Gradient nanopore structure NiSe cathode material growing on surface of foamed nickel in situ and preparation method and application of gradient nanopore structure NiSe cathode material

Abstract

The invention discloses a gradient nanopore structure NiSe cathode material growing on the surface of foamed nickel in situ and a preparation method and application thereof.The method comprises the steps that 1, NiCl2. 5H2O and 4-4 '-biphenyl dicarboxylic acid are taken and added into DMF, a solution A is obtained, ethyl alcohol and ultrapure water are added into the solution A, a solution B is obtained, the foamed nickel is soaked in the solution B and moved into a high-pressure reaction kettle, the high-pressure reaction kettle is placed in an oven, and the temperature of the high-pressure reaction kettle is kept constant; the preparation method comprises the following steps: preparing a Ni-MOF-coated foamed nickel precursor, reacting at 100-150 DEG C for 7-9 hours, washing and drying to obtain a Ni-MOF-coated foamed nickel precursor C, and calcining at 300-400 DEG C for 2-3 hours to obtain a Ni-MOF-coated foamed nickel precursor D with a nano-porous structure; 2, Se powder is taken and added into ultrapure water to obtain a solution E, NaBH4 is taken and added into ethyl alcohol to obtain a solution F, the solution E is added into the solution F to obtain a solution G, the precursor D is immersed into the solution G and moved to a high-pressure reaction kettle, reaction is conducted for 1-2 h at the temperature of 160-200 DEG C, washing and drying are conducted, and the gradient nanopore structure NiSe cathode material growing on the surface of foamed nickel in situ is obtained and has good structural stability and high specific surface area capacity. And charging and discharging of the water-based nickel-zinc battery can be accelerated.

Description

Technical Field

[0001] The present invention relates to a cathode material for aqueous nickel-zinc batteries, and specifically to a NiSe cathode material with a gradient nanoporous structure in-situ grown on the surface of nickel foam, and a preparation method and application thereof. Background Art

[0002] With the over-exploitation and rapid consumption of fossil energy, energy problems and environmental deterioration have attracted much attention. Developing clean and low-cost environmentally friendly energy storage components to alleviate the current social energy crisis is of great significance for the development of the national economy and the realization of sustainable development. As an emerging energy storage component, nickel-zinc batteries are considered to be one of the effective ways. Research shows that: ① Compared with lithium-ion batteries, nickel-zinc batteries have a higher power density and can achieve rapid charge and discharge; ② Aqueous nickel-zinc batteries have the characteristics of being green, pollution-free and environmentally friendly; it can be seen that nickel-zinc batteries have extremely high application value in the field of power energy.

[0003] NiSe has abundant surface active sites, metallic conductivity, a high specific surface area and good hydrophilicity, and is one of the most attractive aqueous Se-based energy storage materials at present, showing great potential in the new generation of high-performance energy storage electrodes and receiving extensive attention. However, when it is applied to the positive electrode material of aqueous nickel-zinc batteries, the electrode reaction often occurs on the surface of NiSe, and is restricted by the small-size gaps inside its lattice, and OH - deep diffusion cannot be formed, and it does not have good nickel-zinc battery storage performance. Therefore, it is necessary to chemically etch it to form a nanoporous structure, so as to prepare a composite material for nickel-zinc batteries with high electrochemical performance.

[0004] However, if NiSe is simply chemically etched, it is impossible to ensure the uniformity of the NiSe etching process and the formation of a gradient nanoporous structure. During the charge and discharge process of nickel-zinc batteries, NiSe is prone to pulverization and structural deterioration. At the same time, NiSe is prone to falling off from the current collector, resulting in a decrease in the material capacity and a continuous decline in the cycle stability, making it difficult to exert the high specific capacity of NiSe.

[0005] Therefore, it is necessary to explore a NiSe with a gradient nanoporous structure that is difficult to fall off from the current collector, and to obtain a highly stable aqueous nickel-zinc battery electrode material without affecting the high specific capacity of the gradient nanoporous structure NiSe. Summary of the Invention

[0006] The purpose of the present invention is to provide a NiSe cathode material with a gradient nanoporous structure in-situ grown on the surface of nickel foam, and a preparation method and application thereof. The material has good structural stability, high power density and high specific surface area capacity, and can promote the rapid charge and discharge of aqueous nickel-zinc batteries.

[0007] The present invention is realized through the following technical solutions:

[0008] A preparation method of a gradient nanoporous structure NiSe cathode material grown in-situ on the surface of nickel foam, comprising the following steps:

[0009] Step 1, preparing a nanoporous structure Ni-MOF@nickel foam precursor

[0010] Step 1.1, according to the ratio of NiCl2·5H2O, 4,4'-biphenyldicarboxylic acid, DMF, absolute ethanol and ultrapure water (0.2 - 0.3 mmol):(0.2 - 0.3 mmol):(10 - 20 mL):(1 - 2 mL):(10 - 20 mL), take NiCl2·5H2O and 4,4'-biphenyldicarboxylic acid and add them to DMF to obtain solution A. Add absolute ethanol and ultrapure water to solution A, and stir evenly with a magnetic stirrer to obtain a green solution B;

[0011] Step 1.2, soak nickel foam in solution B, then transfer the solution B soaked with nickel foam into a high-pressure reaction kettle. Then place the high-pressure reaction kettle in an oven and carry out a hydrothermal reaction at 100 - 150 °C for 7 - 9 h. Cool to room temperature, take out the nickel foam, wash and dry it under vacuum in sequence to obtain the Ni-MOF@nickel foam precursor C;

[0012] Step 1.3, place the Ni-MOF@nickel foam precursor C in a tubular furnace and calcine it at 300 - 400 °C for 2 - 3 h to obtain the nanoporous structure Ni-MOF@nickel foam precursor D;

[0013] Step 2, preparing a gradient nanoporous structure NiSe cathode material

[0014] Step 2.1, according to the ratio of Se powder, ultrapure water, NaBH4 and absolute ethanol (40 - 50 mg):(6 - 10 mL):(60 - 70 mg):(5 - 8 mL), take Se powder and add it to ultrapure water, stir well to obtain solution E. At the same time, take NaBH4 and add it to absolute ethanol, dissolve it fully to obtain solution F. Then add solution E to solution F and mix evenly to obtain a mixed solution G;

[0015] Step 2.2, immerse the nanoporous structure Ni-MOF@nickel foam precursor D in the mixed solution G, and transfer it to a high-pressure reaction kettle. Carry out a hydrothermal reaction at 160 - 200 °C for 1 - 2 h. Cool to room temperature, wash and dry it under vacuum in sequence to obtain the gradient nanoporous structure NiSe cathode material grown in-situ on the surface of nickel foam.

[0016] Further, in the step 1.1, the ratio of NiCl2·5H2O, 4,4'-biphenyldicarboxylic acid, DMF, absolute ethanol and ultrapure water is 0.24 mmol: 0.24 mmol: 15 mL: 1.5 mL: 15 mL.

[0017] Further, in the step 1.2, the size of the nickel foam is 1 cm × 3 cm.

[0018] Further, in the steps 1.2 and 2.2, the washing is carried out by washing 3 times with absolute ethanol and ultrapure water in sequence.

[0019] Further, in the steps 1.2 and 2.2, the vacuum drying is carried out at 50 - 70 °C for 10 - 12 h.

[0020] Further, in the step 2.1, the ratio of Se powder, ultrapure water, NaBH4 and absolute ethanol is 47.4 mg: 9 mL: 68.4 mg: 6 mL.

[0021] A cathode material of NiSe with a gradient nanoporous structure in-situ grown on the surface of nickel foam.

[0022] Application of a cathode material of NiSe with a gradient nanoporous structure in-situ grown on the surface of nickel foam as a cathode material for aqueous nickel-zinc batteries.

[0023] The present invention has the following beneficial technical effects:

[0024] 1), on the one hand, by means of the design strategy of the gradient nanoporous structure, the present invention first constructs a NiSe nanosheet array structure, in which there are mesoporous and macroporous structures of about 20 - 100 nm between the sheets, and then uses etching technology to construct a microporous structure of about 5 nm on the surface of the NiSe nanosheets. During the etching process, a large number of Se vacancies are formed simultaneously, thus forming a gradient nanoporous structure of macropores / mesopores - micropores - vacancies. Due to the capillary action of the macropores / mesopores, it can promote the wetting of the electrolyte with the electrode surface, increase the effective contact between the two, the micropores can promote the deep diffusion of OH - in the electrolyte, and the Se vacancies can reduce the adsorption energy barrier of adjacent Ni sites, promoting the surface adsorption of OH - Therefore, the gradient nanoporous structure NiSe can effectively promote the deep diffusion of OH - , expose more electrochemically active sites of the NiSe nanosheets, reduce the adsorption energy barrier of the NiSe nanosheets to OH - , thus improving the adsorption ability of the NiSe cathode to OH - , promoting the interfacial contact between OH - in the electrolyte and the cathode material, and accelerating the interfacial contact of OH -The diffusion process improves the power density and areal specific capacity of NiSe nanosheets. On the other hand, integrating the NiSe material with a gradient nanoporous structure of macropores / mesopores - micropores - vacancies on the surface of nickel foam constructs an integrated NiSe@Ni material, which is not easy to fall off from the current collector and has good structural stability. On the other hand, sintering the Ni-MOF@nickel foam precursor improves the stability of the gradient nanoporous structure of macropores / mesopores - micropores - vacancies, making the NiSe material with a gradient nanoporous structure not prone to pulverization and fission. In summary, the cathode material of NiSe with a gradient nanoporous structure in-situ grown on the surface of nickel foam prepared by the present invention has high power density, high areal specific capacity and good structural stability. When used as the cathode material of an aqueous nickel-zinc battery, it can promote the rapid charge and discharge of the aqueous nickel-zinc battery, endowing it with excellent electrochemical performance.

[0025] 2), The present invention combines hydrothermal method and low-temperature sintering to prepare the cathode material of NiSe with a gradient nanoporous structure in-situ grown on the surface of nickel foam. The preparation method is simple and low-cost, with high economic value, laying a good foundation for the development of aqueous nickel-zinc batteries. Description of the Drawings

[0026] Figure 1 : XRD pattern of the cathode material of NiSe with a gradient nanoporous structure in-situ grown on the surface of nickel foam prepared in Example 1 of the present invention;

[0027] Figure 2 : EPR pattern of the cathode material of NiSe with a gradient nanoporous structure in-situ grown on the surface of nickel foam prepared in Example 1 of the present invention;

[0028] Figure 3 : SEM image of the cathode material of NiSe with a gradient nanoporous structure in-situ grown on the surface of nickel foam prepared in Example 1 of the present invention;

[0029] Figure 4 : Galvanostatic charge-discharge profiles of the nickel-zinc battery assembled with the cathode material of NiSe with a gradient nanoporous structure in-situ grown on the surface of nickel foam prepared in Example 1 of the present invention at different current densities;

[0030] Figure 5 : Galvanostatic charge-discharge profiles of the nickel-zinc battery assembled with the cathode material of nanoporous NiSe in-situ grown on the surface of nickel foam prepared in Comparative Example 1 of the present invention at different current densities. Detailed Embodiments

[0031] The following further detailed description of the present invention is made in conjunction with specific embodiments, which is an explanation rather than a limitation of the present invention.

[0032] Example 1

[0033] Step 1. Prepare the nano-porous structure Ni-MOF@nickel foam precursor

[0034] Step 1.1. Weigh 0.24 mmol of NiCl2·5H2O and 0.24 mmol of 4,4'-biphenyldicarboxylic acid, add them to 15 mL of DMF to obtain solution A. Then add 1.5 mL of absolute ethanol and 15 mL of ultrapure water to solution A, and stir magnetically to obtain a green solution B;

[0035] Step 1.2. Immerse a 1 cm×3 cm nickel foam in solution B, then transfer the solution B with the immersed nickel foam into a high-pressure reaction kettle. Next, place the high-pressure reaction kettle in an oven and carry out a hydrothermal reaction at 100 °C for 7 h. Cool to room temperature, take out the nickel foam, wash it 3 times with absolute ethanol and ultrapure water respectively, and vacuum dry it at 50 °C for 10 h to obtain the Ni-MOF@nickel foam precursor C;

[0036] Step 1.3. Place the Ni-MOF@nickel foam precursor C in a tubular furnace and calcine it at 300 °C for 2 h to obtain the nano-porous structure Ni-MOF@nickel foam precursor D;

[0037] Step 2. Prepare the gradient nano-porous structure NiSe cathode material

[0038] Step 2.1. Take 47.4 mg of Se powder and add it to 9 mL of ultrapure water, stir well to obtain solution E. At the same time, take 68.4 mg of NaBH4 and add it to 6 mL of absolute ethanol, dissolve it completely to obtain solution F. Then add solution E to solution F and mix evenly to obtain a mixed solution G;

[0039] Step 2.2. Immerse the nano-porous structure Ni-MOF@nickel foam precursor D in the mixed solution G, and transfer it to a high-pressure reaction kettle. Carry out a hydrothermal reaction at 160 °C for 1 h, cool to room temperature, wash it 3 times with absolute ethanol and ultrapure water respectively, and vacuum dry it at 50 °C for 10 h to obtain the gradient nano-porous structure NiSe cathode material grown in-situ on the surface of nickel foam, denoted as NiSe@Ni.

[0040] It can be seen that Figure 1 when 2θ is 32.8°, 50.1°, and 61.2°, the diffraction peaks of the (101), (110), and (201) crystal planes of the NiSe material are observed. When 2θ is 44.5°, 51.8°, and 76.5°, the diffraction peaks of Ni are observed, indicating that the NiSe material grown in-situ on the surface of nickel foam was successfully prepared in Example 1.

[0041] It can be seen from Figure 2It can be seen that there are a large number of surface Se vacancies in the NiSe material grown in-situ on the surface of nickel foam, which can reduce the OH- adsorption energy barrier of adjacent Ni sites, thereby enhancing the energy storage effect of nickel-zinc batteries.

[0042] From Figure 3 It can be seen that the gradient nanoporous structure NiSe cathode material grown in-situ on the surface of nickel foam has a surface gradient nanoporous structure, that is, there are mesopores and macropores with a size of about 20-100 nm between the sheets of the NiSe nanosheet array structure. The etching technology is used to construct a microporous structure of about 5 nm on the surface of the NiSe nanosheets, which not only helps to stabilize the structure of the gradient nanoporous NiSe material, but also increases the specific surface area of the material and promotes the deep diffusion of OH - , enhancing the storage effect of OH - , that is, endowing the material with good structural stability and high specific surface area capacity.

[0043] Example 2

[0044] Step 1. Prepare a nanoporous structure Ni-MOF@nickel foam precursor

[0045] Step 1.1. Weigh 0.25 mmol of NiCl2·5H2O and 0.25 mmol of 4,4'-biphenyldicarboxylic acid, add them to 15 mL of DMF to obtain solution A, then add 1.5 mL of absolute ethanol and 15 mL of ultrapure water to solution A, and stir magnetically to obtain a green solution B;

[0046] Step 1.2. Immerse a 1 cm×3 cm nickel foam in solution B, then transfer the solution B soaked with nickel foam into a high-pressure reaction kettle, and then place the high-pressure reaction kettle in an oven. At 120 °C, carry out a hydrothermal reaction for 7 h, cool to room temperature, take out the nickel foam, wash it 3 times with absolute ethanol and ultrapure water respectively, and dry it in vacuum at 60 °C for 12 h to obtain the Ni-MOF@nickel foam precursor C;

[0047] Step 1.3. Place the Ni-MOF@nickel foam precursor C in a tubular furnace and calcine it at 300 °C for 2 h to obtain a nanoporous structure Ni-MOF@nickel foam precursor D;

[0048] Step 2. Prepare a gradient nanoporous structure NiSe cathode material

[0049] Step 2.1. Take 44 mg of Se powder and add it to 6 mL of ultrapure water, stir well to obtain solution E. At the same time, take 64 mg of NaBH4 and add it to 7 mL of absolute ethanol, dissolve it fully to obtain solution F, and then add solution E to solution F and mix evenly to obtain a mixed solution G;

[0050] Step 2.2, immerse the nanoporous structure Ni-MOF@nickel foam precursor D into the mixed solution G and transfer it to a high-pressure reactor, hydrothermally react at 180°C for 1 hour, cool to room temperature, wash with anhydrous ethanol and ultrapure water for 3 times respectively, and vacuum dry at 60°C for 12 hours to obtain a gradient nanoporous structure NiSe cathode material in situ grown on the surface of nickel foam, recorded as NiSe@Ni.

[0051] Example 3

[0052] Step 1: Preparation of nanoporous Ni-MOF@foam nickel precursor

[0053] Step 1.1, weigh 0.3 mmol NiCl2·5H2O and 0.3 mmol 4-4′-biphenyl dicarboxylic acid, add to 10 mL DMF to obtain solution A, then add 2 mL anhydrous ethanol and 20 mL ultrapure water to solution A, stir magnetically to obtain a green solution B;

[0054] Step 1.2, soak 1 cm × 3 cm nickel foam in solution B, then transfer solution B soaked with nickel foam into a high-pressure reactor, then place the high-pressure reactor in an oven, perform hydrothermal reaction at 100 ° C for 8 hours, cool to room temperature, take out the nickel foam, wash it with anhydrous ethanol and ultrapure water three times respectively, and vacuum dry it at 70 ° C for 10 hours to obtain Ni-MOF@nickel foam precursor C;

[0055] Step 1.3, placing the Ni-MOF@nickel foam precursor C in a tube furnace and calcining it at 350° C. for 2 h to obtain a nanoporous Ni-MOF@nickel foam precursor D;

[0056] Step 2: Preparation of NiSe cathode material with gradient nanopore structure

[0057] Step 2.1, add 40 mg of Se powder to 7 mL of ultrapure water and stir thoroughly to obtain solution E. At the same time, add 65 mg of NaBH4 to 8 mL of anhydrous ethanol and dissolve thoroughly to obtain solution F. Then add solution E to solution F and mix well to obtain a mixed solution G.

[0058] Step 2.2, immerse the nanoporous structure Ni-MOF@nickel foam precursor D into the mixed solution G and transfer it to a high-pressure reactor, perform hydrothermal reaction at 180°C for 1.5 hours, cool to room temperature, wash with anhydrous ethanol and ultrapure water three times each, and vacuum dry at 70°C for 10 hours to obtain a gradient nanoporous structure NiSe cathode material in situ grown on the surface of nickel foam, recorded as NiSe@Ni.

[0059] Example 4

[0060] Step 1. Prepare the nano-porous structure Ni-MOF@nickel foam precursor

[0061] Step 1.1. Weigh 0.2 mmol of NiCl2·5H2O and 0.2 mmol of 4,4'-biphenyldicarboxylic acid, add them to 10 mL of DMF to obtain solution A, then add 1 mL of absolute ethanol and 10 mL of ultrapure water to solution A, and stir magnetically to obtain green solution B;

[0062] Step 1.2. Immerse a 1 cm×3 cm nickel foam in solution B, then transfer the solution B soaked with nickel foam into a high-pressure reaction kettle, then place the high-pressure reaction kettle in an oven, carry out a hydrothermal reaction at 150 °C for 8 h, cool to room temperature, take out the nickel foam, wash it 3 times with absolute ethanol and ultrapure water respectively, and carry out vacuum drying at 50 °C for 10 h to obtain the Ni-MOF@nickel foam precursor C;

[0063] Step 1.3. Place the Ni-MOF@nickel foam precursor C in a tubular furnace and calcine it at 400 °C for 2 h to obtain the nano-porous structure Ni-MOF@nickel foam precursor D;

[0064] Step 2. Prepare the gradient nano-porous structure NiSe cathode material

[0065] Step 2.1. Take 45 mg of Se powder and add it to 8 mL of ultrapure water, stir well to obtain solution E. At the same time, take 60 mg of NaBH4 and add it to 5 mL of absolute ethanol, dissolve it fully to obtain solution F, then add solution E to solution F and mix evenly to obtain the mixed solution G;

[0066] Step 2.2. Immerse the nano-porous structure Ni-MOF@nickel foam precursor D in the mixed solution G, transfer it to a high-pressure reaction kettle, carry out a hydrothermal reaction at 200 °C for 1 h, cool to room temperature, wash it 3 times with absolute ethanol and ultrapure water respectively, and carry out vacuum drying at 50 °C for 10 h to obtain the gradient nano-porous structure NiSe cathode material grown in-situ on the surface of the nickel foam, denoted as NiSe@Ni.

[0067] Example 5

[0068] Step 1. Prepare the nano-porous structure Ni-MOF@nickel foam precursor

[0069] Step 1.1. Weigh 0.25 mmol of NiCl2·5H2O and 0.25 mmol of 4,4'-biphenyldicarboxylic acid, add them to 20 mL of DMF to obtain solution A, then add 1.5 mL of absolute ethanol and 15 mL of ultrapure water to solution A, and stir magnetically to obtain green solution B;

[0070] Step 1.2: Immerse a 1 cm × 3 cm nickel foam in Solution B, then transfer the solution B with the immersed nickel foam into a high-pressure reactor. Next, place the high-pressure reactor in an oven and carry out a hydrothermal reaction at 100 °C for 9 h. Cool to room temperature, take out the nickel foam, wash it 3 times with absolute ethanol and ultrapure water respectively, and vacuum dry it at 50 °C for 10 h to obtain the Ni-MOF@nickel foam precursor C;

[0071] Step 1.3: Place the Ni-MOF@nickel foam precursor C in a tubular furnace and calcine it at 400 °C for 2 h to obtain the nano-porous structure Ni-MOF@nickel foam precursor D;

[0072] Step 2: Prepare the gradient nano-porous structure NiSe cathode material

[0073] Step 2.1: Take 50 mg of Se powder and add it to 10 mL of ultrapure water, stir well to obtain Solution E. At the same time, take 70 mg of NaBH4 and add it to 5 mL of absolute ethanol, dissolve it completely to obtain Solution F. Then add Solution E to Solution F and mix evenly to obtain the mixed solution G;

[0074] Step 2.2: Immerse the nano-porous structure Ni-MOF@nickel foam precursor D in the mixed solution G, and transfer it to a high-pressure reactor. Carry out a hydrothermal reaction at 160 °C for 2 h, cool to room temperature, wash it 3 times with absolute ethanol and ultrapure water respectively, and vacuum dry it at 60 °C for 11 h to obtain the gradient nano-porous structure NiSe cathode material grown in-situ on the surface of the nickel foam, denoted as NiSe@Ni.

[0075] Comparative Example 1

[0076] Step 1: Prepare the nano-porous structure Ni-MOF@nickel foam precursor

[0077] Step 1.1: Weigh 0.24 mmol of NiCl2·5H2O and 0.24 mmol of 4,4'-biphenyldicarboxylic acid, add them to 15 mL of DMF to obtain Solution A. Then add 1.5 mL of absolute ethanol and 15 mL of ultrapure water to Solution A and stir magnetically to obtain a green Solution B;

[0078] Step 1.2: Immerse a 1 cm × 3 cm nickel foam in Solution B, then transfer the solution B with the immersed nickel foam into a high-pressure reactor. Next, place the high-pressure reactor in an oven and carry out a hydrothermal reaction at 100 °C for 7 h. Cool to room temperature, take out the nickel foam, wash it 3 times with absolute ethanol and ultrapure water respectively, and vacuum dry it at 50 °C for 10 h to obtain the Ni-MOF@nickel foam precursor C;

[0079] Step 1.3: Place the Ni-MOF@nickel foam precursor C in a tube furnace and calcine it at 300 °C for 2 h to obtain the nano-porous structured Ni-MOF@nickel foam precursor D;

[0080] Step 2: Prepare the nano-porous structured NiSe cathode material

[0081] Step 2.1: Take 47.4 mg of Se powder and add it to 9 mL of ultrapure water, stir well to obtain solution E;

[0082] Step 2.2: Immerse the nano-porous structured Ni-MOF@nickel foam precursor D in the mixed solution E, transfer it to a high-pressure reaction kettle, carry out a hydrothermal reaction at 160 °C for 1 h, cool it to room temperature, wash it 3 times with anhydrous ethanol and ultrapure water respectively, and vacuum dry it at 50 °C for 10 h to obtain the nano-porous structured NiSe cathode material grown in-situ on the surface of the nickel foam.

[0083] Assemble nickel-zinc batteries with the nano-porous structured NiSe cathode material grown in-situ on the surface of the nickel foam prepared in Example 1 and the nano-porous structured NiSe cathode material grown in-situ on the surface of the nickel foam prepared in Comparative Example 1 respectively, and test their constant current charge and discharge capacities. The results are as follows: Figures 4 to 5 shown:

[0084] From Figure 4 it can be seen that at current densities of 0.5 A·g -1 、1 A·g -1 、2 A·g -1 、3 A·g -1 、4 A·g -1 and 5 A·g -1 conditions, the capacities of the nickel-zinc batteries assembled with the nano-porous structured NiSe cathode material grown in-situ on the surface of the nickel foam prepared in Example 1 are 185 mAh·g -1 、171.5 mAh·g -1 、152.7 mAh·g -1 、136.5 mAh·g -1 、121.7 mAh·g -1 and 109.7 mAh·g -1 ;

[0085] From Figure 5 it can be seen that at current densities of 0.5 A·g -1 、1 A·g -1 、2 A·g -1 、3 A·g -1 、4 A·g -1 and 5 A·g -1Under the conditions, the capacities of the nickel-zinc batteries assembled with the NiSe cathode materials with in-situ grown nanoporous structures on the surface of nickel foam prepared in Comparative Example 1 are 146.5 mAh·g -1 , 142.7 mAh·g -1 , 133.7 mAh·g -1 , 123.8 mAh·g -1 , 115.6 mAh·g -1 and 109.4 mAh·g -1 ;

[0086] Comparison Figure 4 and Figure 5 It can be found that the nickel-zinc battery assembled with the NiSe cathode material with a gradient nanoporous structure in-situ grown on the surface of nickel foam prepared in Example 1 has a higher specific capacity and power density compared to the nickel-zinc battery assembled with the NiSe cathode material with a nanoporous structure in-situ grown on the surface of nickel foam prepared in Comparative Example 1. This shows that when the NiSe cathode material with a gradient nanoporous structure in-situ grown on the surface of nickel foam prepared in Example 1 is used as the cathode material of the aqueous nickel-zinc battery, it can accelerate the charge and discharge process of the aqueous nickel-zinc battery system.

Claims

1. A preparation method of a gradient nanoporous structure NiSe cathode material in-situ grown on the surface of nickel foam, characterized in that, It includes the following steps: Step 1. Prepare a nano-porous structure Ni-MOF@nickel foam precursor Step 1.

1. According to the ratio of NiCl2·5H2O, 4,4'-biphenyldicarboxylic acid, DMF, absolute ethanol and ultrapure water of (0.2 - 0.3 mmol):(0.2 - 0.3 mmol):(10 - 20 mL):(1 - 2 mL):(10 - 20 mL), take NiCl2·5H2O and 4,4'-biphenyldicarboxylic acid and add them into DMF to obtain solution A. Add absolute ethanol and ultrapure water to solution A, and stir magnetically until evenly mixed to obtain a green solution B; Step 1.

2. Immerse the nickel foam in solution B, then transfer the solution B with the immersed nickel foam into a high-pressure reaction kettle. Then place the high-pressure reaction kettle in an oven and carry out a hydrothermal reaction at 100 - 150 °C for 7 - 9 h. Cool to room temperature, take out the nickel foam, wash it successively and dry it under vacuum to obtain the Ni-MOF@nickel foam precursor C; Step 1.

3. Place the Ni-MOF@nickel foam precursor C in a tubular furnace and calcine it at 300 - 400 °C for 2 - 3 h to obtain a nano-porous structure Ni-MOF@nickel foam precursor D; Step 2. Prepare a gradient nano-porous structure NiSe cathode material Step 2.

1. According to the ratio of Se powder, ultrapure water, NaBH4 and absolute ethanol of (40 - 50 mg):(6 - 10 mL):(60 - 70 mg):(5 - 8 mL), take Se powder and add it into ultrapure water, stir well to obtain solution E. At the same time, take NaBH4 and add it into absolute ethanol, dissolve it fully to obtain solution F. Then add solution E into solution F and mix evenly to obtain a mixed solution G; Step 2.

2. Immerse the nano-porous structure Ni-MOF@nickel foam precursor D in the mixed solution G and transfer it to a high-pressure reaction kettle. Carry out a hydrothermal reaction at 160 - 200 °C for 1 - 2 h. Cool to room temperature, wash it successively and dry it under vacuum to obtain a gradient nano-porous structure NiSe cathode material grown in-situ on the surface of the nickel foam.

2. The preparation method of the NiSe cathode material with a gradient nanoporous structure in-situ grown on the surface of nickel foam according to claim 1, characterized in that, In the said Step 1.1, the ratio of NiCl2·5H2O, 4,4'-biphenyldicarboxylic acid, DMF, absolute ethanol and ultrapure water is 0.24 mmol:0.24 mmol:15 mL:1.5 mL:15 mL.

3. The preparation method of the gradient nanoporous structure NiSe cathode material grown in-situ on the surface of nickel foam according to claim 1, characterized in that, In the said Step 1.2, the area of the nickel foam is 1 cm × 3 cm.

4. The preparation method of the gradient nanoporous structure NiSe cathode material in-situ grown on the surface of nickel foam according to claim 1, characterized in that, The washing in the said Step 1.2 and Step 2.2 is to wash 3 times successively with absolute ethanol and ultrapure water respectively.

5. The preparation method of the gradient nanoporous structure NiSe cathode material in-situ grown on the surface of nickel foam according to claim 1, characterized in that, The vacuum drying in the said Step 1.2 and Step 2.2 is carried out at 50 - 70 °C for 10 - 12 h under vacuum.

6. The preparation method of the gradient nanoporous structure NiSe cathode material in-situ grown on the surface of nickel foam according to claim 1, characterized in that, In the said Step 2.1, the ratio of Se powder, ultrapure water, NaBH4 and absolute ethanol is 47.4 mg:9 mL:68.4 mg:6 mL.

7. A gradient nano-porous structure NiSe cathode material grown in-situ on the surface of nickel foam prepared by the method according to any one of claims 1 - 6.

8. Application of the gradient nano-porous structure NiSe cathode material grown in-situ on the surface of nickel foam according to claim 7 as a cathode material for an aqueous nickel-zinc battery.

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