant performance tests were performed on the Examples 1-10 and Comparative Examples 1-5 prepared above: Cycle life At 25°C, the nickel-zinc battery prepared in each embodiment and comparative example was charged to 1.9V at 1C, then charged to a cut-off current of 13.5mA at 1.9V constant voltage, and discharged to 1.3V at 1C. The charge and discharge were repeated until the battery capacity dropped to 60% of the initial charge, and the number of cycles was recorded. High-temperature cycle capacity retention rate (1) At 25°C, the battery was fully charged in a constant current and constant voltage charging mode, charged to 1.9V at 0.2C, and then charged to a cut-off current of 13.5mA at 1.9V constant voltage, and the charging was terminated; (2) The fully charged battery was placed in a 60°C oven and stored for 28 days; (3) After storage, the battery was discharged to 1.3V at 0.2C, and then charged in the same charging mode as (1), left for 10 min, and then discharged to 1.3V at 0.2C. The above charging and discharging steps were repeated 3 times.

[0068] The test results obtained are entered in Table 1.

[0069] Table 1 It can be seen from the test results in Table 1 that the cycle performance of Examples 1-10 is better than that of Comparative Examples 1-5, which indicates that the presence of the composite coating helps to improve the cycle life of the battery. The barrier effect of the first coating and the repair function of the second coating work together to inhibit the corrosion and dendrite growth of the zinc negative electrode, so that the battery can still have good cycle performance under the conditions of multiple charge and discharge. In Example 1, polyamide 6T is used as the first coating material and zinc phosphate is used as the second coating material. The synergistic effect of the two enables the battery to cycle 285 times, while in Comparative Example 1, without adding the second coating material, the number of cycles is reduced to 220 times; In terms of capacity retention after storage at 60°C, Example 2 and Examples 7-8 have relatively high capacity retention rates, reaching 55%, 60%, and 58%, respectively, while among Comparative Examples 1-5, except for Comparative Example 5 which is 50%, the others are all between 40% and 45%, which indicates that the composite coating can better maintain the performance of the battery in a high temperature environment. It is speculated that the second coating plays a key role in repairing coating defects caused by temperature influence and maintaining electrode integrity at high temperatures, preventing the substantial capacity attenuation caused by coating damage, thereby improving the capacity retention rate; It can be seen from the test results of Example 6 that compared with Example 1 and Example 4, Example 6 has the best test results. The reason is that, compared with Example 1 and Example 4, the first material of Example 6 in the preparation of the first coating includes both benzamide and polyamide 6T, and the benzamide and polyamide 6T can work synergistically to improve the battery performance.

[0070] It can be concluded from the specific test results of Example 7 that when preparing the zinc negative electrode in Example 7, tetraethylammonium chloride and cerium oxide material are simultaneously added to the second coating of the composite material, and the capacity retention rate is high after high-temperature storage; As for the capacity recovery rate, the capacity recovery rates of Examples 1-10 are mostly between 90% and 95%, while those of Comparative Examples 1-5 are between 86% and 90%, which further reflects that the battery with the composite coating has a stronger capacity recovery ability after high-temperature storage and charge and discharge cycles, further proving the improvement effect of the composite coating on battery performance, which helps the battery maintain good performance stability under complex working conditions.

[0071] In summary, the test results of the specific embodiments fully verify the beneficial effects of the composite coating on the zinc negative electrode on the cycle performance and safety of the nickel-zinc battery. The composite coating can effectively inhibit the corrosion and dendrite growth of the zinc negative electrode, and improve the battery performance in terms of cycle life, high-temperature cycle capacity retention rate and capacity recovery rate.

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A zinc negative electrode, characterized in that It comprises a negative electrode substrate, a negative electrode active layer and a composite coating, wherein the composite coating comprises a first coating and a second coating, the negative electrode active layer is arranged on the surface of the negative electrode substrate, the second coating is arranged on the side of the negative electrode active layer away from the negative electrode substrate, and the first coating is arranged on the side of the second coating away from the negative electrode active layer; The first coating layer includes a first material, and the second coating layer includes a second material. The first material includes an amide polymer and / or an amide non-polymer, and the second material includes one or more of an ionic liquid material, a zinc phosphate material, and a cerium oxide material.

2. A zinc negative electrode according to claim 1, characterized in that: The amide non-polymer includes one or more of stearic acid amide, erucic acid amide, benzamide and hydroxybenzamide.

3. A zinc negative electrode according to claim 1, characterized in that: The amide polymer includes one or more of the following structural unit formulas: [-OC(CH2)4-CO-NH-(CH2)6NH-] n 、[-OC(CH2)8-CO-NH-(CH2) 10 NH-] n 、 [-NH(CH2)6-CO-NH-(C6H4)CO-] n ; The value of n is 5-10.

4. A zinc negative electrode according to claim 3, characterized in that: The amide polymer includes one or more of polyamide 66, polyamide 610 and polyamide 6T.

5. A zinc negative electrode according to claim 1, characterized in that: The ionic liquid material includes an ionic liquid, and the ionic liquid includes one or more of N-butylpyridinium tetrafluoroborate, tetraethylammonium chloride, tetrabutylphosphine chloride, and 1-butyl-3-methylimidazolium hexafluorophosphate.

6. A zinc negative electrode according to claim 1, characterized in that: In the slurry used to form the first coating, the mass percentage of the first material is 0.1-2%; In the slurry used to form the second coating layer, the mass percentage of the second material is 0.1-2%.

7. A zinc negative electrode according to claim 1, characterized in that: The coating thickness of the first coating is 2-10 μm; The coating thickness of the second coating layer is 2-10 μm.

8. A zinc negative electrode according to claim 1, characterized in that: The negative electrode active layer comprises a negative electrode active material, a conductive agent, a thickener, a dispersant and a binder; In the negative electrode active layer, the mass percentage of the negative electrode active material is 95.1%-97.5%, the mass percentage of the conductive agent is 1%-2%, the mass percentage of the thickener is 0.2%-0.4%, the mass percentage of the dispersant is 1%-2%, and the mass percentage of the binder is 0.3%-0.5%.

9. A method for preparing a zinc negative electrode according to any one of claims 1 to 8, characterized in that: The following operations are included: After mixing the conductive agent, thickener, dispersant and binder, add the negative electrode active material and mix well to obtain the negative electrode active slurry; Taking a first material and a first solvent, mixing them to obtain a slurry of a first coating; Take a second material and a second solvent, mix them to obtain a slurry of a second coating; Taking a negative electrode substrate, coating the negative electrode active slurry on the surface of the negative electrode substrate to obtain a prefabricated negative electrode; The slurry of the second material is coated on the surface of the prefabricated negative electrode, and then the slurry of the first material is coated on the surface of the slurry of the second material to obtain a zinc negative electrode.

10. The method for preparing a zinc negative electrode according to claim 9, characterized in that: The coating method of the slurry of the first coating layer and the slurry of the second coating layer on the surface of the prefabricated negative electrode includes one or more of dipping, brushing, spraying and spin coating.

11. The method for preparing a zinc negative electrode according to claim 9, characterized in that: The mass ratio of the first solvent to the total mass of the first material is 10:1-8:1; The mass ratio of the second solvent to the total mass of the second material is 10:1-8:

1.

12. A nickel-zinc battery, characterized in that: The invention comprises a positive electrode, a separator, an electrolyte and a zinc negative electrode prepared by the zinc negative electrode preparation method according to any one of claims 1 to 8 or any one of claims 9 to 11.

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