Core-shell fiber catalyst layer, preparation method and application thereof, membrane electrode and zinc-air flow battery

Abstract

The invention relates to the technical field of electrochemistry, in particular to a core-shell fiber catalyst layer, a preparation method and application thereof, a membrane electrode and a zinc-air flow battery. The catalyst layer comprises a core layer with polymer nanofibers and a metal-doped COP catalyst coated on the core layer; the catalyst layer has electrical conductivity. The core-shell fiber catalyst layer has the flexibility and pore structure of a nanofiber membrane, and the porous structure can accelerate substance transfer, so that active substances can be quickly diffused to active sites, and the reaction rate is further accelerated.

Description

Technical Field

[0001] The present invention relates to the field of electrochemistry technology, and particularly relates to a core-shell fiber catalyst layer, a preparation method and application thereof, a membrane electrode and a zinc-air flow battery. Background Art

[0002] The zinc-air flow battery has a relatively high theoretical energy density (1312 Wh kg -1 ), which is four times that of commercial lithium batteries (300 Wh kg -1 ). As the active material of the negative electrode, metallic zinc is very abundant in the earth's crust and relatively inexpensive. The zinc-air flow battery combines the advantages of traditional zinc-air batteries and redox flow batteries, and is an emerging and attractive energy storage technology. Due to the unique open system of the zinc-air flow battery, the positive active material is oxygen in the air, and the available air volume is infinite under normal working conditions, so it has a very high theoretical capacity. Secondly, due to the convection caused by the continuously flowing electrolyte, mass transfer is significantly enhanced. More importantly, the flowing electrolyte can effectively improve the long-term cycle stability, especially the stability of the zinc electrode. Therefore, this battery system can be used as a large-scale energy storage device.

[0003] Although the zinc-air flow battery has many advantages, the positive electrode polarization is serious, which requires an efficient bifunctional oxygen electrocatalyst to reduce the reaction overpotential. Due to the high catalytic activity and good stability of noble metal-based catalysts, the electrocatalytic reactions involved in the cathode of the zinc-air flow battery still rely on noble metal-based catalysts. However, their scarcity and high cost determine that they ultimately cannot achieve large-scale commercial applications. In recent years, efforts have been made to explore alternative, low-cost, and earth-abundant electrocatalysts to achieve renewable energy conversion.

[0004] However, most of the reported nanostructured catalysts are powdery or blocky and cannot be directly used as electrodes without the help of polymer binders such as Nafion. The addition of insulating binders inevitably increases the "dead volume" of the electrode material, hinders the electrolyte from entering the active sites, and increases the electrode resistance. At the same time, problems such as the uncontrollability of the microstructure, the burial of active sites, high conductive resistance, inhibition of mass transfer, and the shedding of catalysts in the bubble formation environment are difficult to solve. Therefore, the preparation of binder-free and self-supporting catalysts is an extremely effective strategy and is expected to promote its further commercialization. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problems of catalyst shedding and failure, few exposed active sites, and weak mass transfer ability existing in the prior art, and provide a core-shell fiber catalyst layer, a preparation method and application thereof, a membrane electrode and a zinc-air flow battery. The active sites are evenly exposed, and the electron and mass transfer abilities are strong.

[0006] To achieve the above object, a core-shell fiber catalytic layer is provided in the first aspect of the present invention. The catalytic layer includes a core layer having polymer nanofibers and a metal-doped COP catalyst coated on the core layer; the catalytic layer has conductivity.

[0007] In the second aspect of the present invention, a preparation method of the core-shell fiber catalytic layer of the present invention is provided. The preparation method includes: (1) electrospinning a spinning dispersion liquid containing a polymer, a metal source, and a conductive agent; (2) performing a hydrothermal reaction on the fiber membrane obtained by electrospinning and a catalytic dispersion liquid containing a reaction catalyst and a nitrogen ligand.

[0008] In the third aspect of the present invention, an application of the core-shell fiber catalytic layer of the present invention in a battery is provided.

[0009] In the fourth aspect of the present invention, a membrane electrode is provided. The membrane electrode includes a hydrophobic gas diffusion layer and a core-shell fiber catalytic layer; the core-shell fiber catalytic layer is the core-shell fiber catalytic layer described in the first aspect of the present invention.

[0010] In the fifth aspect of the present invention, a zinc-air flow battery is provided. The battery includes an anode, a membrane electrode as a cathode, an electrolyte, and an electrolytic solution. The membrane electrode is the membrane electrode described in the fourth aspect of the present invention.

[0011] Through the above technical solutions, the present invention has at least the following beneficial effects:

[0012] (1) The polymer nanofibers have a void structure. The core-shell fiber catalytic layer in the present invention has the flexibility and pore structure of a nanofiber membrane. The porous structure can accelerate mass transfer, facilitate the rapid diffusion of active substances to active sites, and thus accelerate the reaction rate.

[0013] (2) The existing catalytic layer cannot obtain a porous fiber network structure, which greatly affects mass transfer; while the new nanofiber catalytic layer has poor conductivity due to the addition of non-conductive polymers. Although it provides a mass transfer channel, electron transfer is hindered. However, the polymer nanofibers in the present invention as the inner layer and the unique core-shell structure of the outer layer catalysis can not only obtain a porous network structure, but also the catalytic layer has conductivity. Rapid electron transfer is carried out through the continuous catalytic shell layer of the outer layer and the special structure of the inner layer, solving the problems faced by the prior art. Description of the Drawings

[0014] Figure 1 It is the SEM characterization diagram of the fiber membrane and the core-shell fiber catalytic layer in Example 1;

[0015] Figure 2 It is the situation diagram of the core-shell fiber catalytic layer in the bent and stretched states in Example 1;

[0016] Figure 3 It is the charge-discharge curve graph of the zinc-air flow battery finally prepared and assembled with the core-shell fiber catalytic layer in Example 1. Detailed implementation manners

[0017] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0018] The first aspect of the present invention provides a core-shell fiber catalytic layer, which includes a core layer having polymer nanofibers and a metal-doped COP catalyst coated on the core layer; the catalytic layer has conductivity.

[0019] The catalytic layer in the present invention has a unique core-shell structure. The high aspect ratio of the polymer nanofibers and the topological structure of the COP material can maximize the exposure of active sites, and the catalytic layer has conductivity, which can construct a three-dimensional conductive network, solving the problems of buried active sites and poor conductivity of traditional electrodes.

[0020] According to a preferred implementation manner of the present invention, the metal-doped COP catalyst grows in-situ and coats on the polymer nanofibers. The foregoing implementation manner grows the catalyst COP in-situ on the surface of the nanofibers. The high aspect ratio of the core-shell structure nanofibers and the topological structure of the COP material can maximize the exposure of active sites and construct a three-dimensional conductive network. Solved the problems of buried active sites and poor conductivity of traditional electrodes.

[0021] According to a preferred implementation manner of the present invention, the metal-doped COP catalyst is a metal-doped non-pyrolytic COP catalyst.

[0022] The non-pyrolytic COP catalyst in the present invention refers to a COP catalyst formed by non-pyrolysis (i.e., below the temperature at which carbonization occurs in the existing art). The non-pyrolytic COP catalyst in the present invention is coated on the core layer having polymer nanofibers, retaining the flexible porous fiber structure, which is beneficial to the three-phase reaction interface and mass transfer, and improves the problems of catalyst shedding and buried active sites of the traditional catalytic layer.

[0023] According to a preferred implementation manner of the present invention, the core layer has a three-dimensional porous framework structure. The catalytic layer of the foregoing implementation manner can accelerate mass transfer, which is beneficial to the rapid diffusion of active substances to active sites, thereby accelerating the reaction rate. The core-shell fiber catalytic layer has excellent charge-discharge efficiency, stability and low resistance during use.

[0024] According to the present invention, as long as the object of the present invention can be achieved, the structure of the polymer nanofibers and the like are not particularly limited. Preferably, the fiber diameter of the polymer nanofibers is 100 - 700 nm, for example, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm or 700 nm, and preferably 300 - 500 nm.

[0025] According to the present invention, as long as the object of the present invention can be achieved, the thickness of the catalytic layer is not particularly limited. In a preferred embodiment, the thickness of the catalytic layer is 0.01 - 0.5 mm, for example, 0.01 mm, 0.03 mm, 0.05 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.3 mm, 0.4 mm or 0.5 mm, and preferably 0.1 - 0.3 mm.

[0026] In a preferred embodiment of the present invention, the thickness of the metal - doped COP catalyst is 2 - 20 nm, for example, 2 nm, 3 nm, 5 nm, 8 nm, 10 nm, 12 nm, 15 nm, 18 nm, 20 nm, and preferably 5 - 15 nm.

[0027] The polymer nanofibers in the present invention have a high specific surface area and a high porosity. Preferably, the porosity of the catalytic layer is 70 - 90%, preferably 75 - 85%; preferably, the specific surface area of the catalytic layer is 20 - 60 m 2 / g, preferably 25 - 40 m 2 / g. The active sites of the catalytic layer in the foregoing embodiments are uniformly exposed, and the electron and mass transfer capabilities are strong.

[0028] In a preferred embodiment of the present invention, the pore size range of the catalytic layer is 1 - 100 nm. The active sites of the catalytic layer in the foregoing embodiments are uniformly exposed, and the electron and mass transfer capabilities are strong.

[0029] The catalytic layer of the present invention is flexible and cut - table. In a preferred embodiment of the present invention, the elongation at break of the catalytic layer is 15% - 30%.

[0030] According to the present invention, the COP material is a novel porous material with a covalently - bonded, periodically - conjugated framework structure that introduces well - defined oxygen reduction sites such as metal active centers coordinated with nitrogen and electronegative heteroatoms into COP. That is, the metal - doped COP catalyst in the present invention is constructed by including metal active centers coordinated with nitrogen. Among them, the metal active centers coordinated with nitrogen can be provided by a metal source capable of providing metal atoms and a nitrogen - containing ligand.

[0031] According to a preferred embodiment of the present invention, in the metal-doped COP catalyst, the content of N is 5 at% - 15 at%, the content of the metal is 0.3 at% - 1 at%, the content of F is 0 at% - 20 at%, the content of O is 5 at% - 15 at%, and the balance is the content of C. The active sites of the catalytic layer in the foregoing embodiment are evenly exposed, and the electron and mass transfer capabilities are strong.

[0032] According to a more preferred embodiment of the present invention, in the metal-doped COP catalyst, the content of N is 5 at% - 10 at%, the content of the metal is 0.5 at% - 1 at%, the content of F is 10 at% - 15 at%, the content of O is 10 at% - 15 at%, and the balance is the content of C. The catalytic layer in the foregoing embodiment has lower conductive resistance and service life.

[0033] In the present invention, the elements and their contents in the metal-doped COP catalyst can be obtained by XPS testing.

[0034] According to a preferred embodiment of the present invention, the nitrogen-containing ligand for constructing the conjugated framework of the metal-doped COP catalyst is selected from one or more of 2,3,5,6-tetrafluoroterephthalonitrile, 3,4,5,6-tetrafluorophthalonitrile, 1,2,4,5-tetracyanobenzene, phthalonitrile, cyclohexene-1-carbonitrile, and cyclohexanecarbonitrile. The active sites of the catalytic layer in the foregoing embodiment are evenly exposed, and the electron and mass transfer capabilities are strong.

[0035] According to a particularly preferred embodiment of the present invention, the nitrogen-containing ligand for constructing the conjugated framework of the metal-doped COP catalyst is selected from 2,3,5,6-tetrafluoroterephthalonitrile and / or 3,4,5,6-tetrafluorophthalonitrile.

[0036] According to the present invention, in order to make the catalytic layer of the present invention conductive, preferably, the catalytic layer contains a conductive agent.

[0037] According to a more preferred embodiment of the present invention, the conductive agent is distributed in the core layer. The unique core-shell structure of the inner layer conducting electricity and the outer layer catalyzing in the catalytic layer in the foregoing embodiment can not only obtain a porous network structure, but also perform rapid electron transfer through the continuous catalytic shell layer on the outer layer and the conductive agent filled in the inner layer, effectively solving the defect that although the mass transfer channel is provided in the prior art, the electron transfer is hindered. The core-shell fiber catalytic layer has excellent charge-discharge efficiency, stability, and low resistance during use.

[0038] According to the present invention, as long as the object of the present invention can be achieved, the type of the conductive agent is not particularly limited and can be a conventional conductive agent in the art. In a preferred embodiment, the conductive agent is at least one of graphite, graphene, polyaniline, copper powder, nickel powder, carbon black, and carbon nanotubes.

[0039] According to a more preferred embodiment of the present invention, the conductive agent is at least one of graphite, carbon black and graphene.

[0040] According to a preferred embodiment of the present invention, the shape of the conductive agent is at least one of spherical, flaky and tubular. The catalytic layer of the foregoing embodiment has higher catalytic activity and conductivity.

[0041] According to a more preferred embodiment of the present invention, the shape of the conductive agent is spherical and / or flaky. The catalytic layer of the foregoing embodiment has better catalytic activity and conductivity.

[0042] According to the present invention, as long as the object of the present invention can be achieved, the size of the conductive agent is not particularly limited. The particle size of the conductive agent is 10 - 300 nm, such as 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 82 nm, 90 nm, 106 nm, 120 nm, 180 nm, 200 nm, 280 nm, 300 nm, and preferably 20 - 120 nm.

[0043] According to the present invention, as long as the object of the present invention can be achieved, the content of the conductive agent is not particularly limited. In a preferred embodiment, the content of the conductive agent in the polymer nanofibers is 3 - 30 wt%, such as 3 wt%, 8 wt%, 10 wt%, 15 wt%, 18 wt%, 20 wt%, 25 wt%, 30 wt%, and preferably 8 - 25 wt%.

[0044] Among them, the content in the polymer nanofibers is calculated from the addition amount of the corresponding raw materials.

[0045] According to the present invention, as long as the object of the present invention can be achieved, the specific type of the metal is not particularly limited. In a preferred embodiment, the metal is selected from at least one of Group VIII, Group IB and Group VIIB.

[0046] According to a preferred embodiment of the present invention, the metal is selected from at least one of iron, cobalt, copper and manganese.

[0047] In the present invention, iron and cobalt are used as metals to exemplify the advantages of the present invention, but the present invention is not limited thereto.

[0048] According to the present invention, the polymer nanofibers are obtained by electrospinning of a high molecular polymer. In order to make the catalytic layer have better water isolation performance during use, in one embodiment, the content of the water-soluble high molecular polymer in the high molecular polymer of the core layer of the polymer fiber is not higher than 40 wt%, such as 0 wt%, 5 wt%, 8 wt%, 10 wt%, 15 wt%, 20 wt%, 30 wt%, 40 wt%.

[0049] According to the present invention, as long as the object of the present invention can be achieved, there is no special limitation on the type of the high molecular polymer. It is preferable to select a polymer that is conducive to spinning to form corresponding polymer nanofibers. In a preferred embodiment, the high molecular polymer in the core layer of the polymer fiber is selected from nitrogen-containing high molecular polymers and / or non-nitrogen-containing high molecular polymers. The catalytic layer in the foregoing embodiment better retains a flexible porous fiber structure, which is conducive to the three-phase reaction interface and mass transfer, and solves the problems of catalyst shedding and active site burial in the traditional catalytic layer.

[0050] According to a preferred embodiment of the present invention, the number-average molecular weight of the high molecular polymer in the core layer of the polymer fiber is 60,000-1,500,000, such as 60,000, 150,000, 200,000, 300,000, 500,000, 650,000, 800,000, 900,000, 1,000,000, 1,200,000, 1,500,000.

[0051] According to a more preferred embodiment of the present invention, the high molecular polymer is selected from nitrogen-containing high molecular polymers and non-nitrogen-containing high molecular polymers. Preferably, the mass ratio of the nitrogen-containing high molecular polymer to the non-nitrogen-containing high molecular polymer is 1:(1-6), such as 1:1, 1:2, 1:3, 1:4, 1:5, 1:6. The catalytic layer in the foregoing embodiment has a unique core-shell structure with inner-layer conductivity and outer-layer catalysis, which can not only obtain a porous network structure, but also perform rapid electron transfer through the continuous catalytic shell layer on the outer layer and the conductive agent filled in the inner layer. The core-shell fiber catalytic layer has excellent charge-discharge efficiency, stability and low resistance during use.

[0052] According to the present invention, the nitrogen-containing high molecular polymer in the present invention refers to a polymer containing nitrogen element in its molecule. As long as the object of the present invention can be achieved, there is no special limitation on the specific type of the nitrogen-containing high molecular polymer. In a preferred embodiment, the nitrogen-containing high molecular polymer is selected from at least one of polyacrylonitrile, polyimide, polyvinylpyrrolidone, polyethyleneimine and polyetherimide. Only several nitrogen-containing high molecular polymers are listed in the specific embodiments and examples of the present invention, but it should not be construed as a limitation to the present invention.

[0053] According to a preferred embodiment of the present invention, the nitrogen content of the nitrogen-containing high molecular polymer is 5wt%-35wt%, such as 5wt%, 10wt%, 12wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, and preferably 10wt%-30wt%.

[0054] According to the present invention, the non-nitrogen-containing polymer in the present invention refers to a polymer that does not contain nitrogen elements in its molecules. As long as the object of the present invention can be achieved, the specific types of non-nitrogen-containing polymers are not particularly limited. In a preferred embodiment, the non-nitrogen-containing polymer is selected from at least one of polytetrafluoroethylene, polyvinylidene chloride, polyvinylidene fluoride, polystyrene, polyvinyl alcohol, polyethylene oxide, and polyacrylic acid. Specific embodiments and examples of the present invention exemplify several non-nitrogen-containing polymers, but should not be construed as a limitation to the present invention.

[0055] According to the present invention, as long as the object of the present invention can be achieved, the preparation method of the core-shell fiber catalyst layer in the present invention is not particularly limited. In order to enable the nitrogen-containing ligand to better undergo a Schiff base reaction polymerization to form a COP configuration during the hydrothermal reaction, it is preferred that the nitrogen-containing ligand reacts under the action of an organic catalyst. Preferably, the second aspect of the present invention provides a preparation method of the core-shell fiber catalyst layer of the present invention, and the preparation method includes: (1) spinning a spinning dispersion liquid containing a polymer, a metal source, and a conductive agent;

[0056] (2) performing a hydrothermal reaction on the fiber membrane obtained by spinning with a catalytic dispersion liquid containing a reaction catalyst and a nitrogen-containing ligand.

[0057] Traditional membrane coating methods (CCM, catalyst coated membrane) and substrate coating methods (CCS, catalyst-coated substrate) cannot obtain a porous fiber network structure, which greatly affects mass transfer; while the new nanofiber catalyst layer has poor conductivity due to the addition of non-conductive polymers. Although it provides a mass transfer channel, electron transfer is hindered. In the present invention, the spinning technology can obtain a porous structure, and the loading method of contacting the fiber membrane obtained by spinning with a catalytic dispersion liquid containing a reaction catalyst and a nitrogen-containing ligand finally obtains a unique core-shell structure with inner layer conductivity and outer layer catalysis and a conductive catalyst layer, which can not only obtain a porous network structure, but also retain the flexibility and pore structure of the nanofiber membrane, can accelerate mass transfer, is beneficial to the rapid diffusion of active substances to active sites, and thus accelerates the reaction rate; in addition, the preparation process of the preparation method of the present invention is simple, has strong scalability, and low cost and energy consumption. Traditional preparation methods of catalyst layers need to first prepare catalysts, generally by high-temperature carbonization, with high energy consumption; subsequently, the catalyst needs to be loaded onto the carbon paper substrate by spraying and scraping methods, and the process is relatively complex.

[0058] According to a preferred embodiment of the present invention, the conditions of the hydrothermal reaction include: the temperature is 60°C - 200°C, preferably 120°C - 180°C. The catalyst layer prepared by the foregoing embodiment can perform rapid electron transfer.

[0059] According to the present invention, as long as the object of the present invention can be achieved, the contact time is not particularly limited. Preferably, the contact conditions include: the time is 1 - 24 h, preferably 4 - 12 h.

[0060] According to a preferred embodiment of the present invention, the spinning is electrospinning.

[0061] According to the present invention, there are no special limitations on the equipment and process conditions for electrospinning in the present invention. A conventional electrospinning machine in the art can be used, and as long as the process conditions can enable the spinning to form polymer nanofibers, the electrospinning conditions will be simply described below.

[0062] According to a preferred embodiment of the present invention, the conditions for electrospinning include: the temperature is 25°C - 50°C, preferably 30°C - 40°C, such as 30°C, 35°C, 38°C, 40°C, and more preferably 38°C.

[0063] According to a preferred embodiment of the present invention, the conditions for electrospinning include: the humidity is 25% - 60%, preferably 30% - 50%, such as 35%, 38%, 40%, 45%, 50%, and more preferably 35%.

[0064] According to a preferred embodiment of the present invention, the conditions for electrospinning include: the voltage is 13 kV - 19 kV, such as 13 kV, 15 kV, 17 kV, 18 kV, 19 kV, and preferably 17 kV - 18 kV.

[0065] According to a preferred embodiment of the present invention, the conditions for electrospinning include: the supply rate of the spinning dispersion is 0.2 ml / h - 0.9 ml / h.

[0066] According to the present invention, those skilled in the art know that when spinning, during electrospinning, the polymer nanofibers obtained by spinning are collected by the roller of the electrospinning machine, and its collection speed can be selected as needed by adjusting the rotation speed of the roller collection to 150 - 300 rpm.

[0067] According to the present invention, those skilled in the art know that the nanofiber membrane precursor obtained after spinning may still contain some solvents, and the solvents and other components can be removed by drying treatment, that is, drying is carried out after spinning to obtain a fiber membrane, preferably at 50°C - 200°C for 60 min - 480 min; the drying can be carried out under normal pressure or under vacuum conditions.

[0068] This preparation method further includes carrying out hydrothermal reaction, washing, and drying.

[0069] According to the present invention, the washing method is not particularly limited as long as it can wash away some solvent impurities. For example, washing can be carried out successively with dilute hydrochloric acid, ethanol, and / or water. The drying conditions are not particularly limited, and those skilled in the art can select according to needs. For example, drying can be carried out at 50°C - 200°C for 10 min - 60 min.

[0070] According to the present invention, in order to enable the nitrogen-containing ligand to better undergo the Schiff base reaction to polymerize into COP, the reaction catalyst is generally a compound that can promote the Schiff base reaction of the heterocyclic organic compound containing the nitrogen-containing ligand to polymerize into COP. In a preferred embodiment, the reaction catalyst is selected from at least one of 1,8-diazabicyclo[5,4,0]undec-7-ene, 2,2-dimethyl-1,3-dioxepane, and 1,4,7-triazacyclononane.

[0071] According to the present invention, as long as the object of the present invention can be achieved, the type of the metal source is not particularly limited. Preferably, in one embodiment, the metal source is a metal salt corresponding to the metal.

[0072] In a more preferred embodiment of the present invention, the metal salt is an anhydrous metal salt. The foregoing embodiment can better form a catalytic shell layer.

[0073] In the present invention, the anhydrous metal salt is generally a chloride salt, nitrate salt, or sulfate salt corresponding to the metal, etc.

[0074] According to the present invention, as is known to those skilled in the art, spinning generally involves dissolving a polymer in a solvent, and the spinning dispersion contains a solvent. As long as the object of the present invention can be achieved, the type of this solvent is not particularly limited. Preferably, the solvent in the spinning dispersion is selected from at least one of acetone, N,N-dimethylformamide, methanol, dichloroethane, dichloromethane, and tetrahydrofuran.

[0075] According to the present invention, the catalytic dispersion in the present invention refers to a dispersion formed by components such as a reaction catalyst and a nitrogen-containing ligand dispersed in a corresponding solvent. The specific type of this solvent is not particularly limited, and an inert solvent can be used. Preferably, the solvent in the catalytic dispersion is selected from at least one of ethylene glycol, propylene glycol, water, ethanol, N,N-dimethylformamide, propylene glycol, and tetrahydrofuran.

[0076] According to the present invention, the mass ratio of the polymer to the metal source is not particularly limited. Preferably, the mass ratio of the polymer to the metal source is 1 - 10:1, for example, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, and preferably 2 - 8:1.

[0077] According to the present invention, as long as the object of the present invention can be achieved, the amount of the conductive agent is not particularly limited. Preferably, the mass ratio of the polymer to the conductive agent is 1-10:1, for example, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, and preferably 3-8:1.

[0078] According to a preferred embodiment of the present invention, the mass ratio of the nitrogen-containing ligand to the reaction catalyst is 1:0.5-1.0, for example, 1:0.5, 1:0.8, 1:1.0.

[0079] According to a preferred embodiment of the present invention, the content of the polymer in the spinning dispersion is 5wt%-85wt%, for example, 5wt%, 10wt%, 15wt%, 20wt%, 30wt%, 45wt%, 50wt%, 60wt%, 70wt%, 80wt%, 85wt%, and preferably 10wt%-30wt%.

[0080] According to a preferred embodiment of the present invention, in the catalytic dispersion, the mass fraction of the nitrogen-containing ligand and the reaction catalyst as solutes is 0.5wt%-5wt%, for example, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 3.5wt%, 4.5wt%, 5wt%, and preferably 1wt%-3wt%.

[0081] In the present invention, the amounts of the fiber membrane and the catalytic dispersion are not particularly limited. Preferably, the mass ratio of the fiber membrane to the catalytic dispersion is (0.005-0.05):1, for example, 0.005:1, 0.008:1, 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1.

[0082] The third aspect of the present invention provides an application of the core-shell fiber catalytic layer described in the present invention in a battery.

[0083] In the present invention, when the core-shell fiber catalytic layer in the present invention is used in a battery, it has a fast electron transfer ability, which is beneficial to the rapid diffusion of the active substance to the active sites, thereby accelerating the reaction rate.

[0084] The fourth aspect of the present invention provides a membrane electrode, which includes a hydrophobic gas diffusion layer and a core-shell fiber catalytic layer; the core-shell fiber catalytic layer is the core-shell fiber catalytic layer described in the first aspect of the present invention.

[0085] In the present invention, when the core-shell fiber catalytic layer in the present invention is used in a membrane electrode, the membrane electrode has a fast electron transfer ability and catalytic stability, and has excellent charge and discharge efficiency and stability as well as low resistance.

[0086] The hydrophobic gas diffusion layer in the present invention is a conventional article in the art, such as hydrophobic carbon paper, and the present invention will not elaborate on this too much.

[0087] The membrane electrode in the present invention can be prepared by a conventional method in the art. For example, after cutting the core-shell fiber catalytic layer and the hydrophobic gas diffusion layer (hydrophobic carbon paper) into the required sizes, hot pressing is carried out under certain pressure and temperature. For example, hot pressing is carried out for 5 - 10 min under the conditions of a pressure of 0.1 - 0.3 MPa and a temperature of 30 - 90 °C.

[0088] The fifth aspect of the present invention provides a zinc-air flow battery, which includes an anode, a membrane electrode as the cathode, and an electrolyte, and the membrane electrode is the membrane electrode described in the fourth aspect of the present invention.

[0089] The zinc-air flow battery in the present invention has an excellent electron transfer rate during use, can accelerate mass transfer, is beneficial to the rapid diffusion of oxygen and active substances to the active sites, thereby accelerating the reaction rate, and at the same time has excellent cycle stability during long-term use.

[0090] According to the present invention, the material of the anode in the zinc-air flow battery is metallic zinc.

[0091] According to the present invention, the electrolyte in the zinc-air flow battery is an aqueous solution of 4 - 10 M KOH + 0.1 - 0.3 M ZnO.

[0092] According to the present invention, the flow rate of the electrolyte in the zinc-air flow battery is 10 - 60 ml / min.

[0093] The present invention will be described in detail below through examples. In the following examples,

[0094] The porosity of the catalytic layer is tested by the mass method: First, measure the total weight of the gas filled inside the material, then expel the internal gas by means such as vacuum drying or heating, and then measure the weight of the material after drying or heating. The formula for calculating the porosity is: (1 - dry weight / total weight) × 100%.

[0095] The elongation at break is obtained by a tensile test.

[0096] The pore size and specific surface area of the catalytic layer are obtained by BET testing.

[0097] Unless otherwise specified, all raw materials can be obtained commercially.

[0098] Example 1

[0099] Preparation of polymer nanofibers:

[0100] ①Disperse 200 mg of polyvinylidene fluoride (number-average molecular weight of 1 million), 50 mg of polyvinylpyrrolidone (nitrogen content 12.6 wt%, number-average molecular weight of 1.3 million), and 50 mg of conductive carbon black (particle size 40 nm, spherical shape) in 2 g of N,N-dimethylformamide, ultrasonicate uniformly and stir for 3 h to obtain a homogeneous solution. Then add 40 mg of metal salt cobalt chloride to the above solution, continuously stir for 6 h, control the temperature at 50 °C, and keep the rotation speed at 500 r / min to obtain a homogeneous spinning solution;

[0101] ②Transfer the spinning solution to a syringe, fix it on an electrospinning machine, set the spinning environment temperature at 30 °C, humidity control at 45%, spinning voltage at 18 kV, spinning solution supply rate at 0.6 ml / h. Wrap the cut aluminum foil around the roller, close the protection door of the spinning box body, turn on the high-voltage power supply, carry out electrospinning, adjust the roller collection rotation speed to 250 rpm until the spinning solution is consumed; Remove the receiver, collect the polymer fiber cloth, and place it in a vacuum oven at 60 °C for drying to constant weight to obtain polymer nanofibers;

[0102] Preparation of the fiber catalytic layer:

[0103] ①Disperse 20 mg of 1,2,4,5-tetracyanobenzene in 1.5 g of ethylene glycol, ultrasonicate to dissolve to obtain a transparent solution, drop in 12 mg of 1,8-diazabicyclo[5,4,0]undec-7-ene and stir evenly to obtain a catalytic reaction feed liquid;

[0104] ②Take 150 mg of the cut polymer nanofibers and put them into a reaction kettle containing 15 g of the catalytic reaction feed liquid;

[0105] ③Place the reaction kettle in a vacuum drying oven, set the temperature at 160 °C, and carry out hydrothermal reaction for 8 h;

[0106] ④Take out the reacted polymer nanofibers from the reaction kettle, wash them successively with dilute hydrochloric acid, deionized water, and ethanol, and then put them in an oven at 60 °C for drying to obtain the fiber catalytic layer.

[0107] The SEM characterization of the polymer nanofibers is as shown in Figure 1 a in; The SEM characterization of the fiber catalytic layer is as shown in Figure 1 b in; From Figure 1 it can be obtained that the surface of the nanofibers in the polymer nanofibers is relatively smooth, the average fiber diameter is 300 nm, and it has a three-dimensional porous framework structure with random staggered distribution; After the hydrothermal reaction, a core-shell structure is formed. The surface of the polymer nanofibers in the fiber catalytic layer is covered with a catalytic layer (metal cobalt-doped COP catalyst), and this catalyst is in a flaky structure and uniformly wraps on the surface of the polymer nanofibers, proving its core-shell fiber structure.

[0108] The situation of the core-shell fiber catalytic layer under bending and stretching is as Figure 2 shown, where a is the situation of the core-shell fiber catalytic layer under the bending state, and b is the situation of the core-shell fiber catalytic layer under the stretching state.

[0109] The thickness of the catalytic layer is 0.3 mm, and the thickness of the metal cobalt-doped COP catalyst is 5 nm;

[0110] Obtained by XPS test, in the metal cobalt-doped COP catalyst using the nitrogen-containing organic ligand (1,2,4,5-tetracyanobenzene): the content of N is 10 at%, the content of C is 75 at%, the content of metal cobalt is 1 at%, and the content of O is 14 at%.

[0111] The porosity of the fiber catalytic layer is 76%, the specific surface area is 30.5 m 2 / g, the pore size range is 35 - 90 nm, and the elongation at break of the fiber catalytic layer is 28%.

[0112] Example 2

[0113] Preparation of polymer nanofibers:

[0114] ① Disperse 150 mg of polystyrene (number average molecular weight of 100,000), 120 mg of polyacrylonitrile (nitrogen content of 26.4 wt%, number average molecular weight of 1.3 million), and 50 mg of conductive agent carbon black (particle size of 40 nm, spherical shape) in 2 g of a solvent (tetrahydrofuran and N,N-dimethylformamide with a volume ratio of 1:4), ultrasonically homogenize and stir for 3 h to obtain a homogeneous solution, then add 40 mg of metal salt ferric sulfate to the above solution, continuously stir for 6 h, control the temperature at 50 °C, and maintain the rotation speed at 500 r / min to obtain a homogeneous spinning solution;

[0115] ② Transfer the spinning solution to a syringe, fix it on an electrospinning machine, set the spinning environment temperature at 40 °C, the humidity at 45%, the spinning voltage at 17 kV, the spinning solution supply speed at 0.6 ml / h, wrap the cut aluminum foil on the roller, close the protection door of the spinning box body, turn on the high-voltage power supply, carry out electrospinning, adjust the roller collection rotation speed to 250 rpm until the spinning solution is consumed; remove the receiver, collect the polymer fiber cloth, and place it in a vacuum oven at 60 °C for drying to constant weight to obtain polymer nanofibers;

[0116] Preparation of the fiber catalytic layer:

[0117] ① Disperse 25 mg of 2,3,5,6-tetrafluoroterephthalonitrile in 1.5 g of ethylene glycol, ultrasonically dissolve to obtain a transparent solution, and drop in 15 mg of 2,2-dimethyl-1,3-dioxepan-5-ene and stir evenly to obtain a catalytic reaction feed liquid;

[0118] ② Put 100 mg of the cut polymer nanofibers into a reaction kettle containing 12 g of the catalytic reaction liquid;

[0119] ③ Place the reaction kettle in a vacuum drying oven, set the temperature to 160 °C, and carry out hydrothermal reaction for 8 h;

[0120] ④ Take out the reacted polymer nanofibers from the reaction kettle, wash them successively with dilute hydrochloric acid, deionized water and ethanol, and then put them into an oven at 60 °C to dry to obtain a fiber catalytic layer.

[0121] The SEM characterization of the polymer nanofibers and the fiber catalytic layer is Figure 1 similar. It can be obtained that the surface of the nanofibers in the polymer nanofibers is relatively smooth, the average fiber diameter is 400 nm, and it has a three-dimensional porous framework structure with random staggered distribution; after hydrothermal reaction, a core-shell structure is formed, and the surface of the polymer nanofibers in the fiber catalytic layer is covered with a catalytic layer (metal iron-doped COP catalyst), and this catalyst is in a flake structure and is evenly wrapped on the surface of the polymer nanofibers, proving its core-shell fiber structure.

[0122] The thickness of the catalytic layer is 0.2 mm, and the thickness of the metal iron-doped COP catalyst is 10 nm;

[0123] Obtained by XPS test, in the metal iron-doped COP catalyst using a nitrogen-containing organic ligand (2,3,5,6-tetrafluoroterephthalonitrile): the content of N is 5 at%, the content of F is 15.2%, the content of C is 67 at%, the content of metal iron is 0.8 at%, and the content of O is 12 at%.

[0124] The porosity of the fiber catalytic layer is 74%, the specific surface area is 28.3 m 2 / g, and the pore size range is 30 - 80 nm.

[0125] The elongation at break of the fiber catalytic layer is 26%.

[0126] Example 3

[0127] Preparation of polymer nanofibers:

[0128] ① Disperse 300 mg of polyvinylidene fluoride (number-average molecular weight of 600,000), 50 mg of polyimide (nitrogen content of 4.5 wt%, number-average molecular weight of 100,000), and 50 mg of graphene (particle size of 50 nm, shape of flakes) in 2 g of N,N-dimethylformamide, ultrasonically homogenize and stir for 3 h to obtain a homogeneous solution, then add 50 mg of metal salt cobalt nitrate to the above solution, continuously stir for 6 h, control the temperature at 50 °C, and keep the rotation speed at 500 r / min to obtain a homogeneous spinning solution;

[0129] ② Transfer the spinning solution into a syringe, fix it on an electrospinning machine, set the spinning environment temperature at 30 °C, humidity controlled at 45%, spinning voltage at 18 kV, spinning solution supply rate at 0.6 ml / h, wrap the cut aluminum foil around the roller, close the protective door of the spinning box body, turn on the high-voltage power supply, conduct electrospinning, adjust the roller collection rotation speed to 250 rpm until the spinning solution is consumed; remove the receiver, collect the polymer fiber cloth, place it in a vacuum oven at 60 °C for drying to constant weight to obtain polymer nanofibers;

[0130] Preparation of the fiber catalytic layer:

[0131] ① Disperse 25 mg of 3,4,5,6-tetrafluorophthalonitrile in 1.4 g of propylene glycol, dissolve it by ultrasonic treatment to obtain a transparent solution, drop in 14 mg of 1,8-diazabicyclo[5,4,0]undec-7-ene and stir evenly to obtain a catalytic reaction feed liquid;

[0132] ② Take 150 mg of the cut polymer nanofibers and put them into a reaction kettle containing 15 g of the catalytic reaction feed liquid;

[0133] ③ Place the reaction kettle in a vacuum drying oven, set the temperature at 150 °C, and continuously react for 8 h for hydrothermal reaction;

[0134] ④ Take out the reacted polymer nanofibers from the reaction kettle, wash them successively with dilute hydrochloric acid, deionized water and ethanol, and then put them into an oven at 60 °C for drying to obtain the fiber catalytic layer.

[0135] SEM characterization of the polymer nanofibers and the fiber catalytic layer is Figure 1 similar. It can be obtained that the surface of the nanofibers in the polymer nanofibers is relatively smooth, the average fiber diameter is 365 nm, and it has a three-dimensional porous framework structure with random interlaced distribution; after hydrothermal reaction, a core-shell structure is formed. The surface of the polymer nanofibers in the fiber catalytic layer is covered with a catalytic layer (metal cobalt-doped COP catalyst). This catalyst is in a flake structure and is evenly wrapped on the surface of the polymer nanofibers, proving its core-shell fiber structure.

[0136] The thickness of the catalytic layer is 0.15 mm, and the thickness of the metal cobalt-doped COP catalyst is 7 nm;

[0137] Obtained by XPS test, in the metal cobalt-doped COP catalyst using a nitrogen-containing organic ligand (3,4,5,6-tetrafluorophthalonitrile): the content of N is 6.8 at%, the content of F is 14.2%, the content of C is 63.5 at%, the content of metallic iron is 1 at%, and the content of O is 14.5 at%.

[0138] The porosity of the fiber catalytic layer is 77%, and the specific surface area is 29.4 m2 / g, with a pore size range of 50 - 100 nm.

[0139] The elongation at break of the fiber catalytic layer is 24%.

[0140] Example 4

[0141] Preparation of polymer nanofibers:

[0142] 270 mg of polyacrylonitrile (nitrogen content 26.4 wt%, number average molecular weight 1.3 million), 50 mg of conductive agent carbon black (particle size 40 nm, spherical shape) were dispersed in 2 g of a solvent (tetrahydrofuran and N,N-dimethylformamide with a volume ratio of 1:4), ultrasonicated uniformly and stirred for 3 h to obtain a uniform solution. Then 40 mg of metal salt ferric sulfate was added to the above solution, and stirring was continued for 6 h, the temperature was controlled at 50 °C, and the rotation speed was maintained at 500 r / min to obtain a uniform spinning solution;

[0143] ② Transfer the spinning solution to a syringe, fix it on an electrospinning machine, set the spinning environment temperature to 40 °C, humidity controlled at 45%, spinning voltage 17 kV, spinning solution supply rate 0.6 ml / h. Wrap the cut aluminum foil around the roller, close the protection door of the spinning box body, turn on the high-voltage power supply, carry out electrospinning, adjust the roller collection rotation speed to 250 rpm until the spinning solution is consumed; remove the receiver, collect the polymer fiber cloth, and place it in a vacuum oven at 60 °C for drying to constant weight to obtain polymer nanofibers;

[0144] Preparation of the fiber catalytic layer:

[0145] ① Disperse 25 mg of 2,3,5,6-tetrafluoroterephthalonitrile in 1.5 g of ethylene glycol, ultrasonicate to dissolve to obtain a transparent solution, and drop in 15 mg of 2,2-dimethyl-1,3-dioxepan-5-ene and stir evenly to obtain a catalytic reaction feed liquid;

[0146] ② Take 100 mg of the cut polymer nanofibers and put them into a reaction kettle containing 12 g of the catalytic reaction feed liquid;

[0147] ③ Place the reaction kettle in a vacuum drying oven, set the temperature to 160 °C, and carry out hydrothermal reaction for 8 h;

[0148] ④ Take out the reacted polymer nanofibers from the reaction kettle and wash them successively with dilute hydrochloric acid, deionized water and ethanol, and then put them in an oven at 60 °C for drying to obtain the fiber catalytic layer.

[0149] SEM characterization of polymer nanofibers and the fiber catalytic layer and Figure 1Similarly, it can be obtained that the surface of the nanofibers in the polymer nanofibers is relatively smooth, the average fiber diameter is 540 nm, and it has a three-dimensional porous framework structure with a randomly interlaced distribution; after the hydrothermal reaction, a core-shell structure is formed, and the surface of the polymer nanofibers in the fiber catalyst layer is covered with a catalyst layer (metal iron-doped COP catalyst). This catalyst is in a flaky structure and uniformly wraps the surface of the polymer nanofibers, proving its core-shell fiber structure.

[0150] The thickness of the catalyst layer is 0.17 mm, and the thickness of the metal iron-doped COP catalyst is 7 nm;

[0151] Obtained by XPS testing, in the metal iron-doped COP catalyst using a nitrogen-containing organic ligand (2,3,5,6-tetrafluoroterephthalonitrile), the content of N is 4.5 at%, the content of F is 14.8%, the content of C is 67.7 at%, the content of metal iron is 1 at%, and the content of O is 12 at%.

[0152] The porosity of the fiber catalyst layer is 78%, the specific surface area is 27.5 m 2 / g, and the pore size range is 40 - 70 nm.

[0153] The elongation at break of the fiber catalyst layer is 25%.

[0154] Example 5

[0155] Preparation of polymer nanofibers:

[0156] ① Disperse 270 mg of polystyrene (number average molecular weight of 100,000) and 50 mg of conductive carbon black (particle size of 40 nm, spherical shape) in 2 g of a solvent (tetrahydrofuran and N,N-dimethylformamide with a volume ratio of 1:4), ultrasonically homogenize and stir for 3 h to obtain a homogeneous solution. Then add 40 mg of metal salt ferric sulfate to the above solution, continuously stir for 6 h, control the temperature at 50 °C, and keep the rotation speed at 500 r / min to obtain a homogeneous spinning solution;

[0157] ② Transfer the spinning solution to a syringe, fix it on an electrospinning machine, set the spinning environment temperature at 40 °C, humidity control at 45%, spinning voltage at 17 kV, spinning solution supply speed at 0.6 ml / h, wrap the cut aluminum foil around the roller, close the protection door of the spinning box body, turn on the high-voltage power supply, perform electrospinning, adjust the roller collection rotation speed to 250 rpm until the spinning solution is consumed; remove the receiver, collect the polymer fiber cloth, and place it in a 60 °C vacuum oven for drying to constant weight to obtain polymer nanofibers;

[0158] Preparation of the fiber catalyst layer:

[0159] ① Disperse 25 mg of 2,3,5,6-tetrafluoroterephthalonitrile in 1.5 g of ethylene glycol, and dissolve it ultrasonically to obtain a transparent solution. Then, add 15 mg of 2,2-dimethyl-1,3-dioxepan-5-ene and stir evenly to obtain the catalytic reaction feed liquid.

[0160] ② Take 100 mg of the cut polymer nanofibers and put them into a reaction kettle containing 12 g of the catalytic reaction feed liquid.

[0161] ③ Place the reaction kettle in a vacuum drying oven, set the temperature to 160 °C, and carry out hydrothermal reaction for 8 h.

[0162] ④ Take out the reacted polymer nanofibers from the reaction kettle, wash them successively with dilute hydrochloric acid, deionized water, and ethanol, and then put them in an oven at 60 °C to dry to obtain the fiber catalytic layer.

[0163] The SEM characterization of the polymer nanofibers and the fiber catalytic layer is Figure 1 similar. It can be obtained that the surface of the nanofibers in the polymer nanofibers is relatively smooth, the average fiber diameter is 480 nm, and it has a three-dimensional porous framework structure with random staggered distribution. After hydrothermal reaction, a core-shell structure is formed. The surface of the polymer nanofibers in the fiber catalytic layer is covered with a catalytic layer (metal iron-doped COP catalyst). This catalyst is in a flaky structure and evenly wraps the surface of the polymer nanofibers, proving its core-shell fiber structure.

[0164] The thickness of the catalytic layer is 0.16 mm, and the thickness of the metal iron-doped COP catalyst is 8 nm.

[0165] Obtained by XPS test, in the metal iron-doped COP catalyst using a nitrogen-containing organic ligand (2,3,5,6-tetrafluoroterephthalonitrile), the content of N is 5.6 at%, the content of F is 14.6%, the content of C is 68.8 at%, the content of metal iron is 1 at%, and the content of O is 10 at%.

[0166] The porosity of the fiber catalytic layer is 81%, the specific surface area is 32 m 2 / g, and the pore size range is 30 - 90 nm.

[0167] The elongation at break of the fiber catalytic layer is 26%.

[0168] Example 6

[0169] Preparation of polymer nanofibers:

[0170] ①Disperse 150 mg of polystyrene (number-average molecular weight of 100,000), 120 mg of polyacrylonitrile (nitrogen content of 26.4%, number-average molecular weight of 1.3 million), and 50 mg of conductive carbon black (particle size of 40 nm, spherical shape) in 2 g of a solvent (tetrahydrofuran and N,N-dimethylformamide with a volume ratio of 1:4). Ultrasonically homogenize and stir for 3 h to obtain a homogeneous solution. Then add 45 mg of ferric sulfate pentahydrate to the above solution, continuously stir for 6 h, control the temperature at 50 °C, and maintain the rotation speed at 500 r / min to obtain a homogeneous spinning solution;

[0171] ②Transfer the spinning solution to a syringe, fix it on an electrospinning machine, set the spinning environment temperature at 40 °C, control the humidity at 45%, set the spinning voltage at 17 kV, and set the supply speed of the spinning solution at 0.6 ml / h. Wrap the cut aluminum foil around a roller, close the protective door of the spinning chamber, turn on the high-voltage power supply, and perform electrospinning. Adjust the collection rotation speed of the roller to 250 rpm until the spinning solution is consumed; Remove the receiver, collect the polymer fiber cloth, and place it in a vacuum oven at 60 °C for drying to constant weight to obtain polymer nanofibers;

[0172] Preparation of the fiber catalytic layer:

[0173] ①Disperse 25 mg of 2,3,5,6-tetrafluoroterephthalonitrile in 1.5 g of ethylene glycol, ultrasonically dissolve to obtain a transparent solution, and drop in 15 mg of 2,2-dimethyl-1,3-dioxepan-5-ene and stir evenly to obtain a catalytic reaction feed liquid;

[0174] ②Take 100 mg of the cut polymer nanofibers and put them into a reaction kettle containing 12 g of the catalytic reaction feed liquid;

[0175] ③Place the reaction kettle in a vacuum drying oven, set the temperature at 160 °C, and continuously react for 8 h to carry out a hydrothermal reaction;

[0176] ④Take out the reacted polymer nanofibers from the reaction kettle, wash them successively with dilute hydrochloric acid, deionized water, and ethanol, and then put them in an oven at 60 °C for drying to obtain the fiber catalytic layer.

[0177] SEM characterization of the polymer nanofibers and the fiber catalytic layer is Figure 1 similar. It can be obtained that the surface of the nanofibers in the polymer nanofibers is relatively smooth, the average fiber diameter is 580 nm, and it has a three-dimensional porous framework structure with random staggered distribution; after the hydrothermal reaction, a core-shell structure is formed. The surface of the polymer nanofibers in the fiber catalytic layer is covered with a catalytic layer (metal iron-doped COP catalyst), and this catalyst is in a flake structure and uniformly wraps on the surface of the polymer nanofibers, proving its core-shell fiber structure.

[0178] The thickness of the catalytic layer is 0.18 mm, and the thickness of the metal iron-doped COP catalyst is 9 nm;

[0179] Obtained by XPS testing, using the nitrogen-containing organic ligand (2,3,5,6-tetrafluoroterephthalonitrile), in the metal iron-doped COP catalyst: the content of N is 5.5 at%, the content of F is 14.8%, the content of C is 67.6 at%, the content of metal iron is 0.6 at%, and the content of O is 11.5 at%.

[0180] The porosity of the fibrous catalytic layer is 72%, the specific surface area is 20.6 m 2 / g, and the pore size range is 60 - 120 nm.

[0181] The elongation at break of the fibrous catalytic layer is 25%.

[0182] Comparative Example 1

[0183] Preparation of COP catalyst:

[0184] ① Disperse 40 mg of the nitrogen-containing ligand 1,2,4,5-tetracyanobenzene in 1.5 g of the solvent ethylene glycol, add 40 mg of the metal salt cobalt chloride, dissolve it by ultrasonic treatment to obtain a transparent solution, and drop in 12 mg of the reaction catalyst 1,8-diazabicyclo[5,4,0]undecene-7 and stir evenly to obtain the catalytic reaction feed liquid;

[0185] ② Put the obtained catalytic reaction feed liquid into a reaction kettle;

[0186] ③ Place the reaction kettle in a vacuum drying oven, set the temperature to 150 °C, and continuously react for 8 h;

[0187] Take out the precipitate obtained by the reaction from the reaction kettle, wash it successively with dilute hydrochloric acid, deionized water and ethanol, and then put it into an oven and dry it at 60 °C to obtain the COP catalyst.

[0188] Application Example

[0189] Preparation of the electrode and assembly of the battery:

[0190] Preparation of Membrane Cathode: The core-shell fiber catalytic layers prepared in the examples were respectively cut into 1.5×1.5 cm squares for standby, and the hydrophobic carbon paper was cut into 1.5×1.5 cm squares for standby. Subsequently, the cut core-shell fiber catalytic layer and the hydrophobic carbon paper were hot-pressed at a pressure of 0.2 MPa and a temperature of 70 °C for 10 min to obtain a membrane electrode (as the cathode); 5 mg of the COP catalyst powder prepared in the comparative example was weighed and added to a mixed solution of 100 μL of ultrapure water and 895 μL of ethanol. The above mixture was ultrasonically dispersed in an ultrasonic wave to ensure the uniformity in all directions of the slurry. Finally, 25 μL of 5% Nafion solution was added and ultrasonically homogenized to be used as catalyst ink. The catalyst ink was uniformly loaded onto the hydrophobic gas diffusion layer by spraying to serve as the oxygen electrode of the comparative example (as the cathode).

[0191] Assembly of Zinc-Air Flow Battery: Using a zinc sheet as the anode and an aqueous solution of 7M KOH + 0.2M ZnO as the electrolyte, zinc-air flow batteries were assembled using the above cathodes respectively, with an electrolyte flow rate of 40 ml / min.

[0192] Charge-Discharge Performance Test: After the zinc-air flow battery system was assembled, charge-discharge tests were carried out. The test conditions were: the charge-discharge current density was set to 20 mA / cm 2 , the charging duration was 30 min, the discharging duration was 30 min, and the first-cycle efficiency of the battery and the efficiency retention rate after 200 cycles of the battery were tested using the Wuhan Blue Electric test system. The results are shown in Table 1.

[0193] The conductive resistance was tested by the four-probe method.

[0194] The charge-discharge curve of the zinc-air flow battery finally prepared and assembled using the core-shell fiber catalytic layer in Example 1 is as Figure 3 shown.

[0195] Through Figure 3 it can be obtained that the oxygen electrode prepared in Example 1 of the present invention has excellent stability and a low overpotential in the zinc-air flow battery.

[0196] Table 1

[0197]

[0198]

[0199] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A core-shell fiber catalyst layer, characterized in that: The catalytic layer comprises a core layer with polymer nanofibers and a metal-doped COP catalyst coated on the core layer; the catalytic layer has electrical conductivity.

2. The catalyst layer according to claim 1, wherein The metal-doped COP catalyst is in-situ grown and coated on the polymer nanofibers; and / or The metal-doped COP catalyst is a metal-doped non-pyrolytic COP catalyst; and / or The core layer has a three-dimensional porous skeleton structure; and / or The fiber diameter of the polymer nanofiber is 100-700 nm, preferably 300-500 nm; and / or The thickness of the catalytic layer is 0.01-0.5 mm, preferably 0.1-0.3 mm; The thickness of the metal-doped COP catalyst is 2-20 nm, preferably 5-15 nm; and / or The porosity of the catalytic layer is 70-90%, preferably 75-85%; and / or The specific surface area of ​​the catalytic layer is 20-60m 2 / g, preferably 25-40m 2 / g; and / or The pore size of the catalytic layer is in the range of 1-100 nm; and / or The breaking elongation of the catalytic layer is 15%-30%.

3. The catalyst layer according to claim 1 or 2, wherein: In the metal-doped COP catalyst, the content of N is 5 at%-15 at%, the content of metal is 0.3 at%-1 at%, the content of F is 0 at%-20 at%, the content of O is 5 at%-15 at%, and the balance is the content of C; and / or The nitrogen-containing ligands for constructing the conjugated framework of the metal-doped COP catalyst are selected from one or more of 2,3,5,6-tetrafluoroterephthalonitrile, 3,4,5,6-tetrafluorophthalonitrile, 1,2,4,5-tetracyanobenzene, phthalonitrile, cyclohexene-1-carbonitrile and cyclohexanecarbonitrile.

4. The catalytic layer according to any one of claims 1 to 3, wherein: The catalyst layer contains a conductive agent, and the conductive agent is preferably distributed in the core layer; Preferably, the conductive agent is at least one of graphite, graphene, polyaniline, copper powder, nickel powder, carbon black and carbon nanotubes, preferably at least one of graphite, carbon black and graphene; and / or The conductive agent is in at least one of a spherical, sheet-like and tubular shape, preferably a spherical and / or sheet-like shape; and / or The particle size of the conductive agent is 10-300 nm, preferably 20-120 nm; and / or The content of the conductive agent in the polymer nanofiber is 3-30wt%, preferably 8-25wt%; and / or The metal is selected from at least one of Group VIII, Group IB and Group VIIB, and is preferably selected from at least one of iron, cobalt, copper and manganese.

5. The catalytic layer according to any one of claims 1 to 4, wherein: The content of water-soluble polymer in the polymer layer of the polymer fiber is not higher than 40wt%; and / or The high molecular polymer of the core layer of the polymer fiber is selected from nitrogen-containing high molecular polymers and / or non-nitrogen-containing high molecular polymers; and / or The number average molecular weight of the high molecular weight polymer of the core layer of the polymer fiber is 60,000-1.5 million; Preferably, The polymer is selected from nitrogen-containing polymers and non-nitrogen-containing polymers, and preferably the mass ratio of the nitrogen-containing polymer to the non-nitrogen-containing polymer is 1:(1-6); and / or The nitrogen-containing high molecular polymer is selected from at least one of polyacrylonitrile, polyimide, polyvinyl pyrrolidone, polyethyleneimine and polyetherimide; and / or The nitrogen content of the nitrogen-containing high molecular polymer is 5wt%-35wt%, preferably 10wt%-30wt%; and / or The non-nitrogen-containing high molecular polymer is selected from at least one of polytetrafluoroethylene, polychlorodifluoroethylene, polyvinylidene fluoride, polystyrene, polyvinyl alcohol, polyethylene oxide and polyacrylic acid.

6. A method for preparing a core-shell fiber catalyst layer according to any one of claims 1 to 5, characterized in that: The preparation method comprises: (1) spinning a spinning dispersion containing a polymer, a metal source and a conductive agent; (2) The fiber membrane obtained by spinning is subjected to a hydrothermal reaction with a catalytic dispersion containing a reaction catalyst and a nitrogen-containing ligand.

7. The preparation method according to claim 6, wherein: The conditions of the hydrothermal reaction include: a temperature of 60°C-200°C, preferably 120°C-180°C; and / or a time of 1-24h, preferably 4-12h; and / or The spinning is electrostatic spinning; Preferably, the electrospinning conditions include: The temperature is 25°C-50°C, preferably 30°C-40°C; and / or Humidity is 25%-60%, preferably 30%-40%; and / or The voltage is 13kV-19kV, preferably 17kV-18kV; and / or The supply rate of the spinning dispersion is 0.2 ml / h-0.9 ml / h.

8. The preparation method according to claim 6 or 7, wherein: The reaction catalyst is selected from at least one of 1,8-diazacyclo[5,4,0]undecene-7, 2,2-dimethyl-1,3-dioxep-5-ene and 1,4,7-triazacyclononane; and / or The metal source is a metal salt corresponding to the metal, and preferably the metal salt is a metal salt without crystal water; and / or The solvent in the spinning dispersion is selected from at least one of acetone, N,N-dimethylformamide, methanol, ethylene dichloride, dichloromethane and tetrahydrofuran; and / or The solvent in the catalytic dispersion is selected from at least one of ethylene glycol, propylene glycol, water, ethanol, N,N-dimethylformamide, propylene glycol and tetrahydrofuran; and / or The mass ratio of the polymer to the metal source is 1-10:1; and / or The mass ratio of the polymer to the conductive agent is 1-10:1; and / or The mass ratio of the nitrogen-containing ligand to the reaction catalyst is 1:0.5-1.0; and / or The content of the polymer in the spinning dispersion is 5wt%-85wt%, preferably 10wt%-30wt%; and / or In the catalytic dispersion, the mass fraction of the nitrogen-containing ligand and the reaction catalyst as solutes is 0.5wt%-5wt%; and / or The mass ratio of the fiber membrane to the catalytic dispersion is (0.005-0.05):

1.

9. Use of the core-shell fiber catalyst layer described in claims 1-5 in batteries.

10. A membrane electrode, characterized in that: The membrane electrode comprises a hydrophobic gas diffusion layer and a core-shell fiber catalytic layer; the core-shell fiber catalytic layer is the core-shell fiber catalytic layer according to any one of claims 1-5.

11. A zinc-air flow battery, characterized in that: The battery comprises an anode, a membrane electrode as a cathode, and an electrolyte, wherein the membrane electrode is the membrane electrode according to claim 10; Preferably, The material of the anode is metallic zinc; and / or The electrolyte is 4-10M KOH+0.1-0.3M ZnO aqueous solution; and / or The flow rate of the electrolyte is 10-60 ml / min.

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