Nickel-zinc battery negative electrode material based on graphene foam-carbon nanotube-transition metal oxide compounding, preparation method of nickel-zinc battery negative electrode material and nickel-zinc battery

Abstract

The invention belongs to the field of nickel-zinc batteries, and particularly relates to a nickel-zinc battery negative electrode material based on graphene foam-carbon nanotube-transition metal oxide compounding, a preparation method of the nickel-zinc battery negative electrode material and a nickel-zinc battery. The nickel-zinc battery negative electrode material based on graphene foam-carbon nano tube-transition metal oxide compounding comprises graphene foam, carbon nano tubes growing on the surfaces of pore walls of the graphene foam, and transition metal oxide loaded on a composite matrix formed by the graphene foam and the carbon nano tubes, and a negative active material deposited on the surface of the transition metal oxide. The transition metal oxide is a composite material of cobaltosic oxide and manganese dioxide, and the negative electrode active material comprises metal zinc nanocrystals and zinc oxide nanoparticles. According to the invention, the problems of serious zinc dendrite growth, short cycle life, large self-discharge, poor rate capability, insufficient low-temperature adaptability and the like in the existing nickel-zinc battery are effectively solved, a feasible technical path is provided for high performance and wide application of the nickel-zinc battery, and the nickel-zinc battery has a wide industrialization prospect.

Description

Technical Field

[0001] This invention relates to the field of nickel-zinc battery technology, specifically to a nickel-zinc battery anode material based on graphene foam-carbon nanotube-transition metal oxide composite, its preparation method, and a nickel-zinc battery. Background Technology

[0002] With the continuous growth of global energy demand and the increasing severity of environmental pollution, the development of efficient, environmentally friendly, and sustainable energy storage technologies has become one of the key directions of current scientific research. Among various rechargeable battery systems, nickel-zinc batteries are considered one of the most promising green batteries due to their high energy density, low cost, and environmental friendliness. However, in practical applications, nickel-zinc batteries still face a series of technical bottlenecks.

[0003] First, the negative electrode material of nickel-zinc batteries is mainly metallic zinc or zinc-containing compounds, which are prone to forming zinc dendrites during repeated charge and discharge processes. These dendrites can continue to grow and penetrate the separator, causing internal short circuits in the battery, posing safety hazards, and seriously affecting the battery's safety and cycle life.

[0004] Secondly, the zinc anode is unstable in alkaline electrolytes and has a high tendency to dissolve, which causes nickel-zinc batteries to continuously lose capacity even when left undisturbed, affecting their storage performance and lifespan.

[0005] Secondly, the poor conductivity of traditional zinc anode materials results in poor rate performance of nickel-zinc batteries, making it difficult to meet the requirements of high-power applications. Furthermore, at low temperatures, the electrochemical activity of the zinc anode decreases significantly, leading to large fluctuations in the overall performance of nickel-zinc batteries and affecting their applicability under complex operating conditions.

[0006] Therefore, there is a need to provide a nickel-zinc battery anode material that is resistant to dendrite formation, has low self-discharge, good rate performance, and low-temperature adaptability. Summary of the Invention

[0007] (a) Technical problems to be solved

[0008] To address the problems of dendrite growth, severe self-discharge, poor rate performance, and poor low-temperature adaptability in existing nickel-zinc battery anode materials, this invention provides a nickel-zinc battery anode material based on graphene foam-carbon nanotube-transition metal oxide composite, its preparation method, and a nickel-zinc battery.

[0009] (2) Technical solution

[0010] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0011] In a first aspect, the present invention provides a nickel-zinc battery anode material based on graphene foam-carbon nanotube-transition metal oxide composite, comprising graphene foam, carbon nanotubes grown on the surface of the pore walls of graphene foam, transition metal oxide loaded on a composite matrix composed of graphene foam and carbon nanotubes, and anode active material deposited on the surface of transition metal oxide.

[0012] The transition metal oxide is a composite material of cobalt tetroxide and manganese dioxide;

[0013] The negative electrode active material includes zinc nanocrystals and zinc oxide nanoparticles.

[0014] The nickel-zinc battery anode material based on graphene foam-carbon nanotube-transition metal oxide composite as described above preferably has a graphene foam pore size of 50-300 μm and a porosity of 85-95%.

[0015] Carbon nanotubes have a diameter of 10-30 nm and a length of 5-20 μm;

[0016] In transition metal oxides, the molar ratio of cobalt ions in cobalt tetroxide to manganese ions in manganese dioxide is 1:1-3:1.

[0017] In the negative electrode active material, the mass ratio of zinc nanocrystals to zinc oxide nanoparticles is 2:1-5:1, the average particle size of zinc nanocrystals is 20-100nm, and the average particle size of zinc oxide nanoparticles is 50-200nm.

[0018] The negative electrode active material accounts for 30-50% of the mass of the negative electrode material in nickel-zinc batteries.

[0019] Secondly, the present invention provides a method for preparing the above-mentioned nickel-zinc battery anode material based on graphene foam-carbon nanotube-transition metal oxide composite, comprising the following steps:

[0020] S1: Carbon nanotubes are grown on the surface of the pore walls of graphene foam through chemical vapor deposition to obtain a composite matrix;

[0021] S2: The composite matrix is ​​immersed in an aqueous solution containing soluble cobalt salt, soluble manganese salt and urea to carry out a hydrothermal reaction to obtain a composite matrix with surface-loaded mixed precursors. Then, the composite matrix is ​​calcined in an inert atmosphere to obtain a composite matrix loaded with transition metal oxides.

[0022] S3: The composite matrix loaded with transition metal oxides is used as the cathode and immersed in an electrolyte containing zinc oxide, strong alkali, tartaric acid and hydrogen peroxide. Electrodeposition is performed using a pulsed current deposition method to deposit zinc nanocrystals and zinc oxide nanoparticles on the surface of the composite matrix loaded with transition metal oxides, thus obtaining the nickel-zinc battery anode material.

[0023] The method for preparing nickel-zinc battery anode material based on graphene foam-carbon nanotube-transition metal oxide composite as described above is preferably as follows: In step S1, graphene oxide suspension is injected into a mold and freeze-dried to obtain graphene oxide framework. The graphene oxide framework is then subjected to a first-stage heat treatment in a mixed atmosphere of argon and hydrogen, followed by a second-stage heat treatment to obtain graphene foam.

[0024] The prepared graphene foam was immersed in a mixed aqueous solution of ferric nitrate and cobalt nitrate for a certain period of time and then dried to obtain the catalyst-supported graphene foam.

[0025] In a mixed atmosphere of argon and hydrogen, graphene foam loaded with a catalyst is heated, and then acetylene is introduced. The chemical vapor deposition reaction is carried out for a certain period of time to obtain a composite matrix.

[0026] The preparation method of nickel-zinc battery anode material based on graphene foam-carbon nanotube-transition metal oxide composite as described above, preferably, has the following conditions: the concentration of graphene oxide suspension is 20-30 mg / mL, the freeze-drying temperature is (-40)-(-50)℃, and the time is 24-48 h;

[0027] In a mixed atmosphere of argon and hydrogen, the volume ratio of the two is 95:5. The temperature of the first stage of heat treatment is 200-300℃ and the time is 1-2h. The temperature of the second stage of heat treatment is 800-900℃ and the time is 1-2h.

[0028] The molar ratio of ferric nitrate to cobalt nitrate is 2:1 to 1:2, and the soaking time is 30 to 40 minutes.

[0029] The graphene foam loaded with the catalyst was placed in a mixed atmosphere of argon and hydrogen and heated to 700-800℃ at a heating rate of 5-8℃ / min. Then, acetylene was introduced and chemical vapor deposition was carried out for 30-40 min to obtain the composite matrix.

[0030] In the preparation method of nickel-zinc battery anode material based on graphene foam-carbon nanotube-transition metal oxide composite as described above, preferably, in step S2, the soluble cobalt salt is any one of cobalt nitrate, cobalt chloride, and cobalt sulfate, and the soluble manganese salt is any one of manganese nitrate, manganese chloride, and manganese sulfate; the molar ratio of cobalt ions in the cobalt salt to manganese ions in the manganese salt is 1:1-3:1, and the molar ratio of urea to cobalt ions is 2:1-3:1;

[0031] The hydrothermal reaction temperature is 140-180℃ and the time is 6-12h, while the calcination treatment temperature is 300-500℃ and the time is 2-4h.

[0032] In the preparation method of nickel-zinc battery anode material based on graphene foam-carbon nanotube-transition metal oxide composite as described above, preferably, in step S3, the concentration of zinc oxide in the electrolyte is 0.5-1 mol / L, the strong base is potassium hydroxide or sodium hydroxide with a concentration of 3-4 mol / L, the concentration of tartaric acid is 0.1-0.3 mol / L, and the mass concentration of hydrogen peroxide is 0.5-1 wt%.

[0033] In the above-described method for preparing nickel-zinc battery anode materials based on graphene foam-carbon nanotube-transition metal oxide composites, preferably, in step S3, electrodeposition is performed using a pulsed current deposition method with a peak current density of 2-10 mA / cm². 2 In one pulse cycle, the power-on time is 5s, the power-off time is 10s, the total deposition time is 20-60min, and the deposition temperature is 40-60℃.

[0034] Thirdly, the present invention also provides a nickel-zinc battery, comprising the above-described nickel-zinc battery anode material or the nickel-zinc battery anode material prepared by the above-described preparation method.

[0035] (III) Beneficial Effects

[0036] This invention provides a nickel-zinc battery anode material based on a graphene foam-carbon nanotube-transition metal oxide composite. It utilizes a three-dimensional porous graphene foam as a conductive framework, with carbon nanotubes grown in situ on the pore walls to form a continuous conductive network, effectively improving the overall conductivity and structural stability of the anode material. A transition metal composite oxide composed of cobalt tetroxide and manganese dioxide is loaded onto this composite matrix, and an anode active material containing zinc nanocrystals and zinc oxide nanoparticles is deposited on its surface, constructing a nickel-zinc battery composite anode system with multiple synergistic functions.

[0037] The nickel-zinc battery anode material of this invention can regulate the zinc ion deposition behavior through the physical confinement effect of graphene foam and the transition metal oxide, significantly suppressing the growth of zinc dendrites. During charge and discharge, zinc ions can achieve uniform nucleation and deposition on the surface of the composite transition metal oxide, avoiding dendrite problems caused by excessively high local current density, thereby greatly improving the cycle life and safety of nickel-zinc batteries.

[0038] In the nickel-zinc battery anode material of the present invention, the composite transition metal oxide formed by cobalt tetroxide and manganese dioxide can effectively capture dissolved oxygen in the electrolyte, reduce the self-dissolution rate of zinc in an alkaline environment, thereby reducing the capacity loss of the battery in a static state, and thus significantly improving the self-discharge problem of nickel-zinc batteries and enhancing their long-term storage performance.

[0039] The highly conductive network composed of carbon nanotubes and graphene foam, along with nanoscale zinc-based active materials, can enhance the electron transport capability and interfacial reaction kinetics of the anode material, enabling nickel-zinc batteries to maintain high capacity output even at high rates. This significantly improves the rate performance of nickel-zinc batteries, allowing them to meet the needs of high-power applications.

[0040] In this invention, the highly conductive network composed of carbon nanotubes and graphene foam maintains good electron transport capabilities at low temperatures. The composite transition metal oxide of cobalt tetroxide and manganese dioxide provides additional pseudocapacitive active sites at low temperatures through the synergistic effect of oxygen vacancies at the heterojunction, promoting the reversible insertion and extraction of zinc ions. Simultaneously, the negative electrode active material composed of zinc nanocrystals and zinc oxide nanoparticles can suppress the disordered deposition of zinc ions, enabling the nickel-zinc battery to maintain a high capacity retention rate even at low temperatures.

[0041] In summary, this invention effectively solves the problems of severe zinc dendrite growth, short cycle life, high self-discharge, poor rate performance, and insufficient low-temperature adaptability in existing nickel-zinc batteries. It provides a practical and feasible technical path for the high performance and widespread application of nickel-zinc batteries and has broad industrialization prospects. Detailed Implementation

[0042] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to specific embodiments.

[0043] This invention provides a nickel-zinc battery anode material based on a graphene foam-carbon nanotube-transition metal oxide composite, comprising graphene foam, carbon nanotubes grown on the pore walls of the graphene foam, a transition metal oxide supported on a composite matrix composed of graphene foam and carbon nanotubes, and an anode active material deposited on the surface of the transition metal oxide. The transition metal oxide is a composite material of cobalt tetroxide and manganese dioxide, and the anode active material includes zinc nanocrystals and zinc oxide nanoparticles.

[0044] Preferably, the graphene foam has a three-dimensional porous structure with a pore size of 50-300 μm and a porosity of 85-95%. The large pore size provides a buffer space for zinc deposition, reducing local current density, while the high porosity ensures electrolyte wetting and shortens ion diffusion paths. The carbon nanotubes have a diameter of 10-30 nm and a length of 5-20 μm. When the diameter of the carbon nanotubes is ≤30 nm, the quantum confinement effect is enhanced, improving electron mobility. In the transition metal oxide, the molar ratio of cobalt ions in cobalt tetroxide to manganese ions in manganese dioxide is 1:1-3:1. By regulating the synergistic effect of the two, the catalytic activity and structural stability are optimized, improving the ability to regulate zinc deposition behavior, thereby reducing interfacial side reactions and increasing cycle life. If cobalt tetroxide is lacking, the transition metal oxide structure may become fragile, easily collapsing or peeling off during cycling, leading to rapid capacity decay. Manganese dioxide has a high specific surface area and abundant surface oxygen vacancies, which can effectively regulate zinc deposition behavior and inhibit dendrite growth. A lack of manganese dioxide may lead to a decline in the overall electrochemical performance of the battery. In the negative electrode active material, the mass ratio of zinc nanocrystals to zinc oxide nanoparticles is 2:1-5:1. The average particle size of the zinc nanocrystals is 20-100 nm, and the average particle size of the zinc oxide nanoparticles is 50-200 nm. The negative electrode active material accounts for 30-50% of the mass of the nickel-zinc battery negative electrode material. Zinc oxide has high chemical stability and is not easily dissolved in the electrolyte. A lack of zinc oxide may make the electrode surface more susceptible to electrolyte corrosion, leading to increased self-discharge and affecting the battery's long-term storage performance.

[0045] The present invention also provides a method for preparing the above-mentioned nickel-zinc battery anode material based on graphene foam-carbon nanotube-transition metal oxide composite, comprising the following steps:

[0046] S1: Carbon nanotubes are grown on the surface of the pore walls of graphene foam through chemical vapor deposition to obtain a composite matrix.

[0047] S2: The composite matrix is ​​immersed in an aqueous solution containing soluble cobalt salt, soluble manganese salt and urea to carry out a hydrothermal reaction to obtain a composite matrix with surface-loaded mixed precursors. Then, the composite matrix is ​​calcined in an inert atmosphere to obtain a composite matrix loaded with transition metal oxides.

[0048] S3: The composite matrix loaded with transition metal oxides is used as the cathode and immersed in an electrolyte containing zinc oxide, strong alkali, tartaric acid and hydrogen peroxide. Electrodeposition is performed using a pulsed current deposition method to deposit zinc nanocrystals and zinc oxide nanoparticles on the surface of the composite matrix loaded with transition metal oxides, thus obtaining the nickel-zinc battery anode material.

[0049] Preferably, in step S1 above, the graphene oxide suspension is injected into a mold and freeze-dried to obtain a graphene oxide framework. The graphene oxide framework is then subjected to a first-stage heat treatment in a mixed atmosphere of argon and hydrogen, followed by a second-stage heat treatment to obtain graphene foam. Specifically, the concentration of the graphene oxide suspension is 20-30 mg / mL, the freeze-drying temperature is -40 to -50 °C, and the time is 24-48 h. The volume ratio of argon to hydrogen in the mixed atmosphere is 95:5. The first-stage heat treatment is performed at 200-300 °C for 1-2 h, primarily to remove oxygen-containing functional groups and improve conductivity. The second-stage heat treatment is performed at 800-900 °C for 1-2 h, primarily for deep deoxidation and graphitization.

[0050] The prepared graphene foam was then immersed in a mixed aqueous solution of ferric nitrate and cobalt nitrate for a certain period of time, followed by drying to obtain catalyst-supported graphene foam. The molar ratio of ferric nitrate to cobalt nitrate was 2:1-1:2, and the immersion time was 30-40 min. The catalyst-supported graphene foam was then placed in a mixed atmosphere of argon and hydrogen (volume ratio 95:5) and heated to 700-800℃ at a heating rate of 5-8℃ / min. Acetylene was then introduced, and a chemical vapor deposition reaction was carried out for 30-40 min to obtain the composite matrix.

[0051] During the heating process described above, the nitrate precursor is thermally decomposed and reduced to catalytically active Fe-Co alloy nanoparticles, which serve as catalytic sites for carbon nanotube growth. Acetylene molecules are cracked and reconstructed on the catalyst surface to form carbon nanotube structures. Ultimately, in-situ growth of vertically oriented carbon nanotubes is achieved on the pore wall surface of graphene foam, resulting in a graphene foam-carbon nanotube composite matrix with a multi-level pore structure, excellent conductivity, and enhanced interfacial stability.

[0052] Preferably, in step S2 above, the soluble cobalt salt is any one of cobalt nitrate, cobalt chloride, and cobalt sulfate; the soluble manganese salt is any one of manganese nitrate, manganese chloride, and manganese sulfate; the molar ratio of cobalt ions in the cobalt salt to manganese ions in the manganese salt is 1:1-3:1; and the molar ratio of urea to cobalt ions is 2:1-3:1. The hydrothermal reaction temperature is 140-180℃, and the time is 6-12 hours; the calcination treatment temperature is 300-500℃, and the time is 2-4 hours.

[0053] In step S2 above, urea, as a mild precipitant and pH buffer, can promote uniform nucleation and prevent uneven precipitation caused by local over-alkaliness. This is beneficial for obtaining precursor materials with uniform particle size and good dispersibility. The hydrothermal reaction can form mixed precursor nanoparticles with high crystallinity and controllable morphology, providing a good foundation for subsequent calcination. Calcination can cause the precursor to undergo thermal decomposition and oxidative reconstruction, ultimately transforming it into a composite material of cobalt tetroxide and manganese dioxide with excellent electrocatalytic performance.

[0054] Preferably, in step S3 above, the concentration of zinc oxide in the electrolyte is 0.5-1 mol / L, the strong alkali is potassium hydroxide or sodium hydroxide with a concentration of 3-4 mol / L, the concentration of tartaric acid is 0.1-0.3 mol / L, and the mass concentration of hydrogen peroxide is 0.5-1 wt%. Electrodeposition is performed using a pulsed current deposition method with a peak current density of 2-10 mA / cm². 2 In one pulse cycle, the power-on time is 5s, the power-off time is 10s, the total deposition time is 20-60min, and the deposition temperature is 40-60℃.

[0055] A zinc oxide concentration of 0.5-1 mol / L provides a stable zinc source, ensuring sufficient zinc supply during the deposition process. A strong alkali concentration of 3-4 mol / L ensures that ZnO is fully dissolved into [Zn(OH)4]2- complex ions, maintaining an alkaline electrolyte environment that is conducive to the directional reduction deposition of zinc. Tartaric acid can partially complex Zn2-. + Ions slow down the deposition rate and regulate the nucleation process, enabling zinc nanocrystals to be deposited more uniformly and densely on the substrate surface. Hydrogen peroxide can decompose to generate reactive oxygen species during pulse power-off, promoting the in-situ oxidation of some deposited zinc to ZnO.

[0056] To further clarify the present invention and its technological advancements, the following description is provided in conjunction with specific embodiments and technical effects.

[0057] Example 1

[0058] This embodiment provides a method for preparing a nickel-zinc battery anode material based on graphene foam-carbon nanotube-transition metal oxide composite, including the following steps:

[0059] S1: A graphene oxide suspension with a concentration of 25 mg / mL was injected into a mold and freeze-dried at -45℃ for 36 h to obtain a graphene oxide framework. The graphene oxide framework underwent a first-stage heat treatment at 250℃ for 1.5 h in a mixed atmosphere of argon and hydrogen (95:5 volume ratio), followed by a second-stage heat treatment at 850℃ for 1.5 h to obtain graphene foam. The graphene foam was immersed in a mixed aqueous solution of ferric nitrate and cobalt nitrate (1:1 molar ratio) for 35 min, followed by drying to obtain catalyst-supported graphene foam. The catalyst-supported graphene foam was placed in a mixed atmosphere of argon and hydrogen (95:5 volume ratio) and heated to 750℃ at a rate of 6℃ / min. Acetylene was then introduced, and a chemical vapor deposition reaction was performed for 35 min to obtain the composite matrix.

[0060] S2: The composite matrix is ​​immersed in an aqueous solution containing cobalt nitrate, manganese nitrate and urea, with a molar ratio of cobalt ions to manganese ions of 2:1 and a molar ratio of urea to cobalt ions of 2.5:1. The composite matrix is ​​subjected to hydrothermal reaction at 160℃ for 10 h to obtain a composite matrix with surface-loaded mixed precursors. Then, the composite matrix is ​​calcined at 400℃ in a nitrogen atmosphere for 3 h to obtain a composite matrix loaded with transition metal oxides.

[0061] S3: A composite matrix loaded with transition metal oxides was used as the cathode and immersed in an electrolyte containing zinc oxide, potassium hydroxide, and tartaric acid. Electrodeposition was performed using a pulsed current deposition method to obtain the nickel-zinc battery anode material. The peak current density was 6 mA / cm². 2 In one pulse cycle, the power-on time is 5s, the power-off time is 10s, the total deposition time is 40min, and the deposition temperature is 50℃.

[0062] In this step, the concentration of zinc oxide in the electrolyte is 0.8 mol / L, the concentration of potassium hydroxide is 3.5 mol / L, the concentration of tartaric acid is 0.2 mol / L, and the mass concentration of hydrogen peroxide is 0.8 wt%.

[0063] Example 2

[0064] This embodiment provides a method for preparing a nickel-zinc battery anode material based on graphene foam-carbon nanotube-transition metal oxide composite, including the following steps:

[0065] S1: A 20 mg / mL graphene oxide suspension was injected into a mold and freeze-dried at -40°C for 24 h to obtain a graphene oxide framework. The graphene oxide framework underwent a first-stage heat treatment at 200°C for 2 h in a mixed atmosphere of argon and hydrogen (95:5 volume ratio), followed by a second-stage heat treatment at 800°C for 2 h to obtain graphene foam. The graphene foam was immersed in a mixed aqueous solution of ferric nitrate and cobalt nitrate (2:1 molar ratio) for 30 min, followed by drying to obtain catalyst-supported graphene foam. The catalyst-supported graphene foam was placed in a mixed atmosphere of argon and hydrogen (95:5 volume ratio) and heated to 700°C at a rate of 5°C / min. Acetylene was then introduced, and a chemical vapor deposition reaction was performed for 30 min to obtain the composite matrix.

[0066] S2: The composite matrix is ​​immersed in an aqueous solution containing cobalt chloride, manganese chloride and urea, with a molar ratio of cobalt ions to manganese ions of 1:1 and a molar ratio of urea to cobalt ions of 2:1. The mixture is hydrothermally reacted at 140°C for 12 hours to obtain a composite matrix with surface-loaded mixed precursors. The composite matrix is ​​then calcined at 300°C in a nitrogen atmosphere for 4 hours to obtain a composite matrix loaded with transition metal oxides.

[0067] S3: A composite matrix loaded with transition metal oxides was used as the cathode and immersed in an electrolyte containing zinc oxide, sodium hydroxide, and tartaric acid. Electrodeposition was performed using a pulsed current deposition method to obtain the nickel-zinc battery anode material. The peak current density was 2 mA / cm². 2 In one pulse cycle, the power-on time is 5s, the power-off time is 10s, the total deposition time is 20min, and the deposition temperature is 40℃.

[0068] In this step, the concentration of zinc oxide in the electrolyte is 0.5 mol / L, the concentration of sodium hydroxide is 3 mol / L, the concentration of tartaric acid is 0.1 mol / L, and the mass concentration of hydrogen peroxide is 0.5 wt%.

[0069] Example 3

[0070] This embodiment provides a method for preparing a nickel-zinc battery anode material based on graphene foam-carbon nanotube-transition metal oxide composite, including the following steps:

[0071] S1: A 30 mg / mL graphene oxide suspension was injected into a mold and freeze-dried at -50°C for 48 h to obtain a graphene oxide framework. The graphene oxide framework underwent a first-stage heat treatment at 300°C for 1 h in a mixed atmosphere of argon and hydrogen (95:5 volume ratio), followed by a second-stage heat treatment at 900°C for 1 h to obtain graphene foam. The graphene foam was immersed in a mixed aqueous solution of ferric nitrate and cobalt nitrate (molar ratio 1:2) for 40 min, followed by drying to obtain catalyst-supported graphene foam. The catalyst-supported graphene foam was placed in a mixed atmosphere of argon and hydrogen (95:5 volume ratio) and heated to 800°C at a rate of 8°C / min. Acetylene was then introduced, and a chemical vapor deposition reaction was performed for 40 min to obtain the composite matrix.

[0072] S2: The composite matrix is ​​immersed in an aqueous solution containing cobalt sulfate, manganese sulfate and urea, with a molar ratio of cobalt ions to manganese ions of 1:1-3:1 and a molar ratio of urea to cobalt ions of 2:1-3:1. The composite matrix is ​​subjected to hydrothermal reaction at 180℃ for 6 hours to obtain a composite matrix with surface-loaded mixed precursors. Then, the composite matrix is ​​calcined at 500℃ in a nitrogen atmosphere for 2 hours to obtain a composite matrix loaded with transition metal oxides.

[0073] S3: A composite matrix loaded with transition metal oxides was used as the cathode and immersed in an electrolyte containing zinc oxide, potassium hydroxide, and tartaric acid. Electrodeposition was performed using a pulsed current deposition method to obtain the nickel-zinc battery anode material. The peak current density was 10 mA / cm². 2 In one pulse cycle, the power-on time is 5s, the power-off time is 10s, the total deposition time is 60min, and the deposition temperature is 60℃.

[0074] In this step, the concentration of zinc oxide in the electrolyte is 1 mol / L, the concentration of potassium hydroxide is 4 mol / L, the concentration of tartaric acid is 0.3 mol / L, and the mass concentration of hydrogen peroxide is 1 wt%.

[0075] Example 4

[0076] This embodiment provides a method for preparing a nickel-zinc battery anode material based on graphene foam-carbon nanotube-transition metal oxide composite, including the following steps:

[0077] S1: A graphene oxide suspension with a concentration of 28 mg / mL was injected into a mold and freeze-dried at -43℃ for 28 h to obtain a graphene oxide framework. The graphene oxide framework underwent a first-stage heat treatment at 240℃ for 1.6 h in a mixed atmosphere of argon and hydrogen (95:5 volume ratio), followed by a second-stage heat treatment at 860℃ for 1 h to obtain graphene foam. The graphene foam was immersed in a mixed aqueous solution of ferric nitrate and cobalt nitrate (molar ratio 1:2) for 33 min, followed by drying to obtain catalyst-supported graphene foam. The catalyst-supported graphene foam was placed in a mixed atmosphere of argon and hydrogen (95:5 volume ratio) and heated to 720℃ at a rate of 7℃ / min. Acetylene was then introduced, and a chemical vapor deposition reaction was performed for 32 min to obtain the composite matrix.

[0078] S2: The composite matrix is ​​immersed in an aqueous solution containing cobalt nitrate, manganese nitrate and urea, with a molar ratio of cobalt ions to manganese ions of 1:1 and a molar ratio of urea to cobalt ions of 2:1. The mixture is hydrothermally reacted at 150°C for 7 hours to obtain a composite matrix with surface-loaded mixed precursors. The composite matrix is ​​then calcined at 300°C in a nitrogen atmosphere for 3.5 hours to obtain a composite matrix loaded with transition metal oxides.

[0079] S3: A composite matrix loaded with transition metal oxides was used as the cathode and immersed in an electrolyte containing zinc oxide, potassium hydroxide, and tartaric acid. Electrodeposition was performed using a pulsed current deposition method to obtain the nickel-zinc battery anode material. The peak current density was 7 mA / cm². 2 In one pulse cycle, the power-on time is 5s, the power-off time is 10s, the total deposition time is 35min, and the deposition temperature is 45℃.

[0080] In this step, the concentration of zinc oxide in the electrolyte is 0.7 mol / L, the concentration of potassium hydroxide is 3.3 mol / L, the concentration of tartaric acid is 0.18 mol / L, and the mass concentration of hydrogen peroxide is 0.7 wt%.

[0081] Comparative Example 1

[0082] This comparative example provides a method for preparing a nickel-zinc battery anode material. The difference from Example 1 is that only graphene foam is obtained in step S1, and carbon nanotubes are not grown.

[0083] Comparative Example 2

[0084] This comparative example provides a method for preparing a nickel-zinc battery anode material. The difference from Example 1 is that step S2 does not contain manganese ions.

[0085] Comparative Example 3

[0086] This comparative example provides a method for preparing a nickel-zinc battery anode material. The difference from Example 1 is that step S3 does not contain tartaric acid and hydrogen peroxide.

[0087] The negative electrode materials prepared in Examples 1-4 and Comparative Examples 1-3 were used to prepare nickel-zinc battery negative electrodes. A nickel-zinc battery positive electrode and an electrolyte were also provided. The components were assembled to obtain a nickel-zinc battery. The electrochemical performance of each nickel-zinc battery was tested (unless otherwise specified, all tests were performed at room temperature), and the results are shown in Table 1.

[0088] Long cycle life test: 200 complete charge-discharge cycles were performed at a current density of 0.1C (1C = 82mAh / g). The discharge capacity was recorded for each cycle, and the capacity retention rate after the 200th cycle was calculated, which is the ratio of the discharge capacity of the 200th cycle to the discharge capacity of the first cycle, expressed as a percentage.

[0089] Self-discharge performance test: After charging the nickel-zinc battery to full capacity, leave it for 7 days, and then conduct a discharge test again. Compare the difference in discharge capacity before and after the leave period, and calculate the percentage of capacity loss of the battery. The percentage of capacity loss is calculated using the following formula:

[0090] Capacity loss percentage = (1 - (discharge capacity after storage / discharge capacity before storage)) × 100%

[0091] Rate performance test: The first discharge capacity of the nickel-zinc battery was tested at current densities of 0.1C and 5C respectively, and the percentage of the first discharge capacity at 5C current density to the first discharge capacity at 0.1C current density was calculated.

[0092] After the nickel-zinc battery was stabilized in an environment of -20°C for a period of time, it was subjected to a complete discharge cycle at a current density of 0.1C. The discharge capacity at this low temperature was recorded and compared with the discharge capacity obtained at room temperature. The low-temperature discharge capacity retention rate was calculated and expressed as a percentage.

[0093] Table 1. Statistical table of electrochemical performance of nickel-zinc batteries corresponding to Examples 1-4 and Comparative Examples 1-3.

[0094]

[0095] As shown in Table 1, the nickel-zinc batteries of Examples 1-4 maintained a capacity retention rate of over 85% after 200 cycles, while the nickel-zinc batteries of Comparative Examples 1-3 showed significantly lower capacity retention rates after 200 cycles. This indicates that the present invention can significantly suppress the growth of zinc dendrites and improve the cycle life of nickel-zinc batteries. After being left idle for 7 days, the capacity loss percentage of the nickel-zinc batteries of Examples 1-4 was only around 2%, while the capacity loss percentage of the nickel-zinc batteries of Comparative Examples 1-3 increased significantly. This indicates that the composite transition metal oxide formed by cobalt tetroxide and manganese dioxide in the present invention significantly improves the self-discharge problem of nickel-zinc batteries. The nickel-zinc batteries of Examples 1-4 achieved 75-80% of the initial discharge capacity at 0.1C at a current density of 5C, demonstrating good high-rate performance. Comparative Example 1, lacking the composite highly conductive network of carbon nanotubes and graphene foam, exhibited poor rate performance. The nickel-zinc batteries in Examples 1-4 maintain a capacity retention rate of over 80% at -20°C and a current density of 0.1C, compared to 65-75% in Comparative Examples 1-3. This demonstrates that the present invention, through a highly conductive network composed of carbon nanotubes and graphene foam, a composite transition metal oxide of cobalt tetroxide and manganese dioxide, and a negative electrode active material composed of zinc nanocrystals and zinc oxide nanoparticles, enables nickel-zinc batteries to maintain a high capacity retention rate even at low temperatures.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A nickel-zinc battery anode material based on graphene foam-carbon nanotube-transition metal oxide composite, characterized in that, It includes graphene foam, carbon nanotubes grown on the surface of the pore walls of graphene foam, transition metal oxides loaded on a composite matrix composed of graphene foam and carbon nanotubes, and negative electrode active materials deposited on the surface of transition metal oxides. The transition metal oxide is a composite material of cobalt tetroxide and manganese dioxide; The negative electrode active material includes zinc nanocrystals and zinc oxide nanoparticles.

2. The nickel-zinc battery anode material based on graphene foam-carbon nanotube-transition metal oxide composite according to claim 1, characterized in that, The pore size of graphene foam is 50-300μm, and the porosity is 85-95%. Carbon nanotubes have a diameter of 10-30 nm and a length of 5-20 μm; In transition metal oxides, the molar ratio of cobalt ions in cobalt tetroxide to manganese ions in manganese dioxide is 1:1-3:

1. In the negative electrode active material, the mass ratio of zinc nanocrystals to zinc oxide nanoparticles is 2:1-5:1, the average particle size of zinc nanocrystals is 20-100nm, and the average particle size of zinc oxide nanoparticles is 50-200nm. The negative electrode active material accounts for 30-50% of the mass of the negative electrode material in nickel-zinc batteries.

3. A method for preparing a nickel-zinc battery anode material based on graphene foam-carbon nanotube-transition metal oxide composite as described in any one of claims 1-2, characterized in that, Includes the following steps: S1: Carbon nanotubes are grown on the surface of the pore walls of graphene foam through chemical vapor deposition to obtain a composite matrix; S2: The composite matrix is ​​immersed in an aqueous solution containing soluble cobalt salt, soluble manganese salt and urea to carry out a hydrothermal reaction to obtain a composite matrix with surface-loaded mixed precursors. Then, the composite matrix is ​​calcined in an inert atmosphere to obtain a composite matrix loaded with transition metal oxides. S3: The composite matrix loaded with transition metal oxides is used as the cathode and immersed in an electrolyte containing zinc oxide, strong alkali, tartaric acid and hydrogen peroxide. Electrodeposition is performed using a pulsed current deposition method to deposit zinc nanocrystals and zinc oxide nanoparticles on the surface of the composite matrix loaded with transition metal oxides, thus obtaining the nickel-zinc battery anode material.

4. The preparation method of the nickel-zinc battery anode material based on graphene foam-carbon nanotube-transition metal oxide composite according to claim 3, characterized in that, In step S1, the graphene oxide suspension is injected into a mold and freeze-dried to obtain a graphene oxide framework. The graphene oxide framework is then subjected to a first-stage heat treatment in a mixed atmosphere of argon and hydrogen, followed by a second-stage heat treatment to obtain graphene foam. The prepared graphene foam was immersed in a mixed aqueous solution of ferric nitrate and cobalt nitrate for a certain period of time and then dried to obtain the catalyst-supported graphene foam. In a mixed atmosphere of argon and hydrogen, graphene foam loaded with a catalyst is heated, and then acetylene is introduced. The chemical vapor deposition reaction is carried out for a certain period of time to obtain a composite matrix.

5. The preparation method of the nickel-zinc battery anode material based on graphene foam-carbon nanotube-transition metal oxide composite according to claim 4, characterized in that, The concentration of the graphene oxide suspension was 20-30 mg / mL, and the freeze-drying temperature was (-40)-(-50)℃ for 24-48 h. In a mixed atmosphere of argon and hydrogen, the volume ratio of the two is 95:

5. The temperature of the first stage of heat treatment is 200-300℃ and the time is 1-2h. The temperature of the second stage of heat treatment is 800-900℃ and the time is 1-2h. The molar ratio of ferric nitrate to cobalt nitrate is 2:1 to 1:2, and the soaking time is 30 to 40 minutes. The graphene foam loaded with the catalyst was placed in a mixed atmosphere of argon and hydrogen and heated to 700-800℃ at a heating rate of 5-8℃ / min. Then, acetylene was introduced and chemical vapor deposition was carried out for 30-40 min to obtain the composite matrix.

6. The preparation method of the nickel-zinc battery anode material based on graphene foam-carbon nanotube-transition metal oxide composite according to claim 3, characterized in that, In step S2, the soluble cobalt salt is any one of cobalt nitrate, cobalt chloride, and cobalt sulfate, and the soluble manganese salt is any one of manganese nitrate, manganese chloride, and manganese sulfate; the molar ratio of cobalt ions in the cobalt salt to manganese ions in the manganese salt is 1:1-3:1, and the molar ratio of urea to cobalt ions is 2:1-3:

1. The hydrothermal reaction temperature is 140-180℃ and the time is 6-12h, while the calcination treatment temperature is 300-500℃ and the time is 2-4h.

7. The method for preparing the nickel-zinc battery anode material based on graphene foam-carbon nanotube-transition metal oxide composite according to claim 3, characterized in that, In step S3, the concentration of zinc oxide in the electrolyte is 0.5-1 mol / L, the strong base is potassium hydroxide or sodium hydroxide with a concentration of 3-4 mol / L, the concentration of tartaric acid is 0.1-0.3 mol / L, and the mass concentration of hydrogen peroxide is 0.5-1 wt%.

8. The preparation method of the nickel-zinc battery anode material based on graphene foam-carbon nanotube-transition metal oxide composite according to claim 3, characterized in that, In step S3, electrodeposition is performed using pulsed current deposition with a peak current density of 2-10 mA / cm³. 2 In one pulse cycle, the power-on time is 5s, the power-off time is 10s, the total deposition time is 20-60min, and the deposition temperature is 40-60℃.

9. A nickel-zinc battery, characterized in that, The nickel-zinc battery anode material includes the nickel-zinc battery anode material according to any one of claims 1-2 or the nickel-zinc battery anode material prepared by the preparation method according to any one of claims 2-8.

Images