A bifunctional electrode, a preparation method thereof and application thereof in a zinc-air battery

Abstract

The application discloses a bifunctional electrode and a preparation method and application thereof in a zinc-air battery, relates to the field of electrochemical power sources, and discloses the following steps: spraying ORR catalyst slurry containing a modified conductive agent and OER catalyst slurry on the same substrate through a template to prepare an interleaved bifunctional electrode, the electrode can avoid high-voltage oxidation damage of the catalytic layer during charging, independently regulate hydrophilicity and hydrophobicity of the two types of catalytic layers, optimize mass transfer and interface reaction, and be applied to the zinc-air battery, so that the ion diffusion path is shortened, uniform deposition and peeling of the zinc electrode are improved, electrochemical activity and stability of the air electrode and the zinc electrode are simultaneously improved, long-time charging and discharging cycle discharge voltage stability and structural stability after the cycle are improved.

Description

Technical Field

[0001] This invention relates to the field of electrochemical power source technology, specifically to a bifunctional electrode, its preparation method, and its application in zinc-air batteries. Background Technology

[0002] Currently, researchers are dedicated to developing new green energy sources and efficient energy storage technologies. Compared to traditional lithium-ion batteries, rechargeable zinc-air batteries have attracted widespread attention due to their numerous advantages, including high theoretical energy density, the safety and reliability of aqueous electrolytes, and abundant zinc resources, and have great application prospects in the field of energy supply and storage.

[0003] Zinc-air batteries mainly consist of three parts: a zinc negative electrode, an electrolyte, and an air positive electrode. The air positive electrode has a relatively complex structure, comprising a catalyst layer, a gas diffusion layer, and a conductive substrate layer. The catalyst layer catalyzes the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), improving the energy conversion efficiency of the zinc-air battery by reducing the electrode overpotential. The gas diffusion layer facilitates the entry and exit of gas to participate in the electrode reaction while preventing electrolyte leakage. Traditional air electrode fabrication methods mainly involve mixing ORR and OER catalysts and loading them onto the surface of the gas diffusion layer. The discharge process is driven by ORR, and the charging process is driven by OER. However, this type of air electrode experiences a high charging voltage during charging, and the carbon-based catalyst with excellent ORR performance is easily oxidized and loses its catalytic activity.

[0004] To address the above issues, existing technologies include separating the ORR and OER electrodes to construct a three-electrode zinc-air battery. While this solves the problem of ORR catalyst oxidation, it complicates the battery structure, affects volumetric energy density, and causes zinc metal oxidation stripping and zinc ion reduction deposition to occur on different surfaces, significantly impairing the stability of the zinc anode. Other technologies place the ORR and OER electrodes on the same side of the zinc electrode, which simplifies the battery structure, but the different ion diffusion paths during charging and discharging lead to the continuous dissolution of zinc corresponding to the ORR and the continuous accumulation of zinc corresponding to the OER, ultimately compromising the stability of the zinc electrode. Additionally, some have attempted to place the OER electrode between the zinc and ORR electrodes, theoretically solving the problems of ORR catalyst oxidation and different zinc ion diffusion paths. However, in actual charging, oxygen accumulation occurs, which cannot be expelled from the air electrode, easily causing a rapid increase in charging voltage.

[0005] In conclusion, the discrete air electrode design still cannot effectively optimize the structure and electrode performance of zinc-air batteries. Therefore, designing and developing novel integrated air electrodes, considering the overall structure of zinc-air batteries and the synergistic optimization of electrode performance, is of great significance. Summary of the Invention

[0006] To address the shortcomings mentioned in the background art, the present invention aims to provide a bifunctional electrode, its preparation method, and its application in zinc-air batteries. The present invention involves spraying ORR catalyst slurry and OER catalyst slurry containing modified conductive agents onto the same substrate using a template to fabricate an interleaved bifunctional electrode. This electrode avoids high-voltage oxidation damage to the catalyst layer during charging, independently regulates the hydrophilicity and hydrophobicity of the two types of catalyst layers, optimizes mass transfer and interfacial reactions, and, when applied to zinc-air batteries, can shorten ion diffusion paths, improve uniform deposition and stripping of the zinc electrode, and simultaneously enhance the electrochemical activity and stability of both the air and zinc electrodes, as well as the long-term charge-discharge cycle voltage stability and post-cycle structural stability.

[0007] The objective of this invention can be achieved through the following technical solutions: A method for preparing a bifunctional electrode includes the following steps: Step 1: Take ORR catalyst and modified conductive agent into reactor, then add a mixture of ionomer dispersion, deionized water and ethanol, and ultrasonically disperse for 15-20 minutes to obtain ORR catalyst slurry. The second step involves placing the OER catalyst and modified conductive agent into a reactor, then adding a mixture of ionomer dispersion, deionized water, and ethanol, and ultrasonically dispersing for 15-20 minutes to obtain the OER catalyst slurry. The third step involves fixing the substrate on a constant-temperature heating plate at 70-80℃, placing the electrode template on the substrate, placing the OER electrode mask with a hollow structure on the electrode template, and spraying it with OER catalyst slurry to form a partial coating layer on the surface of the electrode template that serves as the OER coupling electrode. After spraying, the OER electrode mask is removed, and the ORR electrode mask with another hollow structure is used to cover part of the coating layer. The ORR catalyst slurry is then sprayed to form a coating layer on the surface of the electrode template that serves as the ORR coupling electrode. Finally, a bifunctional electrode is formed on the same side surface of the substrate. The modified conductive agent is prepared by reacting 1H-furano[3,4-c]pyrrole-1,3(5H)-dione with taurine to obtain a modified pyrrole precursor, and then neutralizing the modified pyrrole precursor with sodium hydroxide to form a salt. The modified pyrrole is then subjected to in-situ polymerization on graphite oxide powder with pyrrole monomer and aniline monomer.

[0008] More preferably, the ORR catalyst in the first step is a noble metal-based catalyst or a non-noble metal-based catalyst.

[0009] More preferably, the ionomer dispersion in the first step is a perfluorosulfonic acid cation exchange ionomer dispersion.

[0010] More preferably, in the first step, the volume ratio of the ionomer dispersion, deionized water, and ethanol in the mixture is 1~5:10:10.

[0011] More preferably, the mass ratio of the ORR catalyst to the modified conductive agent in the first step is 1:1~10.

[0012] More preferably, in the first step, the total mass of ORR catalyst and modified conductive agent in the ORR catalyst slurry and the solid-liquid ratio of the mixture are 5~20 mg / mL.

[0013] More preferably, the OER catalyst in the second step is a noble metal-based catalyst or a non-noble metal-based catalyst.

[0014] More preferably, the mass ratio of the OER catalyst to the modified conductive agent in the second step is 1:1~10.

[0015] More preferably, the ionomer dispersion in the second step is a perfluorosulfonic acid cation exchange ionomer dispersion.

[0016] More preferably, the volume ratio of the ionomer dispersion, deionized water, and ethanol in the mixture in the second step is 1~5:10:10.

[0017] More preferably, in the second step, the total mass of the OER catalyst and the modified conductive agent in the OER catalyst slurry has a solid-liquid ratio of 5~20 mg / mL to the mixture.

[0018] More preferably, the substrate in the third step is any one of polytetrafluoroethylene film, polyvinyl chloride film, polypropylene film, polyethylene film, hydrophobically modified nylon fabric, hydrophobically modified nonwoven fabric, or hydrophobically modified fiber film.

[0019] More preferably, the electrode template in the third step is an electrode template with an alternating arrangement structure.

[0020] More preferably, the hollow structure in the third step is a comb-shaped hollow structure.

[0021] More preferably, the preparation method of the modified conductive agent includes the following steps: S1. Add 1H-furano[3,4-c]pyrrole-1,3(5H)-dione and N,N-dimethylformamide to the reactor, stir until the solid is completely dissolved, then add taurine and triethylamine, and stir the reaction at room temperature for 8~12h to obtain the modified pyrrole precursor. S2. Add the modified pyrrole precursor and deionized water to the reactor, and slowly add sodium hydroxide aqueous solution dropwise under ice bath conditions of 0~5℃. When the pH of the reaction solution reaches 7~8, stop the dropwise addition, remove some of the deionized water by rotary evaporation, and then dry the product to obtain modified pyrrole. S3. Take graphite oxide powder, grind it, add it to deionized water, and ultrasonically disperse it for 1-2 hours to obtain a dispersion. Then add pyrrole monomer, aniline monomer, modified pyrrole and sodium polystyrene sulfonate to the dispersion. After ultrasonically dispersing at room temperature for 2-3 hours, transfer the system to an ice bath at 0-5℃. Adjust the pH of the system to 1-2 with p-toluenesulfonic acid. Then add ferric chloride hexahydrate aqueous solution dropwise while stirring. After the addition is complete, continue to stir and react under ice bath conditions for 20-24 hours to obtain the modified conductive agent.

[0022] More preferably, in step S1, the molar ratio of 1H-furano[3,4-c]pyrrole-1,3(5H)-dione, taurine and triethylamine is 1:1~1.2:1.5~2.0.

[0023] More preferably, the molar concentration of the sodium hydroxide aqueous solution in step S2 is 1~2 mol / L.

[0024] More preferably, in step S3, the solid-liquid ratio of graphite powder to deionized water is 1~2 mg / mL.

[0025] More preferably, in step S3, the molar ratio of pyrrole monomer, aniline monomer and modified pyrrole is 1:1~1.2:0.1~0.2.

[0026] More preferably, in step S3, the solid-liquid ratio of the ferric chloride hexahydrate aqueous solution is 0.02~0.05 g / mL, wherein the molar ratio of ferric chloride hexahydrate to pyrrole monomer in the ferric chloride hexahydrate aqueous solution is 1.8~2.2:1.

[0027] More preferably, in step S3, the mass of sodium polystyrene sulfonate is 0.5 to 1.0 of the total mass of pyrrole monomer, aniline monomer, and modified pyrrole.

[0028] The above-mentioned bifunctional electrode is used in zinc-air batteries, and is used as an air positive electrode in the preparation of zinc-air batteries.

[0029] More preferably, the method for preparing the zinc-air battery includes the following steps: Using a zinc plate as the negative electrode, the surface of the plate is polished with sandpaper and then cleaned with ethanol. The plates are stacked in the following order: lower end plate, zinc plate electrode, sealing gasket, intermediate electrolytic cell, sealing gasket, dual-function electrode, porous support plate, and upper end plate. The plates are then tightened with screws. The electrolyte is then injected into the intermediate electrolytic cell, and the injection port is sealed with a silicone plug to obtain a zinc-air battery.

[0030] More preferably, the lower end plate, the intermediate electrolytic cell, and the upper end plate are any one of polymethyl methacrylate, polyvinyl chloride, or polytetrafluoroethylene.

[0031] More preferably, the upper end plate is a completely hollow structure or a porous structure.

[0032] More preferably, the sealing gasket is a silicone rubber sealing gasket.

[0033] More preferably, the porous support plate is a polymethyl methacrylate porous plate or a polytetrafluoroethylene porous plate.

[0034] More preferably, the electrolyte is an alkaline potassium hydroxide electrolyte or a neutral electrolyte containing metal ions.

[0035] The beneficial effects of this invention are: This invention employs an interleaved structure to physically isolate the ORR and OER electrodes in space, preventing oxidation of the catalyst layer at high charging potentials, while allowing independent control of the hydrophilicity / hydrophobicity and catalyst loading in both regions. A core-shell structure is constructed using a modified conductive agent coated with pyrrole-aniline in-situ copolymer. The introduction of aniline improves the conjugation degree and charge transport efficiency of the copolymer chains, resulting in a more uniform and dense coating layer. The polypyrrole shell, due to its higher oxidation potential than the carbon support, preferentially withstands the anodic potential, further inhibiting carbon support oxidation at the material level, forming a dual stabilization mechanism of structural isolation and material protection. This mechanism significantly delays the performance degradation of the air electrode during battery charge-discharge cycles, maintaining lower voltage polarization during long-term charge-discharge cycles, thereby extending the effective cycle life and reducing the maintenance cost of electrode replacement.

[0036] The staggered bifunctional electrodes in this invention ensure a uniform distribution of ion current on the zinc anode surface, effectively suppressing dendrite growth and electrode deformation. Simultaneously, the sodium carboxylate groups in the modified conductive agent significantly enhance the affinity of the catalyst layer for the electrolyte, promoting thorough wetting of the electrode's internal pores. The sodium sulfonate groups, on the one hand, act as a dopant, injecting charge carriers into the polypyrrole backbone to ensure high conductivity of the coating layer; on the other hand, they provide additional ion transport channels. These two elements synergistically optimize electron-ion mixed conduction and reduce interfacial impedance. The uniform current distribution on the zinc anode surface allows for more uniform anode stripping and deposition during high-current charging and discharging, preventing localized protrusions from forming dendrites that pierce the separator, thereby improving battery safety and cycle reversibility. Furthermore, the reduced interfacial impedance contributes to improved battery energy efficiency and rate performance.

[0037] The polypyrrole backbone of the modified conductive agent in this invention possesses redox activity, contributing additional pseudocapacitance and reducing charge-discharge polarization. The aniline copolymer component further enhances the π-π stacking interaction between polymer chains, improving the structural density and electrochemical stability of the coating layer. Furthermore, the material modification and the staggered spatial design create synergistic benefits. The spatial structure addresses the uneven distribution of macroscopic ion current, while the modified conductive agent improves microscopic interfacial mass transfer and stability. This simultaneously enhances electrode performance from both intrinsic material stability and interfacial ion transport perspectives, providing a dual guarantee for extending battery cycle life. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of the electrode template and the mask template. Figure 1 Figure A shows the OER electrode mask. Figure 1 Figure B shows an interlaced electrode template. Figure 1 Figure C is the ORR electrode mask template; Figure 2 This is a schematic diagram of the substrate and the coated bifunctional electrode. Figure 2 Figure a is the base. Figure 2 Figure b shows the coated bifunctional electrode; Figure 3 This is a schematic diagram of a zinc-air battery assembly; Reference numerals: 1-lower end plate, 2-metal electrode, 3-sealing gasket, 4-electrolytic cell, 5-sealing gasket, 6-dual-function electrode, 7-porous support plate, 8-upper end plate. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] The 1H-furano[3,4-c]pyrrole-1,3(5H)-dione involved in the following examples and comparative examples has the CAS number 6711-68-8.

[0042] Example 1: A method for preparing a modified conductive agent, comprising the following steps: S1. Add 6 mg of 1H-furano[3,4-c]pyrrole-1,3(5H)-dione and 0.5 mL of N,N-dimethylformamide to the reactor and stir until the solid is completely dissolved. Then add 5.4 mg of taurine and 0.01 mL of triethylamine and stir at room temperature for 12 h. After the reaction is completed, remove part of the solvent by rotary evaporation of the reaction solution, precipitate with anhydrous ethanol, filter, wash the obtained solid with dilute hydrochloric acid aqueous solution and deionized water respectively, and then dry to obtain the modified pyrrole precursor. S2. Add 9.4 mg of modified pyrrole precursor and 2 mL of deionized water to the reactor. Slowly add a 1 mol / L sodium hydroxide aqueous solution under 0°C ice bath conditions. Stop adding the solution when the pH reaches 7. Remove some of the deionized water by rotary evaporation and then dry the product to obtain modified pyrrole. S3. Take 21 mg of graphite oxide powder, grind it, add it to 15 mL of deionized water, and sonicate it for 2 h to obtain a dispersion. Then add 0.019 mL of pyrrole monomer, 0.028 mL of aniline monomer, 41.3 mg of modified pyrrole and 60 mg of sodium polystyrene sulfonate to the dispersion. After sonicating it for 3 h at room temperature, transfer the system to an ice bath at 0 °C. Adjust the pH of the system to 1.5 with p-toluenesulfonic acid. Then, while stirring, add an aqueous solution of ferric chloride hexahydrate composed of 0.15 g of ferric chloride hexahydrate and 7 mL of deionized water dropwise. After the addition is complete, continue to stir the reaction under ice bath conditions for 24 h. After the reaction is completed, wash the reaction solution with a mixed solution of ethanol and deionized water and filter it. Freeze-dry the filtered solid for 24 h to obtain the modified conductive agent.

[0043] Example 2: A method for preparing a bifunctional electrode, comprising the following steps: Step 1: Take 5 mg of nitrogen-doped carbon-iron single-atom catalyst and 25 mg of the modified conductive agent prepared in Example 1 into the reactor, and then add a mixture of 0.3 mL Nafion solution, 1.5 mL deionized water and 1.5 mL ethanol. Disperse the mixture by ultrasonication for 15 min to obtain ORR catalyst slurry. The second step involves placing 5 mg of ruthenium dioxide catalyst and 25 mg of modified conductive agent into a reactor, then adding a mixture of 0.3 mL Nafion solution, 1.5 mL deionized water, and 1.5 mL ethanol, and ultrasonically dispersing for 15 min to obtain the OER catalyst slurry. Step 3, as follows Figure 1 As shown in Figure B, a stainless steel sheet with a thickness of 0.5mm is cut into a size of 4cm×5.5cm using laser cutting technology, and an electrode area with a size of 3cm×3cm is cut out inside. The hollowed-out width is 2mm, the length is 25mm, and the partition width is 1mm, forming an interlaced electrode template. like Figure 1 As shown in Figure A, laser cutting technology is used to cut a 0.5mm thick stainless steel sheet into an OER electrode mask with a cutout width of 2mm, a length of 25mm, and a partition width of 3mm. like Figure 1 As shown in C, using laser cutting technology, a stainless steel sheet with a thickness of 0.5mm is cut into an ORR electrode mask with a cutout width of 2mm, a length of 25mm, and a partition width of 3mm. Step 4, such as Figure 2 As shown in Figure a, according to the battery size, a polytetrafluoroethylene (PTFE) film is cut into 4cm × 5.5cm pieces to serve as a substrate. This substrate is then fixed to an 80℃ constant-temperature heating plate. An interlaced electrode template is placed on the substrate, followed by an OER electrode mask. OER catalyst slurry is then sprayed onto the substrate using a spray gun to obtain an OER coupled electrode. The OER electrode mask is then replaced in situ with an ORR electrode mask, and ORR catalyst slurry is sprayed onto the substrate again to obtain an ORR coupled electrode. Finally, a [details about the electrode structure and process are missing from the original text] is fabricated on the same side of the substrate. Figure 2 The bifunctional electrode shown in b; A method for preparing a zinc-air battery includes the following steps: like Figure 3As shown, a zinc plate with dimensions of 8mm×3mm×1mm is used as the negative electrode. After polishing its surface with 1000-grit sandpaper, it is cleaned with ethanol. The zinc plate is stacked in the following order: PTFE lower end plate 1, zinc plate electrode 2, silicone rubber sealing gasket 3, PTFE intermediate electrolytic cell 4, silicone rubber sealing gasket 5, bifunctional electrode 6, PTFE porous support plate 7, and PTFE hollow upper end plate 8. The plates are then tightened with screws. A mixed solution of 0.2mol / L zinc acetate and 6mol / L potassium hydroxide is used as the electrolyte to fill the electrolytic cell. The injection port is then sealed with a silicone plug to obtain a zinc-air battery.

[0044] Example 3: A method for preparing a bifunctional electrode, comprising the following steps: Step 1: Take 5 mg of platinum-carbon catalyst and 25 mg of the modified conductive agent prepared in Example 1 into a reactor, and then add a mixture of 0.3 mL Nafion solution, 1.5 mL deionized water and 1.5 mL ethanol. Disperse the mixture by ultrasonication for 15-20 min to obtain ORR catalyst slurry. Step 2: Take 5 mg of ruthenium dioxide catalyst and 25 mg of the modified conductive agent prepared in Example 1 into the reactor, and then add a mixture of 0.3 mL Nafion solution, 1.5 mL deionized water and 1.5 mL ethanol. Disperse the mixture by ultrasonication for 15 min to obtain OER catalyst slurry. Step 3, as follows Figure 1 As shown in Figure B, a stainless steel sheet with a thickness of 0.5mm is cut into a size of 4cm×5.5cm using laser cutting technology, and an electrode area with a size of 3cm×3cm is cut out inside. The hollowed-out width is 2mm, the length is 25mm, and the partition width is 1mm, forming an interlaced electrode template. like Figure 1 As shown in Figure A, laser cutting technology is used to cut a 0.5mm thick stainless steel sheet into an OER electrode mask with a cutout width of 2mm, a length of 25mm, and a partition width of 3mm. like Figure 1 As shown in C, using laser cutting technology, a stainless steel sheet with a thickness of 0.5mm is cut into an ORR electrode mask with a cutout width of 2mm, a length of 25mm, and a partition width of 3mm. Step 4, such as Figure 2As shown in Figure a, according to the battery size, non-woven fabric coated with polytetrafluoroethylene emulsion was cut into 4cm × 5.5cm pieces to serve as a substrate. This substrate was then fixed to an 80℃ constant-temperature heating plate. An interlaced electrode template was placed on the substrate, followed by an OER electrode mask. OER catalyst slurry was then sprayed onto the substrate using a spray gun to obtain an OER coupled electrode. The OER electrode mask was then replaced in situ with an ORR electrode mask, and ORR catalyst slurry was sprayed onto the substrate again to obtain an ORR coupled electrode. Finally, a structure resembling the image was fabricated on the same side of the substrate. Figure 2 The bifunctional electrode shown in b; A method for preparing a zinc-air battery includes the following steps: like Figure 3 As shown, a zinc plate with dimensions of 8mm×3mm×1mm is used as the negative electrode. After polishing its surface with 1000-grit sandpaper, it is cleaned with ethanol. The zinc plate is stacked in the following order: PTFE lower end plate 1, zinc plate electrode 2, silicone rubber sealing gasket 3, PTFE intermediate electrolytic cell 4, silicone rubber sealing gasket 5, bifunctional electrode 6, PTFE porous support plate 7, and PTFE hollow upper end plate 8. The plates are then tightened with screws. A mixed solution of 0.2mol / L zinc acetate and 6mol / L potassium hydroxide is used as the electrolyte to fill the electrolytic cell. The injection port is then sealed with a silicone plug to obtain a zinc-air battery.

[0045] Example 4: A method for preparing a bifunctional electrode, comprising the following steps: Step 1: Take 5 mg of platinum-carbon catalyst and 25 mg of the modified conductive agent prepared in Example 1 into the reactor, and then add a mixture of 0.3 mL Nafion solution, 1.5 mL deionized water and 1.5 mL ethanol. Disperse the mixture by ultrasonication for 15 min to obtain ORR catalyst slurry. Step 2: Take 5 mg of ruthenium dioxide catalyst and 25 mg of the modified conductive agent prepared in Example 1 into the reactor, and then add a mixture of 0.3 mL Nafion solution, 1.5 mL deionized water and 1.5 mL ethanol. Disperse the mixture by ultrasonication for 15 min to obtain OER catalyst slurry. Step 3, as follows Figure 1 As shown in Figure B, a stainless steel sheet with a thickness of 0.5mm is cut into a size of 4cm×5.5cm using laser cutting technology, and an electrode area with a size of 3cm×3cm is cut out inside. The hollowed-out width is 2mm, the length is 25mm, and the partition width is 1mm, forming an interlaced electrode template. like Figure 1 As shown in Figure A, laser cutting technology is used to cut a 0.5mm thick stainless steel sheet into an OER electrode mask with a cutout width of 2mm, a length of 25mm, and a partition width of 3mm. like Figure 1 As shown in C, using laser cutting technology, a stainless steel sheet with a thickness of 0.5mm is cut into an ORR electrode mask with a cutout width of 2mm, a length of 25mm, and a partition width of 3mm. Step 4, such as Figure 2 As shown in Figure a, according to the battery size, a polypropylene film is cut into 4cm × 5.5cm pieces to serve as a substrate. This substrate is then fixed to an 80℃ constant-temperature heating plate. An interlaced electrode template is placed on the substrate, followed by an OER electrode mask. OER catalyst slurry is then sprayed onto the substrate using a spray gun to obtain an OER coupled electrode. The OER electrode mask is then replaced in situ with an ORR electrode mask, and ORR catalyst slurry is sprayed onto the substrate again to obtain an ORR coupled electrode. Finally, a composite electrode is fabricated on the same side surface of the substrate as shown in Figure a. Figure 2 The bifunctional electrode shown in b; A method for preparing a zinc-air battery includes the following steps: like Figure 3 As shown, a zinc plate with dimensions of 8mm×3mm×1mm is used as the negative electrode. After polishing its surface with 1000-grit sandpaper, it is cleaned with ethanol. The zinc plate is stacked in the following order: PTFE lower end plate 1, zinc plate electrode 2, silicone rubber sealing gasket 3, PTFE intermediate electrolytic cell 4, silicone rubber sealing gasket 5, bifunctional electrode 6, PTFE porous support plate 7, and PTFE hollow upper end plate 8. The plates are then tightened with screws. The electrolytic cell is filled with 1mol / L zinc sulfate solution as the electrolyte. Finally, the injection port is sealed with a silicone plug to obtain a zinc-air battery.

[0046] Comparative Example 1: A method for preparing a bifunctional electrode, comprising the following steps: Step 1: Take 5 mg of platinum carbon catalyst and 25 mg of carbon black powder into the reactor, then add a mixture of 0.3 mL Nafion solution, 1.5 mL deionized water and 1.5 mL ethanol, and ultrasonically disperse for 15 min to obtain ORR catalyst slurry; The second step involves placing 5 mg of ruthenium dioxide catalyst and 25 mg of carbon black powder into a reactor, then adding a mixture of 0.3 mL Nafion solution, 1.5 mL deionized water, and 1.5 mL ethanol, and ultrasonically dispersing for 15 min to obtain the OER catalyst slurry. Step 3, as follows Figure 1 As shown in Figure B, a stainless steel sheet with a thickness of 0.5mm is cut into a size of 4cm×5.5cm using laser cutting technology, and an electrode area with a size of 3cm×3cm is cut out inside. The hollowed-out width is 2mm, the length is 25mm, and the partition width is 1mm, forming an interlaced electrode template. like Figure 1 As shown in Figure A, laser cutting technology is used to cut a 0.5mm thick stainless steel sheet into an OER electrode mask with a cutout width of 2mm, a length of 25mm, and a partition width of 3mm. like Figure 1 As shown in C, using laser cutting technology, a stainless steel sheet with a thickness of 0.5mm is cut into an ORR electrode mask with a cutout width of 2mm, a length of 25mm, and a partition width of 3mm. Step 4, such as Figure 2 As shown in Figure a, according to the battery size, a polypropylene film is cut into 4cm × 5.5cm pieces to serve as a substrate. This substrate is then fixed to an 80℃ constant-temperature heating plate. An interlaced electrode template is placed on the substrate, followed by an OER electrode mask. OER catalyst slurry is then sprayed onto the substrate using a spray gun to obtain an OER coupled electrode. The OER electrode mask is then replaced in situ with an ORR electrode mask, and ORR catalyst slurry is sprayed onto the substrate again to obtain an ORR coupled electrode. Finally, a composite electrode is fabricated on the same side surface of the substrate as shown in Figure a. Figure 2 The bifunctional electrode shown in b; A method for preparing a zinc-air battery includes the following steps: A zinc plate with dimensions of 8mm×3mm×1mm was used as the negative electrode. After polishing its surface with 1000-grit sandpaper, it was cleaned with ethanol. The zinc plate electrode, the PTFE lower end plate, the silicone rubber sealing gasket, the PTFE intermediate electrolytic cell, the silicone rubber sealing gasket, the bifunctional electrode, the PTFE porous support plate, and the PTFE hollow upper end plate were stacked in sequence and then tightened with screws. The electrolytic cell was filled with a 1mol / L zinc sulfate solution and the injection port was then sealed with a silicone plug to obtain a zinc-air battery.

[0047] The difference between this comparative example and Example 4 is that the modified conductive agent is replaced with carbon black powder, while the rest of the preparation process is the same as in Example 4.

[0048] Comparative Example 2: A method for preparing a bifunctional electrode, comprising the following steps: Step 1: Take 5 mg of platinum carbon catalyst, 5 mg of ruthenium dioxide catalyst, and 50 mg of the modified conductive agent prepared in Example 1 into a reactor, and then add a mixture of 0.6 mL Nafion solution, 3.0 mL deionized water and 3.0 mL ethanol. Disperse the mixture by ultrasonication for 20 min to obtain a mixed catalyst slurry. The second step is to use laser cutting technology to cut a 0.5mm thick stainless steel sheet into 4cm×5.5cm pieces, and then cut out an electrode template with a 3cm×3cm hollow electrode area inside. The third step is to cut the polypropylene film into 4cm×5.5cm sizes according to the battery size, use it as a base, fix it on an 80℃ constant temperature heating plate, place the electrode template on the base, and then use a spray gun to spray the mixed catalyst slurry onto the base so that the catalyst evenly covers the entire electrode area to obtain a mixed electrode. A method for preparing a zinc-air battery includes the following steps: A zinc plate with dimensions of 8mm×3mm×1mm was used as the negative electrode. After polishing its surface with 1000-grit sandpaper, it was cleaned with ethanol. The zinc plate electrode, the PTFE lower end plate, the PTFE sealing gasket, the PTFE intermediate electrolytic cell, the PTFE sealing gasket, the mixed electrode, the PTFE porous support plate, and the PTFE hollow upper end plate were stacked in sequence and then tightened with screws. The electrolytic cell was filled with a 1mol / L zinc sulfate solution and the injection port was then sealed with a silicone plug to obtain a zinc-air battery.

[0049] The difference between this comparative example and Example 4 is that the ORR catalyst and the OER catalyst are physically mixed and then sprayed onto the substrate in one step to form a hybrid electrode. The staggered template and step-by-step spraying process are not used. The preparation process is the same as that of Example 4.

[0050] Comparative Example 3: A method for preparing a bifunctional electrode, comprising the following steps: Step 1: Take 5 mg of platinum carbon catalyst, 5 mg of ruthenium dioxide catalyst, and 50 mg of carbon black powder into a reactor, then add a mixture of 0.6 mL of Nafion solution, 3.0 mL of deionized water, and 3.0 mL of ethanol, and ultrasonically disperse for 20 min to obtain a mixed catalyst slurry; The second step is to use laser cutting technology to cut a 0.5mm thick stainless steel sheet into 4cm×5.5cm pieces, and then cut out an electrode template with a 3cm×3cm hollow electrode area inside. The third step is to cut the polypropylene film into 4cm×5.5cm sizes according to the battery size, use it as a base, fix it on an 80℃ constant temperature heating plate, place the electrode template on the base, and then use a spray gun to spray the mixed catalyst slurry onto the base so that the catalyst evenly covers the entire electrode area to obtain a mixed electrode. A method for preparing a zinc-air battery includes the following steps: A zinc plate with dimensions of 8mm×3mm×1mm was used as the negative electrode. After polishing its surface with 1000-grit sandpaper, it was cleaned with ethanol. The zinc plate electrode, the PTFE lower end plate, the PTFE sealing gasket, the PTFE intermediate electrolytic cell, the PTFE sealing gasket, the mixed electrode, the PTFE porous support plate, and the PTFE hollow upper end plate were stacked in sequence and then tightened with screws. The electrolytic cell was filled with a 1mol / L zinc sulfate solution and the injection port was then sealed with a silicone plug to obtain a zinc-air battery.

[0051] The difference between this comparative example and Example 4 is that the modified conductive agent is replaced with carbon black powder, and the ORR catalyst and OER catalyst are physically mixed and then sprayed onto the substrate in one go to form a hybrid electrode. The staggered template and step-by-step spraying process are not used. The preparation process is the same as that of Example 4.

[0052] Performance testing A. Charge-discharge cycle stability and structural stability testing: Using the Wuhan Landian Battery Testing System, charge-discharge cycle tests were performed on the battery samples prepared in Examples 2-4 and Comparative Examples 1-3 respectively: Examples 2-4 and Comparative Example 1: The positive terminal of the battery was connected to the ORR coupling electrode for discharge, and the negative terminal was connected to the zinc electrode. After discharging for 5 hours at a current density of 5 mA / cm², the battery was switched to the OER coupling electrode and charged for 5 hours at the same current density. The cycle was repeated until the battery discharge voltage dropped to 80% of the initial value. The number of cycles was recorded. Comparative Examples 2-3: Connect the positive terminal of the battery to the hybrid electrode for discharge, and connect the negative terminal to the zinc electrode. Discharge for 5 hours under the same conditions, and then charge for 5 hours on the same hybrid electrode. Repeat this cycle until the battery discharge voltage drops to 80% of the initial value. Record the number of cycles. After the cycle stability test was completed, the battery was disassembled, the air electrode was removed, gently rinsed with deionized water and dried, and the surface morphology of the zinc anode and catalyst layer was observed. The charge-discharge cycle stability and the morphology of the electrode catalyst layer after cycling are shown in Table 1.

[0053] Table 1: Statistical Table of Charge-Discharge Cycle Stability and Structural Stability Test Results

[0054] As shown in Table 1, Examples 2-4 achieved 300-500 cycles at 5 mA / cm², and the zinc anode and catalyst layer remained intact after cycling. Comparative Example 1 decreased to 150 cycles and dendrites and spalling appeared. Comparative Examples 2 and 3 decreased to 30-80 cycles, and dendrites and spalling intensified. This indicates that the modified conductive agent and the interlaced structure of the present invention significantly improved the cycling stability and structural integrity.

[0055] B. Interfacial Electrochemical Activity Detection: Using an electrochemical workstation, the electrode samples of Examples 2-4 and Comparative Examples 1-3 were used as working electrodes, Hg / HgO electrodes as reference electrodes, and platinum sheet electrodes as counter electrodes. The electrolyte was a mixed solution of 0.2 mol / L zinc acetate and 6 mol / L potassium hydroxide, assembled into a three-electrode system. Electrochemical impedance spectroscopy was performed at open circuit potential, with a frequency range of 100 kHz to 10 mHz and an amplitude of 5 mV. The electrochemical impedance of each group was recorded. Each sample was tested three times, and the average value was taken. The results of the interfacial electrochemical activity detection are shown in Table 2.

[0056] Table 2: Statistical Table of Interfacial Electrochemical Activity Detection Results

[0057] As can be seen from Table 2, the electrochemical impedance of Examples 2-4 is significantly lower than that of Comparative Examples 1-3, indicating that the modified conductive agent and the interlaced structure of the present invention effectively reduce the interfacial charge transfer impedance and improve the electrode reaction kinetics.

[0058] C. Electrolyte wettability test: Referring to GB / T 30693-2014, 2 μL of deionized water was dropped onto the surface of the electrode samples of Examples 2-4 and Comparative Examples 1-3 at room temperature. After the droplet stabilized, its static contact angle was measured. At least 5 different positions were selected for measurement for each sample, and the average value was taken. The electrolyte wettability test results are shown in Table 3.

[0059] Table 3: Statistical Table of Electrolyte Wettability Test Results

[0060] As can be seen from Table 3, the static contact angles of Examples 2-4 are smaller than those of Comparative Examples 1 and 3, and are comparable to those of Comparative Example 2, which also uses a modified conductive agent. This indicates that the modified conductive agent significantly improves the hydrophilicity of the electrode, which is beneficial for electrolyte wetting and ion transport.

[0061] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A method for preparing a bifunctional electrode, characterized in that, Includes the following steps: Step 1: Take ORR catalyst and modified conductive agent into reactor, then add a mixture of ionomer dispersion, deionized water and ethanol, and ultrasonically disperse for 15-20 minutes to obtain ORR catalyst slurry. The second step involves placing the OER catalyst and modified conductive agent into a reactor, then adding a mixture of ionomer dispersion, deionized water, and ethanol, and ultrasonically dispersing for 15-20 minutes to obtain the OER catalyst slurry. The third step involves fixing the substrate on a constant-temperature heating plate at 70-80℃, placing the electrode template on the substrate, placing the OER electrode mask with a hollow structure on the electrode template, and spraying it with OER catalyst slurry to form a partial coating layer on the surface of the electrode template that serves as the OER coupling electrode. After spraying, the OER electrode mask is removed, and the ORR electrode mask with another hollow structure is used to cover part of the coating layer. The ORR catalyst slurry is then sprayed to form a coating layer on the surface of the electrode template that serves as the ORR coupling electrode. Finally, a bifunctional electrode is formed on the same side surface of the substrate. The modified conductive agent is prepared by reacting 1H-furano[3,4-c]pyrrole-1,3(5H)-dione with taurine to obtain a modified pyrrole precursor, and then neutralizing the modified pyrrole precursor with sodium hydroxide to form a salt. The modified pyrrole is then subjected to in-situ polymerization on graphite oxide powder with pyrrole monomer and aniline monomer.

2. The method for preparing a bifunctional electrode according to claim 1, characterized in that, The ORR catalyst in the first step is a noble metal-based catalyst or a non-noble metal-based catalyst, the ionomer dispersion is a perfluorosulfonic acid cation exchange ionomer dispersion, the volume ratio of the ionomer dispersion, deionized water and ethanol in the mixture is 1~5:10:10, the mass ratio of the ORR catalyst to the modified conductive agent is 1:1~10, and the total mass of the ORR catalyst and the modified conductive agent in the ORR catalyst slurry and the solid-liquid ratio of the mixture is 5~20 mg / mL.

3. The method for preparing a bifunctional electrode according to claim 1, characterized in that, In the second step, the OER catalyst is a noble metal-based catalyst or a non-noble metal-based catalyst, the ionomer dispersion is a perfluorosulfonic acid cation exchange ionomer dispersion, the volume ratio of the ionomer dispersion, deionized water and ethanol in the mixture is 1~5:10:10, the mass ratio of the OER catalyst to the modified conductive agent is 1:1~10, and the total mass of the OER catalyst and the modified conductive agent in the OER catalyst slurry and the solid-liquid ratio of the mixture is 5~20 mg / mL.

4. The method for preparing a bifunctional electrode according to claim 1, characterized in that, The substrate in the third step is any one of polytetrafluoroethylene film, polyvinyl chloride film, polypropylene film, polyethylene film, hydrophobically modified nylon cloth, hydrophobically modified non-woven fabric, or hydrophobically modified fiber film. The electrode template is an electrode template with an interlaced arrangement structure, and the hollow structure is a comb-shaped hollow structure.

5. The method for preparing a bifunctional electrode according to claim 1, characterized in that, The preparation method of the modified conductive agent includes the following steps: S1. Add 1H-furano[3,4-c]pyrrole-1,3(5H)-dione and N,N-dimethylformamide to the reactor, stir until the solid is completely dissolved, then add taurine and triethylamine, and stir the reaction at room temperature for 8~12h to obtain the modified pyrrole precursor. S2. Add the modified pyrrole precursor and deionized water to the reactor, and slowly add sodium hydroxide aqueous solution dropwise under ice bath conditions of 0~5℃. When the pH of the reaction solution reaches 7~8, stop the dropwise addition, remove some of the deionized water by rotary evaporation, and then dry the product to obtain modified pyrrole. S3. Take graphite oxide powder, grind it, add it to deionized water, and ultrasonically disperse it for 1-2 hours to obtain a dispersion. Then add pyrrole monomer, aniline monomer, modified pyrrole and sodium polystyrene sulfonate to the dispersion. After ultrasonically dispersing at room temperature for 2-3 hours, transfer the system to an ice bath at 0-5℃. Adjust the pH of the system to 1-2 with p-toluenesulfonic acid. Then add ferric chloride hexahydrate aqueous solution dropwise while stirring. After the addition is complete, continue to stir and react under ice bath conditions for 20-24 hours to obtain the modified conductive agent.

6. The method for preparing a bifunctional electrode according to claim 5, characterized in that, In step S2, the molar concentration of the sodium hydroxide aqueous solution is 1~2 mol / L, and in step S3, the solid-liquid ratio of graphite oxide powder to deionized water is 1~2 mg / mL.

7. A bifunctional electrode, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 6.

8. The application of a bifunctional electrode according to claim 7 in a zinc-air battery, characterized in that, The bifunctional electrode is used as an air positive electrode in the preparation of zinc-air batteries.

9. The application of a bifunctional electrode in a zinc-air battery according to claim 8, characterized in that, The method for preparing the zinc-air battery includes the following steps: Using a zinc plate as the negative electrode, the surface of the plate is polished with sandpaper and then cleaned with ethanol. The plates are stacked in the following order: lower end plate, zinc plate electrode, sealing gasket, intermediate electrolytic cell, sealing gasket, dual-function electrode, porous support plate, and upper end plate. The plates are then tightened with screws. The electrolyte is then injected into the intermediate electrolytic cell, and the injection port is sealed with a silicone plug to obtain a zinc-air battery.

10. The application of a bifunctional electrode in a zinc-air battery according to claim 9, characterized in that, The lower end plate, the intermediate electrolytic cell, and the upper end plate are any one of polymethyl methacrylate, polyvinyl chloride, or polytetrafluoroethylene. The upper end plate has a completely hollow structure or a porous structure. The sealing gasket is a silicone rubber sealing gasket. The porous support plate is a polymethyl methacrylate porous plate or a polytetrafluoroethylene porous plate. The electrolyte is a potassium hydroxide alkaline electrolyte containing metal ions or a neutral electrolyte.

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