A multi-scale hierarchical porous electrode, a preparation method and application thereof

Abstract

The application discloses a multi-scale hierarchical porous electrode and a preparation method and application thereof, and relates to the technical field of electrode preparation. The multi-scale hierarchical porous electrode comprises a substrate and a carbon network modification layer modified in the substrate; the carbon network modification layer is formed by carbonization of amphiphilic polymers, the amphiphilic polymer molecular chains contain hydrophilic groups and hydrophobic groups at the same time, can be dissolved in water and oil respectively, and can play a stabilizing role at the liquid-liquid interface; the phase separation of the polymers between fibers is driven by solvent controlled evaporation, and solidification is achieved; finally, the electrode is obtained by high-temperature carbonization. The application improves the active sites without destroying the macro-pores of the carbon cloth, adopts a liquid-liquid phase separation method to construct a multi-scale carbon network on the fiber surface in situ, spontaneously induces a surface tension during a solvent drying process, forms a modification structure with different pores on the surface of the carbon fiber and between the fibers, improves the electrochemical performance of the electrode, and can improve the energy and power density of the battery.

Description

Technical Field

[0001] This invention relates to the field of electrode fabrication technology, specifically to a multi-scale hierarchical porous electrode, its fabrication method, and its application. Background Technology

[0002] Carbon cloth or carbon felt, as a porous material woven from carbon fibers, possesses a unique ordered woven structure that creates a high permeability tensor, exhibiting excellent mass transport capabilities. Therefore, it is widely used as an ideal electrode substrate in electrochemical devices. Its three-dimensional interconnected macroporous structure not only facilitates rapid electrolyte penetration but also provides a good loading platform for active materials, ensuring the mass transfer efficiency of the electrode under high current density operating conditions.

[0003] However, in practical applications, the original carbon cloth or carbon felt has an inherent drawback of low specific surface area. The smooth surface of carbon fiber and the scarcity of active sites result in a limited amount of catalytically active material that can be loaded per unit geometric area, which severely restricts the electrochemical reaction rate and overall performance of the electrode under high current density.

[0004] To address this issue, existing technologies typically employ methods such as introducing nanostructures or coating high-surface-area materials onto the carbon fiber surface to increase active sites. Currently, common modification strategies fall into two main categories: one is to grow carbon nanotubes, graphene, or metal oxides in situ on the carbon fiber surface using methods such as chemical vapor deposition and hydrothermal synthesis; the other is to load activated carbon materials, conductive polymers, etc., onto the carbon cloth surface using coating or impregnation methods. Although these methods improve the electrochemical performance of carbon cloth to some extent, they still have the following technical problems: First, existing modification methods often struggle to significantly increase the number of active sites without damaging the macroporous structure of the carbon cloth. Nanomaterials introduced by some methods can easily clog the macropores between fibers, leading to increased electrolyte penetration resistance and weakening the original mass transfer advantages of the carbon cloth. Second, hydrothermal and vapor deposition processes are demanding and complex, and nanostructures are prone to detachment or aggregation during long-term electrochemical cycling, resulting in insufficient stability.

[0005] Therefore, how to efficiently and stably increase the density of active sites on carbon cloth while retaining its original high-permeability macroporous structure, so as to improve the electrochemical reaction rate under high current density, remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a multi-scale hierarchical porous electrode and its preparation method and application. In order to solve the above-mentioned technical problems, this invention enhances the active sites of carbon fiber matrix without destroying the macroscopic large channels of carbon cloth and other carbon fiber matrices. Amphiphilic polymers are constructed in situ on the fiber surface in the carbon fiber matrix. The amphiphilic polymer molecular chains contain both hydrophilic and hydrophobic groups. Phase separation and solidification occur between the fibers, forming a modified structure with different pore sizes on the carbon fiber surface and between the fibers, forming a multi-scale carbon network structure. An electrode with a multi-level porous structure is obtained by high-temperature carbonization.

[0007] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a multi-scale hierarchical porous electrode, the multi-scale hierarchical porous electrode comprising a substrate and a carbon network modification layer modified in the substrate; the carbon network modification layer is formed by carbonization of an amphiphilic polymer, wherein the molecular chain of the amphiphilic polymer contains hydrophilic groups and hydrophobic groups. The matrix is ​​a fiber-containing matrix, and the carbon network modification layer modifies the fiber surface in the matrix and the gaps between the fibers in the matrix. The carbon network modification layer forms a structure with a first micropore on the fiber surface in the matrix, and the carbon network modification layer forms a structure with a second micropore in the gap between the fibers in the matrix, wherein the pore size of the first micropore is smaller than the pore size of the second micropore.

[0008] In a preferred embodiment of the present invention, the hydrophilic group includes at least one of hydroxyl, carboxyl, amino, sulfonic acid, amide, aldehyde and quaternary ammonium groups, and the hydrophobic group includes at least one of benzene ring, chloro, methyl and ethyl groups.

[0009] In a preferred embodiment of the present invention, the pore size of the first micropore is 1 μm to 2 μm, and the pore size of the second micropore is 5 μm to 15 μm.

[0010] In a preferred embodiment of the present invention, the amphiphilic polymer comprises at least one of poly(styrene-co-vinylbenzyl chloride), poly(styrene-co-vinylbenzyl chloride), poly(styrene-co-4-vinylpyridine), poly(styrene-co-p-styrene sulfonate), and poly(styrene-co-N,N-dimethyl-4-vinylaniline). The substrate includes at least one of carbon cloth, carbon felt, graphite felt, and carbon paper.

[0011] Secondly, the present invention provides a method for preparing the aforementioned multi-scale hierarchical porous electrode, comprising the following steps: S1. The initiator, the first solvent containing hydrophilic groups, and the second monomer containing hydrophobic groups are mixed and reacted under an inert gas atmosphere to obtain an amphiphilic polymer. S2. The amphiphilic polymer is added to the second solvent and emulsified to form an emulsion. The matrix is ​​immersed in the emulsion, and the matrix is ​​removed and dried. S3. The substrate is carbonized in an inert gas atmosphere to obtain the multi-scale hierarchical porous electrode.

[0012] In a preferred embodiment of the present invention, S3 further includes sulfonating the matrix before the carbonization treatment. The sulfonation treatment method includes immersing the matrix in concentrated sulfuric acid at 70°C to 90°C for 1 to 3 hours, and then rinsing with deionized water until the pH of the filtrate reaches neutral.

[0013] In a preferred embodiment of the present invention, in S1, the second monomer containing a hydrophobic group includes at least one of styrene, vinyl benzyl chloride, divinylbenzene, α-methylstyrene, p-chlorostyrene, pentafluorostyrene, 4-vinylbiphenyl, phenyl methacrylate, and benzyl methacrylate. The initiator is 2,2'-azobis(2-methylpropionamide) dihydrochloride; the first solvent is a mixed solvent of water and ethanol, with a volume ratio of water to ethanol of 2.5~3.5:2; The ratio of the second monomer containing a hydrophobic group, the initiator, and the first solvent containing a hydrophilic group is 7 mL~8 mL: 0.04 g~0.06 g: 40 mL~60 mL; The reaction temperature is 70℃~90℃, and the reaction time is 14 hours~18 hours.

[0014] More preferably, the second monomer containing the hydrophobic group is selected from styrene and vinyl benzyl chloride, wherein the volume ratio of styrene to vinyl benzyl chloride is 2:1.

[0015] In a preferred embodiment of the present invention, S1 further includes adding a first monomer containing a hydrophilic group to react together to obtain the amphiphilic polymer; The first monomer containing a hydrophilic group includes at least one of sodium p-styrene sulfonate, 4-vinylpyridine, 4-vinylbenzoic acid, N,N-dimethyl-4-vinylaniline, and N-phenylacrylamide; The volume ratio of the first monomer containing a hydrophilic group to the second monomer containing a hydrophobic group is 2.0~3.0 : 4.5~5.5.

[0016] In a preferred embodiment of the present invention, in S2, the second solvent is a mixture of an organic solvent and water, wherein the mass ratio of the organic solvent to water is 1:0.1 to 0.5, and the organic solvent includes toluene; the mass ratio of the amphiphilic polymer to the organic solvent is 0.1:1.1 to 1.3.

[0017] In a preferred embodiment of the present invention, in step S3, the carbonization treatment conditions include: heating to 800°C to 1100°C at a rate of 8°C to 12°C per minute for 30 min to 180 min.

[0018] Thirdly, the present invention provides the application of the multi-scale hierarchical porous electrode or the multi-scale hierarchical porous electrode obtained by the preparation method described above in batteries.

[0019] This invention has at least one of the following beneficial effects: 1. In order to solve the technical problem that the low specific surface area of ​​the original carbon cloth or carbon felt limits its electrochemical reaction rate under high current density, this invention modifies the matrix with an amphiphilic polymer and then carbonizes the amphiphilic polymer at high temperature to form a carbon network modification layer, thereby obtaining an electrode with a multi-level porous structure, which balances mass transfer and electrochemical reaction, and improves the energy and power density of the battery.

[0020] 2. This invention enhances active sites without damaging the macroscopic pores of carbon cloth. A multi-scale carbon network is constructed in situ on the fiber surface using a liquid-liquid phase separation method. Specifically, an amphiphilic polymer is added to a second solvent, which is then emulsified to form an emulsion. The matrix is ​​then immersed in the emulsion. Through the spontaneous induction of surface tension during solvent drying, a modified structure with different pore sizes is formed between the carbon fiber surface and the fibers. This multi-scale hierarchical porous structure facilitates both mass transfer and electrochemical reactions, thereby improving the electrochemical performance of the electrode prepared by this invention. Applying the electrode of this invention to batteries can improve the energy and power density of the battery. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the preparation process of the polymer network modified electrode in Example 1; wherein, (a) in the figure is a schematic diagram of two-phase emulsion immersion, (b) in the figure is a schematic diagram of evaporation and phase separation, and (c) in the figure is a schematic diagram of interface stabilization and framework formation.

[0022] Figure 2 The images show the preparation process of the polymer emulsion in Example 1; in the images, (a) is copolymer powder, (b) is oil phase solution, (c) is mixture after adding water, and (d) is emulsion after ultrasonication.

[0023] Figure 3The figures show the morphology of the electrodes prepared in Examples 1 to 3; where (a) corresponds to Example 2, (b) corresponds to Example 1, and (c) corresponds to Example 3.

[0024] Figure 4 Impedance diagrams of the electrodes prepared in Examples 1, 4 to 6; wherein, (a) in the figure is the EIS curve of the positive electrode electrolyte, and (b) in the figure is the EIS curve of the negative electrode electrolyte.

[0025] Figure 5 This is a schematic diagram of the morphological changes of the electrode in Example 1; where (a) is the original carbon cloth, (b) is the copolymer network modified carbon cloth electrode, and (c) is the carbon network modified carbon cloth electrode.

[0026] Figure 6 shows SEM images of the electrodes in Example 1; where (a) is the original carbon cloth, (b) is the copolymer network modified carbon cloth electrode, and (c) is the carbon network modified carbon cloth electrode.

[0027] Figure 7 The image shows a SEM image of the carbon network modified electrode in Example 1; where (a) is the fiber surface, (b) is the whole, and (c) is a morphological comparison between fibers.

[0028] Figure 8 The Raman curves of the original carbon cloth, the copolymer network modified carbon cloth electrode, and the carbon network modified carbon cloth electrode in Example 1 are compared.

[0029] Figure 9 The images shown are SEM and EDS scan images of the electrodes in Example 1; where (a) is the original carbon cloth, (b) is the copolymer network modified carbon cloth electrode, and (c) is the carbon network modified carbon cloth electrode.

[0030] Figure 10 The figures show the XPS spectra of the electrodes before and after modification in Example 1; where (a) is the full spectrum, (b) is the C1s fine spectrum, and (c) is the O1s fine spectrum.

[0031] Figure 11 The figure shows the relationship between the peak current density of the electrode and the square root of the scan rate in Example 1; where (a) in the figure represents the positive electrode electrolyte and (b) in the figure represents the negative electrode electrolyte.

[0032] Figure 12 shows the charge-discharge curves of the electrode assembly battery in Example 1; where (a) in the figure represents 100 mA / cm. 2 At the current density, (b) in the figure is 200 mA / cm². 2 At the current density, (c) in the figure is 300 mA / cm².2 At current density.

[0033] Figure 13 The figure shows the rate performance of the electrode assembly battery of Example 1; where (a) represents coulombic efficiency and voltage efficiency, (b) represents energy efficiency, and (c) represents electrolyte utilization.

[0034] Figure 14 The image shows the discharge polarization curve of the electrode assembly battery in Example 1. Detailed Implementation

[0035] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0036] An embodiment of the present invention provides a multi-scale hierarchical porous electrode, the electrode comprising a substrate and a carbon network modification layer modified on the substrate; the carbon network modification layer is formed by carbonization of an amphiphilic polymer, the molecular chain of the amphiphilic polymer containing hydrophilic and hydrophobic groups; the substrate is a fiber-containing substrate, the carbon network modification layer is modified on the fiber surface in the substrate and modified in the gaps between the fibers in the substrate; the carbon network modification layer forms a structure with first micropores on the fiber surface in the substrate, and forms a structure with second micropores in the gaps between the fibers in the substrate, the pore size of the first micropores being smaller than the pore size of the second micropores.

[0037] "Multi-scale" means that the electrode prepared in the embodiments of the present invention contains at least two different sizes of micropores.

[0038] "Grading" refers to the highly ordered and functionally partitioned multi-scale morphological features exhibited by the electrodes prepared in the embodiments of the present invention. Specifically, it means that the fiber surface in the matrix has a microporous structure dominated by fine micropores, and the gaps between fibers in the matrix have a microporous structure dominated by macropores.

[0039] This invention optimizes the structure to balance mass transfer and electrochemical reaction. It utilizes the large pores between fibers as channels for efficient electrolyte flow to ensure macroscopic mass transfer throughout the entire range, while using the small pores on the fiber surface to provide sufficient effective reaction area. Thus, while maintaining extremely low voltage drop, it greatly improves the energy and power density of the battery.

[0040] In some embodiments, the hydrophilic group includes at least one of hydroxyl, carboxyl, amino, sulfonic acid, amide, aldehyde, and quaternary ammonium groups, and the hydrophobic group includes at least one of benzene ring, chloro, methyl, and ethyl groups.

[0041] This invention utilizes polymer molecular chains that simultaneously contain hydrophilic groups (such as at least one of hydroxyl, carboxyl, amino, sulfonic acid, amide, aldehyde, and quaternary ammonium groups) and hydrophobic groups that are easily soluble in organic solvents (such as at least one of benzene ring, chloro, methyl, and ethyl groups). This amphiphilic structure allows for phase separation and solidification between fibers, and finally, through high-temperature carbonization, an electrode with a multi-level porous structure is obtained. The electrode with a multi-level porous structure can balance mass transfer and electrochemical reactions, thereby improving the energy and power density of the battery.

[0042] In some embodiments, the first micropore and the second micropore are both at least one of circular, approximately circular, elliptical and irregular opening shapes.

[0043] In some embodiments, the pore size of the first micropore is 1 μm to 2 μm, and the pore size of the second micropore is 5 μm to 15 μm. It should be noted that "pore size" here refers to the diameter or effective width of the hole. When the first micropore and the second micropore are circular or approximately circular, "pore size" refers to the diameter. When the first micropore and the second micropore are elliptical or irregularly shaped, "pore size" refers to the effective width.

[0044] In some embodiments, the amphiphilic polymer is an amphiphilic copolymer comprising at least two different repeating units selected from polystyrene, polyvinylbenzyl chloride, poly(N,N-dimethyl-4-vinylaniline), polydivinylbenzene, sodium terephthalate sulfonate, poly(4-vinylpyridine), poly(α-methylstyrene), poly(p-chlorostyrene), poly(pentafluorostyrene), poly(4-vinylbiphenyl), polyphenyl methacrylate, polybenzyl methacrylate, poly(N-phenylacrylamide), and poly(4-vinylbenzoic acid); preferably, the amphiphilic polymer is poly(styrene-co-vinylbenzyl chloride).

[0045] Specifically, the amphiphilic polymer comprises at least one of poly(styrene-co-vinylbenzyl chloride), poly(styrene-co-vinylbenzyl chloride), poly(styrene-co-4-vinylpyridine), poly(styrene-co-p-styrene sulfonate), and poly(styrene-co-N,N-dimethyl-4-vinylaniline); Poly(styrene-co-vinylbenzyl chloride) is preferred as an amphiphilic precursor. Its advantages are: (1) the styrene segments have good hydrophobicity and carbonization ability, which can form a stable conductive carbon skeleton; (2) the vinylbenzyl chloride segments have strong polarity, which is beneficial to the stability of the oil-water interface and subsequent sulfonation crosslinking; (3) the copolymer can stabilize the emulsion system and induce the formation of a continuous porous network during evaporation; (4) after carbonization, it can take into account conductivity, pore structure and surface active sites. Therefore, the amphiphilic polymer poly(styrene-co-vinylbenzyl chloride) has both good interfacial stability and carbonization ability, which can stabilize the oil-water emulsion and induce the formation of a continuous porous network structure during drying; after carbonization, it can form a conductive carbon skeleton while retaining abundant defect sites and active sites, which is beneficial to improving the mass transfer performance and electrochemical activity of the electrode.

[0046] In some embodiments, the substrate includes at least one of carbon cloth, carbon felt, graphite felt, and carbon paper.

[0047] Preferably, the substrate is carbon cloth or carbon cloth with a three-dimensional interconnected macroporous structure, excellent conductivity and good electrolyte penetration ability, which is conducive to the in-situ attachment of polymer network and subsequent construction of hierarchical pore structure, thereby taking into account both mass transfer performance and reactivity.

[0048] In some embodiments, the thickness of the substrate is 2 mm to 10 mm, preferably 3 mm to 6 mm.

[0049] Another embodiment of the present invention provides a method for preparing the electrode, comprising the following steps: S1. The initiator, the first solvent containing hydrophilic groups, and the second monomer containing hydrophobic groups are mixed and reacted under an inert gas atmosphere to obtain an amphiphilic polymer. S2. The amphiphilic polymer is added to the second solvent and emulsified to form an emulsion. The matrix is ​​immersed in the emulsion, and the matrix is ​​taken out and dried. A multi-scale carbon network is constructed in the matrix using a liquid-liquid phase separation method. Through the spontaneous induction of surface tension during solvent drying, a modified structure with different pores is formed on the matrix surface and in the gaps between fibers in the matrix. S3. The substrate is carbonized in an inert gas atmosphere to obtain the electrode.

[0050] The preparation method of the present invention is simple and practical. It only requires adding the amphiphilic polymer to a second solvent containing water and an organic solvent. The polymer is driven to undergo phase separation and solidification between fibers by controlled evaporation of the solvent. Finally, an electrode with a multi-level porous structure is obtained by high-temperature carbonization.

[0051] In some embodiments, S3 further includes sulfonating the matrix before the carbonization treatment, wherein the sulfonation treatment method includes immersing the matrix in concentrated sulfuric acid at 70°C to 90°C for 1 to 3 hours, and then rinsing with deionized water until the pH of the filtrate reaches neutral.

[0052] Sulfonation can promote cross-linking between copolymer molecular chains and introduce sulfur-containing polar functional groups on the material surface, thereby enhancing the interfacial bonding force between the polymer network and the carbon fiber matrix. At the same time, it is beneficial to form a stable conductive carbon skeleton and defective active sites during the subsequent carbonization process, further improving structural stability, conductivity and electrochemical activity.

[0053] In some embodiments, in S1, the second monomer containing a hydrophobic group includes at least one of styrene, vinyl benzyl chloride, divinylbenzene, α-methylstyrene, p-chlorostyrene, pentafluorostyrene, 4-vinylbiphenyl, phenyl methacrylate, and benzyl methacrylate. In some embodiments, in S1, the initiator is 2,2'-azobis(2-methylpropionamide) dihydrochloride; the first solvent is a mixed solvent of deionized water and ethanol, wherein the volume ratio of deionized water to ethanol is 2.5~3.5:2; The ratio of the second monomer containing the hydrophobic group, the initiator, and the first solvent is 7 mL~8 mL: 0.04 g~0.06 g: 40 mL~60 mL; the reaction temperature is 70℃~90℃; and the reaction time is 14 hours~18 hours.

[0054] More preferably, the second monomer containing a hydrophobic group is selected from 4-vinylbenzyl chloride and styrene, wherein the volume ratio of 4-vinylbenzyl chloride to styrene is 1:2; the initiator is 2,2'-azobis(2-methylpropionamide) dihydrochloride; the first solvent containing a hydrophilic group is a mixed solvent of deionized water and ethanol, wherein the volume ratio of deionized water to ethanol is 3:2; the addition ratio of the second monomer containing a hydrophobic group, the initiator, and the first solvent containing a hydrophilic group is 7.5 mL:0.05 g:50 mL; the reaction temperature is 80°C, and the reaction time is 16 hours.

[0055] In some embodiments, S1 further includes adding a first monomer containing a hydrophilic group to react together to obtain the amphiphilic polymer; The first monomer containing a hydrophilic group includes at least one of sodium p-styrene sulfonate, 4-vinylpyridine, 4-vinylbenzoic acid, N,N-dimethyl-4-vinylaniline, and N-phenylacrylamide; The volume ratio of the first monomer containing a hydrophilic group to the second monomer containing a hydrophobic group is 2.0~3.0 : 4.5~5.5.

[0056] In some embodiments, in S2, the second solvent is a mixture of an organic solvent and water, wherein the mass ratio of the organic solvent to water is 1:0.1~0.5; and the mass ratio of the amphiphilic polymer to the organic solvent is 0.1:1.1~1.3. Preferably, the mass ratio of the organic solvent to water is 1:0.2~0.4, and the mass ratio of the amphiphilic polymer to the organic solvent is 0.1:1.15~1.25. More preferably, the mass ratio of the organic solvent to water is 1:0.25~0.35, and the mass ratio of the amphiphilic polymer to the organic solvent is 0.1:1.2.

[0057] The specific process of emulsifying the amphiphilic polymer in a second solvent includes: adding the amphiphilic polymer to a mixture of an organic solvent and water, followed by ultrasonic emulsification to form a stable emulsion; in this emulsion, hydrophilic segments extend into the aqueous phase, while hydrophobic segments are anchored in the organic phase, thereby stabilizing the oil-water interface and inhibiting droplet aggregation. During the subsequent drying process, the aqueous droplets in the emulsion gradually evaporate as a soft template, and the polymer undergoes phase separation and solidification on the fiber surface and between fibers, ultimately forming a multi-scale hierarchical porous structure, thereby increasing the specific surface area and active site density without damaging the macroscopic flow channels of the matrix.

[0058] The preferred mass ratio of organic solvent to water is because this ratio can form a stable and uniformly dispersed emulsion system. When the water phase ratio is too low, it is difficult to form an effective pore structure. When the water phase ratio is too high, droplet aggregation is likely to occur, leading to pore structure collapse.

[0059] The organic solvent includes at least one of toluene, xylene, chlorobenzene, and tetrahydrofuran, preferably toluene.

[0060] In some embodiments, in S3, the carbonization treatment conditions include: heating to 800°C to 1100°C at a rate of 8°C to 12°C per minute and treating for 30 to 180 minutes. Preferably, heating to 900°C to 1100°C at a rate of 9°C to 11°C per minute and treating for 60 to 180 minutes. More preferably, heating to 1000°C to 1100°C at a rate of 10°C per minute and treating for 60 to 120 minutes.

[0061] Another embodiment of the present invention provides the application of the electrode described herein or the electrode obtained by the preparation method described herein in a battery.

[0062] The multi-scale hierarchical porous electrode of the present invention can be applied to electrochemical devices such as flow batteries, fuel cells and electrolyzers, and is preferably applied to vanadium redox flow batteries as a positive or negative electrode.

[0063] The multi-scale hierarchical porous structure can increase the density of active sites while maintaining efficient electrolyte transport, thereby reducing mass transfer resistance and interfacial polarization, improving electrolyte utilization, reaction kinetics at current density, and battery energy efficiency and power density.

[0064] Applying the electrodes of this invention to batteries can improve their energy and power density. Furthermore, compared to traditional carbon cloth or carbon felt, this invention utilizes a liquid-liquid phase separation method to construct a multi-scale carbon network in situ on the fiber surface, significantly reducing the interfacial activation barrier and effectively extending the battery's charge-discharge depth. Therefore, this invention not only improves battery energy efficiency, electrolyte utilization, and charge-discharge depth, but also relatively suppresses side reactions.

[0065] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited to the following specific embodiments.

[0066] Example 1 This embodiment provides a method for preparing a multi-scale hierarchical porous electrode, including the following steps: (1) First, poly(styrene-co-vinylbenzyl chloride) was prepared as a precursor material for electrode modification. The specific steps are as follows: Approximately 0.05 g of 2,2'-azobis(2-methylpropionamide) dihydrochloride, used as an initiator, was dissolved in 50 mL of a cosolvent prepared by mixing deionized water and ethanol in a 3:2 volume ratio. Then, 7.5 mL of a monomer mixture was added to the system, with the volume ratio of 4-vinylbenzyl chloride to styrene strictly controlled at 1:2. After sealing the reaction vessel and continuously purging with nitrogen for 20 minutes to completely eliminate oxygen interference, the vessel was placed in a constant temperature environment of 80°C for 16 hours. The white copolymer precipitate after the reaction was completed was washed three times with ethanol and dried in a vacuum oven at 60°C for at least 12 hours to ensure the acquisition of a high-purity copolymer powder, namely poly(styrene-co-vinylbenzyl chloride).

[0067] (2) Modify the carbon cloth with the precursor material poly(styrene-co-vinylbenzyl chloride). The specific steps are as follows: To construct a uniform porous coating on the surface of carbon fiber, 0.10 g of the copolymer powder synthesized in step (1) was dissolved in 1.20 g of toluene solvent, and 0.36 g of deionized water (water-to-oil mass ratio of 0.3) was added according to the experimental design. The mixture was emulsified for 20 seconds using a high-power ultrasonic pulverizer at a preset output power to form a stable water / polymer / toluene emulsion. A carbon fiber disc with a diameter of 13 mm was immersed in the emulsion to allow the emulsion to penetrate the pores of the carbon fiber. After drying at room temperature, an electrode loaded with a porous polymer structure (i.e., a copolymer network modified carbon fiber electrode) was formed. To further enhance structural stability and improve conductivity, the electrode was immersed in concentrated sulfuric acid at 80°C for 2 hours to complete the crosslinking and sulfonation reaction, and then repeatedly rinsed with deionized water until the pH of the filtrate reached neutral. Finally, the dried sample was placed in a tube furnace under argon protection and heated to 1100°C at a rate of 10°C per minute for 60 minutes for high-temperature carbonization treatment, thus preparing a multi-scale hierarchical porous electrode with high electrochemical activity (i.e., carbon network modified carbon cloth electrode).

[0068] like Figure 1 As shown, this embodiment employs a liquid-liquid phase separation method to construct a multi-scale carbon network modification layer in situ on a carbon cloth substrate. The aim is to create a modification structure with varying pore sizes between the carbon fiber surface and the fibers through the spontaneous induction of surface tension during solvent drying. First, a stable ternary copolymer emulsion needs to be prepared, and the original carbon cloth electrode is then fully immersed in the emulsion. See details below. Figure 1 (a) In this process, the fully impregnated carbon is dried at room temperature. During this process, the solvent gradually evaporates to form the framework structure of the copolymer, as detailed in (a). Figure 1 (b) of the example. The chemical formula of the polymer prepared in Example 1 is as follows: Figure 1 As shown in (c), where x, y, and z represent the relative content of each unit in the polymer, it can be seen that the formed polymer molecular chain simultaneously contains strongly hydrophilic hydroxyl groups (-OH) and benzene rings and chlorine groups (-Cl) that are easily soluble in organic solvents (such as toluene). This unique amphiphilic structure allows it to accumulate at the oil-water interface, effectively reducing interfacial tension and stabilizing the two-phase emulsion. See [details omitted]. Figure 1 (c) in the text; it should be noted that, Figure 1 The polymer chain shown in (c) contains strongly hydrophilic hydroxyl groups (-OH) because ethanol, used as a solvent in the actual reaction, participates in partial substitution, grafting, or subsequent oxidation processes, which may result in a small number of oxygen-containing functional groups in the final characterization. Therefore, this amphiphilic structure allows it to dissolve separately in the aqueous and oil phases, thus playing a stabilizing role at the liquid-liquid interface. Without this polymer, the oil and water phases would rapidly separate due to immiscibility, failing to form a network framework; however, under the action of the polymer, the small droplets in the aqueous phase, broken up by ultrasonic treatment, can be stably suspended in the oil phase without coalescence.

[0069] like Figure 2 As shown, in the experiment, the copolymer powder was first dissolved in the toluene oil phase, followed by the addition of deionized water in a specific ratio. After high-energy ultrasonic treatment, the hydrophilic groups extended into the aqueous phase, while the lipophilic groups anchored in the oil phase, forming a uniform, non-stratified milky-white emulsion. Without this type of copolymer, the oil-water mixture would rapidly undergo macroscopic phase separation, preventing the formation of an effective modification network on the electrode surface during subsequent evaporation. Subsequently, the carbon cloth was completely immersed in the emulsion, and controlled solvent evaporation was used to drive phase separation and solidification of the polymer between the fibers. Finally, a multi-scale hierarchical porous electrode was obtained through high-temperature carbonization.

[0070] Example 2 The difference from Example 1 is that in step (2), the amount of deionized water added is changed to 0.12 g, that is, the water-oil mass ratio is 0.1, and the rest is the same as in Example 1.

[0071] Example 3 The difference from Example 1 is that in step (2), the amount of deionized water added is changed to 0.6g, that is, the water-oil mass ratio is 0.5, and the rest is the same as Example 1.

[0072] Example 4 The difference from Example 1 is that in step (2), the carbonization temperature is changed to 800°C, while the rest is the same as in Example 1.

[0073] Example 5 The difference from Example 1 is that in step (2), the carbonization temperature is changed to 900°C, while the rest is the same as in Example 1.

[0074] Example 6 The difference from Example 1 is that in step (2), the carbonization temperature is changed to 1000℃, while the rest is the same as in Example 1.

[0075] Example 7 The difference from Example 1 is that “poly(styrene-co-vinylbenzyl chloride)” is replaced with “poly(styrene-co-4-vinylpyridine)”, otherwise it is the same as Example 1.

[0076] Example 8 The difference from Example 1 is that: before step (2), the carbon cloth is first immersed in concentrated sulfuric acid at 80°C for 2 hours, then washed with deionized water until neutral and dried. The other steps are the same as in Example 1.

[0077] Comparative Example 1 The difference from Example 1 is that “poly(styrene-co-vinylbenzyl chloride)” is replaced with “polystyrene”, otherwise it is the same as Example 1.

[0078] Comparative Example 2 The difference from Example 1 is that deionized water is not added in step (2), and only copolymer / toluene solution is used for impregnation. Otherwise, it is the same as Example 1.

[0079] Tests and Results: The multi-scale hierarchical porous electrodes prepared in the examples and the electrodes prepared in the comparative examples were characterized and tested, and the results are as follows: 1. Characterization The key to electrode morphology control lies in optimizing the water-to-oil ratio and selecting the appropriate carbonization temperature. For example... Figure 3 As shown, the water-to-oil ratio is a key parameter determining the microstructure of the modified electrode. When the water-to-oil ratio is 0.1, due to the insufficient water content of the dispersed phase and its surrounding by a large amount of oil phase, the pores are easily covered by a thick polymer framework after evaporation, making it difficult to form an effective modification network. (See details...) Figure 3 (a) In this context, when the water-to-oil ratio is increased to 0.3, the broken deionized water droplets are most evenly and stably distributed in toluene, and a large number of clear porous framework structures can be observed between the fibers. (See section (a) for details.) Figure 3 (b) If the ratio is further increased to 0.5, the excessively high proportion of water phase will cause droplet coalescence during the heating and evaporation process, leading to the fracture of the resulting framework structure due to uneven stress. See details in section (b). Figure 3 (c) Therefore, this invention determines 0.3 as the optimal water-to-oil ratio. In optimizing electrode performance, the selection of the carbonization temperature is crucial for improving the electrochemical kinetics of the electrode. For example... Figure 4 As shown in the electrochemical impedance spectroscopy, as the carbonization temperature gradually increased from 800°C to 1100°C (corresponding to Examples 2-6), the intersection point of the high-frequency region and the real axis shifted significantly to the left, indicating that the ohmic impedance decreased significantly with increasing temperature. This is mainly attributed to the high-temperature treatment promoting the complete carbonization of the polymer network precursor, which significantly improved the electrical contact interface between the carbon network and the original carbon cloth fiber substrate while enhancing the intrinsic conductivity of the material. Simultaneously, the semicircular diameter of the mid-frequency region, representing the charge transfer impedance, also drastically decreased. Electrodes prepared at 1100°C exhibited the lowest polarization impedance in both positive and negative electrode electrolytes. This fully demonstrates that the high-temperature carbonization process endows the carbon network with a more active electrocatalytic surface and superior electron transport capability, thereby significantly accelerating the redox reaction kinetics of vanadium ions at the interface. Therefore, the optimal process conditions were determined to be: a water-to-oil ratio of 0.3 and a carbonization temperature of 1100°C.

[0080] The modified electrode in Example 1 exhibits highly ordered and functionally partitioned multi-scale morphological features, and its evolution process is as follows: Figure 5 As shown in the schematic diagram: from the original carbon cloth with a smooth surface, see details... Figure 5In (a), it evolves into a modified carbon cloth covered by a polymer network, see details. Figure 5 In (b), the final process involves carbonization to transform the material into a conductive carbon network framework, as detailed in [link to documentation]. Figure 5 (c) in Example 1. Furthermore, the modified electrode in Example 1 exhibits highly ordered and functionally partitioned multi-scale morphological features, such as... Figures 6-7 The morphological observations shown demonstrate that this process successfully constructed a differentiated pore gradient through phase separation: on the surface of a single fiber, see details... Figure 6 In (a), due to the physical constraints of the extremely thin liquid film and the affinity of the fiber surface, a dense modification layer dominated by 1μm~2μm micropores was formed; while in the triangular region where the fiber bundles intersect, see [details omitted]. Figure 6 In (c), driven by surface tension, the emulsion converges towards the gaps and undergoes moderate droplet coalescence, evolving into an irregular macroporous structure with a diameter of 5μm~15μm. The design logic of this gradient distribution is that structural optimization is beneficial for balancing mass transfer and electrochemical reaction. If the entire structure is covered by micropores, although it can provide an extremely high specific surface area, it will lead to severe fluid resistance, preventing the electrolyte from penetrating deep into the electrode; if the entire structure is macropores, although the mass transfer is good, there is a lack of sufficient active sites, limiting the overall power output. The multi-scale design in this study utilizes the macropores between fibers as channels for efficient electrolyte flow to ensure macroscopic mass transfer throughout the entire domain, while utilizing the micropores on the fiber surface to provide sufficient effective reaction area, thereby greatly improving the energy and power density of the battery while maintaining an extremely low voltage drop.

[0081] Furthermore, experimental results show that, similar to Example 1, the modified electrode in Example 7 also exhibits highly ordered and functionally partitioned multi-scale morphological features. Therefore, multi-scale hierarchical porous electrodes can also be prepared using poly(styrene-co-4-vinylpyridine) as a raw material. Similarly, the modified electrode in Example 8 also exhibits highly ordered and functionally partitioned multi-scale morphological features. However, the electrode prepared in Comparative Example 1 did not form multi-scale morphological features because a single hydrophobic polymer cannot form a stable oil-water interface, making it difficult to construct a continuous porous network, resulting in poor electrode pore structure and electrochemical performance. Similarly, the electrode prepared in Comparative Example 2 also did not form multi-scale morphological features because "emulsion template" and "liquid-liquid phase separation" play a very important role in forming a hierarchical porous structure. Since deionized water was not added in Comparative Example 2, a stable water / copolymer / toluene emulsion could not be formed, and the spontaneous induction of surface tension during solvent drying could not lead to the formation of a modified structure with different pore sizes on the carbon fiber surface and between the fibers.

[0082] 2. Material property testing The surface structure of the electrodes before and after modification was characterized using Raman spectroscopy. For example... Figure 8As shown, the original carbon fiber electrode, the copolymer network modified electrode, and the carbon network modified electrode are compared at 100 cm⁻¹. -1 ~3600 cm -1 A distinct D band (~1350 cm) was observed throughout the range. -1 (representing the disorder and defect sites of carbon atoms) and the G-band (1590 cm⁻¹) -1 (Representing a graphitized structure with sp2 hybridization). Calculations show that the ID / IG ratio of the carbon network-modified electrode (approximately 1.39) is significantly higher than that of the original carbon cloth (approximately 1.32). This indicates that the carbon network, derived from the polymer precursor, introduces edge active sites and structural defects, providing more physical active centers for redox reactions. Notably, due to the large number of pores exposing the original fibers in the porous network, and the laser focusing at the fiber center during testing, the test curves of each sample show a certain similarity. This indirectly confirms that the modified layer achieves functional enhancement while maintaining the integrity of the substrate structure.

[0083] Elemental scanning via EDS ( Figure 9 ) and XPS spectra ( Figure 10 The chemical composition changes on the electrode surface were quantitatively analyzed. EDS results confirmed that carbon and oxygen elements were uniformly distributed on the modified fiber surface. Figure 9 Compared to highly graphitized carbon cloth, polymer carbonization may introduce more oxygen-containing functional groups, which was verified in XPS tests.

[0084] like Figure 10 As shown in (a), the XPS full spectrum further confirms that the oxygen signal peak intensity of the modified electrode is increased by an order of magnitude compared to the original carbon cloth. Figure 10 As shown in (b) of the figure, in the C 1s fine spectrum, the peak area ratio of the modified electrode at 286.5 eV (CO bond) and 288.5 eV (C=O bond) is significantly increased. Meanwhile, as... Figure 10 As shown in (c), the O 1s fine spectrum also exhibits a consistent trend, with a significant increase in the signal intensity representing C=O bonds (531.5 eV) and CO bonds (532.8 eV). This dramatic increase in the proportion of oxygen-containing functional groups is mainly due to the selective retention and transformation of oxygen-rich molecular chain segments in the ternary copolymer precursor during controlled carbonization. The introduction of these polar functional groups not only improves the hydrophilicity of the carbon cloth surface, giving it a better wetting angle in aqueous electrolytes, but more importantly, these oxygen-containing groups can act as chemically active sites, significantly accelerating the electron exchange efficiency of vanadium ions at the electrode interface by lowering the charge transfer energy barrier, thereby comprehensively enhancing the electrochemical reactivity of RFB.

[0085] 3. Electrochemical performance testing (1) Three-electrode test This invention provides a detailed evaluation of the positive electrode electrochemical kinetics of the carbon network-modified carbon cloth (i.e., a multi-scale hierarchical porous electrode) in Example 1 using a three-electrode system. The electrode prepared in Example 1 was used as the working electrode, and a saturated calomel electrode was used as the reference electrode. A 2 cm² electrode was used as the reference electrode. 2 ×2 cm 2 Platinum wire was used as the counter electrode for testing in a solution containing 0.1 mol / L VO2. 2+ or V 3 + The reaction kinetics were analyzed using ions and an electrolyte of 3.0 mol / L H₂SO₄, covering both positive and negative half-cells. Cyclic voltammetry was used to investigate redox reaction rates at different scan rates from 1 mV / s to 10 mV / s, and Tafel slope analysis was performed to evaluate the ease of charge transfer.

[0086] The results showed that at a scan rate of 10 mV / s, the oxidation peak current of the original carbon cloth was approximately 22.2 mA (at 1.305 V), and the reduction peak current was approximately -14.0 mA (at 0.452 V), with a peak potential interval as high as 853 mV. After modification with a carbon network, at the same scan rate, the oxidation peak current significantly increased to approximately 33.1 mA and the peak potential shifted to the left to around 1.305 V; the reduction peak current increased to approximately -31.8 mA and the peak potential shifted to around 0.645 V, resulting in a significant reduction in the peak potential interval to 470 mV. This indicates that the carbon network exhibits stronger redox reversibility and superior electrocatalytic activity in the positive electrode reaction. Tests for the negative electrode reaction were conducted in a solution containing 0.1 mol / L V. 3+ Developed in an electrolyte of 3.0 mol / L H₂SO₄ at a scan rate of 10 mV / s, the original carbon cloth exhibited significantly sluggish kinetics, with an oxidation peak current of only about 11.7 mA (located at -0.141 V) and no obvious reduction peak observed in the reduction direction. This is because the surface of the original carbon cloth lacks catalytic activity, leading to excessive polarization of the vanadium reduction reaction, which severely overlaps with the hydrogen evolution reaction, masking the reduction current. In contrast, the carbon network-modified electrode showed a significant increase in oxidation peak current to 27.5 mA (located at -0.234 V) at the same scan rate, and exhibited a clear reduction peak (approximately -30.4 mA, located at -0.831 V), with a peak potential interval of only 597 mV. These results intuitively demonstrate that the carbon network induced by phase separation can significantly reduce the charge transfer barrier.

[0087] pass Figure 11 A linear fit between the peak current density and the square root of the sweep rate reveals a very high linear correlation between the two (R0). 2>0.99). This result quantitatively confirms that the redox reaction of vanadium ions on the carbon network-modified electrode surface is dominated by the diffusion process. Particularly significant is the substantial increase in the fitting slope of the modified electrode compared to the original carbon cloth. Since the slope is positively correlated with the square root of the effective reaction area and the diffusion coefficient, this fully demonstrates that the phase separation-induced multi-scale structure not only achieves the growth of active sites through numerous hierarchical micropores but also ensures electrolyte transport by forming macropores between fibers, thereby significantly enhancing the interfacial transport kinetics and current response of ions.

[0088] (2) Full battery performance test The electrodes prepared in Example 1 were assembled into a full cell as follows: First, a stainless steel end plate was placed flat on a horizontal platform, followed by the stacking of an insulating plate and a gold-plated copper current collector. Then, a graphite bipolar plate with flow field grooves was embedded. A pre-cut silicone gasket was laid flat within the sealing groove on the outer edge of the electrode plate, and the carbon cloth electrode (the multi-scale hierarchical porous electrode of Example 1), pre-impregnated with electrolyte, was precisely embedded into the central region of the flow field, ensuring a tight fit between the carbon cloth edge and the gasket. Next, a swollen ion exchange membrane was laid flat above the gasket, ensuring the membrane surface covered all sealing areas without any wrinkles or air bubbles. Then, the assembly stage began. A sealing gasket from the other side was placed on top of the separator, the carbon cloth electrode was embedded, and the second graphite bipolar plate and current collector were fastened. Before installing the top end plate, it was confirmed that the inlet and outlet connectors were wrapped with PTFE tape and screwed into the electrode plate. Finally, insert the eight bolts symmetrically into the holes in the end plate, and use a torque wrench to tighten them one by one in three stages (50%, 80%, and 100% of the design torque) according to the "diagonal cross" principle, so that the gaskets will deform evenly until the predetermined carbon cloth compression thickness is reached, thus completing the structural fastening.

[0089] Full cell charge-discharge curves with different electrodes ( Figure 12 This revealed the significant role of structural optimization in reducing polarization. (At 100 mA / cm) 2 Below, the discharge capacities of the original carbon cloth and the modified carbon cloth are 0.806 Ah and 0.812 Ah, respectively. See details below. Figure 12 (a) shows that as the current density increases, the charge-discharge voltage difference of the original carbon cloth battery increases, while its capacity decreases significantly. Its initial charge-discharge voltage difference is around 200 mA / cm². 2 The voltage is 50 mV, see details. Figure 12 (b) in the example is at 300 mA / cm 2 The voltage even reached as high as 239 mV, see details below. Figure 12 (c) In contrast, the carbon network modified electrode significantly suppressed electrochemical polarization, with a discharge capacity of 200 mA / cm². 2 The voltage was maintained at 0.776 Ah (original carbon cloth was 0.714 Ah) at 300 mA / cm.2 The voltage is still as high as 0.703 Ah, while the original carbon cloth is only 0.572 Ah, representing an increase of 22.9%. Notably, due to the significant reduction in polarization, the modified electrode has a lower charging voltage and a higher discharging voltage at the beginning of the charge and discharge phases. Its initial charging voltage is even lower than the discharge voltage level of the original electrode, showing a significant difference from the original electrode.

[0090] Ratio performance data ( Figure 13 This more intuitively reveals the comprehensive improvement in battery efficiency brought about by carbon network modification. Figure 13 As shown in (a), the coulombic efficiency of both battery groups remained above 96% at all tested current densities. However, the voltage efficiency showed a significant difference with increasing current density: at 200 mA / cm²... 2 300 mA / cm 2 and 400 mA / cm 2 At current densities of [value missing], the carbon network-modified electrode showed improvements of 9.0%, 11.6%, and 14.1% compared to the original carbon cloth, respectively. This was particularly evident at 400 mA / cm². 2 At that time, the voltage efficiency of the modified electrode cell was approximately 78.5%, significantly higher than the 64.6% of the original carbon cloth cell. The energy efficiency showed a similar evolution trend, as detailed in [link to relevant documentation]. Figure 13 (b) in the example is at 200 mA / cm 2 300mA / cm 2 and 400 mA / cm 2 At these levels, the energy efficiency improvements were 9.94%, 12.1%, and 14.8%, respectively. Specifically, at 300 mA / cm²... 2 At that time, the average energy efficiency of the modified electrode cell was approximately 82.4%, while that of the original carbon cloth cell was only 70.2%; at 400 mA / cm 2 At that time, the average energy efficiency of the modified electrode battery was approximately 77.7%, while that of the original carbon cloth battery was only 63.3%, showing a significant improvement. Furthermore, the improvement in electrolyte utilization became increasingly pronounced with increasing current density, as detailed in [see details]. Figure 13 (c) in: at 200 mA / cm 2 300 mA / cm 2 and 400 mA / cm 2 At these levels, the utilization rates increased by 11.2%, 19.9%, and 32.8%, respectively. Specifically, at 300 mA / cm²... 2 At current density, the utilization rate of the assembled modified electrode cell jumped from 57.2% with the original carbon cloth to 77.3%; at 400 mA / cm², 2 The 32.8% improvement under high current density fully demonstrates that this multi-scale ordered structure has superior performance under high current density.

[0091] Figure 14 The discharge polarization curves show that the peak power density of the modified electrode reaches 1.28 W / cm². 2 Compared to the original carbon cloth's 0.92 W / cm 2 It increased by approximately 39.1%.

[0092] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A multi-scale hierarchical porous electrode, characterized in that, The multi-scale hierarchical porous electrode includes a substrate and a carbon network modification layer modified in the substrate; The carbon network modification layer is formed by carbonization of an amphiphilic polymer, wherein the molecular chain of the amphiphilic polymer contains hydrophilic and hydrophobic groups; The matrix is ​​a fiber-containing matrix, and the carbon network modification layer modifies the fiber surface in the matrix and the gaps between the fibers in the matrix. The carbon network modification layer forms a structure with a first micropore on the fiber surface in the matrix, and the carbon network modification layer forms a structure with a second micropore in the gap between the fibers in the matrix, wherein the pore size of the first micropore is smaller than the pore size of the second micropore. The amphiphilic polymer is at least one of poly(styrene-co-vinylbenzyl chloride), poly(styrene-co-4-vinylpyridine), poly(styrene-co-sodium p-styrene sulfonate), and poly(styrene-co-N,N-dimethyl-4-vinylaniline); The substrate is at least one of carbon cloth, carbon felt, graphite felt, and carbon paper.

2. The multi-scale hierarchical porous electrode according to claim 1, characterized in that, The first micropore has a pore size of 1μm to 2μm, and the second micropore has a pore size of 5μm to 15μm.

3. The method for preparing the multi-scale hierarchical porous electrode according to claim 1 or 2, characterized in that, Includes the following steps: S1. An initiator, a first solvent containing hydrophilic groups, styrene, and vinyl benzyl chloride are mixed and reacted under an inert gas atmosphere to obtain an amphiphilic polymer; the first solvent containing hydrophilic groups is a mixed solvent of water and ethanol. S2. The amphiphilic polymer is added to a second solvent and emulsified to form an emulsion. The matrix is ​​then immersed in the emulsion, removed, and dried. The second solvent is a mixture of an organic solvent and water, with a mass ratio of 1:0.2 to 0.

4. S3. The substrate is carbonized in an inert gas atmosphere to obtain the multi-scale hierarchical porous electrode.

4. The method for preparing the multi-scale hierarchical porous electrode according to claim 1 or 2, characterized in that, Includes the following steps: S1. An initiator, a first solvent containing a hydrophilic group, and styrene are mixed and reacted under an inert gas atmosphere to obtain an amphiphilic polymer; the reaction also includes adding a first monomer containing a hydrophilic group; wherein the first monomer containing a hydrophilic group is at least one of sodium p-styrene sulfonate, 4-vinylpyridine, and N,N-dimethyl-4-vinylaniline. S2. The amphiphilic polymer is added to a second solvent and emulsified to form an emulsion. The matrix is ​​then immersed in the emulsion, removed, and dried. The second solvent is a mixture of an organic solvent and water, with a mass ratio of 1:0.2 to 0.

4. S3. The substrate is carbonized in an inert gas atmosphere to obtain the multi-scale hierarchical porous electrode.

5. The preparation method according to claim 3 or 4, characterized in that, S3 further includes sulfonating the matrix prior to the carbonization treatment, wherein the sulfonation treatment method includes: The matrix is ​​immersed in concentrated sulfuric acid at 70°C to 90°C for 1 to 3 hours, and then rinsed with deionized water until the pH of the filtrate reaches neutral.

6. The preparation method according to claim 3, characterized in that, In S1, The volume ratio of water to ethanol is 2.5~3.5:2; The reaction temperature is 70℃~90℃, and the reaction time is 14 hours~18 hours.

7. The preparation method according to claim 4, characterized in that, In S1, The first solvent containing hydrophilic groups is a mixed solvent of water and ethanol, with a volume ratio of water to ethanol of 2.5 to 3.5:

2. The reaction temperature is 70℃~90℃, and the reaction time is 14 hours~18 hours.

8. The preparation method according to claim 4, characterized in that, The volume ratio of the first monomer containing the hydrophilic group to styrene is 2.0~3.0 : 4.5~5.

5.

9. The preparation method according to claim 3 or 4, characterized in that, In S2, the organic solvent is toluene; the mass ratio of the amphiphilic polymer to the organic solvent is 0.1:1.1~1.3; In S3, the carbonization treatment conditions include: heating to 800℃~1100℃ at a rate of 8℃~12℃ per minute and treating for 30 min~180 min.

10. The application of the multi-scale hierarchical porous electrode according to any one of claims 1 to 2 or the multi-scale hierarchical porous electrode obtained by the preparation method according to any one of claims 3 to 9 in a battery.

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