Metal powder negative electrode for water-based metal-air battery, water-based metal-air battery and preparation method of water-based metal-air battery

Abstract

The invention discloses a metal powder negative electrode for a water-based metal-air battery, the water-based metal-air battery and a preparation method of the water-based metal-air battery, and the metal powder negative electrode comprises a foamed nickel substrate with a porous structure inside; the porous structure is filled with the metal powder; the leakage-proof layer is arranged on the foamed nickel substrate and is used for preventing the metal powder from leaking out; the PPI of the foamed nickel matrix is 10 to 110; the diameter of the metal powder ranges from 0.018 mm to 0.18 mm. The metal powder negative electrode is good in corrosion resistance, adjustability and machinability and low in cost, the contact between the metal powder and the current collector is stable, and the phenomena of corrosion, passivation and the like of the metal powder negative electrode are greatly relieved, so that the utilization rate of the metal powder and the discharge performance of the metal-air battery are improved. The metal-air battery has excellent discharge capacity and discharge time under high current density.

Description

Technical Field

[0001] The present invention relates to the technical field of aqueous air batteries, and in particular to a metal powder negative electrode for an aqueous metal-air battery, an aqueous metal-air battery and a preparation method thereof. Background Art

[0002] Zinc-air battery has high theoretical energy density (1086Wh kg -1 ), low cost, safe and environmentally friendly. The negative electrode material is zinc metal, which is abundant in the earth's crust. The positive electrode active material is oxygen, which can be obtained directly from the air. There are many types of zinc-air batteries, including aqueous batteries, solid-state batteries, flexible batteries, and button batteries. Among them, aqueous zinc-air batteries are most suitable for large-scale energy storage. The energy density of aluminum-air batteries is 8100Wh kg -1 , the energy density is higher than that of zinc-air batteries, and the negative electrode material is aluminum metal, but the corrosion of aluminum negative electrode is more serious than that of zinc. The main configurations of aluminum-air batteries are aqueous batteries and solid-state batteries. Like zinc-air batteries, aqueous aluminum-air batteries have broader application prospects.

[0003] At present, the preparation method of the negative electrode of the metal powder-based metal-air battery is to mix the metal powder, binder, conductive agent and corrosion inhibitor to form a metal paste, apply it to the surface of the negative electrode current collector after stirring evenly, place it at a certain temperature to dry and form, and use it after cooling. This method is cumbersome to operate, and the added binder is unstable in the strong alkaline electrolyte. Under long-term discharge conditions, the metal powder will inevitably fall off the current collector. In addition, the binder is not conductive, and the added corrosion inhibitor forms an anti-corrosion film on the surface of the metal powder, which will hinder the contact between the metal powder particles, resulting in unstable discharge at high current density. Some binders and corrosion inhibitors are costly and are not suitable for large-scale commercial applications. Therefore, the existing technology has defects and needs to be improved and developed. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a metal powder negative electrode for an aqueous metal-air battery, an aqueous metal-air battery and a preparation method thereof in view of the above-mentioned defects of the prior art, aiming to solve the problems of cumbersome operation, poor stability and high cost of the metal powder negative electrode of the metal-air battery in the prior art.

[0005] The technical solution adopted by the present invention to solve the technical problem is as follows:

[0006] A metal powder negative electrode for an aqueous metal-air battery, comprising:

[0007] A nickel foam substrate with a porous structure formed inside;

[0008] Metal powder, filled in the porous structure; the metal powder is selected from at least one of zinc powder, aluminum powder, magnesium powder and iron powder;

[0009] A leak-proof layer, disposed on the nickel foam substrate, and used to prevent the metal powder from leaking out;

[0010] Wherein, the PPI of the foamed nickel matrix is ​​10-110; and the diameter of the metal powder is 0.018 mm-0.18 mm.

[0011] Nickel foam is a material with a porous structure, which is composed of many small holes with regular geometric shapes and connecting channels, showing a very large specific surface area and porosity. Therefore, nickel foam has the characteristics of high conductivity, light weight, uniform structure, good corrosion resistance, high porosity, etc. At present, the method of the prior art uses a binder to connect metal powders together to form a metal paste. The binder, such as polytetrafluoroethylene, polyvinylidene fluoride, carboxymethyl cellulose, etc., is not conductive and will reduce the reactivity of the metal powder. Conductive agents such as carbon black, carbon nanotubes, graphene, polyaniline and other materials need to be added. The binder is unstable during long-term discharge, and the metal paste will fall off the surface of the current collector. The present application disperses the metal powder in the pores of the nickel foam matrix to increase the contact area between the metal powder and the nickel foam matrix. The three-dimensional pore structure of the nickel foam can stabilize the metal powder, and no additional binder and conductive agent are required, which effectively prevents the metal powder from falling off.

[0012] The PPI of nickel foam matrix is ​​10-110. The PPI of nickel foam refers to the number of pores per inch. The higher the PPI value, the smaller the pore size of the nickel foam matrix and the more pores there are; the lower the PPI value, the larger the pore size of the nickel foam matrix and the fewer pores there are. The pore size of the nickel foam matrix is ​​0.42mm-3.57mm, and the pore size of the nickel foam matrix is ​​larger than the diameter of the metal powder. Therefore, nickel foam matrices with different pore sizes and metal powders with different diameters are crucial to the dispersion state and reaction activity of the metal powder.

[0013] When nickel foam matrices with different pore sizes are loaded with metal powders of the same diameter, from the perspective of negative electrode reaction, firstly, the small-pore nickel foam matrix means that a single pore unit of the nickel foam matrix can accommodate less metal powder, and the contact area between metal powders is smaller. On the contrary, the contact area between metal powders and electrolyte is larger, that is, the metal powders are in more complete contact with the electrolyte, resulting in a faster reaction rate of the metal powders. Secondly, compared with the large-pore nickel foam matrix, the local OH in the small-pore nickel foam matrix is - The higher the concentration, the faster the reaction rate of the metal powder.

[0014] From the perspective of passivation, the smaller pore size of the nickel foam matrix will increase the transmission resistance of reaction products such as ZnO and electrolyte. This makes it difficult for ZnO to fall off the surface of the metal powder, reducing the conductivity of the negative electrode, resulting in uneven stripping of the metal powder, and reducing the discharge voltage and discharge time. However, when the pore size of the nickel foam matrix increases to a certain extent, the metal powder will fall off from the pore size of the nickel foam matrix, reducing the utilization rate of the metal powder.

[0015] When the nickel foam matrix with the same pore size is loaded with metal powders of different diameters, if the particle size of the metal powder is too small, the specific surface area of ​​the metal powder will increase, and the corrosion rate of the metal powder will increase; if the particle size of the metal powder is too large, it will be difficult for the metal powder to enter the voids of the nickel foam matrix, resulting in uneven dispersion of the metal powder. The smaller the diameter of the metal powder, the more metal powder can be accommodated in a single pore unit of the nickel foam matrix, and the larger the contact area between the metal powders. On the contrary, the contact area between the metal powders and the electrolyte is smaller, that is, the metal powders are less in contact with the electrolyte, resulting in a decrease in the reaction rate of the metal powders.

[0016] Therefore, when the pore size of the nickel foam matrix is ​​within a suitable range and the diameter of the metal powder is within a suitable range, that is, the PPI of the nickel foam matrix is ​​10-110, and the diameter of the metal powder is 0.018mm-0.18mm, the comprehensive performance of the metal powder negative electrode is better, for example, the utilization rate of the metal powder is higher, the load reliability of the metal powder is higher, the discharge voltage is higher, the discharge time is longer, and the capacity is larger.

[0017] The mass ratio of the nickel foam matrix to the metal powder is 1:0.65-1.5. If the mass of the metal powder is too small, the discharge time of the battery will be reduced; if the mass of the metal powder is too small, the metal powder will more easily overflow from the pores of the nickel foam.

[0018] The metal powder negative electrode for an aqueous metal-air battery, wherein when the metal powder is zinc powder, the PPI of the foamed nickel matrix is ​​10-30; when the metal powder is aluminum powder, the PPI of the foamed nickel is 20-75; and the leak-proof layer is a waterproof and breathable membrane.

[0019] Preferably, when the metal powder is zinc powder, the PPI of the nickel foam matrix is ​​10-30, the pore size of the nickel foam matrix is ​​1.72-3.57 mm, and the aqueous zinc-air battery has a good discharge effect. When the metal powder is aluminum powder, the PPI of the nickel foam matrix is ​​20-75, the pore size of the nickel foam matrix is ​​0.6-2.49 mm, and the aqueous aluminum-air battery has a good discharge effect. The leak-proof layer can be a waterproof breathable film, and the leak-proof layer can also be a mesh layer.

[0020] An aqueous metal-air battery, comprising:

[0021] a housing having a window;

[0022] A positive electrode, disposed at the position of the window in the housing;

[0023] A negative electrode, which is a metal powder negative electrode for an aqueous metal-air battery as described in any one of the above, and is located in the housing at a position away from the window;

[0024] an alkaline electrolyte, located in the housing;

[0025] Wherein, the positive electrode and the negative electrode are both located below the liquid surface of the alkaline electrolyte.

[0026] Specifically, the positive electrode is an air positive electrode, which reacts with oxygen in the air, and air enters the positive electrode through the window. The negative electrode is a metal powder negative electrode, and the electrolyte is an alkaline electrolyte. The metal powder reacts with the hydroxide in the alkaline electrolyte.

[0027] The aqueous metal-air battery, wherein the alkaline electrolyte comprises: soluble acetate, strong alkali and water; wherein the concentration of the soluble acetate is 0.04 mol L -1 ~0.3mol L -1 ; The concentration of strong base is 1 mol L -1 ~6mol L -1 .

[0028] Specifically, the alkaline electrolyte includes: soluble acetate, strong base and water, and the concentration of soluble acetate is 0.04 molL -1 ~0.3mol L -1 ; The concentration of strong base is 1 mol L -1 ~6mol L -1 The soluble acetate may be zinc acetate Zn(AC)2, sodium acetate, potassium acetate, ammonium acetate, aluminum acetate, etc. The strong base may be KOH or NaOH. Preferably, the concentration of the soluble acetate is 0.2 mol L -1 When the metal powder is zinc powder or iron powder, the concentration of the strong base is 6 mol L -1 For example, the concentration of KOH is 6 mol L -1 When the metal powder is aluminum powder or magnesium powder, the concentration of the strong base is 1 mol L -1 For example, the concentration of KOH is 1 mol L -1 When the metal powder is aluminum powder or magnesium powder, a corrosion inhibitor such as propylene glycol, ethylene glycol, methanol, dimethyl sulfoxide, cyclopentane, etc. may be added to the alkaline electrolyte.

[0029] In the aqueous metal-air battery, the positive electrode comprises: a current collector, a waterproof and breathable conductive membrane and a catalyst layer arranged in sequence; wherein the catalyst layer is made of a catalyst, a conductive carbon material and polytetrafluoroethylene.

[0030] Specifically, the current collector is used to connect the catalyst layer and the external circuit. The thickness of the waterproof breathable conductive film is 0.3 to 1 mm. The waterproof breathable conductive film is used to construct a three-phase interface to prevent the electrolyte from completely permeating the catalyst in the catalyst layer and reducing its catalytic activity, while not hindering the entry of air.

[0031] In the aqueous metal-air battery, the current collector extends out of the liquid surface to form a positive electrode connection portion; and the nickel foam matrix in the negative electrode extends out of the liquid surface to form a negative electrode connection portion.

[0032] Specifically, in order to facilitate the connection to the external circuit, a positive electrode connection portion is extended on the current collector, and a negative electrode connection portion is extended on the negative electrode, and the positive electrode connection portion and the negative electrode connection portion are used to connect to the external circuit. The waterproof and breathable conductive film and the catalyst layer in the positive electrode are both located below the liquid surface of the alkaline electrolyte, while the positive electrode connection portion is located above the liquid surface of the alkaline electrolyte. The negative electrode connection portion does not carry metal powder.

[0033] In the aqueous metal-air battery, the current collector is made of foamed nickel.

[0034] Specifically, the current collector may be made of nickel foam.

[0035] A method for preparing an aqueous metal-air battery as described in any one of the above, comprising the steps of:

[0036] Prepare a positive electrode, and assemble the positive electrode into a shell;

[0037] preparing a negative electrode, and assembling the negative electrode in a casing;

[0038] Alkaline electrolyte is injected into the housing.

[0039] Specifically, the positive electrode, the negative electrode and the alkaline electrolyte can be prepared separately, and then the positive electrode is assembled in the shell, the negative electrode is assembled in the shell, and the alkaline electrolyte is injected into the shell to form an aqueous metal-air battery.

[0040] The method for preparing the aqueous metal-air battery, wherein the step of preparing the negative electrode and assembling the negative electrode in a housing comprises:

[0041] cutting and bending the nickel foam to obtain a nickel foam matrix;

[0042] The anti-leakage layer is connected to the nickel foam substrate, and metal powder is poured into it to obtain a negative electrode;

[0043] The negative electrode is assembled into a casing.

[0044] Specifically, the nickel foam substrate is obtained by cutting and bending the nickel foam. After bending, a part of the nickel foam substrate is used as a load portion to load metal powder, and the other part is used as a negative electrode connection portion to connect an external circuit. The metal powder is poured into the load portion of the nickel foam substrate and slightly shaken to allow the metal powder to fully enter the load portion of the nickel foam substrate. The nickel foam substrate is L-shaped. In order to make the height of the load portion in the negative electrode roughly the same as the height of the catalyst in the positive electrode, a padding layer can be used to raise the nickel foam substrate. The padding layer can be made of polyethylene sponge.

[0045] The method for preparing the aqueous metal-air battery, wherein the preparation of the positive electrode and the assembly of the positive electrode in the housing include:

[0046] The catalyst, the conductive carbon material, the polytetrafluoroethylene and the volatile solvent are mixed and rolled into a catalyst layer;

[0047] The waterproof and breathable conductive film and the catalyst layer are sequentially stacked on the current collector to obtain a positive electrode;

[0048] The positive electrode is assembled in a casing.

[0049] Specifically, the preparation method of the catalytic layer is as follows: provide a catalyst, a conductive carbon material, a slurry of polytetrafluoroethylene and anhydrous ethanol; place the oxygen catalyst and the conductive carbon material in a mortar, drop anhydrous ethanol and the slurry of polytetrafluoroethylene, grind to a sheet, roll into a thin layer, dry and cut to obtain the catalytic layer. The conductive carbon material is used to enhance the conductivity of the catalyst, the anhydrous ethanol is used to make the catalyst and the conductive carbon material mix evenly, and the slurry of polytetrafluoroethylene is used to make the catalyst and the conductive carbon material form a film.

[0050] The nickel foam-loaded metal powder negative electrode obtained by the preparation method of the present invention has a simple preparation method, alleviates the problems of metal powder corrosion, passivation and poor contact between metal powder and current collector, and is suitable for large-scale practical applications. The metal-air battery has excellent discharge specific capacity and discharge time at high current density. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 1 is an optical photograph of nickel foams with different PPIs in the embodiments of the present invention.

[0052] Figure 2 1 is a scanning electron microscope photograph of nickel foams with different PPIs in the embodiments of the present invention.

[0053] Figure 3 It is a scanning electron microscope photograph of 100-250 mesh (0.058-0.15 mm) zinc powder loaded on nickel foam with different PPI in the embodiment of the present invention.

[0054] Figure 4These are optical photos of the preparation process of the 30PPI nickel foam loaded with 100-250 mesh (0.058-0.15mm) zinc powder negative electrode and the aqueous battery at different angles in the embodiment of the present invention.

[0055] Figure 5 Schematic diagram of a zinc-air battery in an embodiment of the present invention.

[0056] Figure 6 In the embodiment of the present invention, different PPI nickel foams are loaded with 100-250 mesh (0.058-0.15 mm) zinc powder and zinc flakes at 100 mA / cm 2 The discharge capacity at a current density of .

[0057] Figure 7 In the embodiment of the present invention, different PPI nickel foams are loaded with 100-250 mesh (0.058-0.15 mm) zinc powder at 100 mA / cm 2 Zinc powder utilization at current density of .

[0058] Figure 8 The results are shown in Table 1. The nickel foam with different PPI loaded with 800 mesh (about 0.018 mm) zinc powder and zinc flakes at 100 mA / cm 2 The discharge capacity at a current density of .

[0059] Fig. 9 The results are as follows: Different PPI nickel foams loaded with 800 mesh (about 0.018 mm) zinc powder at 100 mA / cm 2 Zinc powder utilization at current density of .

[0060] Fig.10 is the concentration of hydroxide ions on the surface of the small hole simulated by finite element method in the embodiment of the present invention.

[0061] Fig.11 is the hydroxyl ion concentration on the macropore surface in the finite element simulation of the embodiment of the present invention.

[0062] Fig.12 The hydrogen evolution potential and current density of different PPI nickel foams and 100-250 mesh (0.058-0.15 mm) zinc powder in the embodiments of the present invention are shown.

[0063] Fig.13 Schematic diagram of the discharge principle of zinc powder loaded with nickel foam of different PPI in an embodiment of the present invention.

[0064] Fig.14 Schematic diagram of the effect of different PPI nickel foams and different mesh sizes of zinc powder on the reaction in the embodiment of the present invention.

[0065] Fig.15It is the discharge capacity of 30PPI nickel foam and 100-250 mesh (0.058-0.15mm) zinc powder in electrolytes of different concentrations in the embodiment of the present invention.

[0066] Fig.16 It is the discharge time of the zinc sheet and 30PPI nickel foam loaded with 1g of 100-250 mesh (0.058-0.15mm) zinc powder in the embodiment of the present invention.

[0067] Fig.17 The results of the experiment are as follows: different PPI nickel foams loaded with 80 mesh (about 0.18 mm) aluminum powder at 5 mA / cm 2 The discharge capacity at a current density of .

[0068] Fig.18 The results of the experiments of the present invention are as follows: different PPI nickel foams loaded with 400 mesh (about 0.036 mm) aluminum powder at 5 mA / cm 2 The discharge capacity at a current density of .

[0069] Fig.19 Schematic diagram of the effect of different PPI nickel foams and different mesh sizes of aluminum powder on the reaction in the embodiment of the present invention. DETAILED DESCRIPTION

[0070] In order to make the purpose, technical solution and advantages of the present invention clearer and more specific, the present invention is further described in detail below with reference to the accompanying drawings and examples. 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.

[0071] Since the reduction potential of zinc and aluminum is more negative than that of hydrogen, metallic zinc or metallic aluminum is thermodynamically unstable in alkaline solution, resulting in hydrogen evolution corrosion reaction on the surface of zinc negative electrode or aluminum negative electrode. Hydrogen evolution corrosion consumes electrons in the battery and reduces the energy conversion efficiency of the battery. In addition, hydrogen evolution corrosion reaction may also be conducive to the passivation of the surface of zinc negative electrode or aluminum negative electrode, further affecting the charge and discharge performance of the battery. The large specific surface area of ​​metal powder exacerbates the corrosion phenomenon.

[0072] In the field of metal powder-based metal air batteries, metal powder is mostly mixed with a binder and a conductive agent, stirred to form a metal paste, and then applied to the surface of the current collector. The optimal ratio between metal powder, binder, and conductive agent requires a lot of research to determine, which is rather cumbersome. In a strong alkaline solution, the binder has poor stability, resulting in a loose contact between the metal paste and the current collector. Binders and conductive agents increase costs and are not suitable for large-scale use.

[0073] The present application adopts a foamed nickel matrix to load metal powder. The foamed nickel matrix limits and fixes the metal powder. The metal powder is not mixed with a binder and a conductive agent. The utilization rate of the metal powder is high and it is suitable for large-scale use.

[0074] Example 1. (1) Cut the polyethylene sponge into 30mm (length) * 20mm (width) * 40mm (thickness) and place it in a battery mold (the battery mold serves as the battery shell), keeping the upper surface of the polyethylene sponge and the center of the catalyst layer of the positive electrode (or the center of the window) at the same horizontal line. Cut the waterproof breathable membrane (the waterproof breathable membrane serves as a leakproof layer) into 30mm (length) * 20mm (width) and place it on the upper surface of the polyethylene sponge. The function of the waterproof breathable membrane is to prevent zinc powder from falling downward. Bend a 30PPI nickel foam substrate of 60mm (length) * 30mm (width) * 3mm (thickness) so that the area of ​​the nickel foam substrate loaded with zinc powder (i.e., the load part) is 30mm (length) * 20mm (width), and place it on the waterproof breathable membrane. The nickel foam substrate that does not load zinc powder (i.e., the negative electrode connecting part) is used to connect external wires. 1 g of 100-250 mesh (0.058-0.15 mm) zinc powder was poured into the loading part of a 30 PPI nickel foam substrate of 30 mm (length)*20 mm (width)*3 mm (thickness).

[0075] (2) Provide 60 mg of catalyst, 10 mg of conductive carbon material, 20 μL of polytetrafluoroethylene slurry and 30 mL of anhydrous ethanol; place the oxygen catalyst and the conductive carbon material in a mortar, add anhydrous ethanol and polytetrafluoroethylene slurry, grind for 30 minutes until it is in a sheet shape, roll it into a thin layer, dry it at 60°C, and cut it to obtain a catalytic layer.

[0076] Specifically, Figure 5 As shown, nickel foam is used as the current collector, the length and width of the current collector are 4cm*5cm, the length and width of the waterproof and breathable conductive film are 3.5cm*3.5cm, and the length and width of the catalyst layer are 1cm*1cm. The thickness of the current collector is 1mm. The current collector is used to connect the catalyst layer and the external circuit. The thickness of the waterproof and breathable conductive film is 0.7mm. After the positive and negative electrodes are prepared, pour 60mL of 6mol L -1 KOH and 0.2 mol L -1 The electrolyte of Zn(AC)2 forms an aqueous zinc-air battery (recorded as 30 / 100-250, where 30 represents the PPI of the foamed nickel matrix and 100-250 is the mesh size of the zinc powder), and discharge begins. The preparation method of the catalyst is:

[0077] Dissolve 113mg Fe(NO3)3·9H2O and 1.09g Zn(NO3)2·6H2O in 30mL methanol solution, and dissolve 1.314g dimethylimidazole in 15mL methanol solution. Mix the above solutions, stir at room temperature for 24h, rinse with methanol and N,N-dimethylformamide three times in sequence, and dry the obtained powder at 70℃ overnight. Then place the sample in a tube furnace, keep it at 900℃ for 3h under nitrogen atmosphere, and cool it to room temperature to obtain black powder. Dissolve 50mg black powder and 0.705g ZnCl2 in 20mL deionized water, stir for 1h, then place the solution in a 50mL hydrothermal autoclave, keep it at 160℃ for 24h, rinse it with deionized water and anhydrous ethanol three times in sequence, and dry the obtained powder at 70℃ overnight. Then place the sample in a tube furnace, keep it at 900℃ for 1h under nitrogen atmosphere, and cool it to room temperature to obtain the catalyst.

[0078] Example 2. Different from Example 1, the zinc powder is loaded on a 75 PPI nickel foam substrate, assembled into an aqueous zinc-air battery (represented as 75 / 100-250, where 75 represents the PPI of the nickel foam substrate and 100-250 is the mesh size of the zinc powder), and discharge is started.

[0079] Example 3. Different from Example 1, the zinc powder is loaded on a 110 PPI nickel foam substrate, assembled into an aqueous zinc-air battery (recorded as 110 / 100-250, where 110 represents the PPI of the nickel foam substrate and 100-250 is the mesh size of the zinc powder), and discharge is started.

[0080] Example 4. Different from Example 1, the zinc powder is loaded on a 20 PPI nickel foam substrate, assembled into an aqueous zinc-air battery (represented as 20 / 100-250, where 20 represents the PPI of the nickel foam substrate and 100-250 is the mesh size of the zinc powder), and discharge is started.

[0081] Example 5. Different from Example 1, the zinc powder is loaded on a 10 PPI nickel foam substrate, assembled into an aqueous zinc-air battery (represented as 10 / 100-250, where 10 represents the PPI of the nickel foam substrate and 100-250 is the mesh size of the zinc powder), and discharge is started.

[0082] Example 6. (1) Cut the polyethylene sponge into 30mm (length) * 20mm (width) * 40mm (thickness) and place it in a battery mold, keeping the upper surface of the polyethylene sponge and the center of the catalyst layer of the positive electrode at the same horizontal line. Cut the waterproof breathable membrane into 30mm (length) * 20mm (width) and place it on the upper surface of the polyethylene sponge. The function of the waterproof breathable membrane is to prevent the zinc powder from falling downward. Bend the 60mm (length) * 30mm (width) * 3mm (thickness) 30PPI nickel foam matrix so that the area of ​​the nickel foam matrix loaded with zinc powder is 30mm (length) * 20mm (width), and place it on the waterproof breathable membrane. The nickel foam matrix that does not load zinc powder is used to connect external wires. Pour 1g of 800 mesh (about 0.018mm) zinc powder into the load portion of the 30PPI nickel foam matrix of 30mm (length) * 20mm (width) * 3mm (thickness).

[0083] (2) Provide 60 mg of catalyst, 10 mg of conductive carbon material, 20 μL of polytetrafluoroethylene slurry and 30 mL of anhydrous ethanol; place the oxygen catalyst and the conductive carbon material in a mortar, add anhydrous ethanol and polytetrafluoroethylene slurry, grind for 30 minutes until it is in a sheet shape, roll it into a thin layer, dry it at 60°C, and cut it to obtain a catalytic layer.

[0084] Specifically, nickel foam is used as the current collector, the length and width of the current collector are 4cm*5cm, the length and width of the waterproof and breathable conductive film are 3.5cm*3.5cm, and the length and width of the catalyst layer are 1cm*1cm. The thickness of the current collector is 1mm. The current collector is used to connect the catalyst layer and the external circuit. The thickness of the waterproof and breathable membrane is 0.7mm. After the positive and negative electrodes are prepared respectively, 60mL of 6MKOH and 0.2M Zn(AC)2 electrolyte are poured into the aqueous zinc-air battery (recorded as 30 / 800, where 30 represents the PPI of the nickel foam matrix and 800 is the mesh size of the zinc powder), and discharge begins.

[0085] Example 7. Different from Example 6, the zinc powder is loaded on a 75 PPI nickel foam substrate, assembled into an aqueous zinc-air battery (represented as 75 / 800, where 75 represents the PPI of the nickel foam substrate and 800 is the mesh size of the zinc powder), and discharge is started.

[0086] Example 8. Different from Example 6, the zinc powder is loaded on a 110 PPI nickel foam substrate, assembled into an aqueous zinc-air battery (represented as 110 / 800, where 110 represents the PPI of the nickel foam substrate and 800 is the mesh size of the zinc powder), and discharge is started.

[0087] Example 9. Different from Example 6, the zinc powder is loaded on a 20 PPI nickel foam substrate, assembled into an aqueous zinc-air battery (represented as 20 / 800, where 20 represents the PPI of the nickel foam substrate and 800 is the mesh size of the zinc powder), and discharge is started.

[0088] Example 10. Different from Example 6, the zinc powder is loaded on a 10 PPI nickel foam substrate, assembled into an aqueous zinc-air battery (denoted as 10 / 800, where 10 represents the PPI of the nickel foam substrate and 800 is the mesh size of the zinc powder), and discharge is started.

[0089] Example 11. The difference from Example 1 is that the electrolyte is 60 mL 4 mol L -1 KOH and 0.2 mol L -1 The electrolyte of Zn(AC)2 is assembled into a battery and begins to discharge.

[0090] Example 12. The difference from Example 1 is that the electrolyte is 60 mL 6 mol L -1 KOH and 0.1 mol L -1 The electrolyte of Zn(AC)2 is assembled into a battery and begins to discharge.

[0091] Example 13. The difference from Example 1 is that the electrolyte is 60 mL 6 mol L -1 KOH and 0.3 mol L -1 The electrolyte of Zn(AC)2 is assembled into a battery and begins to discharge.

[0092] Comparative Example: Different from Example 1, 1 g of high-purity zinc sheet (purity 99.999%, thickness 0.3 mm) was placed in a battery mold, assembled into a battery (referred to as zinc sheet), and discharge was started.

[0093] like Figure 1 As shown in Figure 3, as the PPI of nickel foam decreases, the pore size of the nickel foam matrix increases.

[0094] like Figure 2 As shown, the nickel foam matrix is ​​a three-dimensional network structure. As the PPI of nickel foam decreases, the pore size of the nickel foam matrix increases and the number of skeletons of the nickel foam matrix decreases. The large pore size of the nickel foam matrix helps to increase the transmission and mass transfer efficiency of ions in the pore size. The pore size of the nickel foam matrix with 110PPI is 0.4 to 0.5mm, the pore size of the nickel foam matrix with 75PPI is about 0.6mm, the pore size of the nickel foam matrix with 30PPI is about 1.72mm, the pore size of the nickel foam matrix with 20PPI is about 2.49mm, and the pore size of the nickel foam matrix with 10PPI is about 3.57mm.

[0095] like Figure 3 As shown, 100-250 mesh (0.058-0.15 mm) zinc powder is filled in the gaps of the foam nickel matrix skeletons with different PPIs, and a small amount of zinc powder is on the skeleton of the foam nickel matrix.

[0096] like Figure 4As shown in Figure (a), the polyethylene sponge is cut into 30mm (length) * 20mm (width) * 40mm (thickness) and placed in the battery mold, keeping the upper surface of the polyethylene sponge and the center of the positive electrode catalyst layer on the same horizontal line. Figure 4 As shown in Figure (b), the waterproof breathable membrane is cut into 30mm (length) * 20mm (width) and placed on the upper surface of the polyethylene sponge. The function of the waterproof breathable membrane is to prevent the zinc powder from falling downwards. Figure 4 As shown in Figure (c), the 30PPI nickel foam substrate of 60mm (length) * 30mm (width) * 3mm (thickness) is bent so that the area of ​​the nickel foam substrate loaded with zinc powder is 30mm (length) * 20mm (width), and is placed on the waterproof breathable membrane. The nickel foam substrate without zinc powder is used to connect external wires. Figure 4 As shown in the middle figure (d), 1 g of 100-250 mesh (0.058-0.15 mm) zinc powder is poured into a 30 PPI nickel foam matrix of 30 mm (length) * 20 mm (width) * 3 mm (thickness). Figure 4 Figure (e) and Figure 4 The middle picture (f) shows real photos of aqueous zinc-air batteries from different angles.

[0097] like Figure 6 As shown, the theoretical battery capacity of 1g zinc is 820mAh. However, due to the corrosion and passivation side reactions of zinc flakes or zinc powder, the actual battery capacity of zinc flakes or zinc powder is lower than the theoretical battery capacity. The actual battery capacity is used for explanation below. The battery capacity of 1g zinc flake in the comparative example is 761mAh; the battery capacity of 1g zinc powder in Example 1 is 611mAh, reaching 80.3% of the battery capacity of zinc flake; the battery capacity of zinc powder in Example 2 is 343.7mAh, reaching 45.2% of the battery capacity of zinc flake; the battery capacity of zinc powder in Example 3 is 241mAh, reaching 31.7% of the battery capacity of zinc flake. The battery capacity of zinc powder in Example 4 is 520.7mAh, reaching 68.4% of the battery capacity of zinc flake; the battery capacity of zinc powder in Example 5 is 494mAh, reaching 65% of the battery capacity of zinc flake. It can be observed that as the PPI of nickel foam gradually decreases from 110 to 30, the pore size of the nickel foam matrix gradually increases, and the capacity of zinc powder gradually increases. As the PPI of nickel foam gradually decreases from 30 to 10, the pore size of the nickel foam matrix continues to increase and the capacity of the zinc powder gradually decreases. The discharge capacity of the batteries formed by the nickel foam matrix of 30PPI, 20PPI and 10PPI is generally greater than the discharge capacity of the batteries formed by the nickel foam matrix of 75PPI and 110PPI.

[0098] like Figure 7As shown, the zinc powder utilization rate of Example 1 is 75%; the zinc powder utilization rate of Example 2 is 42%; the zinc powder utilization rate of Example 3 is 29.4%; the zinc powder utilization rate of Example 4 is 63.5; and the zinc powder utilization rate of Example 5 is 60.2%. As the PPI of nickel foam gradually decreases from 110 to 30, the pore size of the nickel foam matrix gradually increases, and the utilization rate of zinc powder gradually increases. As the PPI of nickel foam gradually decreases from 30 to 10, the pore size of the nickel foam matrix continues to increase, and the utilization rate of zinc powder gradually decreases. The zinc powder utilization rate of batteries formed by nickel foam matrices of 30PPI, 20PPI and 10PPI is generally greater than the zinc powder utilization rate of batteries formed by nickel foam matrices of 75PPI and 110PPI.

[0099] like Figure 8 As shown, the capacity of 1g zinc sheet battery of the comparative example is 761mAh; the capacity of zinc powder battery of Example 6 is 505mAh, reaching 66.4% of the capacity of zinc sheet battery; the capacity of zinc powder battery of Example 7 is 445mAh, reaching 58.5% of the capacity of zinc sheet battery; the capacity of zinc powder battery of Example 8 is 357mAh / g, reaching 46.9% of the capacity of zinc sheet battery. The capacity of zinc powder battery of Example 9 is 556mAh, reaching 67.8% of the capacity of zinc sheet battery; the capacity of zinc powder battery of Example 9 is 556mAh, reaching 67.8% of the capacity of zinc sheet battery; the capacity of zinc powder battery of Example 10 is 516.6mAh, reaching 63% of the capacity of zinc sheet battery. It can be observed that as the PPI of nickel foam gradually decreases from 110 to 20, the pore size of the nickel foam matrix gradually increases, and the battery capacity of zinc powder gradually increases. As the PPI of nickel foam decreases from 20 to 10, the pore size of the nickel foam matrix continues to increase, the battery capacity of zinc powder decreases, and the discharge capacity of batteries formed by nickel foam matrices of 30PPI, 20PPI and 10PPI is generally greater than the discharge capacity of batteries formed by nickel foam matrices of 75PPI and 110PPI.

[0100] like Fig. 9 As shown, the zinc powder utilization rate of Example 6 is 61.6%; the zinc powder utilization rate of Example 7 is 54.3%; the zinc powder utilization rate of Example 8 is 43.5%; the zinc powder utilization rate of Example 9 is 67.9%; and the zinc powder utilization rate of Example 10 is 63%. As the PPI of nickel foam gradually decreases from 110 to 20, the pore size of the nickel foam matrix gradually increases, and the utilization rate of zinc powder gradually increases. As the PPI of nickel foam decreases from 20 to 10, the pore size of the nickel foam matrix continues to increase, and the utilization rate of zinc powder decreases. The utilization rates of zinc powder of the nickel foam matrix of 30PPI, 20PPI and 10PPI are generally greater than the utilization rates of zinc powder of the nickel foam matrix of 75PPI and 110PPI.

[0101] like Fig.10 and Fig.11As shown in the figure, the finite element simulation of the surface hydroxide ion concentration of small and large pores. The small pores of the same volume of nickel foam matrix correspond to more pores, and the large pores correspond to fewer pores. The finite element simulation only studies the effect of pore size on the hydroxide ion concentration in the pore diameter of the nickel foam matrix. For the convenience of modeling, the shapes of small and large pores are set to triangles and rectangles. Fig.10 A total of 14 small holes are displayed, of which four are on the upper and lower surfaces of the model, and six are in the middle. The hydroxide ion concentration on the surface of the sphere is 5×10 4 molcm -3 . Fig.11 A total of 9 large holes are shown, of which three holes are on the upper and lower surfaces of the sphere, and three holes are in the middle. The hydroxide ion concentration on the surface of the sphere is 4×10 4 molcm -3 As the PPI of nickel foam decreases, the pore size of the nickel foam matrix increases and the concentration of hydroxide ions on the pore surface gradually decreases.

[0102] The reaction formula of alkaline zinc-air battery is as follows: Under alkaline conditions, the zinc negative electrode reaction process:

[0103]

[0104] Under alkaline conditions, the formation reaction of the zinc negative electrode passivation layer is:

[0105]

[0106] (1) is the dissolution reaction of the zinc negative electrode under alkaline conditions, and (2) and (3) are the formation reactions of the passivation layer.

[0107] Under alkaline conditions, a conjugate corrosion reaction occurs on the zinc negative electrode:

[0108]

[0109] 2H2O+2e - →2OH - +H2↑(4).

[0110] Under alkaline conditions, the cathode reaction process:

[0111]

[0112] like Fig.13 As shown in the figure, during the discharge process of the zinc-air battery, as shown in reactions (1) to (3) at the negative electrode, the zinc negative electrode loses electrons and becomes Zn(OH)4 2- , Zn(OH)4 2-After reaching saturation in the electrolyte, it will decompose into ZnO. This is the dissolution and passivation process of zinc. This dissolution and passivation process is an important part of the normal operation of zinc-air batteries in an alkaline environment. The oxygen at the positive electrode obtains the electrons lost by zinc from the external circuit and is reduced to hydroxide ions. The dissolution and passivation behavior of the zinc negative electrode plays an important role in the performance of zinc-air batteries. The fast-dissolving zinc negative electrode can enable the battery to provide a large current. However, the high passivation rate of the zinc negative electrode also greatly shortens the battery life. While maintaining the activity of the zinc negative electrode, moderately inhibiting the passivation rate of the zinc negative electrode can improve the discharge performance of the battery. Therefore, it is necessary to promote reaction (1) and inhibit reaction (2) and reaction (3).

[0113] Reaction (4) is a hydrogen evolution corrosion reaction. Reaction (1), reaction (3) and reaction (4) form a conjugate corrosion reaction. The electrons formed on the zinc surface by reaction (1) and the active water molecules formed on the zinc surface by reaction (3) can react (4) and release hydrogen. Of course, isolated water molecules in the electrolyte can also react (4) on the zinc surface. Reaction (4) consumes the electrons obtained by reaction (1), reducing the energy conversion efficiency of the battery. Inhibiting reaction (4) can improve the discharge performance of the battery.

[0114] The factors affecting reaction (1) are: Zn activity and hydroxide ion concentration c[OH - ]. The smaller the particle size of zinc powder, the higher the activity of Zn, which can promote reaction (1); the smaller the pore size of nickel foam matrix, the higher the hydroxide concentration, which can promote reaction (1). Conversely, the larger the particle size of zinc powder, the lower the activity of Zn, which can inhibit reaction (1); the larger the pore size of nickel foam matrix, the lower the hydroxide concentration, which can inhibit reaction (1).

[0115] The factors affecting reactions (2) and (3) are: Zn(OH)4 2- The concentration of c[Zn(OH)4 2- ]. The larger the pore size of the nickel foam matrix, the more Zn(OH)4 2- The faster the mass transfer, the faster the c[Zn(OH)4 2- ], the passivation layer is less likely to form, which can inhibit reactions (2) and (3); the larger the particle size of zinc powder, the greater the c[Zn(OH)4 2- ], the less likely the passivation layer is to form, which can inhibit reactions (2) and (3). On the contrary, the smaller the pore size of the nickel foam matrix, the more likely Zn(OH)4 2- The slower the mass transfer, the 2- ], the easier it is to form a passivation layer, which can promote reactions (2) and (3); the smaller the particle size of zinc powder, the greater the c[Zn(OH)4 2-] is higher, the easier it is for the passivation layer to form, which can promote reactions (2) and (3).

[0116] Reaction (4) is related to reaction (1) and reaction (3). The electrons on the surface of the zinc negative electrode obtained in reaction (1) and the active water molecules on the surface of the zinc negative electrode obtained in reaction (3) are easy to react (4) to obtain hydrogen. Therefore, reaction (4) can be inhibited only by inhibiting reaction (1) and reaction (3).

[0117] In order to improve the discharge performance of the battery, it is necessary to promote reaction (1) and inhibit reactions (2) to (4). The particle size of zinc powder has opposite effects on reaction (1) and reaction (2) to (4), and the pore size of the nickel foam matrix has opposite effects on reaction (1) and reaction (2) to (4). Therefore, when the particle size of zinc powder is within a suitable particle size range and the pore size of the nickel foam matrix is ​​within a suitable pore size range, it is beneficial to promote reaction (1) and inhibit reactions (2) to (4).

[0118] like Fig.14 As shown, when the particle size of zinc powder is within the appropriate particle size range and the pore size of the nickel foam matrix is ​​within the appropriate pore size range, and the small-pore nickel foam is used with the small-particle zinc powder, the main performance is to promote reaction (1). When the particle size of zinc powder is within the appropriate particle size range and the pore size of the nickel foam matrix is ​​within the appropriate pore size range, and the large-pore nickel foam is used with the large-particle zinc powder, the main performance is to inhibit reactions (2) to (4). When the particle size of zinc powder is within the appropriate particle size range and the pore size of the nickel foam matrix is ​​within the appropriate pore size range, and the small-pore nickel foam is used with the large-particle zinc powder, the performance is to promote reaction (1) and inhibit reactions (2) to (4). When the particle size of zinc powder is within the appropriate particle size range and the pore size of the nickel foam matrix is ​​within the appropriate pore size range, and the large-pore nickel foam is used with the small-particle zinc powder, the performance is to promote reaction (1) and inhibit reactions (2) to (4).

[0119] Specifically, first, when OH near the zinc powder negative electrode - When the concentration increases or the particle size of zinc powder decreases, Zn is more likely to react with OH. - The reaction generates Zn(OH)4 2- At the same time, Zn(OH)4 2- The increase in Zn(OH)2 and ZnO directly leads to the increase in OH near the negative electrode of zinc powder. - The increase in concentration and the decrease in the particle size of zinc powder will increase the reactivity of zinc, but will also accelerate the passivation of zinc powder. Secondly, the Zn(OH)2 and ZnO passivation films formed after zinc dissolution will prevent further oxidation of zinc powder to a certain extent on the surface of zinc powder, thus inhibiting the dissolution of zinc. However, ZnO -The concentration is unstable, and Zn is easily dissolved by the electrolyte, causing the Zn(OH)2 and ZnO passivation films to fall off from the surface of the zinc powder, exposing active Zn, which further aggravates the passivation of the zinc powder. During the shedding process, the Zn(OH)2 and ZnO passivation films will bring some unreacted zinc powder into the electrolyte, reducing the utilization rate of the zinc powder, resulting in unstable and fluctuating battery discharge voltage, and reduced battery discharge capacity. The passivation film will also hinder the contact between zinc powder and the electrolyte and between zinc powders, resulting in the inhibition of the electrochemical activity of zinc powder.

[0120] Secondly, the standard reduction potential of zinc / zinc oxide (-1.26V vs. SHE) is lower than the potential of hydrogen evolution reaction (-0.83V vs. SHE), so zinc is thermodynamically unstable in water or aqueous solution. The oxidation of zinc and the reduction of hydrogen ions in the electrolyte near zinc constitute a microbattery. As shown in the conjugate reaction process, namely reaction (1), reaction (3), and reaction (4), zinc dissolves to produce electrons, Zn(OH)2 dehydrates, and water releases hydrogen at the cathode, forming a conjugate corrosion reaction. When the ionized hydrogen ions in the electrolyte solution obtain enough electrons released by the oxidation of zinc, they will combine to form H2. This reaction usually occurs on the surface of the zinc negative electrode. The general steps of the cathode reduction reaction of H2O molecules on the zinc surface are as follows: the H2O molecules that release hydrogen at the cathode migrate to the zinc surface, the H2O molecules obtain electrons on the zinc surface to generate H atoms adsorbed on the zinc surface, the H atoms recombine to form H2 molecules on the zinc surface, and the H2 molecules desorb to form H2 bubbles and precipitate.

[0121] Since H2 is continuously released from the electrolyte solution into the air after being generated, the activity of the product of reaction (4) in the electrolyte solution is relatively low. From a kinetic point of view, more Zn reacts with OH - The reaction produces more electrons, which combine with H2O on the zinc surface to generate more H2. The hydrogen produced will also isolate zinc powder and electrolyte, increasing Zn(OH)4 2- and OH - transfer impedance, reducing battery capacity and voltage.

[0122] Thirdly, when the pore size of nickel foam is large and the particle size of zinc powder is small, it is not conducive to the fixation of zinc powder by nickel foam, and some zinc powder will fall off from the pore size of nickel foam matrix into the electrolyte. That is, when the pore size of nickel foam matrix increases to a certain extent, the number of three-dimensional skeletons of nickel foam matrix decreases, which will lead to the weakening of confinement effect of nickel foam matrix on zinc powder, thereby reducing the discharge capacity and utilization rate of zinc powder.

[0123] like Fig.12As shown, as the PPI of nickel foam gradually decreases from 110 to 30, the hydrogen evolution potential of zinc powder moves significantly to the negative direction, and the hydrogen evolution current decreases significantly. When the PPI of nickel foam gradually decreases from 30 to 10, the hydrogen evolution potential of zinc powder moves slightly to the negative direction, and the hydrogen evolution current decreases slightly. This shows that when the PPI of the nickel foam matrix decreases to a certain value, that is, when the pore size of the nickel foam matrix increases to a certain value, the effect of the pore size change of the nickel foam matrix on the hydrogen evolution of zinc powder is not significant. In other words, when the pore size is small (75 / 100-250, 110 / 100-250), hydrogen evolution is more serious, which will promote reaction (4) to a greater extent; when the pore size is large (30 / 100-250, 20 / 100-250, 10 / 100-250), hydrogen evolution is relatively minor, which will promote reaction (1) to a certain extent, as shown in the following figure. Fig.14 shown.

[0124] like Fig.13 As shown in the figure, when the nickel foam matrix with the same volume and different pore sizes is loaded with zinc powder of different particle sizes, the concentration of hydroxide ions in the pore unit of the nickel foam matrix with large pore size is lower. Although it inhibits reaction (1) to a certain extent, it can also inhibit reactions (2) to (4) to a certain extent. Although the small pore size promotes reaction (1) to a certain extent, as discussed above, it will promote (2) to (4) while promoting reaction (1). As the discharge proceeds, the small pore size will cause the passivation and hydrogen evolution of zinc powder to become more serious. The large pore size nickel foam matrix means that a single pore unit of the nickel foam matrix can accommodate more zinc powder, so that the contact area between the zinc powder in each pore is larger, and the contact area between the zinc powder and the electrolyte is smaller, which can inhibit reaction (1) and, to a certain extent, also inhibit reactions (2) to (4). Compared with zinc powder with large particle size, zinc powder with small particle size has a larger specific surface area and higher activity, and is more likely to promote reaction (1) and, at the same time, promote (2) to (4). Therefore, there is a corresponding optimal local hydroxide ion concentration for zinc powders of different particle sizes.

[0125] For example, the local hydroxide ion concentrations in the pores of the nickel foam matrix of 110PPI, 75PPI, 30PPI, 20PPI, and 10PPI are c[OH - ] 110 , c[OH - ] 75 , c[OH - ] 30 , c[OH - ] 20 , c[OH - ] 10 , where c[OH - ] 110 >c[OH - ] 75 >c[OH- ] 30 >c[OH - ] 20 >c[OH - ] 10 (The overall hydroxide ion concentration of the alkaline electrolyte is basically the same. Due to the different pore sizes of the nickel foam matrix, the local hydroxide ion concentration in the pores is different.) Therefore, zinc powder with a mesh size of 100-250 (0.058-0.15 mm) is most suitable for c[OH - ] 30 The concentration (specifically Figure 6 As shown, the 30 / 100-250 sample has the best effect), c[OH - ] 110 and c[OH - ] 75 The local hydroxyl ion concentration is high, which will aggravate the passivation and hydrogen evolution corrosion of zinc powder (for example Figure 6 As shown in the figure, the effects of 110 / 100-250 and 75 / 100-250 samples are poor). The larger pore sizes of 20PPI and 10PPI will reduce the activity of zinc powder (as shown in the figure). Figure 6 As shown, the effect of 20 / 100-250 sample and 10 / 100-250 sample is slightly worse). 800 mesh (0.058-0.15 mm) zinc powder is most suitable for c[OH - ] 20 The concentration (specifically Figure 8 As shown, the 20 / 800 sample has the best effect), c[OH - ] 110 , c[OH - ] 75 and c[OH - ] 30 The local hydroxyl ion concentration is high, which will aggravate the corrosion of zinc powder (for example Figure 8 As shown in the figure, the effects of 110 / 800 and 75 / 800 samples are poor, and the effect of 30 / 800 sample is slightly poor). The larger pore size of 10PPI will reduce the activity of zinc powder (for example, Figure 8 As shown, the 10 / 800 sample has a slightly worse effect).

[0126] Therefore, under the premise of using 6M KOH and 0.2M Zn(AC)2 electrolyte, by using nickel foam matrix with different pore sizes and regulating the local hydroxide ion concentration near zinc powder with different mesh sizes, the corrosion of zinc powder can be effectively reduced to obtain the optimal discharge capacity and zinc powder utilization.

[0127] Compared with the currently commonly used method of configuring zinc powder into zinc paste, the present invention does not need to add a binder and a conductive agent, does not need to stir for a long time or even dry the steps, is simple to operate, and has low cost. In a strong alkaline electrolyte, during a long time and a large current discharge process, the zinc paste will fall off from the current collector surface, reducing the utilization rate of the zinc powder and the battery capacity. In addition, the binder is not conductive, which hinders the contact between the zinc powder particles, inevitably hinders the transmission of zinc ions, and reduces the activity of the zinc powder. The greater the current density, the higher the requirement of the battery discharge for the ion transmission between the zinc powder particles. Therefore, the method of configuring zinc powder into zinc paste cannot adapt to the requirement of a large discharge current density for good contact between the zinc powder particles, which will cause the battery discharge voltage to be unstable.

[0128] like Fig.15 As shown, the discharge capacity and average discharge voltage of the battery in the electrolyte of 6M KOH and 0.2M Zn(AC)2 are better than those in the electrolyte of 4M KOH and 0.2M Zn(AC)2. At present, the electrolyte of alkaline zinc-air batteries is usually 6M KOH and 0.2M Zn(AC)2, which takes into account the conductivity of the electrolyte and the activity of the positive and negative electrodes. The low hydroxide ion concentration described above will inhibit the corrosion of zinc powder, but too low hydroxide ion concentration such as 4M KOH will reduce the conductivity of the electrolyte and reduce the dissolution of zinc oxide generated at the negative electrode, making it impossible for zinc powder to contact the electrolyte. In addition, too low hydroxide ion concentration will reduce the activity of oxygen reduction at the positive electrode.

[0129] like Fig.16 As shown, the discharge capacity of zinc powder was tested by constant current discharge, and the test conditions were discharge for 30 minutes and standby for 30 minutes. 30PPI nickel foam matrix, 250mm, 1g zinc powder working time is 10.7h, 1g zinc sheet working time is 13.3h, and the working time of zinc powder reaches 81% of zinc sheet.

[0130] Fig.16 The zinc sheet used is specially for laboratory testing. The thickness of the experimental-grade zinc sheet is only 0.3mm, the purity is 99.999%, and the test scale is relatively small. When zinc-air batteries are used on a large scale, the amount of application-grade zinc sheet used as the negative electrode can reach the kilogram level. If the thickness of the application-grade zinc sheet needs to be maintained at about 0.3mm, this will increase the manufacturing cost greatly. However, the increase in the thickness of the application-grade zinc sheet will make the application-grade zinc sheet more easily passivated, that is, the generated poorly conductive and dense zinc oxide covering the surface of the application-grade zinc sheet will cause the inside of the zinc sheet to be unable to contact the electrolyte and continue to participate in the reaction, which will significantly reduce the utilization rate of the application-grade zinc sheet and the discharge capacity of the battery. The number of times the application-grade zinc sheet is replaced will increase, and there will be an additional process for processing the oxide film on the surface of the application-grade zinc sheet.

[0131] Large-scale applications require the negative electrode to be stable during operation and easy to use. The application-grade zinc sheet, which is used as both the negative electrode current collector and the active material, has the following problems: (1) If the external wire connecting the application-grade zinc sheet is immersed in the electrolyte, as the reaction proceeds, the application-grade zinc sheet is consumed in large quantities, and there are serious problems such as perforation and falling off, which will cause the connection between the application-grade zinc sheet and the external circuit to be unstable, which will cause the battery to fail and even cause safety problems. (2) If a part of the application-grade zinc sheet is placed above the electrolyte to connect to the external circuit, this will reduce the efficiency of the use of this part of the application-grade zinc sheet. Moreover, the application-grade zinc sheet connected to the external circuit will inevitably be corroded, resulting in the inability to accurately judge the quality of the application-grade zinc sheet in the actual reaction, making it difficult to calculate the battery energy density.

[0132] When used on a large scale, zinc powder has the advantages of low cost, adjustability and processability compared with application-grade zinc sheets. The mass of zinc powder participating in the reaction can be accurately quantified, and it is expected to achieve the same discharge capacity as application-grade zinc sheets or even surpass application-grade zinc sheets. In addition, the zinc powder is loaded in the pores of the foamed nickel matrix, that is, the negative electrode active material and the current collector are separated. The rich three-dimensional pore structure of the foamed nickel matrix maintains the contact area between the zinc powder and the current collector, which increases the discharge stability and safety of the battery. After the zinc powder is completely reacted, it is only necessary to pour new zinc powder into the foamed nickel matrix, which is easy to operate and saves time. On the whole, compared with configuring the zinc powder into zinc paste and zinc sheets, the zinc powder negative electrode for aqueous zinc-air batteries, aqueous zinc-air batteries and preparation methods thereof of the present invention are more suitable for large-scale practical applications.

[0133] Example 14. (1) Cut the polyethylene sponge into 30mm (length) * 20mm (width) * 40mm (thickness) and place it in a battery mold (the battery mold serves as the battery shell), keeping the upper surface of the polyethylene sponge and the center of the catalyst layer of the positive electrode (or the center of the window) at the same horizontal line. Cut the waterproof breathable membrane (the waterproof breathable membrane serves as a leakproof layer) into 30mm (length) * 20mm (width) and place it on the upper surface of the polyethylene sponge. The function of the waterproof breathable membrane is to prevent aluminum powder from falling downward. Bend a 30PPI nickel foam substrate of 60mm (length) * 30mm (width) * 3mm (thickness) so that the area of ​​the nickel foam substrate loaded with aluminum powder (i.e., the load part) is 30mm (length) * 20mm (width), and place it on the waterproof breathable membrane. The nickel foam substrate that does not load aluminum powder (i.e., the negative electrode connecting part) is used to connect external wires. 0.2 g of 80 mesh (0.18 mm) aluminum powder was poured into the support part of the 30 PPI nickel foam substrate of 30 mm (length)*20 mm (width)*3 mm (thickness).

[0134] (2) Provide 60 mg of catalyst, 10 mg of conductive carbon material, 20 μL of polytetrafluoroethylene slurry and 30 mL of anhydrous ethanol; place the oxygen catalyst and the conductive carbon material in a mortar, add anhydrous ethanol and polytetrafluoroethylene slurry, grind for 30 minutes until it is in a sheet shape, roll it into a thin layer, dry it at 60°C, and cut it to obtain a catalytic layer.

[0135] Specifically, Figure 5 As shown, nickel foam is used as the current collector, the length and width of the current collector are 4cm*5cm, the length and width of the waterproof and breathable conductive membrane are 3.5cm*3.5cm, and the length and width of the catalyst layer are 1cm*1cm. The thickness of the current collector is 1mm. The current collector is used to connect the catalyst layer and the external circuit. The thickness of the waterproof and breathable conductive membrane is 0.7mm. After the positive and negative electrodes are prepared, pour 48mL of 1mol L -1 KOH, 12 mL glycerol and 0.04 mol L -1 The electrolyte of Zn(AC)2 forms an aqueous aluminum-air battery (recorded as 30 / 80, where 30 represents the PPI of the foamed nickel matrix and 80 represents the mesh size of the aluminum powder) and starts to discharge. The catalyst is the self-made catalyst mentioned above.

[0136] Example 15. Different from Example 14, the aluminum powder is loaded on a 10 PPI nickel foam substrate, assembled into an aqueous aluminum-air battery (represented as 10 / 80, where 10 represents the PPI of the nickel foam substrate and 80 is the mesh size of the aluminum powder), and discharge begins.

[0137] Example 16. Different from Example 14, the aluminum powder is loaded on a 20 PPI nickel foam substrate, assembled into an aqueous aluminum-air battery (represented as 20 / 80, where 20 represents the PPI of the nickel foam substrate and 80 is the mesh size of the aluminum powder), and discharge begins.

[0138] Example 17. Different from Example 14, the aluminum powder is loaded on a 75 PPI nickel foam substrate, assembled into an aqueous aluminum-air battery (represented as 75 / 80, where 75 represents the PPI of the nickel foam substrate and 80 is the mesh size of the aluminum powder), and discharge begins.

[0139] Example 18. Different from Example 14, the aluminum powder is loaded on a 110 PPI nickel foam substrate, assembled into an aqueous aluminum-air battery (represented as 110 / 80, where 110 represents the PPI of the nickel foam substrate and 80 is the mesh size of the aluminum powder), and discharge begins.

[0140] Example 19. (1) Cut the polyethylene sponge into 30mm (length) * 20mm (width) * 40mm (thickness) and place it in a battery mold (the battery mold serves as the battery shell), keeping the upper surface of the polyethylene sponge and the center of the catalyst layer of the positive electrode (or the center of the window) at the same horizontal line. Cut the waterproof breathable membrane (the waterproof breathable membrane serves as a leakproof layer) into 30mm (length) * 20mm (width) and place it on the upper surface of the polyethylene sponge. The function of the waterproof breathable membrane is to prevent aluminum powder from falling downward. Bend a 30PPI nickel foam substrate of 60mm (length) * 30mm (width) * 3mm (thickness) so that the area of ​​the nickel foam substrate loaded with aluminum powder (i.e., the load part) is 30mm (length) * 20mm (width), and place it on the waterproof breathable membrane. The nickel foam substrate that does not load aluminum powder (i.e., the negative electrode connecting part) is used to connect external wires. 0.2 g of 400 mesh (0.036 mm) aluminum powder was poured into the support part of the 30 PPI nickel foam substrate of 30 mm (length)*20 mm (width)*3 mm (thickness).

[0141] (2) Provide 60 mg of catalyst, 10 mg of conductive carbon material, 20 μL of polytetrafluoroethylene slurry and 30 mL of anhydrous ethanol; place the oxygen catalyst and the conductive carbon material in a mortar, add anhydrous ethanol and polytetrafluoroethylene slurry, grind for 30 minutes until it is in a sheet shape, roll it into a thin layer, dry it at 60°C, and cut it to obtain a catalytic layer.

[0142] Specifically, Figure 5 As shown, nickel foam is used as the current collector, the length and width of the current collector are 4cm*5cm, the length and width of the waterproof and breathable conductive membrane are 3.5cm*3.5cm, and the length and width of the catalyst layer are 1cm*1cm. The thickness of the current collector is 1mm. The current collector is used to connect the catalyst layer and the external circuit. The thickness of the waterproof and breathable conductive membrane is 0.7mm. After the positive and negative electrodes are prepared, pour 48mL of 1mol L -1 KOH, 12 mL glycerol and 0.04 mol L -1 The electrolyte of Zn(AC)2 forms an aqueous aluminum-air battery (recorded as 30 / 400, where 30 represents the PPI of the foamed nickel matrix and 400 is the mesh size of the aluminum powder) and starts to discharge. The catalyst is the self-made catalyst mentioned above.

[0143] Example 20. Different from Example 19, the aluminum powder is loaded on a 10 PPI nickel foam substrate, assembled into an aqueous aluminum-air battery (represented as 10 / 400, where 10 represents the PPI of the nickel foam substrate and 400 is the mesh size of the aluminum powder), and discharge begins.

[0144] Example 21. Different from Example 19, the aluminum powder is loaded on a 20 PPI nickel foam substrate, assembled into an aqueous aluminum-air battery (represented as 20 / 400, where 20 represents the PPI of the nickel foam substrate and 400 is the mesh size of the aluminum powder), and discharge begins.

[0145] Example 22. Different from Example 19, the aluminum powder is loaded on a 75 PPI nickel foam substrate, assembled into an aqueous aluminum-air battery (represented as 75 / 400, where 75 represents the PPI of the nickel foam substrate and 400 is the mesh size of the aluminum powder), and discharge begins.

[0146] Example 23. Different from Example 19, the aluminum powder is loaded on a 110 PPI nickel foam substrate, assembled into an aqueous aluminum-air battery (represented as 110 / 400, where 110 represents the PPI of the nickel foam substrate and 400 is the mesh size of the aluminum powder), and discharge begins.

[0147] like Fig.17 As shown, the capacity of the aluminum powder battery in Example 14 is 54.6mAh; the capacity of the aluminum powder battery in Example 15 is 17.7mAh; and the capacity of the aluminum powder battery in Example 16 is 43mAh. The capacity of the aluminum powder battery in Example 17 is 40.4mAh; and the capacity of the aluminum powder battery in Example 18 is 39mAh. It can be observed that as the PPI of the nickel foam gradually decreases from 110 to 30, the pore size of the nickel foam matrix gradually increases, and the capacity of the aluminum powder gradually increases. As the PPI of the nickel foam gradually decreases from 30 to 10, the pore size of the nickel foam matrix continues to increase, and the capacity of the aluminum powder gradually decreases. The discharge capacity of the battery formed by the nickel foam matrix of 30PPI, 20PPI and 75PPI is generally greater than the discharge capacity of the battery formed by the nickel foam matrix of 10PPI and 110PPI.

[0148] like Fig.18 As shown, the aluminum powder battery capacity of Example 19 is 36.9mAh; the aluminum powder battery capacity of Example 20 is 10.8mAh; and the aluminum powder battery capacity of Example 21 is 35.8mAh / g. The aluminum powder battery capacity of Example 22 is 28.5mAh; and the aluminum powder battery capacity of Example 23 is 9.8mAh. It can be observed that as the PPI of nickel foam gradually decreases from 110 to 20, the pore size of the nickel foam matrix gradually increases, and the battery capacity of aluminum powder gradually increases. As the PPI of nickel foam decreases from 20 to 10, the pore size of the nickel foam matrix continues to increase, and the battery capacity of aluminum powder decreases. The discharge capacity of batteries formed with nickel foam matrices of 30PPI, 20PPI and 75PPI is generally greater than the discharge capacity of batteries formed with nickel foam matrices of 10PPI and 110PPI.

[0149] The reaction formula of alkaline aluminum-air battery is as follows: Under alkaline conditions, the aluminum negative electrode reaction process:

[0150]

[0151] Under alkaline conditions, the formation reaction of the aluminum negative electrode passivation layer is:

[0152]

[0153] (6) is the dissolution reaction of the aluminum negative electrode under alkaline conditions, and (7) and (8) are the formation reactions of the passivation layer.

[0154] Under alkaline conditions, a conjugate corrosion reaction occurs on the aluminum negative electrode:

[0155]

[0156] 4H2O+3e - →4OH - +2H2↑(9).

[0157] Under alkaline conditions, the cathode reaction process:

[0158]

[0159] During the discharge process of aluminum-air batteries, as shown in reactions (6) to (8) at the negative electrode, the aluminum negative electrode loses electrons and becomes Al(OH)4 - , Al(OH)4 - After reaching saturation in the electrolyte, it will decompose into Al2O3. This is the dissolution and passivation process of aluminum. This dissolution and passivation process is an important part of the normal operation of aluminum-air batteries in an alkaline environment. The oxygen at the positive electrode obtains the electrons lost by aluminum from the external circuit and is reduced to hydroxide ions. The dissolution and passivation behavior of the aluminum negative electrode plays an important role in the performance of aluminum-air batteries. The rapidly dissolving aluminum negative electrode can enable the battery to provide a large current. However, the high passivation rate of the aluminum negative electrode also greatly shortens the battery life. While maintaining the activity of the aluminum negative electrode, moderately inhibiting the passivation rate of the aluminum negative electrode can improve the discharge performance of the battery. Therefore, it is necessary to promote reaction (6) and inhibit reaction (7) and reaction (8).

[0160] Reaction (9) is a hydrogen evolution corrosion reaction. Reaction (6), reaction (8) and reaction (9) form a conjugate corrosion reaction. The electrons formed on the aluminum surface by reaction (6) and the active water molecules formed on the aluminum surface by reaction (8) can react (9) and release hydrogen. Of course, isolated water molecules in the electrolyte can also react (9) on the aluminum surface. Reaction (9) consumes the electrons obtained by reaction (6), reducing the energy conversion efficiency of the battery. Inhibiting reaction (9) can improve the discharge performance of the battery.

[0161] The factors affecting reaction (6) are: the activity of Al and the concentration of hydroxide ions c[OH -]. The smaller the particle size of aluminum powder, the higher the activity of Al, which can promote the reaction (6); the smaller the pore size of the nickel foam matrix, the higher the hydroxide concentration, which can promote the reaction (6). Conversely, the larger the particle size of aluminum powder, the lower the activity of Al, which can inhibit the reaction (6); the larger the pore size of the nickel foam matrix, the lower the hydroxide concentration, which can inhibit the reaction (6).

[0162] The factors affecting reactions (7) and (8) are: Al(OH)4 - The concentration of c[Al(OH)4 - The larger the pore size of the nickel foam matrix, the greater the Al(OH)4 - The faster the mass transfer, the faster the c[Al(OH)4 - ], the less likely the passivation layer is to form, which can inhibit reactions (7) and (8); the larger the particle size of the aluminum powder, the greater the c[Al(OH)4 - ], the less likely the passivation layer is to form, which can inhibit reactions (7) and (8). On the contrary, the smaller the pore size of the nickel foam matrix, the more likely Al(OH)4 - The slower the mass transfer, the slower the - ], the easier it is to form a passivation layer, which can promote reactions (7) and (8); the smaller the particle size of the aluminum powder, the smaller the c[Al(OH)4 - ] is higher, the easier it is for the passivation layer to form, which can promote reactions (7) and (8).

[0163] Reaction (9) is related to reaction (6) and reaction (8). The electrons on the surface of the aluminum negative electrode obtained in reaction (6) and the active water molecules on the surface of the aluminum negative electrode obtained in reaction (8) are easy to react (9) to obtain hydrogen. Therefore, reaction (6) and reaction (8) can be inhibited to inhibit reaction (9).

[0164] In order to improve the discharge performance of the battery, it is necessary to promote reaction (6) and inhibit reactions (7) to (9). The particle size of aluminum powder has opposite effects on reaction (6) and reaction (7) to (9), and the pore size of the nickel foam matrix has opposite effects on reaction (6) and reaction (7) to (9). Therefore, when the particle size of aluminum powder is within a suitable particle size range and the pore size of the nickel foam matrix is ​​within a suitable pore size range, it is beneficial to promote reaction (6) and inhibit reactions (7) to (9).

[0165] like Fig.19As shown, when the particle size of the aluminum powder is within the appropriate particle size range and the pore size of the nickel foam matrix is ​​within the appropriate pore size range, and the small-pore nickel foam is used with the small-particle aluminum powder, the main performance is to promote reaction (6). When the particle size of the aluminum powder is within the appropriate particle size range and the pore size of the nickel foam matrix is ​​within the appropriate pore size range, and the large-pore nickel foam is used with the large-particle aluminum powder, the main performance is to inhibit reactions (7) to (9). When the particle size of the aluminum powder is within the appropriate particle size range and the pore size of the nickel foam matrix is ​​within the appropriate pore size range, and the small-pore nickel foam is used with the large-particle aluminum powder, the performance is to promote reaction (6) and inhibit reactions (7) to (9). When the particle size of the aluminum powder is within the appropriate particle size range and the pore size of the nickel foam matrix is ​​within the appropriate pore size range, and the large-pore nickel foam is used with the small-particle aluminum powder, the performance is to promote reaction (6) and inhibit reactions (7) to (9).

[0166] Specifically, first, when the OH near the negative electrode of aluminum powder - When the concentration increases or the particle size of aluminum powder decreases, Al is more likely to react with OH. - The reaction generates Al(OH)4 - At the same time, Al(OH)4 - The increase in Al(OH)3 and Al2O3 directly leads to the increase in OH near the negative electrode of aluminum powder. - The increase in concentration and the decrease in the particle size of aluminum powder will increase the reactivity of aluminum, but will also accelerate the passivation of aluminum powder. Secondly, the Al(OH)3 and Al2O3 passivation films formed after aluminum dissolution will prevent further oxidation of aluminum powder to a certain extent on the surface of aluminum powder, thus inhibiting the dissolution of aluminum. However, Al2O3 - It is unstable under low concentration. Al is easily dissolved by the electrolyte, causing the Al(OH)3 and Al2O3 passivation films to fall off from the surface of the aluminum powder, exposing active Al, which further aggravates the passivation of the aluminum powder. During the shedding process, the Al(OH)3 and Al2O3 passivation films will bring some unreacted aluminum powder into the electrolyte, reducing the utilization rate of the aluminum powder, resulting in unstable and fluctuating battery discharge voltage, and reduced battery discharge capacity. The passivation film will also hinder the contact between the aluminum powder and the electrolyte and between the aluminum powders, resulting in the inhibition of the electrochemical activity of the aluminum powder.

[0167] Secondly, the standard reduction potential of aluminum / aluminum oxide (-2.35V vs. SHE) is lower than the potential of hydrogen evolution reaction (-0.83V vs. SHE), so aluminum is thermodynamically unstable in water or aqueous solution. The oxidation of aluminum and the reduction of hydrogen ions in the electrolyte near aluminum constitute a microbattery. As shown in the conjugate reaction process, that is, reaction (6), reaction (8), and reaction (9), aluminum dissolves to produce electrons, Al(OH)3 dehydrates, and water releases hydrogen at the cathode, forming a conjugate corrosion reaction. When the ionized hydrogen ions in the electrolyte solution obtain enough electrons released by the oxidation of aluminum, they will combine to form H2. This reaction usually occurs on the surface of the aluminum negative electrode. The general steps of the cathode reduction reaction of H2O molecules on the aluminum surface are as follows: the H2O molecules that release hydrogen at the cathode migrate to the aluminum surface, the H2O molecules obtain electrons on the aluminum surface to generate H atoms adsorbed on the aluminum surface, the H atoms recombine to form H2 molecules on the aluminum surface, and the H2 molecules desorb to form H2 bubbles and precipitate.

[0168] Since H2 is continuously released from the electrolyte solution into the air after being generated, the activity of the product of reaction (9) in the electrolyte solution is relatively low. From a kinetic point of view, more Al and OH - The reaction produces more electrons, which combine with H2O on the aluminum surface to generate more H2. The hydrogen produced will also isolate the aluminum powder and the electrolyte, increasing the Al(OH)4 - and OH - transfer impedance, reducing battery capacity and voltage.

[0169] Thirdly, when the pore size of nickel foam is large and the particle size of aluminum powder is small, it is not conducive to the fixation of aluminum powder by nickel foam, and some aluminum powder will fall off from the pore size of the nickel foam matrix into the electrolyte. That is, when the pore size of the nickel foam matrix increases to a certain extent, the number of three-dimensional skeletons of the nickel foam matrix decreases, which will lead to the weakening of the confinement effect of the nickel foam matrix on aluminum powder, thereby reducing the discharge capacity and utilization rate of the aluminum powder.

[0170] Example 24: Different from Example 14, the aluminum powder is replaced with magnesium powder, and an aqueous magnesium-air battery is assembled and discharged.

[0171] Example 25. Different from Example 14, the aluminum powder is replaced by iron powder, and an aqueous iron-air battery is assembled and discharged.

[0172] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A metal powder negative electrode for an aqueous metal-air battery, characterized in that: include: A nickel foam substrate with a porous structure formed inside; Metal powder, filled in the porous structure; the metal powder is selected from at least one of zinc powder, aluminum powder, magnesium powder and iron powder; A leak-proof layer, disposed on the nickel foam substrate, and used to prevent the metal powder from leaking out; Wherein, the PPI of the nickel foam matrix is ​​10 to 110; The diameter of the metal powder is 0.018 mm to 0.18 mm.

2. The metal powder negative electrode for aqueous metal-air battery according to claim 1, characterized in that: When the metal powder is zinc powder, the PPI of the foamed nickel matrix is ​​10-30; when the metal powder is aluminum powder, the PPI of the foamed nickel is 20-75; and the anti-leakage layer is a waterproof and breathable membrane.

3. An aqueous metal-air battery, characterized in that: include: a housing having a window; A positive electrode, disposed at the position of the window in the housing; A negative electrode, which is a metal powder negative electrode for an aqueous metal-air battery as claimed in any one of claims 1 to 2 and is located in the housing at a position away from the window; an alkaline electrolyte, located in the housing; Wherein, the positive electrode and the negative electrode are both located below the liquid surface of the alkaline electrolyte.

4. The aqueous metal-air battery according to claim 3, characterized in that: The alkaline electrolyte comprises: Soluble in acetate, strong alkali and water; The concentration of soluble acetate is 0.04 mol L -1 ~0.3mol L -1 ; The concentration of a strong base is 1 mol L -1 ~6mol L -1 .

5. The aqueous metal-air battery according to claim 3, characterized in that: The positive electrode comprises: A current collector, a waterproof and breathable conductive membrane and a catalyst layer are arranged in sequence; Wherein, the catalytic layer is made of catalyst, conductive carbon material and polytetrafluoroethylene.

6. The aqueous metal-air battery according to claim 5, characterized in that: The current collector extends out of the liquid surface to form a positive electrode connection portion; the foamed nickel matrix in the negative electrode extends out of the liquid surface to form a negative electrode connection portion.

7. The aqueous metal-air battery according to claim 5, characterized in that: The current collector is made of foam nickel or carbon cloth.

8. A method for preparing an aqueous metal-air battery according to any one of claims 3 to 7, characterized in that: Includes steps: Prepare a positive electrode, and assemble the positive electrode into a shell; preparing a negative electrode, and assembling the negative electrode in a shell; Alkaline electrolyte is injected into the housing.

9. The method for preparing an aqueous metal-air battery according to claim 8, characterized in that: The method of preparing a negative electrode and assembling the negative electrode in a shell comprises: cutting and bending the nickel foam to obtain a nickel foam matrix; The anti-leakage layer is connected to the nickel foam substrate, and metal powder is poured into it to obtain a negative electrode; The negative electrode is assembled into a casing.

10. The method for preparing an aqueous metal-air battery according to claim 8, characterized in that: The method of preparing a positive electrode and assembling the positive electrode in a shell comprises: The catalyst, the conductive carbon material, the polytetrafluoroethylene and the volatile solvent are mixed and rolled into a catalyst layer; The waterproof and breathable conductive film and the catalyst layer are sequentially stacked on the current collector to obtain a positive electrode; The positive electrode is assembled in a casing.

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