A gasified bi-c composite deposition type graphite felt electrode material, a preparation method thereof and application thereof in a flow battery

Abstract

The application discloses a kind of gasification Bi-C composite deposition type graphite felt electrode material and its preparation method and application in flow battery, belong to energy storage battery electrode material technical field.The application uses bismuth-containing organic molecules as integrated bismuth source and carbon source, by high-temperature pyrolysis to produce gasification bismuth element and carbon precursor gas, using partition temperature control gas phase deposition process, in-situ co-deposition metal bismuth nanoparticles and carbon nanometer functional layer on the surface of graphite felt fiber, build the closely coupled Bi-C composite modification structure.The application can realize that functional component is uniformly loaded on graphite felt three-dimensional fiber network by gas phase deposition method, avoid the defects such as uneven load, serious agglomeration and weak binding force of traditional impregnation, coating and electrodeposition process.The preparation process of the application is simple, controllable, low in cost, widely applicable, suitable for large-scale industrial production, and provides a new technical path for high-performance, long-life flow battery electrode modification.

Description

Technical Field

[0001] This invention belongs to the field of energy storage battery electrode material technology, specifically relating to a vaporized Bi-C composite deposition type graphite felt electrode material, its preparation method, and its application in flow batteries. Background Technology

[0002] Flow batteries, as one of the core technologies in large-scale energy storage, have advantages such as high safety, long cycle life, independently designable capacity and power, and strong environmental adaptability. They are widely used in scenarios such as wind power, photovoltaic new energy consumption, and grid peak shaving and valley filling. Graphite felt, due to its three-dimensional porous structure, excellent conductivity, corrosion resistance, and low cost, is the most mainstream electrode material for flow batteries. Its surface physicochemical properties directly determine the battery's electrocatalytic efficiency, the degree of hydrogen evolution side reaction, and cycle life.

[0003] Existing commercially available raw graphite felt has significant technical defects: strong surface chemical inertness, few active reaction sites, poor electrolyte wettability, and insufficient catalytic ability for redox reactions of vanadium ions and iron-chromium ions; at the same time, the graphite felt negative electrode interface is severely polarized, and hydrogen evolution side reaction is very likely to occur in aqueous electrolyte system, which not only reduces battery energy efficiency, but also damages the electrode interface structure and accelerates battery performance degradation.

[0004] Bismuth (Bi) is an excellent hydrogen evolution inhibitor and a catalyst modifier for the negative electrode of flow batteries, possessing advantages such as high hydrogen overpotential, suitable electrochemical activity, and low cost, and is widely used in the research of graphite felt electrode modification. However, existing bismuth modification technologies suffer from stability defects: bismuth-modified graphite felts prepared by traditional impregnation, coating, and electrochemical deposition methods often have bismuth particles attached to the graphite felt surface in the form of exposed particles with weak bonding. On the one hand, bismuth exhibits slight chemical dissolution in the acidic aqueous electrolyte of flow batteries, leading to continuous loss of bismuth components under long-term immersion; on the other hand, in the strong electrochemical environment of battery charge-discharge cycles, exposed bismuth nanoparticles are prone to oxidation and corrosion, particle aggregation and detachment, resulting in rapid decay of electrode catalytic activity, gradual loss of hydrogen evolution inhibition effect, and a significant decrease in battery cycle stability.

[0005] In addition, traditional modification processes are all solid-liquid contact modifications, which have the problem of poor load uniformity. Bismuth particles tend to agglomerate and accumulate on the surface of graphite felt, and the internal pores of the fiber cannot effectively load functional components, resulting in uneven overall electrode activity and severe local polarization, making it impossible to achieve large-scale stable application.

[0006] To address the technical bottlenecks of existing technologies, such as poor stability, uneven loading, prominent side reactions, and short lifespan, there is an urgent need to develop a graphite felt electrode modification technology that can achieve stable fixation of bismuth components, uniform loading across the entire catalytic domain, and possess both high catalytic activity and high stability. Summary of the Invention

[0007] This invention aims to address the core problems of existing pure bismuth-modified graphite felt electrodes, such as poor chemical stability, easy electrochemical cycle failure, uneven loading of functional components, weak bonding, and severe hydrogen evolution side reactions at the negative electrode. It provides a vaporized Bi-C composite deposition type graphite felt electrode material, its preparation method, and its applications. Through high-temperature vaporization of an integrated organic bismuth source and zoned temperature-controlled co-deposition technology, a carbon-coated and anchored Bi-C composite modified structure is constructed, simultaneously achieving uniform loading and long-term stability of functional components, significantly improving the working efficiency and cycle life of flow batteries.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A method for preparing a vaporized Bi-C composite deposition type graphite felt electrode material includes the following steps:

[0010] 1) Raw material pyrolysis gas generation: Bismuth-containing organic molecules are placed in a crucible and placed in the high-temperature zone of a tube furnace. Under the protection of nitrogen or an inert atmosphere, the furnace is heated at a constant temperature of 800℃~1000℃ to continuously pyrolyze the bismuth-containing organic molecules and generate a mixed functional gas containing gasified Bi element and carbon precursor. The mixed gas flows directionally to the low-temperature zone of the furnace with the inert carrier gas.

[0011] 2) Zoned vapor deposition: The original graphite felt or activated graphite felt is fixed in the low temperature zone of the same furnace body of the tube furnace. The temperature of the low temperature zone is precisely controlled at 500℃~700℃. The gasified Bi generated by high temperature pyrolysis and the mixed gas of carbon precursor are synergistically deposited in this temperature zone and uniformly attached to the surface of the single fiber of graphite felt, forming a Bi-C composite functional modified layer in situ.

[0012] 3) Cooling and molding: After the reaction is completed, the sample is taken out and cooled to room temperature to obtain a stable and uniformly loaded vaporized Bi-C composite deposition graphite felt electrode material.

[0013] Further, in step 1), the bismuth-containing organic molecule includes one or more of long-chain fatty acid bismuth and aromatic bismuth; the long-chain fatty acid bismuth is one or more of stearate bismuth, oleate bismuth, and palmitate bismuth; the aromatic bismuth is one or more of bismuth benzoate, p-methylbenzoate bismuth, and phthalate bismuth; the bismuth-containing organic molecule is an organic bismuth compound that can be simultaneously pyrolyzed at high temperature to generate gasified bismuth element and carbon nanotube precursor.

[0014] Furthermore, in step 1), the inert carrier gas is either nitrogen or argon. The carrier gas flow rate is precisely controlled so that the proportion of pyrolysis gas is controlled at 5% to 20%, ensuring that the mixed gas forms a stable laminar flow state in the furnace tube and is transported uniformly and directionally, so as to achieve uniform and controllable deposition process.

[0015] Further, in step 2), the activated graphite felt is a graphite felt modified by any one or more of the following methods: acid treatment, high temperature heat treatment, plasma treatment, electrochemical activation, etc. The activation treatment can increase the surface defects and active sites of the graphite felt fibers and strengthen the bonding and adhesion of the Bi-C composite layer.

[0016] Furthermore, in step 2), the temperature gradient fluctuation of the low-temperature deposition zone is ≤ ±10 ℃ to ensure uniform deposition of gasified Bi and carbon precursor, and to avoid agglomeration of functional components and local load loss.

[0017] This invention also protects the Bi-C composite deposition type graphite felt electrode material prepared by the above preparation method. The graphite felt fiber surface of the electrode material is uniformly coated with a tightly coupled Bi-C composite layer, and the metallic bismuth nanoparticles are uniformly coated and anchored by the in-situ generated carbon nanonetwork layer, without obvious agglomeration or exposed bismuth. Compared with pure bismuth modified graphite felt, the Bi-C composite structure can significantly improve the chemical stability and electrochemical cycle stability of the bismuth component in the acidic aqueous solution system, and effectively inhibit the dissolution and loss of bismuth and oxidation failure.

[0018] Applications of this electrode material in vanadium redox flow batteries and iron-chromium redox flow batteries.

[0019] This invention innovatively utilizes the carbon matrix coating and anchoring effect to completely solve the core problems of pure bismuth modified electrodes, such as easy dissolution in acidic aqueous solutions in flow batteries, easy oxidation and detachment during electrochemical cycling, and structural instability. Simultaneously, the vapor deposition method enables uniform loading of functional components across the entire three-dimensional fiber network of graphite felt, avoiding the defects of uneven loading, severe agglomeration, and weak bonding in traditional impregnation, coating, and electrodeposition processes. The modified graphite felt electrode exhibits excellent conductivity, redox electrocatalytic activity, and hydrogen evolution inhibition capability, significantly improving the energy efficiency and long-cycle stability of vanadium redox flow batteries. The preparation process of this invention is simple, highly controllable, low-cost, and widely applicable, suitable for large-scale industrial production, providing a new technical path for the modification of high-performance, long-life flow battery electrodes.

[0020] Beneficial effects

[0021] Compared with the prior art, this invention has the following core innovations:

[0022] 1. A unique Bi-C in-situ co-deposition structure solves the problems of aqueous solution stability and electrochemical stability of bismuth components.

[0023] The core drawback of existing pure bismuth modified electrodes is the poor stability of elemental bismuth: in the acidic aqueous electrolyte of flow batteries, exposed bismuth particles are prone to chemical dissolution and loss; during charge-discharge electrochemical cycling, bismuth is easily oxidized to generate soluble bismuth ions, leading to rapid loss of active components and continuous degradation of electrode performance. This invention uses bismuth-containing organic molecules as an integrated source. After high-temperature pyrolysis, vaporized bismuth is simultaneously deposited with a carbon precursor, forming an in-situ composite structure of carbon nanonetworks coating metallic bismuth particles. The carbon layer can comprehensively encapsulate and anchor the bismuth nanoparticles, isolating them from direct contact with the acidic electrolyte and significantly inhibiting the chemical dissolution of bismuth in aqueous solution; on the other hand, it buffers interfacial stress during electrochemical cycling, preventing bismuth particle oxidation, aggregation, and detachment, significantly improving the electrochemical cycling stability of the bismuth component and solving the long-standing stability bottleneck that has hindered the industrialization of bismuth modified electrodes.

[0024] 2. The vapor-phase partitioned deposition process achieves uniform loading of functional components across the entire domain, far exceeding traditional liquid-phase modification processes.

[0025] Traditional liquid-phase modification processes such as impregnation, coating, and electrodeposition can only achieve shallow surface loading of graphite felt, making it difficult to modify the internal pores of the fibers. Furthermore, bismuth particles are prone to agglomeration, resulting in extremely poor loading uniformity. This invention employs a zoned temperature-controlled process of high-temperature vaporization and low-temperature deposition. Both the bismuth and carbon sources diffuse in gaseous molecular form with the carrier gas, penetrating the three-dimensional porous network of the graphite felt. This achieves full-area, uniform, and thin-layer deposition on the surface and pore walls of each fiber, preventing agglomeration and missed deposition. The overall distribution of active sites on the electrode is uniform, and the interface polarization is highly consistent, completely solving the problem of uneven loading in traditional processes. Simultaneously, the Bi-C composite layer formed by vapor deposition is in-situ bonded to the graphite felt substrate, with a bonding strength far exceeding that of traditional physical adhesion methods, making it less prone to detachment and failure.

[0026] 3. Synergistic effect: Combining high catalytic activity with strong hydrogen evolution inhibition capability, it significantly improves the overall performance of the battery.

[0027] Bismuth metal possesses a high hydrogen overpotential, which can effectively suppress the hydrogen evolution side reaction at the negative electrode of flow batteries. In-situ generated carbon nanomaterials exhibit high conductivity, high specific surface area, and excellent ion transport capabilities, significantly improving the conductivity, electrolyte wettability, and redox catalytic activity of graphite felt electrodes. The Bi-C composite structure creates a synergistic effect, retaining the hydrogen evolution suppression advantage of bismuth while enhancing electron transport and ion diffusion efficiency through the carbon network. This compensates for the dual deficiencies of weak hydrogen evolution suppression in pure carbon materials and insufficient conductivity and stability in pure bismuth materials, significantly reducing battery polarization losses and improving battery voltage and energy efficiency.

[0028] 4. The process is simple and controllable, the cost is low, and it is suitable for large-scale mass production.

[0029] This invention employs a single-furnace, partitioned reaction process throughout, eliminating the need for complex equipment and expensive reagents. The process parameters are highly controllable and reproducible. Bismuth-containing organic raw materials are widely available and inexpensive, and the preparation process is pollution-free and waste-free, making it environmentally friendly. Furthermore, this invention is highly versatile and compatible with mainstream flow battery systems such as vanadium redox flow and iron-chromium redox flow batteries, making it suitable for large-scale industrial production applications. Attached Figure Description

[0030] Figure 1 The CV curves of the Bi-C composite deposited graphite felt electrode Bi-C@AGF prepared in Example 1, the pure bismuth modified graphite felt electrode Bi@AGF prepared in Comparative Example 1, the pure carbon deposited graphite felt electrode C@AGF prepared in Comparative Example 2, and the original graphite felt GF electrode in 0.1 M VOSO4 + 2.0 M H2SO4 solution are shown. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to specific embodiments.

[0032] Example 1

[0033] A method for preparing a vaporized Bi-C composite deposition type graphite felt electrode material, comprising the following steps:

[0034] 1) Weigh 4g of bismuth benzoate and place it in a crucible, then place it in the high-temperature zone of a tube furnace; select a graphite felt that has been activated by hot air at 500℃ for 2 hours and fix it vertically in the low-temperature zone; introduce argon gas as a protective gas at a flow rate of 80 mL / min, and heat the high-temperature zone to 1000℃ for isothermal pyrolysis.

[0035] 2) The temperature in the low-temperature zone is controlled at 700℃. After the high-temperature zone stabilizes and produces gas, the temperature is continuously constant for 4 hours to allow the gasified Bi and carbon precursor to be deposited synchronously and uniformly on the surface of the graphite felt fiber.

[0036] 3) After deposition, stop heating, maintain nitrogen atmosphere and cool the furnace to room temperature, remove the sample, and obtain Bi-C composite deposition type graphite felt electrode material Bi-C@AGF-1.

[0037] Example 2

[0038] A method for preparing a vaporized Bi-C composite deposition type graphite felt electrode material, comprising the following steps:

[0039] 1) Weigh 5g of bismuth stearate and place it in a ceramic crucible. Place the crucible in the high-temperature zone of the tube furnace. Place the original graphite felt vertically in the low-temperature zone of the tube furnace. Purge the air in the furnace with high-purity nitrogen gas, and set the nitrogen flow rate to 100 mL / min. Heat to 900 ℃ and pyrolyze at a constant temperature in the high-temperature zone.

[0040] 2) Control the deposition temperature in the low-temperature zone to 700 ℃. After the high-temperature zone stabilizes and produces gas, continue to deposit at a constant temperature for 3 h to allow the gasified Bi and carbon precursor to be deposited synchronously and uniformly on the surface of the graphite felt fiber.

[0041] 3) After deposition, stop heating, maintain nitrogen atmosphere and cool the furnace to room temperature, remove the sample, and obtain Bi-C composite deposition type graphite felt electrode material Bi-C@AGF-2.

[0042] Example 3

[0043] 1) Mix 6g of bismuth palmitate and bismuth p-toluene at a mass ratio of 1:1 and place them in the high-temperature zone of a tube furnace; place the graphite felt activated by plasma for 30 min vertically in the low-temperature zone of the tube furnace, purge the air in the furnace with high-purity nitrogen gas, and set the nitrogen gas flow rate to 150 mL / min; raise the temperature to 950 ℃ and pyrolyze at a constant temperature in the high-temperature zone.

[0044] 2) The temperature of the low-temperature zone is set to 650℃. After the high-temperature zone stabilizes and produces gas, the temperature is maintained for 2 hours to allow the gasified Bi and carbon precursor to be deposited synchronously and uniformly on the surface of the graphite felt fiber.

[0045] 3) Cool and discharge the material to obtain a uniformly loaded Bi-C composite modified graphite felt electrode Bi-C@AGF-3.

[0046] Comparative Example 1 (Pure Bi deposited graphite felt electrode Bi@AGF)

[0047] 1) Weigh 5g of metallic bismuth powder and place it in a ceramic crucible, then place it in the high-temperature zone of a tube furnace; fix the original graphite felt in the low-temperature zone of the same tube furnace; seal the furnace body, introduce high-purity nitrogen to purge the air, with a nitrogen carrier gas flow rate of 100 mL / min; raise the temperature of the high-temperature zone to 900 ℃ to vaporize the metallic bismuth.

[0048] 2) The deposition temperature was controlled at 700 ℃ in the low-temperature zone, and the deposition was carried out at a constant temperature for 3 h. Bismuth vapor was deposited on the surface of the graphite felt fiber to obtain a pure Bi modified graphite felt electrode loaded only with metallic bismuth.

[0049] 3) After deposition, maintain a nitrogen atmosphere and cool the furnace to room temperature before removing the sample. The electrode surface obtained in this comparative example consists of bare metallic bismuth particles without carbon layer coating and anchoring. Bismuth is easily dissolved in acidic electrolytes and is easily oxidized and detached during electrochemical cycling, resulting in poor long-term stability. At the same time, single bismuth vapor is prone to agglomeration, and the uniformity of the load is not as good as the organic bismuth simultaneous pyrolysis co-deposition system of this invention.

[0050] Comparative Example 2 (Pure carbon deposited graphite felt electrode C@AGF)

[0051] 1) Weigh 5g of benzoic acid and place it in a ceramic crucible, then place it in the high-temperature zone of a tube furnace; place the original graphite felt in the low-temperature zone; introduce high-purity nitrogen gas at a flow rate of 100 mL / min; raise the temperature in the high-temperature zone to 900 ℃, and benzoic acid will undergo high-temperature pyrolysis to produce carbon precursor gas.

[0052] 2) The temperature in the low-temperature zone is maintained at 600 ℃, and the carbon precursor is deposited at a constant temperature for 3 h. The carbon precursor is pyrolyzed and deposited on the surface of the graphite felt fiber to obtain a pure carbon modified graphite felt electrode.

[0053] 3) The sample was obtained by cooling the furnace to room temperature under an inert atmosphere and then unloading. This comparative example only relies on the carbon layer to improve the electrode conductivity and electrolyte wettability. It lacks the high hydrogen overpotential bismuth metal component, which cannot effectively suppress the hydrogen evolution side reaction at the negative electrode of the flow battery. The side reaction losses during the charge and discharge process are significant, and the improvement in battery energy efficiency is limited.

[0054] Example 4 Performance Test Results

[0055] 1. The Bi-C composite deposited graphite felt electrode Bi-C@AGF prepared in Example 1 and the pure bismuth modified graphite felt electrode Bi@AGF prepared in Comparative Example 1 were immersed in vanadium battery electrolyte (1.6 MV). 3.5+ The content of Bi on the electrode surface before and after immersion in +2.0 M H2SO4 for 500 h was investigated by ICP. The results showed that the bismuth component loss rate of the pure bismuth modified electrode reached 38.6%, while the bismuth component loss rate of the Bi-C composite electrode of this invention was only 3.2%.

[0056] 2. Electrochemical CV tests were performed on the Bi-C composite deposited graphite felt electrode Bi-C@AGF prepared in Example 1, the pure bismuth modified graphite felt electrode Bi@AGF prepared in Comparative Example 1, the pure carbon deposited graphite felt electrode C@AGF prepared in Comparative Example 2, and the original graphite felt GF electrode, respectively. The results are as follows: Figure 1 As shown, the redox peak potential difference of the Bi-C composite electrode of the present invention is significantly reduced compared with that of the original graphite felt, and the peak current is significantly increased, indicating that the electrode reaction kinetics are accelerated and the electrochemical activity is significantly improved; the hydrogen evolution side reaction at a lower potential is significantly suppressed, confirming that the carbon layer coating effectively improves the selectivity of the electrode.

[0057] Single cells were assembled using the Bi-C composite deposited graphite felt electrode Bi-C@AGF-1 prepared in Example 1, the pure bismuth modified graphite felt electrode Bi@AGF prepared in Comparative Example 1, and the pure carbon deposited graphite felt electrode C@AGF prepared in Comparative Example 2, respectively. Nafion 212 was used as the separator and graphite as the bipolar plate. The electrodes were tested at 250 mA cm⁻¹. -2 The results of 500 charge-discharge cycles at the current density are shown in Table 1.

[0058] Table 1

[0059] Sample grouping Electrode structural features Metal loss rate after 500h electrolyte immersion Energy efficiency degradation after 500 charge-discharge cycles Energy efficiency Comparative Example 1 Bi@AGF 38.6% 2.1% 76.3% Comparative Example 2 C@AGF — 3.5% 74.2% Example 1 Bi-C@AGF-1 3.2% 1.1% 78.6% Example 2 Bi-C@AGF-1 3.3% 1.2% 78.4% Example 3 Bi-C@AGF-1 3.1% 1.0% 78.9%

[0060] Battery data shows that pure carbon-deposited electrodes (C@AGF) lack hydrogen evolution inhibition performance and may even exacerbate side reactions due to their high specific surface area, leading to decreased battery performance and significant energy efficiency degradation. Pure Bi-deposited electrodes (Bi@AGF) have metal catalysts exposed on the fiber surface with small particles, making them easily leached and lost in the electrolyte, resulting in rapid performance degradation even under long-term cycling, although battery performance is significantly improved compared to C@AGF. In contrast, the Bi-C@AGF-1 prepared in this invention effectively reduces Bi loss through carbon coating, while the carbon and Bi on the electrode surface synergistically enhance each other, giving the electrode both excellent catalytic kinetics and hydrogen evolution inhibition capabilities, resulting in significantly improved battery energy efficiency and cycle stability.

Claims

1. A method for preparing a vaporized Bi-C composite deposition type graphite felt electrode material, characterized in that, Includes the following steps: 1) Raw material pyrolysis gas generation: Bismuth-containing organic molecules are placed in the high-temperature zone of a tube furnace and heated at a constant temperature of 800℃~1000℃ under the protection of an inert atmosphere, so that the bismuth-containing organic molecules are continuously pyrolyzed to generate a mixed functional gas containing gasified Bi element and carbon precursor. The mixed gas flows directionally to the low-temperature zone of the furnace body with the inert carrier gas. 2) Zoned vapor deposition: The original graphite felt or activated graphite felt is fixed in the low temperature zone of the same furnace body of the tube furnace. The temperature of the low temperature zone is precisely controlled at 500℃~700℃. The gasified Bi element produced by high temperature pyrolysis and the mixed functional gas of carbon precursor are synergistically deposited in this temperature zone and uniformly attached to the surface of the single fiber of the original graphite felt or activated graphite felt, forming a Bi-C composite functional modified layer in situ. 3) Cooling and molding: After the reaction is completed, the sample is taken out and cooled to room temperature to obtain a stable and uniformly loaded vaporized Bi-C composite deposition graphite felt electrode material.

2. The method for preparing a vaporized Bi-C composite deposition type graphite felt electrode material according to claim 1, characterized in that, In step 1), the bismuth-containing organic molecule is an organic bismuth compound that is simultaneously pyrolyzed at high temperature to generate gaseous bismuth element and carbon nanotube precursor.

3. The method for preparing a vaporized Bi-C composite deposition type graphite felt electrode material according to claim 2, characterized in that, In step 1), the bismuth-containing organic molecule includes one or more of long-chain fatty acid bismuth and aromatic bismuth; the long-chain fatty acid bismuth is one or more of bismuth stearate, bismuth oleate, and bismuth palmitate; the aromatic bismuth is one or more of bismuth benzoate, bismuth p-methylbenzoate, and bismuth phthalate.

4. The method for preparing a vaporized Bi-C composite deposition type graphite felt electrode material according to claim 1, characterized in that, In step 1), the inert carrier gas is either nitrogen or argon. The inert carrier gas flow rate is precisely controlled so that the proportion of the mixed functional gas containing gasified Bi and carbon precursor is controlled at 5% to 20%, ensuring that the mixed gas forms a stable laminar flow state in the furnace tube and is transported uniformly and directionally, so as to achieve uniform and controllable deposition process.

5. The method for preparing a vaporized Bi-C composite deposition type graphite felt electrode material according to claim 1, characterized in that, In step 2), the activated graphite felt is a graphite felt modified by any one or more of the following methods: acid treatment, high-temperature heat treatment, plasma treatment, electrochemical activation, etc.

6. The method for preparing a vaporized Bi-C composite deposition type graphite felt electrode material according to claim 1, characterized in that, In step 2), the temperature fluctuation in the low-temperature zone is ≤ ±10 ℃.

7. A vaporized Bi-C composite deposition type graphite felt electrode material obtained by the preparation method according to any one of claims 1-6, characterized in that, The surface of the graphite felt fiber of the electrode material is uniformly coated with a tightly coupled Bi-C composite layer, and the bismuth nanoparticles are uniformly coated and anchored by the in-situ generated carbon nanonetwork layer.

8. The application of the vaporized Bi-C composite deposition type graphite felt electrode material as described in claim 7 in a flow battery.

9. The application according to claim 8, characterized in that, The flow batteries include vanadium redox flow batteries and iron-chromium redox flow batteries.

Images