A bipolar plate for zinc-bromine flow battery based on ppy / SA and pedot / SA, a preparation method and application thereof

Abstract

The application discloses a zinc-bromine flow battery bipolar plate based on PPy / SA and PEDOT / SA, a preparation method and application, and belongs to the technical field of electrochemical energy storage. The method comprises the following steps: spraying PPy / SA composite dispersion liquid prepared by in-situ polymerization of sodium alginate and pyrrole monomers at a low temperature on the positive electrode side, and spraying PEDOT / SA composite dispersion liquid prepared by in-situ polymerization of sodium alginate and 3,4-ethylenedioxythiophene monomers at a low temperature on the negative electrode side. The conjugated conductive network of PPy and the hydrophilic network of SA in the PPy / SA composite layer are used to synergistically inhibit bromine permeation, reduce bromine reaction activation energy and improve interface wettability. The high-conductive network of PEDOT and the hydrophilic network of SA in the PEDOT / SA composite layer are used to synergistically eliminate potential gradient, homogenize zinc ion distribution, lock free water and buffer pH, synchronously inhibit zinc dendrite growth and hydrogen evolution side reaction, and realize systematic improvement of the electrical performance of the battery.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage technology, specifically relating to a zinc-bromine flow battery bipolar plate based on PPy / SA and PEDOT / SA, its preparation method, and its application. Background Technology

[0002] Zinc-bromine flow batteries possess advantages such as high energy density, low cost, and long cycle life, and have broad application prospects in large-scale energy storage. However, their industrialization has long been limited by the following core bottlenecks: the active bromine species in the positive electrode (Br3). - / Br2) penetrates the membrane, triggering self-discharge, leading to a sharp drop in coulombic efficiency and continuous capacity decay; bromine / bromine (Br2 / Br) at the positive electrode - The conversion reaction involves multiple steps and requires high activation energy. Furthermore, to improve the solubility of bromine (Br2) and prevent its volatilization, complexing agents are typically added, but this complicates the reaction pathway, slows down the Br2 reaction kinetics, and becomes a bottleneck in battery performance, leading to high polarization voltage, low voltage efficiency, and limited power density, ultimately resulting in low energy efficiency. Uneven electric field distribution at the negative electrode makes it easy for zinc deposition to form dendrites, which can easily puncture the separator and cause a short circuit. It also easily leads to hydrogen evolution reaction, threatening safety and limiting cycle life. In addition, traditional carbon-plastic bipolar plates also suffer from insufficient resistance to bromine corrosion, high interfacial resistance, and inertness to bromine reactions.

[0003] Chinese patent application CN122025691A discloses a carbon-plastic bipolar plate for a zinc-bromine flow battery, employing a positive and negative electrode partitioning modification strategy. The positive electrode side is loaded with nitrogen-doped hollow carbon nanotubes, utilizing their nitrogen-doped sites to catalyze the bromine reaction; the hollow structure adsorbs bromine species to inhibit bromine permeation. The negative electrode side is loaded with boron-nitrogen co-doped carbon, utilizing the zinc-loving sites of BN to guide uniform zinc deposition and inhibit dendrite growth. However, both the nitrogen-doped hollow carbon nanotubes and the boron-nitrogen co-doped carbon materials used require high-temperature pyrolysis at 800-1000℃. Furthermore, while the negative electrode modification layer can guide zinc deposition, its suppression of the hydrogen evolution side reaction mainly relies on charge regulation, lacking direct management of the interfacial microenvironment, such as water activity and pH. Simultaneously, this scheme does not mention how to systematically reduce the interfacial contact resistance between the bipolar plate and the electrodes or improve electrolyte wettability. Chinese patent application CN121307076A discloses a multifunctional bipolar plate with positive and negative electrode partitioning modification. The positive electrode side is loaded with polyaniline, which utilizes its electrostatic repulsion to block bromide anions and accelerates electron transfer through redox reactions; the negative electrode side is loaded with a cyclodextrin polymer / Nafion composite coating, which utilizes the nanochannels of cyclodextrin to confine Zn. 2+In the diffusion direction, Nafion forms ion channels to stabilize the interfacial pH and synergistically regulate zinc deposition. Its negative electrode modifier is a cyclodextrin polymer / Nafion organic system, which, while possessing some ion regulation capability, has poor electronic conductivity and cannot provide an efficient electron transport pathway for the zinc deposition / dissolution reaction. Its mechanism for inhibiting zinc dendrite formation mainly relies on physical confinement and ion conduction, lacking specific targeting of Zn. 2+ The active sites with strong chemisorption properties have limited effectiveness in guiding uniform zinc nucleation and fundamentally inhibiting dendrite growth. Furthermore, the long-term stability of polyaniline and cyclodextrin polymers in strong oxidizing and acidic environments also faces challenges.

[0004] Therefore, there is an urgent need to develop a novel bipolar plate material that combines high catalytic activity, high ion / electron conductivity, strong chemical stability, and simple preparation process to simultaneously solve key problems such as bromine permeation, slow reaction kinetics, and zinc dendrite growth. This is of great significance for improving the performance of zinc-bromine flow batteries and promoting their practical application. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a zinc-bromine flow battery bipolar plate based on PPy / SA and PEDOT / SA, as well as its preparation method and application, to solve the technical problem that existing zinc-bromine flow battery bipolar plates are unable to simultaneously achieve bromine permeation suppression and catalytic activity on the positive electrode side, and zinc dendrite growth suppression and hydrogen evolution side reaction control on the negative electrode side.

[0006] To achieve the above objectives, the present invention employs the following technical solution: This invention discloses a method for preparing a zinc-bromine flow battery bipolar plate based on PPy / SA and PEDOT / SA, comprising: Sodium alginate powder was dissolved in deionized water to obtain an SA aqueous solution; p-Toluenesulfonic acid, pyrrole monomer, and ammonium persulfate were added to an aqueous SA solution, and an in-situ polymerization reaction was carried out under ice bath conditions to obtain a PPy / SA composite dispersion. The PPy / SA composite dispersion was sprayed onto the positive electrode side of a pretreated carbon-plastic bipolar plate, and after drying, a PPy / SA modified positive carbon-plastic bipolar plate was obtained. Sodium polystyrene sulfonate, 3,4-ethylenedioxythiophene monomer, and ammonium persulfate were added to an aqueous SA solution, and an in-situ polymerization reaction was carried out under ice bath conditions to obtain a PEDOT / SA composite dispersion. The PEDOT / SA composite dispersion was sprayed onto the negative electrode side of a pretreated carbon-plastic bipolar plate, and after drying, a PEDOT / SA modified negative electrode carbon-plastic bipolar plate was obtained.

[0007] Preferably, the pretreatment of the carbon-plastic bipolar plate includes: ultrasonically cleaning the carbon-plastic bipolar plate with ethanol or deionized water for 15-30 min, and then drying it in a vacuum drying oven at 40-60℃ for 12-24 h.

[0008] Preferably, in the preparation of the PPy / SA composite dispersion, the ratio of sodium alginate powder, p-toluenesulfonic acid, pyrrole monomer and ammonium persulfate is (500-2500) mg: 100 mg: (1000-3000) mg: (40-60) mL; the molar concentration of ammonium persulfate is 0.5 mol / L; and the mass concentration of the SA aqueous solution is 5-25 mg / mL.

[0009] Preferably, in the preparation of the PPy / SA composite dispersion, the temperature of the in-situ polymerization reaction is 0-5℃, and the time of the in-situ polymerization reaction is 4-6 h.

[0010] Preferably, in the preparation of the PPy / SA modified positive carbon-plastic bipolar plate, the spraying speed of the PPy / SA composite dispersion is 5-10 mL / min, the spraying time is 5-10 min, the drying temperature is 60-80℃, and the drying time is 6-12 h.

[0011] Preferably, in the preparation of the PEDOT / SA composite dispersion, the ratio of sodium alginate powder, sodium polystyrene sulfonate, 3,4-ethylenedioxythiophene monomer and ammonium persulfate is (500-2500) mg: 100 mg: (500-2500) mg: (40-60) mL; and the mass concentration of the SA aqueous solution is 5-25 mg / mL.

[0012] Preferably, in the preparation of the PEDOT / SA composite dispersion, the temperature of the in-situ polymerization reaction is 0-5℃, and the time of the in-situ polymerization reaction is 4-6 h.

[0013] Preferably, in the preparation of the PEDOT / SA modified negative electrode carbon-plastic bipolar plate, the spraying speed of the PEDOT / SA composite dispersion is 5-10 mL / min, the spraying time is 5-10 min, the drying temperature is 60-80℃, and the drying time is 6-12 h.

[0014] The present invention also discloses a zinc-bromine flow battery bipolar plate based on PPy / SA and PEDOT / SA, which is prepared by the above-mentioned preparation method of zinc-bromine flow battery bipolar plate based on PPy / SA and PEDOT / SA.

[0015] The present invention also discloses the application of the above-mentioned zinc-bromine flow battery bipolar plates based on PPy / SA and PEDOT / SA in the preparation of zinc-bromine flow batteries, wherein the coulombic efficiency of the zinc-bromine flow batteries is 91.4%-97.1%; the voltage efficiency is 83.2%-87.2%; and the energy efficiency is 76.04%-84.67%.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a method for preparing a zinc-bromine flow battery bipolar plate based on PPy / SA and PEDOT / SA. The method involves modifying the positive electrode side of the PPy / SA and PEDOT / SA-based zinc-bromine flow battery bipolar plate with a PPy / SA composite dispersion. SA polymer chains intertwine with PPy particles / networks to construct microchannels with specific pore size distribution and tortuous structures. Compared to Br... - The polybrominated compounds (Br3) generated at the positive electrode - / Br5 - With a larger Stokes radius and stronger hydration, PPy experiences significant steric hindrance and tortuous path effects when traversing the modified layer, resulting in a decreased apparent diffusion coefficient. This effectively reduces the free diffusion of bromine, mitigating bromine permeation, lowering self-discharge and capacity decay, and significantly improving the battery's coulombic efficiency and cycle capacity retention. PPy can compensate for potential micro-insulation points, oxide films, or resistivity inhomogeneities on the bipolar plate surface, leading to a more uniform current distribution. This uniform current distribution avoids localized reaction hotspots, allowing bromine redox to occur more evenly across the entire positive electrode interface, resulting in a lower redox overpotential and a more complete reaction. PPy is a conjugated polymer with a main chain composed of alternating single and double bonds. π electrons are delocalized along the main chain, forming delocalized π bonds. This delocalized π electron system gives PPy metallic-like conductivity, and the carbon and nitrogen atoms on the main chain exist in different oxidation states, possessing the ability to accept or donate electrons. In the redox reaction of bromine, electrons can be transferred via delocalized π bonds, making electron transfer more continuous and faster, thereby lowering the activation energy of the reaction; the conjugated π system can react with the reactant species (Br). - Br2 and Br3 - The formation of weak π-π or electrostatic interactions stabilizes the reaction transition state, significantly enhancing the bromine reaction kinetics; by optimizing the electron transfer path and stabilizing the transition state, Br... -The oxidation and Br2 reduction reaction pathways are smoother and the kinetics are faster. SA is rich in hydrophilic groups -OH and -COONa, which can improve the wettability of the bipolar plate surface to the bromine electrolyte, reduce dry spots and micro-gaps, allow the electrolyte to contact the conductive layer more fully, improve the utilization of the reaction interface, and expand the effective reaction area, thereby allowing more effective reaction sites to participate in the bromine redox reaction. The PPy / SA composite layer improves the reaction kinetics and interface utilization of bromine through the synergistic effect of PPy conductivity equalization, PPy catalysis and SA increasing the reaction area, thereby improving the effect of bromine reaction. The PPy / SA composite layer significantly reduces the ohmic internal resistance of the battery by constructing electron and interface synergistic channels. On the one hand, PPy, as a highly conductive conjugated polymer, forms a continuous conductive network on the surface of the bipolar plate, which can effectively bridge and bypass possible micro-insulating spots, oxide films or uneven wetting areas on the substrate surface, providing additional parallel conductive paths, thereby significantly reducing surface resistance. On the other hand, SA's strong hydrophilicity greatly improves the wettability of the electrolyte to the bipolar plate interface, eliminates micro-gaps and contact blind zones, and reduces the additional contact resistance caused by physical contact discontinuities. This directly reduces the ohmic internal resistance of the battery during operation, thereby improving the battery's voltage efficiency and energy efficiency. The PPy / SA composite layer simultaneously suppresses activation polarization, concentration polarization, and local non-uniform polarization through multi-dimensional regulation. First, PPy's conjugated π system not only provides sufficient electron supply but also optimizes Br through redox-mediated action. - The charge transfer kinetics of the reaction with Br2 are improved, thereby reducing the activation overpotential. Secondly, the hydrophilic network and uniform film structure constructed by SA ensure uniform electrolyte distribution at the interface, effectively eliminating dead zones and local concentration gradients, significantly alleviating concentration polarization caused by limited mass transfer, thus improving the battery's voltage and energy efficiency. Modification with a PEDOT / SA composite dispersion on the negative electrode side of the bipolar plate allows the hydrophilic groups such as -OH and -COONa in the SA molecular chain to bind a large amount of water, forming a hydrogel / polymer-water network. This network provides a relatively ordered / continuous ion transport environment, promoting Zn... 2+ More uniform transmission allows Zn to be distributed closer to the surface of the bipolar plate. 2+ The distribution is smoother, thus avoiding the formation and growth of zinc dendrites. SA can also improve the surface wettability of the bipolar plate, reduce dry spots and localized electrolyte deficiency, thereby alleviating near-interface Zn... 2+Uneven supply and concentrated local current density facilitate more uniform zinc nucleation, reduce preferential nucleation and early vertical growth at defects / protrusions, promote a relatively dense two-dimensional deposition morphology, further suppress dendrites, and improve battery cycle life and safety. PEDOT has good conductivity, which eliminates the potential gradient on the bipolar plate surface, thus avoiding excessively high local current density caused by the tip effect. This promotes uniform distribution of zinc atoms, rather than random growth at protrusions, thereby achieving dense two-dimensional layered deposition of zinc, further effectively suppressing dendrites and improving battery cycle life and safety. On the one hand, SA molecular chains lock a large number of water molecules through hydrogen bonding and entanglement, significantly reducing the activity and quantity of free water, reducing HER reactants from the source; on the other hand, the -COO on the SA chain segments... - The / -COOH group affects local H + / OH - The distribution acts as a buffer, stabilizing the interface pH value and preventing localized acidification from exacerbating the hydrogen evolution reaction, thereby inhibiting the occurrence of the hydrogen evolution reaction and improving the battery coulombic efficiency. To improve the bipolar plate's resistance to bromine corrosion, PPy / SA composite dispersion and PEDOT / SA composite dispersion are used to modify the positive and negative electrode sides of the bipolar plate, respectively. The PPy / SA and PEDOT / SA coatings block direct contact between the electrolyte and the bipolar plate, and PPy and PEDOT themselves have excellent chemical inertness and oxidation resistance, effectively preventing embrittlement, perforation, or increased resistance of the bipolar plate caused by bromine corrosion. The PPy / SA composite layer significantly improves the positive electrode performance of zinc-bromine flow batteries through a synergistic mechanism of electrons and interfaces: the SA hydrophilic network constructs tortuous ion channels, utilizing steric hindrance and electrostatic repulsion to suppress polybromide penetration and reduce self-discharge; the PPy conjugated conductive network compensates for surface defects in the bipolar plates, homogenizes current distribution to avoid overpotential hotspots, and reduces the bromine redox activation energy and stabilizes the transition state through the delocalized π-electron system, accelerating reaction kinetics; simultaneously, SA improves wettability to eliminate dry spots and expand the effective reaction area. The two work synergistically to reduce ohmic internal resistance and activation / concentration polarization, reduce bromine shuttle and voltage loss, ultimately achieving a comprehensive improvement in battery coulombic efficiency, energy efficiency, and cycle stability. The PEDOT / SA composite layer also improves the performance of the negative electrode through multiple synergistic mechanisms: the SA hydrophilic network constructs ordered ion channels, homogenizing Zn... 2+The PPy / SA and PEDOT / SA inert composite layers distribute and eliminate dry spots, suppressing dendrite formation and localized current concentration. The highly conductive PEDOT network eliminates potential gradients, promoting two-dimensional dense deposition. Simultaneously, SA locks in free water and buffers pH, inhibiting hydrogen evolution reaction at its source. Furthermore, this PPy / SA and PEDOT / SA inert composite layer blocks direct contact between the electrolyte and the substrate, effectively resisting bromine corrosion with excellent chemical stability, significantly improving battery cycle life, coulombic efficiency, and safety. This invention achieves a systematic improvement in battery performance through the synergistic design of the positive electrode PPy / SA layer and the negative electrode PEDOT / SA layer: on the positive electrode side, bromine permeation is suppressed, the activation energy of the bromine reaction is reduced, reaction kinetics are accelerated, and ohmic resistance and concentration polarization are reduced; on the negative electrode side, the homogenized electric field suppresses zinc dendrite formation, locks in free water, buffers pH, effectively suppresses hydrogen evolution, and also reduces ohmic resistance and concentration polarization. The combined effect of these two layers results in a significant simultaneous improvement in both voltage efficiency and coulombic efficiency; Example 15 shows a voltage efficiency of 87.2% and a coulombic efficiency of 97.1%.

[0017] This invention discloses a zinc-bromine flow battery bipolar plate based on PPy / SA and PEDOT / SA. The zinc-bromine flow battery bipolar plate based on PPy / SA and PEDOT / SA, prepared using the method of this invention, features SA polymer chains interwoven with PPy particles / networks on the positive electrode side, forming a certain equivalent porosity and channels. Compared to Br... - The polybrominated compounds (Br3) generated at the positive electrode - / Br5 -With a larger Stokes radius and stronger hydration, the diffusion path is more tortuous when passing through these channels, resulting in a lower apparent diffusion coefficient. This effectively reduces the free diffusion of bromine, thereby alleviating bromine permeation, reducing self-discharge and capacity decay, and significantly improving the coulombic efficiency and cycle capacity retention of the battery. PPy can compensate for potential micro-insulation points, oxide films, or uneven resistivity on the surface of the bipolar plate, making current collection more uniform. Uniform current distribution avoids local reaction hotspots, allowing bromine oxidation-reduction to occur more evenly across the entire positive electrode interface, resulting in a lower redox overpotential and a more complete reaction. PPy's delocalized π-electron system gives it metal-like conductivity. Bromine oxidation-reduction electrons can be transferred via delocalized π bonds, reducing the activation energy of electron transfer. The conjugated π system can form weak π-π or electrostatic interactions with reactants, stabilizing the reaction transition state and lowering the reaction energy barrier. SA is rich in hydrophilic groups, which can improve the wettability of the bipolar plate surface to the bromine electrolyte, reduce dry spots and micro-gaps, allowing the electrolyte to contact the conductive layer more fully, improving the utilization rate of the reaction interface, and expanding the effective reaction area. The PPy / SA composite layer enhances the reaction kinetics and interfacial utilization of bromine through the synergistic effects of PPy's conductive current equalization, PPy catalysis, and SA's increased reaction area. Simultaneously, the PPy / SA composite layer significantly reduces the battery's ohmic resistance by constructing synergistic electron and interfacial channels: PPy forms a continuous conductive network, drastically reducing surface resistance; SA improves wettability, eliminates micro-gaps and contact blind zones, and reduces contact resistance. The PPy / SA composite layer also simultaneously suppresses activation polarization, concentration polarization, and localized non-uniform polarization through multi-dimensional regulation. On the negative electrode side, the hydrophilic groups such as -OH and -COONa in the SA molecular chain can bind a large amount of water, forming a hydrogel / polymer-water network, providing an ordered ion transport environment and promoting Zn... 2+ More uniform transmission, avoiding zinc dendrite formation; SA can also improve the surface wetting of the bipolar plate and alleviate near-interface Zn 2+ Uneven supply promotes dense two-dimensional deposition; PEDOT has good conductivity, eliminating the potential gradient on the surface of the bipolar plate, avoiding the tip effect, and achieving dense two-dimensional layered deposition of zinc; SA molecular chains lock a large number of water molecules through hydrogen bonding and entanglement, reducing free water activity, while the -COO on the SA chain segments... - The / -COOH group affects local H + / OH - The coatings act as a buffer, stabilizing the interface pH and inhibiting the hydrogen evolution reaction. Furthermore, the PPy / SA and PEDOT / SA coatings block direct contact between the electrolyte and the bipolar plate, and PPy and PEDOT themselves possess excellent chemical inertness and oxidation resistance, effectively preventing embrittlement, perforation, or increased resistance of the bipolar plate due to bromine corrosion.

[0018] This invention discloses the application of the PPy / SA and PEDOT / SA-based zinc-bromine flow battery bipolar plate in the fabrication of zinc-bromine flow batteries. Using this invention's PPy / SA and PEDOT / SA-based zinc-bromine flow battery bipolar plate to fabricate zinc-bromine flow batteries can achieve a comprehensive improvement in coulombic efficiency, energy efficiency, and cycle stability. On the positive electrode side, the PPy / SA composite layer, through an electronic and interfacial synergistic mechanism, utilizes the SA hydrophilic network to inhibit polybromination and reduce self-discharge, the PPy conductive network to homogenize current, reduce activation energy, and accelerate reaction kinetics, and the SA to improve wettability and expand the reaction area. Together, these mechanisms reduce ohmic internal resistance and activation / concentration polarization, minimizing bromine shuttle and voltage loss. On the negative electrode side, the PEDOT / SA composite layer, through multiple synergistic mechanisms, utilizes the SA hydrophilic network to homogenize Zn. 2+ The PEDOT high-conductivity network distributes and suppresses dendrites, eliminates potential gradients, and promotes two-dimensional dense deposition. SA locks in free water and buffers pH, inhibiting hydrogen evolution reaction. At the same time, the PPy / SA and PEDOT / SA inert composite layer effectively resists bromine corrosion. Ultimately, the coulombic efficiency, voltage efficiency, and energy efficiency of the zinc-bromine flow battery are systematically improved, and the cycle life is significantly extended. Detailed Implementation

[0019] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0021] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0022] In this invention, unless otherwise specified, percentage (%) or parts refer to weight percentage or parts relative to the composition.

[0023] In this invention, unless otherwise specified, the components involved or their preferred components can be combined to form new technical solutions.

[0024] In this invention, unless otherwise specified, the numerical range "ab" is an abbreviation for any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "6-22" indicates that all real numbers between "6-22" have been listed in this document, and "6-22" is simply an abbreviation for these numerical combinations.

[0025] The "scope" disclosed in this invention can be in the form of a lower limit and an upper limit, and can be one or more lower limits and one or more upper limits, respectively.

[0026] The term “and / or” as used in this invention refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes such combinations.

[0027] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this invention.

[0028] This invention provides a method for preparing a zinc-bromine flow battery bipolar plate based on PPy / SA and PEDOT / SA, comprising the following steps: 1) Pretreatment of carbon-plastic bipolar plates For an area of ​​9cm 2 The carbon-plastic bipolar plates with a thickness of 1.2 mm are cleaned by ultrasonic cleaning with ethanol or deionized water for 15-30 minutes to remove impurities and contaminants on the surface. Then, they are dried in a vacuum drying oven at 40-60℃ for 12-24 hours for later use.

[0029] 2) Preparation of polypyrrole / sodium alginate (PPy / SA) composite dispersion Dissolve 500-2500 mg of sodium alginate (SA) powder in 30 mL of deionized water and stir until completely dissolved to obtain an SA aqueous solution of a certain concentration.

[0030] Add 100 mg of p-toluenesulfonic acid to 30 mL of SA aqueous solution and stir until dissolved; then add 1000-3000 mg of pyrrole monomer dropwise, stirring to disperse evenly. Place the mixture in an ice-water bath at 0-5℃ and maintain the low temperature; slowly add 40-60 mL of 0.5 mol / L ammonium persulfate while stirring, and then make up to 100 mL with deionized water. Continue stirring and reacting in an ice bath for 4-6 h. The solution gradually darkens to obtain a PPy / SA composite dispersion, in which the concentration of SA is 5-25 mg / mL and the concentration of pyrrole monomer is 10-30 mg / mL.

[0031] Preferably, in the preparation of the PPy / SA composite dispersion, the amount of pyrrole monomer used is 2000-3000 mg, and the amount of sodium alginate powder used is 1500-2500 mg.

[0032] 3) Modification of the positive electrode side of carbon-plastic bipolar plates by PPy / SA Take 50 mL of the above PPy / SA composite dispersion and spray the suspension evenly onto the positive electrode side of the carbon-plastic bipolar plate of the zinc-bromine flow battery using a spray gun. The spraying speed is 5-10 mL / min and the spraying time is 5-10 min. Place the sprayed carbon-plastic bipolar plate in a vacuum drying oven and dry it at 60-80℃ for 6-12 h to complete the modification of the positive electrode side of the carbon-plastic bipolar plate by PPy / SA.

[0033] 4) Preparation of poly(3,4-ethylenedioxythiophene) / sodium alginate (PEDOT / SA) dispersion Dissolve 500-2500 mg of sodium alginate powder in 30 mL of deionized water and stir until completely dissolved to obtain an aqueous solution of SA of a certain concentration.

[0034] Add 100 mg of sodium polystyrene sulfonate to 30 mL of SA aqueous solution and stir until dissolved; then add 500-2500 mg of 3,4-ethylenedioxythiophene (EDOT) monomer dropwise and stir to disperse it evenly. Place the mixture in an ice-water bath at 0-5℃ and keep it at a low temperature; slowly add 40-60 mL of ammonium persulfate while stirring, and then make up the volume to 100 mL with deionized water. Continue stirring and reacting in an ice bath for 4-6 hours. The solution gradually darkens, and the PEDOT / SA composite dispersion is obtained, in which the concentration of SA is 5-25 mg / mL and the concentration of EDOT is 5-25 mg / mL.

[0035] Preferably, in the preparation of the PEDOT / SA composite dispersion, the amount of 3,4-ethylenedioxythiophene monomer is 1000-2000 mg, and the amount of sodium alginate powder is 1500-2500 mg.

[0036] 5) Modification of the negative electrode side of carbon-plastic bipolar plates by PEDOT / SA Take 50 mL of the above PEDOT / SA composite dispersion and spray the suspension evenly onto the negative electrode side of the carbon-plastic bipolar plate of the zinc-bromine flow battery using a spray gun. The spraying speed is 5-10 mL / min and the spraying time is 5-10 min. Place the sprayed carbon-plastic bipolar plate in a vacuum drying oven and dry it at 60-80℃ for 6-12 h to complete the modification of the negative electrode side of the carbon-plastic bipolar plate by PEDOT / SA.

[0037] This invention provides a method for preparing a zinc-bromine flow battery bipolar plate based on PPy / SA and PEDOT / SA. By loading PPy / SA and PEDOT / SA onto the positive and negative bipolar plates of the zinc-bromine flow battery respectively, a systematic improvement in battery performance is achieved. The positive electrode side of the bipolar plate is modified with a PPy / SA composite dispersion. The flexible polymer chains of SA intertwine and interweave with the polypyrrole (PPy) conductive nanoparticles in the system, forming a certain equivalent pore and channel. Due to the presence of polybrominated ions (such as Br3+), the bipolar plate can effectively conduct polybrominated ions (such as Br3+). - and Br5 - The large size of bromine and its tendency to form even larger hydrated layers in aqueous solutions lead to more tortuous diffusion paths through these channels, resulting in a lower apparent diffusion coefficient. This effectively reduces the free diffusion of bromine, mitigating bromine permeation, lowering self-discharge and capacity decay, and significantly improving the battery's coulombic efficiency and cycle capacity retention. Modification with a PEDOT / SA composite dispersion on the negative electrode side of the bipolar plate allows the hydrophilic groups such as -OH and -COONa in the SA molecular chain to bind a large number of water molecules, forming a three-dimensional polymer in situ. A hydrogel network, possessing continuous and relatively ordered hydrated ion transport channels, promotes Zn 2 + More uniform transmission allows Zn to be distributed closer to the surface of the bipolar plate. 2+ The distribution is smoother, thus avoiding the formation and growth of zinc dendrites.

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The components of the embodiments of the present invention shown herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0039] The technical solution of the present invention will be described in detail below with reference to specific embodiments. These embodiments do not constitute a limitation on the present invention.

[0040] Table 1. Synthesis conditions of carbon-plastic bipolar plates in different embodiments

[0041] Example 1 A method for preparing a zinc-bromine flow battery bipolar plate based on PPy / SA and PEDOT / SA includes the following steps: 1) Pretreatment of carbon-plastic bipolar plates The carbon-plastic bipolar plate was cleaned by ultrasonic cleaning with deionized water for 20 minutes to remove impurities and contaminants from the surface, and then dried in a vacuum drying oven at 50°C for 12 hours for later use.

[0042] 2) Preparation of PPy / SA composite dispersion Dissolve 500 mg of sodium alginate powder in 30 mL of deionized water and stir until completely dissolved to obtain an SA aqueous solution.

[0043] Add 100 mg of p-toluenesulfonic acid to 30 mL of SA aqueous solution and stir until dissolved; then add 1000 mg of pyrrole monomer dropwise and stir to disperse evenly. Place the mixture in an ice-water bath at 2 °C to maintain the low temperature; slowly add 50 mL of ammonium persulfate while stirring, and then make up to 100 mL with deionized water. Continue stirring and reacting for 5 h in an ice bath. The solution gradually darkens, thus obtaining the PPy / SA composite dispersion, in which the SA concentration is 5 mg / mL and the pyrrole monomer concentration is 10 mg / mL.

[0044] 3) Modification of the positive electrode side of carbon-plastic bipolar plates by PPy / SA Take 50 mL of the above PPy / SA composite dispersion and spray the suspension evenly onto the positive electrode side of the carbon-plastic bipolar plate of the zinc-bromine flow battery using a spray gun. The spraying speed is 5 mL / min and the spraying time is 10 min. Place the sprayed carbon-plastic bipolar plate in a vacuum drying oven and dry it at 60℃ for 12 h to complete the modification of the positive electrode side of the carbon-plastic bipolar plate by PPy / SA.

[0045] 4) Preparation of PEDOT / SA composite dispersion Dissolve 500 mg of sodium alginate powder in 30 mL of deionized water and stir until completely dissolved to obtain an SA aqueous solution.

[0046] Add 100 mg of sodium polystyrene sulfonate to 30 mL of SA aqueous solution and stir until dissolved; then add 500 mg of 3,4-ethylenedioxythiophene monomer dropwise and stir to disperse evenly. Place the mixture in an ice-water bath at 2 °C to maintain the low temperature; slowly add 50 mL of ammonium persulfate while stirring, and then make up to 100 mL with deionized water. Continue stirring and reacting in an ice bath for 5 h. The solution gradually darkens, thus obtaining the PEDOT / SA composite dispersion, in which the SA concentration is 5 mg / mL and the 3,4-ethylenedioxythiophene monomer concentration is 5 mg / mL.

[0047] 5) Modification of the negative electrode side of carbon-plastic bipolar plates by PEDOT / SA Take 50 mL of the above PEDOT / SA composite dispersion and spray the suspension evenly onto the negative electrode side of the carbon-plastic bipolar plate of the zinc-bromine flow battery using a spray gun. The spraying speed is 5 mL / min and the spraying time is 10 min. Place the sprayed carbon-plastic bipolar plate in a vacuum drying oven and dry it at 60℃ for 12 h to complete the modification of the negative electrode side of the carbon-plastic bipolar plate by PEDOT / SA.

[0048] Example 2 The difference from Example 1 is as follows: In step 2), add 1500 mg of pyrrole monomer.

[0049] Example 3 The difference from Example 1 is as follows: In step 2), add 2000 mg of pyrrole monomer.

[0050] Example 4 The difference from Example 1 is as follows: In step 2), add 2500 mg of pyrrole monomer.

[0051] Example 5 The difference from Example 1 is as follows: In step 2), add 3000 mg of pyrrole monomer.

[0052] Example 6 1) The pretreatment of the carbon-plastic bipolar plate is the same as in Example 1.

[0053] 2) Preparation of PPy / SA composite dispersion Dissolve 1000 mg of sodium alginate powder in 30 mL of deionized water and stir until completely dissolved to obtain an SA aqueous solution.

[0054] The PPy / SA composite dispersion was prepared in the same manner as in Example 4, except that the SA concentration was 10 mg / mL.

[0055] 3) The modification of the positive electrode side of the carbon-plastic bipolar plate by PPy / SA is the same as in Example 1.

[0056] 4) The preparation of the PEDOT / SA composite dispersion is the same as in Example 1.

[0057] 5) The modification of the negative electrode side of the carbon-plastic bipolar plate by PEDOT / SA is the same as in Example 1.

[0058] Example 7 1) The pretreatment of the carbon-plastic bipolar plate is the same as in Example 1.

[0059] 2) Preparation of PPy / SA composite dispersion Dissolve 1500 mg of sodium alginate powder in 3 mL of deionized water and stir until completely dissolved to obtain an SA aqueous solution.

[0060] The PPy / SA composite dispersion was prepared in the same manner as in Example 4, except that the SA concentration was 15 mg / mL.

[0061] 3) The modification of the positive electrode side of the carbon-plastic bipolar plate by PPy / SA is the same as in Example 1.

[0062] 4) The preparation of the PEDOT / SA composite dispersion is the same as in Example 1.

[0063] 5) The modification of the negative electrode side of the carbon-plastic bipolar plate by PEDOT / SA is the same as in Example 1.

[0064] Example 8 1) The pretreatment of the carbon-plastic bipolar plate is the same as in Example 1.

[0065] 2) Preparation of PPy / SA composite dispersion Dissolve 2000 mg of sodium alginate powder in 30 mL of deionized water and stir until completely dissolved to obtain an SA aqueous solution.

[0066] The PPy / SA composite dispersion was prepared in the same manner as in Example 4, except that the SA concentration was 20 mg / mL.

[0067] 3) The modification of the positive electrode side of the carbon-plastic bipolar plate by PPy / SA is the same as in Example 1.

[0068] 4) The preparation of the PEDOT / SA composite dispersion is the same as in Example 1.

[0069] 5) The modification of the negative electrode side of the carbon-plastic bipolar plate by PEDOT / SA is the same as in Example 1.

[0070] Example 9 1) The pretreatment of the carbon-plastic bipolar plate is the same as in Example 1.

[0071] 2) Preparation of PPy / SA composite dispersion Dissolve 2500 mg of sodium alginate powder in 30 mL of deionized water and stir until completely dissolved to obtain an SA aqueous solution.

[0072] The PPy / SA composite dispersion was prepared in the same manner as in Example 4, except that the SA concentration was 25 mg / mL.

[0073] 3) The modification of the positive electrode side of the carbon-plastic bipolar plate by PPy / SA is the same as in Example 1.

[0074] 4) The preparation of the PEDOT / SA composite dispersion is the same as in Example 1.

[0075] 5) The modification of the negative electrode side of the carbon-plastic bipolar plate by PEDOT / SA is the same as in Example 1.

[0076] Example 10 1) The pretreatment of the carbon-plastic bipolar plate is the same as in Example 1.

[0077] 2) Preparation of PPy / SA composite dispersion The preparation of SA aqueous solution is the same as in Example 8.

[0078] The PPy / SA composite dispersion was prepared in the same manner as in Example 4.

[0079] 3) The modification of the positive electrode side of the carbon-plastic bipolar plate by PPy / SA is the same as in Example 1.

[0080] 4) Preparation of PEDOT / SA composite dispersion The preparation of SA aqueous solution is the same as in Example 1.

[0081] Add 100 mg of sodium polystyrene sulfonate to 30 mL of SA aqueous solution and stir until dissolved; then add 1000 mg of 3,4-ethylenedioxythiophene monomer dropwise and stir to disperse evenly. Place the mixture in an ice-water bath at 2 °C to maintain the low temperature; slowly add 50 mL of ammonium persulfate while stirring, and then make up to 100 mL with deionized water. Continue stirring and reacting for 5 h in an ice bath. The solution gradually darkens, thus obtaining the PEDOT / SA composite dispersion, in which the concentration of 3,4-ethylenedioxythiophene monomer is 10 mg / mL.

[0082] 5) The modification of the negative electrode side of the carbon-plastic bipolar plate by PEDOT / SA is the same as in Example 1.

[0083] Example 11 1) The pretreatment of the carbon-plastic bipolar plate is the same as in Example 1.

[0084] 2) Preparation of PPy / SA composite dispersion The preparation of SA aqueous solution is the same as in Example 8.

[0085] The PPy / SA composite dispersion was prepared in the same manner as in Example 4.

[0086] 3) The modification of the positive electrode side of the carbon-plastic bipolar plate by PPy / SA is the same as in Example 1.

[0087] 4) Preparation of PEDOT / SA composite dispersion The preparation of SA aqueous solution is the same as in Example 1.

[0088] Add 100 mg of sodium polystyrene sulfonate to 30 mL of SA aqueous solution and stir until dissolved; then add 1500 mg of 3,4-ethylenedioxythiophene monomer dropwise and stir to disperse evenly. Place the mixture in an ice-water bath at 2 °C to maintain the low temperature; slowly add 50 mL of ammonium persulfate while stirring, and then make up to 100 mL with deionized water. Continue stirring and reacting for 5 h in an ice bath. The solution gradually darkens, thus obtaining the PEDOT / SA composite dispersion, in which the concentration of 3,4-ethylenedioxythiophene monomer is 15 mg / mL.

[0089] 5) The modification of the negative electrode side of the carbon-plastic bipolar plate by PEDOT / SA is the same as in Example 1.

[0090] Example 12 1) The pretreatment of the carbon-plastic bipolar plate is the same as in Example 1.

[0091] 2) Preparation of PPy / SA composite dispersion The preparation of SA aqueous solution is the same as in Example 8.

[0092] The PPy / SA composite dispersion was prepared in the same manner as in Example 4.

[0093] 3) The modification of the positive electrode side of the carbon-plastic bipolar plate by PPy / SA is the same as in Example 1.

[0094] 4) Preparation of PEDOT / SA composite dispersion The preparation of SA aqueous solution is the same as in Example 1.

[0095] Add 100 mg of sodium polystyrene sulfonate to 30 mL of SA aqueous solution and stir until dissolved; then add 2000 mg of 3,4-ethylenedioxythiophene monomer dropwise and stir to disperse evenly. Place the mixture in an ice-water bath at 2 °C to maintain the low temperature; slowly add 50 mL of ammonium persulfate while stirring, and then make up to 100 mL with deionized water. Continue stirring and reacting for 5 h in an ice bath. The solution gradually darkens, thus obtaining the PEDOT / SA composite dispersion, in which the concentration of 3,4-ethylenedioxythiophene monomer is 20 mg / mL.

[0096] 5) The modification of the negative electrode side of the carbon-plastic bipolar plate by PEDOT / SA is the same as in Example 1.

[0097] Example 13 1) The pretreatment of the carbon-plastic bipolar plate is the same as in Example 1.

[0098] 2) Preparation of PPy / SA composite dispersion The preparation of SA aqueous solution is the same as in Example 8.

[0099] The PPy / SA composite dispersion was prepared in the same manner as in Example 4.

[0100] 3) The modification of the positive electrode side of the carbon-plastic bipolar plate by PPy / SA is the same as in Example 1.

[0101] 4) Preparation of PEDOT / SA composite dispersion Dissolve 1000 mg of sodium alginate powder in 30 mL of deionized water and stir until completely dissolved to obtain an SA aqueous solution.

[0102] The PEDOT / SA composite dispersion was prepared in the same manner as in Example 12, except that the SA concentration was 10 mg / mL.

[0103] 5) The modification of the negative electrode side of the carbon-plastic bipolar plate by PEDOT / SA is the same as in Example 1.

[0104] Example 14 1) The pretreatment of the carbon-plastic bipolar plate is the same as in Example 1.

[0105] 2) Preparation of PPy / SA composite dispersion The preparation of SA aqueous solution is the same as in Example 8.

[0106] The PPy / SA composite dispersion was prepared in the same manner as in Example 4.

[0107] 3) The modification of the positive electrode side of the carbon-plastic bipolar plate by PPy / SA is the same as in Example 1.

[0108] 4) Preparation of PEDOT / SA composite dispersion Dissolve 1500 mg of sodium alginate powder in 30 mL of deionized water and stir until completely dissolved to obtain an SA aqueous solution.

[0109] The PEDOT / SA composite dispersion was prepared in the same manner as in Example 12, except that the SA concentration was 15 mg / mL.

[0110] 5) The modification of the negative electrode side of the carbon-plastic bipolar plate by PEDOT / SA is the same as in Example 1.

[0111] Example 15 1) The pretreatment of the carbon-plastic bipolar plate is the same as in Example 1.

[0112] 2) Preparation of PPy / SA composite dispersion The preparation of SA aqueous solution is the same as in Example 8.

[0113] The PPy / SA composite dispersion was prepared in the same manner as in Example 4.

[0114] 3) The modification of the positive electrode side of the carbon-plastic bipolar plate by PPy / SA is the same as in Example 1.

[0115] 4) Preparation of PEDOT / SA composite dispersion Dissolve 2000 mg of sodium alginate powder in 30 mL of deionized water and stir until completely dissolved to obtain an SA aqueous solution.

[0116] The PEDOT / SA composite dispersion was prepared in the same manner as in Example 12, except that the SA concentration was 20 mg / mL.

[0117] 5) The modification of the negative electrode side of the carbon-plastic bipolar plate by PEDOT / SA is the same as in Example 1.

[0118] Example 16 1) The pretreatment of the carbon-plastic bipolar plate is the same as in Example 1.

[0119] 2) Preparation of PPy / SA composite dispersion The preparation of SA aqueous solution is the same as in Example 8.

[0120] The PPy / SA composite dispersion was prepared in the same manner as in Example 4.

[0121] 3) The modification of the positive electrode side of the carbon-plastic bipolar plate by PPy / SA is the same as in Example 1.

[0122] 4) Preparation of PEDOT / SA composite dispersion Dissolve 2500 mg of sodium alginate powder in 30 mL of deionized water and stir until completely dissolved to obtain an SA aqueous solution.

[0123] The PEDOT / SA composite dispersion was prepared in the same manner as in Example 12, except that the SA concentration was 25 mg / mL.

[0124] 5) The modification of the negative electrode side of the carbon-plastic bipolar plate by PEDOT / SA is the same as in Example 1.

[0125] Example 17 1) The pretreatment of the carbon-plastic bipolar plate is the same as in Example 1.

[0126] 2) Preparation of PPy / SA composite dispersion The preparation of SA aqueous solution is the same as in Example 8.

[0127] The PPy / SA composite dispersion was prepared in the same manner as in Example 4.

[0128] 3) Modification of the positive electrode side of carbon-plastic bipolar plates by PPy / SA Take 50 mL of the above PPy / SA composite dispersion and spray the suspension evenly onto the positive electrode side of the carbon-plastic bipolar plate of the zinc-bromine flow battery using a spray gun. The spraying speed is 7 mL / min and the spraying time is 7 min. Place the sprayed carbon-plastic bipolar plate in a vacuum drying oven and dry it at 60℃ for 12 h to complete the modification of the positive electrode side of the carbon-plastic bipolar plate by PPy / SA.

[0129] 4) Preparation of PEDOT / SA composite dispersion The SA aqueous solution is the same as in Example 15.

[0130] The preparation of the PEDOT / SA composite dispersion is the same as in Example 12.

[0131] 5) Modification of the negative electrode side of carbon-plastic bipolar plates by PEDOT / SA Take 50 mL of the above PEDOT / SA composite dispersion and spray the suspension evenly onto the negative electrode side of the carbon-plastic bipolar plate of the zinc-bromine flow battery using a spray gun. The spraying speed is 7 mL / min and the spraying time is 7 min. Place the sprayed carbon-plastic bipolar plate in a vacuum drying oven and dry it at 60℃ for 12 h to complete the modification of the negative electrode side of the carbon-plastic bipolar plate by PEDOT / SA.

[0132] Example 18 1) The pretreatment of the carbon-plastic bipolar plate is the same as in Example 1.

[0133] 2) Preparation of PPy / SA composite dispersion The preparation of SA aqueous solution is the same as in Example 8.

[0134] The PPy / SA composite dispersion was prepared in the same manner as in Example 4.

[0135] 3) Modification of the positive electrode side of carbon-plastic bipolar plates by PPy / SA Take 50 mL of the above PPy / SA composite dispersion and spray the suspension evenly onto the positive electrode side of the carbon-plastic bipolar plate of the zinc-bromine flow battery using a spray gun. The spraying speed is 10 mL / min and the spraying time is 5 min. Place the sprayed carbon-plastic bipolar plate in a vacuum drying oven and dry it at 60℃ for 12 h to complete the modification of the positive electrode side of the carbon-plastic bipolar plate by PPy / SA.

[0136] 4) Preparation of PEDOT / SA composite dispersion The SA aqueous solution is the same as in Example 15.

[0137] The preparation of the PEDOT / SA composite dispersion is the same as in Example 12.

[0138] 5) Modification of the negative electrode side of carbon-plastic bipolar plates by PEDOT / SA Take 50 mL of the above PEDOT / SA composite dispersion and spray the suspension evenly onto the negative electrode side of the carbon-plastic bipolar plate of the zinc-bromine flow battery using a spray gun. The spraying speed is 10 mL / min and the spraying time is 5 min. Place the sprayed carbon-plastic bipolar plate in a vacuum drying oven and dry it at 60℃ for 12 h to complete the modification of the negative electrode side of the carbon-plastic bipolar plate by PEDOT / SA.

[0139] Example 19 A method for preparing a zinc-bromine flow battery bipolar plate based on PPy / SA and PEDOT / SA includes the following steps: 1) Pretreatment of carbon-plastic bipolar plates The carbon-plastic bipolar plate was cleaned by ultrasonic cleaning with ethanol for 15 minutes, and then dried in a vacuum drying oven at 40°C for 24 hours for later use.

[0140] 2) Preparation of PPy / SA composite dispersion Dissolve 500 mg of sodium alginate powder in 30 mL of deionized water and stir until completely dissolved to obtain an SA aqueous solution.

[0141] Add 100 mg of p-toluenesulfonic acid to 30 mL of SA aqueous solution and stir until dissolved; then add 1000 mg of pyrrole monomer dropwise and stir to disperse evenly. Place the mixture in an ice-water bath at 0 °C; slowly add 40 mL of ammonium persulfate while stirring, and then make up to 100 mL with deionized water. Continue stirring and reacting in an ice bath for 4 h to obtain a PPy / SA composite dispersion, wherein the SA concentration is 5 mg / mL and the pyrrole monomer concentration is 10 mg / mL.

[0142] 3) Modification of the positive electrode side of carbon-plastic bipolar plates by PPy / SA Take 50 mL of PPy / SA composite dispersion and spray it onto the positive electrode side of the carbon-plastic bipolar plate using a spray gun. The spraying speed is 5 mL / min and the spraying time is 10 min. Then dry it in a vacuum drying oven at 60 °C for 6 h.

[0143] 4) Preparation of PEDOT / SA composite dispersion Dissolve 2500 mg of sodium alginate powder in 30 mL of deionized water and stir until completely dissolved to obtain an SA aqueous solution.

[0144] Add 100 mg of sodium polystyrene sulfonate to 30 mL of SA aqueous solution and stir until dissolved; then add 2500 mg of 3,4-ethylenedioxythiophene monomer dropwise and stir to disperse evenly. Place the mixture in an ice-water bath at 0 °C; slowly add 40 mL of ammonium persulfate while stirring, and then make up to 100 mL with deionized water. Continue stirring and reacting in an ice bath for 4 h to obtain a PEDOT / SA composite dispersion, wherein the concentration of SA is 25 mg / mL and the concentration of 3,4-ethylenedioxythiophene monomer is 25 mg / mL.

[0145] 5) Modification of the negative electrode side of carbon-plastic bipolar plates by PEDOT / SA Take 50 mL of PEDOT / SA composite dispersion and spray it onto the negative electrode side of the carbon-plastic bipolar plate using a spray gun. The spraying speed is 5 mL / min and the spraying time is 10 min. Then dry it in a vacuum drying oven at 60℃ for 6 h.

[0146] Example 20 1) Pretreatment of carbon-plastic bipolar plates The carbon-plastic bipolar plate was cleaned by ultrasonic cleaning with ethanol for 30 minutes, and then dried in a vacuum drying oven at 60°C for 24 hours for later use.

[0147] 2) Preparation of PPy / SA composite dispersion Dissolve 2500 mg of sodium alginate powder in 30 mL of deionized water and stir until completely dissolved to obtain an SA aqueous solution.

[0148] Add 100 mg of p-toluenesulfonic acid to 30 mL of SA aqueous solution and stir until dissolved; then add 3000 mg of pyrrole monomer dropwise and stir to disperse evenly. Place the mixture in an ice-water bath at 5 °C; slowly add 60 mL of ammonium persulfate while stirring, and then make up to 100 mL with deionized water. Continue stirring and reacting for 6 h in an ice bath to obtain a PPy / SA composite dispersion, wherein the SA concentration is 25 mg / mL and the pyrrole monomer concentration is 30 mg / mL.

[0149] 3) Modification of the positive electrode side of carbon-plastic bipolar plates by PPy / SA Take 50 mL of PPy / SA composite dispersion and spray it onto the positive electrode side of the carbon-plastic bipolar plate using a spray gun. The spraying speed is 10 mL / min and the spraying time is 5 min. Then dry it in a vacuum drying oven at 80℃ for 12 h.

[0150] 4) Preparation of PEDOT / SA composite dispersion Dissolve 500 mg of sodium alginate powder in 30 mL of deionized water and stir until completely dissolved to obtain an SA aqueous solution.

[0151] Add 100 mg of sodium polystyrene sulfonate to 30 mL of SA aqueous solution and stir until dissolved; then add 500 mg of 3,4-ethylenedioxythiophene monomer dropwise and stir to disperse evenly. Place the mixture in an ice-water bath at 5 °C; slowly add 60 mL of ammonium persulfate while stirring, and then make up to 100 mL with deionized water. Continue stirring and reacting in an ice bath for 6 h to obtain a PEDOT / SA composite dispersion, wherein the concentration of SA is 5 mg / mL and the concentration of 3,4-ethylenedioxythiophene monomer is 5 mg / mL.

[0152] 5) Modification of the negative electrode side of carbon-plastic bipolar plates by PEDOT / SA Take 50 mL of PEDOT / SA composite dispersion and spray it onto the negative electrode side of the carbon-plastic bipolar plate using a spray gun. The spraying speed is 10 mL / min and the spraying time is 5 min. Then dry it in a vacuum drying oven at 80℃ for 12 h.

[0153] Comparative Example 1 1) The pretreatment of the carbon-plastic bipolar plate is the same as in Example 1.

[0154] 2) The preparation of the PPy / SA composite dispersion is the same as in Example 8.

[0155] 3) The modification of the positive electrode side of the carbon-plastic bipolar plate by PPy / SA is the same as in Example 1.

[0156] The negative electrode side of Comparative Example 1 was not modified.

[0157] Comparative Example 2 1) The pretreatment of the carbon-plastic bipolar plate is the same as in Example 1.

[0158] 2) The preparation of the PEDOT / SA composite dispersion is the same as in Example 15.

[0159] 3) The modification of the negative electrode side of the carbon-plastic bipolar plate by PEDOT / SA is the same as in Example 1.

[0160] The positive electrode side of Comparative Example 2 was not modified.

[0161] Comparative Example 3 The pretreatment process for the carbon-plastic bipolar plate is the same as in Example 1. No modification treatment is performed on the positive and negative sides of Comparative Example 3.

[0162] To test the performance of the carbon-plastic bipolar plate materials used in Examples 1-18 and Comparative Examples 1-3 of the zinc-bromine flow battery, batteries were assembled using conventional separator materials and electrolyte systems for zinc-bromine flow batteries. Charge-discharge tests were performed on a battery testing system with a charge-discharge rate of 20 mA / cm². 2 The charging time was 2 hours, the test temperature was 25℃, and the test results are shown in Table 2.

[0163] Table 2 Comparison of electrochemical performance of zinc-bromine flow batteries under different embodiment conditions

[0164] As can be seen from Table 2, Examples 1-18 and Comparative Examples 1-3, especially Examples 1-18 and Comparative Examples 1-2, all showed better electrochemical performance data than Comparative Example 1. This indicates that modifying the bipolar plate of the zinc-bromine flow battery with PPy / SA and PEDOT / SA resulted in better electrochemical performance. This demonstrates that the carbon-plastic bipolar plate modified with PPy / SA and PEDOT / SA has a significant impact on improving bromine barrier capacity, reducing battery internal resistance, increasing conductivity, reducing dead zinc, and inhibiting zinc dendrite formation.

[0165] Comparing Examples 1-18 with Comparative Examples 1-2, Examples 1-18 all showed better electrochemical performance data than Comparative Examples 1-2. This indicates that when PPy / SA and PEDOT / SA are used to modify the positive and negative electrodes of the carbon-plastic bipolar plate of the zinc-bromine flow battery at the same time, the battery has better electrochemical performance. This shows that after PPy / SA and PEDOT / SA modify the positive and negative electrodes of the carbon-plastic bipolar plate respectively, they have a significant impact on improving the bromine barrier capacity, reducing the battery internal resistance, improving the conductivity, reducing dead zinc, and inhibiting the zinc dendrite formation.

[0166] Comparing Examples 1-5, when different concentrations of PPy were used to modify the positive electrode side of the carbon-plastic bipolar plate in a zinc-bromine flow battery, the measured electrochemical performance data of the battery improved with increasing PPy solution concentration, indicating that the concentration of PPy solution has a significant impact on improving bromine barrier capacity and accelerating bromine reaction. However, when the PPy concentration is too high, PPy is prone to agglomeration and uneven distribution, which can lead to increased interfacial resistance and decreased conductivity.

[0167] Comparing Examples 4 and 6-9, when SA of different concentrations was used to modify the positive electrode side of the carbon-plastic bipolar plate in a zinc-bromine flow battery, the measured electrochemical performance data of the battery improved with increasing SA solution concentration. This indicates that the concentration of SA solution has a significant impact on improving bromine barrier capacity and accelerating bromine reaction. However, when the SA concentration is too high, SA will coat or separate the conductive PPy particles, making it difficult for these conductive PPy particles to form a pathway, resulting in increased interfacial resistance and decreased conductivity.

[0168] The hydrophilic SA network constructs tortuous ion channels, utilizing steric hindrance and electrostatic repulsion to suppress polybromination and reduce self-discharge. The PPy conjugated conductive network compensates for surface defects in the bipolar plates, homogenizes current distribution, and lowers the activation energy of the bromine redox reaction and stabilizes the transition state through the delocalized π-electron system, accelerating reaction kinetics. Simultaneously, SA improves wettability to eliminate dry spots and expand the effective reaction area. These two components synergistically reduce ohmic resistance and concentration polarization, decrease bromine shuttle and voltage loss, ultimately achieving a comprehensive improvement in battery coulombic efficiency, energy efficiency, and cycle stability.

[0169] PPy can compensate for potential micro-insulation points, oxide films, or resistivity inhomogeneities on the surface of bipolar plates, essentially introducing parallel conductive paths at the interface, resulting in more uniform current collection. This uniform current distribution avoids localized overpotential hotspots, allowing bromine oxidation-reduction to occur more evenly across the entire positive electrode interface, leading to a decrease in redox overpotential and a more complete reaction. PPy is a conjugated polymer with a main chain composed of alternating single and double bonds. π electrons are delocalized along the main chain, forming delocalized π bonds. This delocalized π electron system gives PPy metallic-like conductivity, and the carbon and nitrogen atoms on the main chain exist in different oxidation states, possessing the ability to accept or donate electrons. Bromine oxidation-reduction electrons can be transferred via delocalized π bonds, thereby lowering the activation energy of electron transfer or making the transfer more continuous; the conjugated π system can react with reactive species (Br... - Br2, Br3 - The formation of weak π-π or electrostatic interactions stabilizes the reaction transition state, lowering the reaction energy barrier. This optimizes the electron transport path and stabilizes the transition state, allowing Br to... - The oxidation / Br2 reduction reaction pathway is smoother and the kinetics are faster. SA, rich in hydrophilic groups (-OH, -COONa), can form a hydrophilic hydration layer on the bipolar plate surface, significantly improving the wettability of the electrolyte on the bipolar plate surface. This helps eliminate localized dry spots and traps micro-gaps at the bipolar plate-carbon felt interface, ensuring more continuous and sufficient contact at the liquid-solid interface, thereby improving the utilization rate of the reaction interface, expanding the effective reaction area, and allowing more effective reaction sites to participate in the bromine oxidation-reduction reaction. The PPy / SA composite layer, through the synergistic effect of PPy conductivity equalization, PPy catalysis, and SA increasing the reaction area, improves the reaction kinetics and interface utilization of bromine, thus enhancing the bromine reaction effect.

[0170] The PPy / SA composite layer significantly reduces the ohmic internal resistance of the battery by constructing synergistic channels between electrons and the interface. On the one hand, PPy, as a highly conductive conjugated polymer, forms a continuous conductive network on the surface of the bipolar plate, effectively bridging and bypassing any micro-insulation spots, oxide films, or uneven wetting areas that may exist on the substrate surface, providing additional parallel conductive paths and thus significantly reducing surface resistance. On the other hand, the strong hydrophilicity of SA greatly improves the wettability of the electrolyte to the bipolar plate interface, eliminates micro-gaps and contact blind zones, and reduces the additional contact resistance caused by physical contact discontinuities. This directly reduces the ohmic internal resistance of the battery during operation, thereby improving the battery's voltage efficiency and energy efficiency.

[0171] The PPy / SA composite layer simultaneously suppressed activation polarization, concentration polarization, and local non-uniform polarization through multi-dimensional modulation. Firstly, the conjugated π system of PPy not only provides ample electron supply but also optimizes Br through redox-mediated reactions. -The charge transfer kinetics of the / Br2 reaction are optimized, thereby reducing the activation overpotential. Secondly, the hydrophilic network and uniform film structure constructed by SA ensure that the electrolyte is uniformly distributed at the interface, effectively eliminating dead zones and local concentration gradients, significantly alleviating concentration polarization caused by limited mass transfer, and thus improving the voltage efficiency and energy efficiency of the battery.

[0172] Comparing Examples 8 and 10-12, when different concentrations of PEDOT were used to modify the negative electrode side of the carbon-plastic bipolar plate in a zinc-bromine flow battery, the measured electrochemical performance data of the battery improved with increasing PEDOT solution concentration, indicating that the concentration of PEDOT solution has a significant impact on suppressing zinc dendrites and hydrogen evolution reaction. However, when the PEDOT concentration is too high, PEDOT is prone to agglomeration and uneven distribution, which can lead to increased interfacial resistance and decreased conductivity.

[0173] Comparing Examples 11 and 13-16, when SA of different concentrations was used to modify the negative electrode side of the carbon-plastic bipolar plate in a zinc-bromine flow battery, the measured electrochemical performance data of the battery improved with increasing SA solution concentration, indicating that the concentration of SA solution has a significant impact on suppressing zinc dendrites and hydrogen evolution reaction. However, when the SA concentration is too high, SA will coat or separate the conductive PEDOT particles, making it difficult for these conductive PEDOT particles to form a pathway, resulting in increased interfacial resistance and decreased conductivity.

[0174] The PEDOT / SA composite layer enhances performance on the negative electrode side through multiple mechanisms: the SA hydrophilic network constructs ordered ion channels and homogenizes Zn. 2+ The PPy / SA and PEDOT / SA inert composite layers distribute and eliminate dry spots, suppressing dendrite formation and localized current concentration. The highly conductive PEDOT network eliminates potential gradients, promoting two-dimensional dense deposition. Simultaneously, SA locks in free water and buffers pH, inhibiting hydrogen evolution reaction at its source. Furthermore, this PPy / SA and PEDOT / SA inert composite layer blocks direct contact between the electrolyte and the bipolar plate, effectively resisting bromine corrosion with excellent chemical stability, significantly improving battery cycle life, coulombic efficiency, and safety.

[0175] PEDOT has good conductivity, which can eliminate the potential gradient on the surface of the bipolar plate, thereby avoiding excessive local current density caused by the tip effect. It promotes the uniform distribution of zinc atoms instead of random growth at the protrusions, thus achieving two-dimensional layered dense deposition of zinc, further effectively suppressing dendrites and improving the cycle life and safety of the battery.

[0176] On the one hand, the SA molecular chain locks in a large number of water molecules through hydrogen bonding and entanglement, significantly reducing the activity and quantity of free water, thus reducing the reactants of the hydrogen evolution reaction (HER) at its source; on the other hand, the -COO groups on the SA chain segments...- The / -COOH group affects local H + / OH - The distribution acts as a buffer, stabilizing the interface pH value and preventing local acidification from exacerbating the hydrogen evolution reaction, thereby inhibiting the occurrence of the hydrogen evolution reaction and improving the battery coulombic efficiency.

[0177] To improve the resistance of bipolar plates to bromine corrosion, PPy / SA composite dispersion and PEDOT / SA composite dispersion were used to modify the positive and negative sides of the bipolar plates, respectively. The PPy / SA and PEDOT / SA coatings blocked the direct contact between the electrolyte and the bipolar plates. PPy and PEDOT themselves have excellent chemical inertness and oxidation resistance, thus effectively preventing the bipolar plates from becoming embrittled, perforated, or having increased resistance due to bromine corrosion.

[0178] The hydrophilic groups such as -OH and -COONa in the SA molecular chain can bind a large amount of water to form a hydrogel / polymer-water network. This network can provide a relatively ordered / continuous ion transport environment, promoting the growth of Zn. 2+ More uniform transmission allows Zn to be distributed closer to the surface of the bipolar plate. 2+ The distribution is smoother, thus avoiding the formation and growth of zinc dendrites.

[0179] SA can also improve the wettability of the bipolar plate surface, reduce dry spots and localized poor solution, thereby alleviating near-interface Zn 2+ Uneven supply and localized current density concentration; this is conducive to more uniform and dispersed zinc nucleation, reduces preferential nucleation and early vertical growth at defects, promotes a relatively dense two-dimensional deposition morphology, further suppresses dendrites, and improves battery cycle life and safety.

[0180] Comparing Examples 15, 17, and 18, Example 15 exhibited relatively superior overall electrochemical performance, demonstrating that within the experimental range, a lower spraying rate combined with a longer spraying time is beneficial for achieving better electrochemical performance. This indicates that different spraying rates and times have a profound impact on the performance of the fabricated bipolar plate. Reducing the spraying rate and extending the spraying time are more conducive to the modification of the carbon-plastic bipolar plate by the PPy / SA and PEDOT / SA dispersions.

[0181] In summary, this invention discloses a zinc-bromine flow battery bipolar plate based on PPy / SA and PEDOT / SA, its preparation method, and its application. The PPy / SA composite layer significantly improves the positive electrode performance of the zinc-bromine flow battery through an electronic and interfacial synergistic mechanism: the SA hydrophilic network constructs tortuous ion channels, utilizing steric hindrance and electrostatic repulsion to suppress polybromide penetration and reduce self-discharge; the PPy conjugated conductive network compensates for surface defects in the bipolar plate, homogenizes the current distribution, and reduces the activation energy of the bromine redox reaction and stabilizes the transition state through the delocalized π-electron system, accelerating the reaction kinetics; simultaneously, SA improves wettability to eliminate dry spots and expand the effective reaction area. The two work synergistically to reduce ohmic internal resistance and activation / concentration polarization, reduce bromine shuttle and voltage loss, ultimately achieving a comprehensive improvement in battery coulombic efficiency, energy efficiency, and cycle stability. The PEDOT / SA composite layer also improves the performance of the negative electrode through multiple mechanisms: the SA hydrophilic network constructs ordered ion channels, homogenizing Zn... 2+ The PPy / SA and PEDOT / SA inert composite layers distribute and eliminate dry spots, suppressing dendrite formation and localized current concentration. The highly conductive PEDOT network eliminates potential gradients, promoting two-dimensional dense deposition. Simultaneously, SA locks in free water and buffers pH, inhibiting hydrogen evolution reaction at its source. Furthermore, this PPy / SA and PEDOT / SA inert composite layer blocks direct contact between the electrolyte and the substrate, effectively resisting bromine corrosion with its excellent chemical stability, significantly improving battery cycle life, coulombic efficiency, and safety.

[0182] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a zinc-bromine flow battery bipolar plate based on PPy / SA and PEDOT / SA, characterized in that, include: Sodium alginate powder was dissolved in deionized water to obtain an SA aqueous solution; p-Toluenesulfonic acid, pyrrole monomer, and ammonium persulfate were added to an aqueous SA solution, and an in-situ polymerization reaction was carried out under ice bath conditions to obtain a PPy / SA composite dispersion. The PPy / SA composite dispersion was sprayed onto the positive electrode side of a pretreated carbon-plastic bipolar plate, and after drying, a PPy / SA modified positive carbon-plastic bipolar plate was obtained. Sodium polystyrene sulfonate, 3,4-ethylenedioxythiophene monomer, and ammonium persulfate were added to an aqueous SA solution, and an in-situ polymerization reaction was carried out under ice bath conditions to obtain a PEDOT / SA composite dispersion. The PEDOT / SA composite dispersion was sprayed onto the negative electrode side of a pretreated carbon-plastic bipolar plate, and after drying, a PEDOT / SA modified negative electrode carbon-plastic bipolar plate was obtained.

2. The method for preparing the zinc-bromine flow battery bipolar plate based on PPy / SA and PEDOT / SA according to claim 1, characterized in that, The pretreatment of carbon-plastic bipolar plates includes: ultrasonically cleaning the carbon-plastic bipolar plates with ethanol or deionized water for 15-30 min, and then drying them in a vacuum drying oven at 40-60℃ for 12-24 h.

3. The method for preparing the zinc-bromine flow battery bipolar plate based on PPy / SA and PEDOT / SA according to claim 1, characterized in that, In the preparation of the PPy / SA composite dispersion, the ratio of sodium alginate powder, p-toluenesulfonic acid, pyrrole monomer and ammonium persulfate is (500-2500) mg: 100 mg: (1000-3000) mg: (40-60) mL; the molar concentration of the ammonium persulfate is 0.5 mol / L; and the mass concentration of the SA aqueous solution is 5-25 mg / mL.

4. The method for preparing the zinc-bromine flow battery bipolar plate based on PPy / SA and PEDOT / SA according to claim 1, characterized in that, In the preparation of the PPy / SA composite dispersion, the in-situ polymerization reaction temperature is 0-5℃ and the in-situ polymerization reaction time is 4-6 h.

5. The method for preparing the zinc-bromine flow battery bipolar plate based on PPy / SA and PEDOT / SA according to claim 1, characterized in that, In the preparation of the PPy / SA modified positive carbon-plastic bipolar plate, the spraying speed of the PPy / SA composite dispersion is 5-10 mL / min, the spraying time is 5-10 min, the drying temperature is 60-80℃, and the drying time is 6-12 h.

6. The method for preparing the zinc-bromine flow battery bipolar plate based on PPy / SA and PEDOT / SA according to claim 1, characterized in that, In the preparation of the PEDOT / SA composite dispersion, the ratio of sodium alginate powder, sodium polystyrene sulfonate, 3,4-ethylenedioxythiophene monomer and ammonium persulfate is (500-2500) mg: 100 mg: (500-2500) mg: (40-60) mL; the mass concentration of the SA aqueous solution is 5-25 mg / mL.

7. The method for preparing the zinc-bromine flow battery bipolar plate based on PPy / SA and PEDOT / SA according to claim 1, characterized in that, In the preparation of the PEDOT / SA composite dispersion, the in-situ polymerization reaction temperature is 0-5℃ and the in-situ polymerization reaction time is 4-6 h.

8. The method for preparing the zinc-bromine flow battery bipolar plate based on PPy / SA and PEDOT / SA according to claim 1, characterized in that, In the preparation of the PEDOT / SA modified negative electrode carbon-plastic bipolar plate, the spraying speed of the PEDOT / SA composite dispersion is 5-10 mL / min, the spraying time is 5-10 min, the drying temperature is 60-80℃, and the drying time is 6-12 h.

9. A zinc-bromine flow battery bipolar plate based on PPy / SA and PEDOT / SA, characterized in that, The bipolar plate of the zinc-bromine flow battery based on PPy / SA and PEDOT / SA, as described in any one of claims 1-8, was prepared.

10. The application of the zinc-bromine flow battery bipolar plate based on PPy / SA and PEDOT / SA as described in claim 9 in the preparation of zinc-bromine flow batteries, characterized in that, The zinc-bromine flow battery has a coulombic efficiency of 91.4%-97.1%, a voltage efficiency of 83.2%-87.2%, and an energy efficiency of 76.04%-84.67%.

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