A composite electrode material rich in oxygen vacancies and a preparation method and application thereof

Abstract

This invention belongs to the field of electrochemical energy storage, specifically disclosing a composite electrode material rich in oxygen vacancies, its preparation method, and its application. The method includes: pre-treatment of a carbon substrate by oxidation activation; mixing a titanium-containing precursor, hydrochloric acid, and a defect inducer in a specific ratio; immersing the activated carbon substrate in the mixture and performing hydrothermal in-situ growth under conditions where the reactor filling degree is controlled at 60%~80%; and inducing lattice reconstruction through heat treatment in a reducing / protective atmosphere to obtain the composite electrode material rich in oxygen vacancies. This invention, through the synergistic effect of "in-situ growth" and "defect engineering," forms strong covalent bonds between carbon fibers and titanium nanoparticles, solving the problem of catalyst detachment. Simultaneously, the high concentration of oxygen vacancies significantly improves the intrinsic electronic conductivity and catalytic active site density of the material. The resulting composite material can be directly applied to iron-chromium redox flow batteries, significantly improving reaction kinetics, single-cell energy efficiency, and long-cycle stability.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage materials and devices, specifically to a composite electrode material rich in oxygen vacancies, its preparation method, and its applications. Background Technology

[0002] In the field of energy storage, iron-chromium redox flow batteries have become one of the core technologies for large-scale grid-scale energy storage due to their advantages such as adjustable capacity, long cycle life, and high safety. The positive and negative electrode reactions of iron-chromium redox flow batteries depend on... and The redox process. However, the negative electrode The redox reaction kinetics are extremely slow, and polarization is severe, which directly limits the battery's voltage efficiency, energy conversion efficiency, and overall power density. Titanium-based materials (such as...) Due to its excellent acid resistance, good environmental friendliness, and certain catalytic potential, it is often used as a key electrocatalyst in iron-chromium redox flow batteries. However, a pure-phase, complete crystal lattice... Essentially a wide-bandgap semiconductor, titanium has extremely low intrinsic electronic conductivity, leading to significant ohmic polarization and charge transfer impedance when applied as an electrode. Furthermore, the perfect crystal surface lacks sufficient catalytic active sites, limiting its ability to adsorb and catalytically activate complexed chromium ions, making it difficult to meet the kinetic requirements of batteries at high current densities. In addition, existing titanium-based catalyst preparation and electrode loading processes face significant technical bottlenecks. Currently, the industry commonly employs a non-in-situ preparation route of "powder synthesis-post-dispersion," where nanoscale chromium is first prepared using conventional hydrothermal methods. The powder is then coated or physically mixed onto a carbon substrate (such as carbon felt or carbon cloth) using a dispersant. This physical coating process has three major drawbacks: Firstly, the catalyst powder and the carbon substrate are only bound by van der Waals forces or very weak physical adsorption. Under the long-term acidic electrolyte flushing of the flow battery, the catalyst particles are very easy to fall off and be lost, resulting in a shortened battery cycle life. Secondly, regardless of the type of dispersant used, there is an extremely high solid-solid interface contact resistance between the powder particles and the conductive substrate, which hinders the rapid transport of electrons. Third, without the guidance of a growth substrate, the simple hydrothermal powder synthesis is prone to severe particle agglomeration, which reduces the effective specific surface area and leads to low utilization of active sites.

[0003] Therefore, there is an urgent need to develop a novel titanium-based composite electrode material and preparation method that combines high electronic conductivity, abundant catalytic active sites, and strong bonding with conductive substrates, in order to fundamentally solve the problems of slow anode kinetics and easy catalyst detachment in iron-chromium redox flow batteries. Summary of the Invention

[0004] To address the problems of poor conductivity, few active sites, and easy detachment of physically dispersed coatings in existing pure-phase titanium-based materials, this invention provides a composite electrode material rich in oxygen vacancies, its preparation method, and its application. Through the synergistic regulation of carbon substrate surface engineering and lattice defect engineering, in-situ anchoring and activation of nano-titanium-based active materials on conductive networks are achieved, significantly improving its electrochemical reaction kinetics and long-term cycling stability in iron-chromium redox flow batteries, thus solving the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a composite electrode material rich in oxygen vacancies, comprising the following steps: S1. Carbon Substrate Activation Pretreatment: The carbon substrate undergoes an oxidative activation pretreatment to introduce oxygen-containing functional groups. This step aims to clean impurities from the carbon fiber surface and introduce abundant oxygen-containing functional groups (such as hydroxyl-OH, carboxyl-COOH, etc.) in situ onto the carbon substrate surface. These functional groups will serve as the basis for subsequent... The nucleation "anchor point" induces the precursor to form uniform heterogeneous nucleation on the fiber surface, fundamentally inhibiting the liquid-phase aggregation of titanium-based particles and replacing the reliance on non-organic dispersants in traditional processes.

[0006] S2. Preparation of defect-inducing precursor mixture: Mix titanium-containing precursor, hydrochloric acid and defect inducer in proportion to obtain a uniform and transparent defect-inducing precursor mixture.

[0007] The addition of hydrochloric acid is used to adjust the pH of the system and inhibit... To prevent excessively rapid hydrolysis and ensure uniformity in subsequent growth, defect-inducing agents (such as substances with reducing properties or those that readily produce reducing gases through pyrolysis) are introduced to form coordination within the precursor network, facilitating lattice distortion and oxygen vacancies during subsequent heat treatment. The generation of ) provides a chemical basis.

[0008] S3. In-situ controlled hydrothermal growth: The activated and pretreated carbon substrate is immersed in a defect-inducing precursor mixture, and then hydrothermal in-situ growth is carried out under the condition that the filling degree of the reactor is controlled at 60%~80%. After cooling, the carbon substrate loaded with precursor is taken out, washed and dried.

[0009] The humidity parameter, which is affected by the external environment, was discarded, and the high-temperature, high-pressure autogenous system inside the reactor was strictly controlled by the filling degree. Under these conditions, the titanium-based precursor, induced by oxygen-containing functional groups, grows in situ along the carbon fiber surface, forming a strong... Covalent bonds are formed, creating a continuous electron transport channel, which greatly reduces the contact resistance at the solid-solid interface.

[0010] S4. Lattice Reconstruction and Vacancy Enrichment: The composite material dried in step S3 is placed in a tube furnace and lattice reconstruction is induced by heat treatment under a reducing / protective atmosphere to obtain a composite electrode material rich in oxygen vacancies.

[0011] The heat treatment process induces a phase transformation in the amorphous titanium-based precursor, crystallizing it into a highly reactive anatase or rutile phase. Simultaneously, with the assistance of an inducing agent and the intrinsic thermal reduction effect of the carbon substrate, Some lattice oxygen is extracted from the crystal lattice, forming a large number of oxygen vacancy defects. The introduction of oxygen vacancies in... New donor levels are generated in the band gap, which significantly improves the intrinsic electronic conductivity of the material and serves as a high-energy catalytic active center, enhancing the adsorption and electron transfer of complexed chromium ions.

[0012] Preferably, in step S1, the carbon substrate is placed in a strongly acidic oxidizing solution for surface activation treatment, washed until neutral and dried; the carbon substrate is selected from carbon felt, carbon cloth or carbon nanotube film; the strongly acidic oxidizing solution is a mixture of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1.

[0013] Preferably, in step S2, the titanium-containing precursor is Solution, The solution concentration is 0.1~1 mol / L; the defect inducing agent is selected from at least one of ascorbic acid, urea, thiourea, or sodium borohydride, and its addition amount is 0.1~0.5 times the amount of the titanium-containing precursor; the hydrochloric acid concentration is 0.1~2 mol / L; The volume ratio of the solution to hydrochloric acid is 1:2~10.

[0014] Preferably, in step S3, the hydrothermal in-situ growth is specifically carried out at a temperature of 160~180℃ for 10~15h.

[0015] Preferably, in step S3, the hydrothermal in-situ growth is specifically carried out at 170°C for 12 hours.

[0016] Preferably, in step S4, the reducing / protective atmosphere is specifically a mixture of high-purity argon, nitrogen, hydrogen, and argon.

[0017] Preferably, the protective atmosphere is high-purity argon or nitrogen; the reducing atmosphere is a mixture of hydrogen and argon (hydrogen volume percentage 5%~10%).

[0018] Preferably, in step S4, the heat treatment specifically involves heating to 400~600°C at a heating rate of 3°C to 5°C per minute and holding at that temperature for 2~4 hours.

[0019] On the other hand, in order to achieve the above objectives, the present invention also provides the following technical solution: a composite electrode material rich in oxygen vacancies.

[0020] Preferably, the oxygen-vacancy-rich composite electrode material is composed of nanoparticles with a particle size distribution ranging from 10 to 20 μm and a specific surface area of ​​50 to 70 m². 2 / g.

[0021] On the other hand, in order to achieve the above objectives, the present invention also provides the following technical solution: the application of a composite electrode material rich in oxygen vacancies in the negative electrode of an iron-chromium flow battery.

[0022] The beneficial effects of this invention are: 1) Breaking through the intrinsic conductivity bottleneck and significantly reducing polarization: This invention abandons the traditional pure phase The ohmic voltage drop problem caused by the insulation properties of powder materials was addressed by constructing a three-dimensional interpenetrating continuous conductive network through in-situ growth on carbon fibers (such as carbon cloth and carbon felt). More importantly, the synergistic effect of heat treatment and induction agents further improved the conductivity of the powder. A high concentration of oxygen vacancy defects is introduced into the crystal lattice. This lattice distortion introduces donor levels into the band gap, significantly increasing the intrinsic electronic conductivity of the titanium-based material and thus reducing the charge transfer resistance (CTR). () significantly reduced.

[0023] 2) Constructing defect-rich active centers to accelerate electrochemical kinetics: Compared to perfect crystal faces, the oxygen vacancies introduced in this invention can disrupt the local charge balance, serving as highly active electrocatalytic centers; during the charge and discharge process of iron-chromium redox flow batteries, these defect sites can effectively promote complexation. The chemical adsorption and electron transfer of ions significantly reduced The activation energy of the redox reaction significantly improves the battery's voltage efficiency (VE) and energy efficiency (EE).

[0024] 3) Formation of strong chemical bonds, achieving ultra-long cycle stability: Existing physical mixing coating processes rely solely on extremely weak van der Waals forces, making them prone to detachment under high-speed scouring of acidic electrolytes. This invention, through pretreatment of oxygen-containing functional groups on the substrate surface, induces in-situ nucleation of the precursor, forming a strong bond between the titanium-based nanoparticles and the carbon substrate. Covalent bonding; this chemical anchoring effect endows the composite electrode with extremely high mechanical stability and resistance to electrolyte erosion, ensuring the capacity retention rate of the iron-chromium redox flow battery during long-term operation.

[0025] 4) Achieving binder-free integrated electrode and eliminating dead volume: The composite material prepared by this invention can be directly used as a three-dimensional porous integrated electrode for iron-chromium flow batteries. This completely eliminates the need for polymer insulating binders (such as PTFE, Nafion, etc.) that must be added in the traditional slurry coating process, avoids the coating and masking of catalytic active sites by binders, and achieves 100% electrochemical utilization of active materials.

[0026] 5) Rigorous scientific process with strong reproducibility and scalability: To address the shortcomings of traditional hydrothermal synthesis which is easily affected by external environmental interference, this invention adopts a more scientific "reactor filling degree" to precisely control the self-generated pressure inside the reactor, combined with a specific concentration of hydrochloric acid to inhibit the hydrolysis rate; the process parameters are clearly set and the mechanism is clear, effectively avoiding the risk of residual organic matter contaminating the electrolyte due to simply relying on additive dispersion. The process has good reproducibility and is highly adaptable to the industrial-scale production needs of core materials for iron-chromium redox flow batteries. Attached Figure Description

[0027] Figure 1 This is a schematic diagram illustrating the energy and voltage efficiency of the titanium-based material prepared in Example 1 of the present invention as a catalyst for an iron-chromium redox flow battery. Figure 2 This is a synchrotron radiation diagram of the titanium-based material prepared in Example 1 of the present invention; Figure 3 The graph shows the viscosity, density, and conductivity of the titanium-based material prepared in Example 1 of this invention. (a) represents viscosity; (b) represents density; and (c) represents conductivity. Figure 4 The diagrams show the microscopic, impedance, and energy efficiency cycles of Embodiment 1 and Comparative Example 1 of the present invention. (a) is a microscopic diagram, (b) is an impedance diagram, and (c) is an energy efficiency cycle diagram. Figure 5 The diagrams are schematic diagrams of the microstructure, impedance, and energy efficiency of Embodiment 2 and Comparative Example 1 of the present invention. (a) is a microscopic diagram, (b) is an impedance diagram, and (c) is an energy efficiency diagram. Figure 6 The diagrams show the microscopic, impedance, and energy efficiency cycles of Embodiment 3 and Comparative Example 1 of the present invention. (a) is a microscopic diagram, (b) is an impedance diagram, and (c) is an energy efficiency cycle diagram. Figure 7 The figures show a comparison of particle size distribution and specific surface area of ​​the titanium-based materials prepared in Examples 1-3 of this invention. (a) shows the particle size distribution, and (b) shows the specific surface area. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1 A composite electrode material TiO2-x / CF-Opt rich in oxygen vacancies and its preparation (1) Carbon substrate pretreatment: Commercial carbon felt is immersed in concentrated sulfuric acid / concentrated nitric acid (volume ratio 3:1), activated at 80°C for 4 hours, washed until neutral, and dried to obtain activated carbon felt with oxygen-containing functional groups on the surface.

[0030] (2) Preparation of defect-inducing precursor: Take 100 mL of 0.5 mol / L TiCl4 solution, add 200 mL of 1.0 mol / L hydrochloric acid, and then add 0.05 mol urea (defect inducer) and stir evenly.

[0031] (3) In-situ controllable hydrothermal: Immerse the activated carbon felt in the above precursor, transfer it to the reactor (70% filling), and react at 170°C for 12 hours.

[0032] (4) Lattice reconstruction: After cleaning, the material was placed in a tube furnace and calcined at 500°C for 2 hours under an argon (Ar) atmosphere at a heating rate of 4°C per minute. After natural cooling, a composite electrode rich in oxygen vacancies (labeled as TiO2-x / CF-Opt) was obtained. A schematic diagram of the energy and voltage efficiency of the prepared titanium-based material as a catalyst in an iron-chromium flow battery is shown below. Figure 1 As shown, the synchrotron radiation pattern of the titanium-based material prepared in Example 1 is as follows. Figure 2 As shown, the viscosity, density, and conductivity of the titanium-based material prepared in Example 1 are as follows: Figure 3 As shown in (a), (b), and (c).

[0033] Example 2 A composite electrode material TiO2 / CF-Air with oxygen-deficient vacancies and its preparation The steps are basically the same as in Example 1, except that urea is not added in step (2), and calcination is carried out at 400°C in air atmosphere in step (4). This condition is intended to repair the crystal lattice and reduce the generation of oxygen vacancies (labeled as TiO2 / CF-Air).

[0034] Example 3 A composite electrode material TiO2-y / CC-Red rich in oxygen vacancies and its preparation The steps are basically the same as in Example 1, except that: in step (1), carbon cloth is used as the substrate; in step (2), 0.05 mol of ascorbic acid is added as a strong reducing agent; in step (4), the mixture is calcined at 450°C for 2 h in a mixed reducing atmosphere of Ar / H2 (5%) (labeled as TiO2-y / CC-Red).

[0035] The particle size distribution and specific surface area comparisons of the titanium-based materials prepared in Examples 1-3 of this invention are shown in the following figures. Figure 7 As shown in (a) and (b).

[0036] Comparative Example 1: Traditional Powder Synthesis and Physical Coating Process This comparative example uses a traditional hydrothermal method to synthesize pure-phase powder, which is then physically coated onto an electrode. The steps are as follows: (1) Mixing raw materials: Take 100 mL of TiCl4 solution with a concentration of 0.5 mol / L, add 300 mL of 0.5 mol / L hydrochloric acid, and stir at room temperature for 20 min.

[0037] (2) Hydrothermal reaction: Transfer to a reaction vessel and keep at 170℃ for 720 min to obtain a hydrothermal sample.

[0038] (3) Post-processing and dispersion: After centrifugation, drying and sieving, add 3% of the sample mass of silica dispersant and sonicate for 30 min to obtain TiO2 powder.

[0039] (4) Electrode preparation: The above TiO2 powder is mixed with PTFE emulsion (binder) to form a slurry, which is then coated on the surface of commercial carbon felt and dried for later use.

[0040] Characterization and performance testing comparison To verify the technical effects of the present invention, the electrode materials prepared in the comparative examples and embodiments above were characterized by X-ray photoelectron spectroscopy (XPS) and tested as single-cell iron-chromium redox flow batteries. Test conditions: current density 80 mA / cm². 2 The electrolyte is 1.5 mol / L FeCl3 + 1.5 mol / L CrCl2 + 2 mol / L HCl.

[0041] XPS oxygen vacancy quantitative analysis: The relative contents of lattice oxygen (O_lat, binding energy approximately 529.8 eV) and defect oxygen / oxygen vacancy (O_vac, binding energy approximately 531.5 eV) were quantitatively analyzed by peak fitting of high-resolution O 1s XPS spectra. Table 1 shows the XPS oxygen vacancy quantitative analysis results of Comparative Example 1 and Examples 1-3.

[0042] Table 1. Quantitative analysis of oxygen vacancy by XPS

[0043] As shown in Table 1, Example 1 successfully increased the oxygen vacancy concentration to 26.5% through the synergistic effect of the inducing agent and the inert atmosphere, and its electrical conductivity was more than 20 times higher than that of Comparative Example 1 (conventional powder). Although Example 3 had the highest oxygen vacancy concentration, excessive lattice destruction caused the collapse of some TiO2 structures, resulting in a slight decrease in electrical conductivity, indicating that the defect concentration of Example 1 was within the optimal range.

[0044] Performance comparison of iron-chromium redox flow batteries: Table 2 shows the performance comparison of iron-chromium redox flow batteries in Comparative Example 1 and Examples 1-3.

[0045] Table 2 Performance Comparison of Iron-Chromium Flow Batteries

[0046] The microscopic, impedance, and energy efficiency cycle diagrams of Embodiment 1 and Comparative Example 1 of the present invention are shown below. Figure 4 As shown in (a), (b), and (c); the microscopic, impedance, and energy efficiency cycle diagrams of Example 2 and Comparative Example 1 are respectively shown in Figures 1-2. Figure 5 As shown in (a), (b), and (c); the microscopic, impedance, and energy efficiency cycle diagrams of Example 1 and Comparative Example 1 are respectively shown in Figures 1-2. Figure 6 As shown in (a), (b), and (c).

[0047] Based on the above tests and Figures 4-7 It can be seen that the batteries prepared using the method of the present invention in Examples 1-3 all outperform Comparative Example 1, which uses a traditional physical coating process, in terms of battery efficiency and cycle stability. Especially in Example 1, the moderate oxygen vacancy concentration (26.5%) not only significantly reduced the ohmic impedance of the electrode but also provided a suitable environment for Cr... 3+ / Cr 2+ The redox reaction provides abundant catalytic active sites, enabling the single-cell voltage efficiency (VE) to jump to 86.2%. At the same time, thanks to the strong chemical bonding of Ti-OC formed by in-situ growth, the fatal problem of easy detachment of catalyst powder in Comparative Example 1 is completely solved. After 100 cycles, the capacity retention rate is as high as 98.1%, which fully demonstrates the excellent technical effect of the dual strategy of "in-situ growth + defect engineering" of this invention.

[0048] Compared to existing physical coating dispersion techniques, this invention utilizes the synergistic effect of "in-situ growth" and "defect engineering" to form a strong bond between carbon fibers and titanium nanoparticles. Covalent bonds completely solve the problem of catalyst detachment; simultaneously, the high concentration of oxygen vacancies significantly improves the intrinsic electronic conductivity and catalytic active site density of the material. The resulting composite material can be directly used as a binder-free integrated electrode in iron-chromium flow batteries, greatly improving performance. The reaction kinetics, single-cell energy efficiency, and long-cycle stability.

[0049] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0050] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0051] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0052] Depending on the context, the word "if" as used here can be interpreted as "when," "when," "in response to determination," or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination," "in response to determination," "when detection (of the stated condition or event)," or "in response to detection (of the stated condition or event)."

[0053] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a composite electrode material rich in oxygen vacancies, characterized in that, Includes the following steps: S1. Carbon substrate activation pretreatment: The carbon substrate is subjected to oxidation activation pretreatment to introduce oxygen-containing functional groups; S2. Preparation of defect-inducing precursor mixture: Mix titanium-containing precursor, hydrochloric acid and defect inducer in proportion to obtain a uniform and transparent defect-inducing precursor mixture. S3. In-situ controllable hydrothermal growth: The activated and pretreated carbon substrate is immersed in a defect-inducing precursor mixture, and then hydrothermal in-situ growth is carried out under the condition that the filling degree of the reactor is controlled at 60%~80%. After cooling, the carbon substrate loaded with precursor is taken out, washed and dried. S4. Lattice Reconstruction and Vacancy Enrichment: The composite material dried in step S3 is placed in a tube furnace and lattice reconstruction is induced by heat treatment under a reducing / protective atmosphere to obtain a composite electrode material rich in oxygen vacancies.

2. The method for preparing the oxygen-vacancy-rich composite electrode material according to claim 1, characterized in that: In step S1, the carbon substrate is placed in a strongly acidic oxidizing solution for surface activation treatment, washed until neutral and dried; the carbon substrate is selected from carbon felt, carbon cloth or carbon nanotube film; the strongly acidic oxidizing solution is a mixture of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 3:

1.

3. The method of claim 1, wherein the method is characterized by: In step S2, the titanium-containing precursor is Solution, The solution concentration is 0.1~1 mol / L; the defect inducing agent is selected from at least one of ascorbic acid, urea, thiourea, or sodium borohydride, and its addition amount is 0.1~0.5 times the amount of the titanium-containing precursor; the hydrochloric acid concentration is 0.1~2 mol / L; The volume ratio of the solution to hydrochloric acid is 1:2~10.

4. The method of claim 1, wherein the method is characterized by: In step S3, the hydrothermal in-situ growth specifically involves a reaction at 160-180°C for 10-15 hours.

5. The method of claim 4, wherein the method further comprises: In step S3, the hydrothermal in-situ growth specifically involves a reaction at 170°C for 12 hours.

6. The method of claim 1, wherein: In step S4, the reducing / protective atmosphere is specifically a mixture of high-purity argon, nitrogen, hydrogen, and argon.

7. The method for preparing the oxygen-vacancy-rich composite electrode material according to claim 1, characterized in that: In step S4, the heat treatment specifically involves heating to 400-600°C at a heating rate of 3°C to 5°C per minute and holding at that temperature for 2-4 hours.

8. An oxygen-vacancy-rich composite electrode material prepared by a method according to any one of claims 1-7.

9. The oxygen-vacancy-rich composite electrode material of claim 8, wherein: The composite electrode material rich in oxygen vacancies is a nano-particle, and the particle size distribution range is 10-20 μm, and the specific surface area is 50-70 m 2 / g.

10. The application of a composite electrode material prepared by the method of preparing an oxygen-vacancy-rich composite electrode material according to any one of claims 1-7, or the composite electrode material prepared by preparing an oxygen-vacancy-rich composite electrode material according to any one of claims 8-9, in the negative electrode of an iron-chromium redox flow battery.

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