Modified graphite felt electrode for all-alkaline manganese-based open-circuit flow battery and preparation method of modified graphite felt electrode
By soaking graphite felt in potassium permanganate solution and electrochemically activating it, oxygen-containing functional groups and a rough surface are introduced, which solves the problems of hydrophobicity and chemical inertness of graphite felt electrode surface, improves the electrochemical activity and high current density performance of fully alkaline manganese-based open-circuit flow battery, and realizes simple and efficient modification of electrode material.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-08
- Publication Date
- 2026-03-27
AI Technical Summary
Existing graphite felt electrodes suffer from insufficient electrolyte wetting due to their surface hydrophobicity and chemical inertness, resulting in a scarcity of electrochemical active sites and sluggish electrochemical reaction kinetics, which limits the energy efficiency and high current density performance of fully alkaline manganese-based open-circuit flow batteries.
Graphite felt was treated by soaking in potassium permanganate solution and electrochemical activation to introduce abundant oxygen-containing functional groups and a rough surface, thereby improving the hydrophilicity and electrochemically active area of the graphite felt. Electrochemical activation was carried out within a specific potential range by cyclic voltammetry.
It significantly improves the electrochemical activity and mass transfer performance of fully alkaline manganese-based open-circuit flow batteries, enhances electrode stability and reaction performance at high current densities, simplifies the preparation process, and reduces costs.
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Figure CN121748424A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of flow battery electrode material technology, specifically relating to a modified graphite felt electrode for a fully alkaline manganese-based open-circuit flow battery and its preparation method. Background Technology
[0002] Currently, the main sources of global electricity generation are still oil and coal, and the carbon dioxide emissions and environmental pollution caused by these fossil fuels are becoming increasingly serious. Flow batteries, with their advantages of long life and high utilization rate of active materials, have become one of the next-generation energy storage technologies that make full use of intermittent renewable energy sources (such as solar, wind and ocean power).
[0003] Manganese, as one of the most abundant and inexpensive transition metals, aligns with the "low-cost, large-scale" development requirements of flow batteries. Under alkaline conditions, manganese redox ion pairs exhibit high potentials, matching the oxidation reactions of most low-potential organic compounds. Furthermore, the stability of manganese redox ion pairs is good in alkaline solutions, suppressing disproportionation reactions and enabling stable charge-discharge cycles. Fully alkaline manganese-based open-circuit flow batteries constructed using manganese cathodes are low-cost, safe, stable, and long-lasting. The use of alkaline electrolytes also reduces instrument corrosion. Carbon-based materials (such as carbon felt and graphite felt) have become the mainstream electrode materials in this field due to their excellent chemical stability, conductivity, corrosion resistance, and cost advantages. However, the C / C bond-dominated structure of original carbon-based materials has inherent defects: surface hydrophobicity leads to insufficient electrolyte wetting, and chemical inertness results in a scarcity of electrochemical active sites, causing sluggish electrode reaction kinetics and significant irreversibility, ultimately limiting the battery's energy efficiency and high current density performance.
[0004] Currently, the main methods for modifying graphite felt surfaces include noble metal loading, which can significantly improve the electrocatalytic performance of electrodes, but its high cost and hydrogen evolution problems caused by side reactions limit its practical application. Metal oxides (such as ZrO2 and Mn3O4) are lower cost alternative catalysts, but they suffer from problems such as nanoparticle agglomeration, uneven distribution, and structural degradation in acidic media. Novel carbon-based materials (such as graphene and carbon nanotubes) show potential due to their high specific surface area and abundant active sites; however, their high cost, harsh synthesis conditions, and high dependence on sacrificial metals limit their practical application. Methods such as non-metallic atom doping (such as N, P, and B) and surface functional group modification (such as introducing carboxyl and hydroxyl groups) can improve reaction kinetics, but they usually require high-temperature treatment or complex process parameter control. Therefore, current research urgently needs to develop electrode modification technologies that combine process simplicity, cost-effectiveness, and scalability potential to overcome the performance bottleneck of flow batteries under high current density conditions. To improve the overall performance of fully alkaline manganese-based open-circuit flow battery systems, it is still necessary to study electrode materials with highly active surfaces. Improving the energy efficiency and rate performance of the system remains a key issue that urgently needs to be addressed. Summary of the Invention
[0005] This invention aims to overcome the shortcomings of existing ordinary graphite felt electrodes, such as small electrochemical active area and strong surface hydrophobicity, which leads to slow electrochemical reaction kinetics in all-alkaline manganese-based open-circuit flow battery systems. Its purpose is to provide a modified graphite felt electrode for all-alkaline manganese-based open-circuit flow batteries and its preparation method.
[0006] This invention is achieved through the following technical solution: A method for preparing a modified graphite felt electrode for a fully alkaline manganese-based open-circuit flow battery includes the following steps: (I) Pretreatment of the graphite felt matrix; The graphite felt substrate was immersed in a KMnO4 solution, followed by repeated washing with a large amount of deionized water until no MnO4 was visible to the naked eye in the washing solution. - The purple color of the ions was then placed in deionized water for ultrasonic treatment, and then dried in air for 24 hours after ultrasonication. The concentration of the KMnO4 solution is 0.1 M ~ 0.5 M; The soaking time in the KMnO4 solution is 30 min to 45 min; The ultrasonic cleaning process uses an ultrasonic frequency of 40 kHz and an ultrasonic time of 30 min to 45 min. Soaking the graphite felt in potassium permanganate can increase its wettability and improve its conductivity. If the soaking time is too short, the graphite felt will have poor conductivity and little improvement in wettability, and the active area will not be effectively utilized in the subsequent electrochemical activation process. If the soaking time is too long, an excessively thick oxide insulating layer will be formed on the surface, resulting in excessively high electrode resistance of the graphite felt. (II) The graphite felt matrix pretreated in step (I) is placed in an electrolyte solution for electrochemical activation treatment: The specific method of the electrochemical activation treatment is as follows: the pretreated graphite felt substrate is used as the working electrode, and together with the counter electrode and the reference electrode, it is placed in the electrolyte for electrochemical activation treatment. The counter electrode is a platinum sheet; The reference electrode is a calomel electrode; The electrolyte is a salt solution or an alkaline solution; the salt solution is at least one of sodium sulfate solution, potassium sulfate solution, or sodium phosphate solution; the concentration of the salt solution is 50 g / L to 200 g / L; the alkaline solution is a potassium hydroxide solution or a sodium hydroxide solution; the concentration of the alkaline solution is 0.1 g / L to 100 g / L. The electrochemical activation potential is -1.1 V to 1.3 V; the electrochemical activation treatment time is 10 h to 15 h. (III) The graphite felt after electrochemical activation treatment in step (II) is cleaned with deionized water to remove residual electrolyte on the surface. After cleaning, it is dried to obtain a modified graphite felt electrode for use in fully alkaline manganese-based open-circuit flow batteries.
[0007] The drying temperature is 50 ℃ ~ 80 ℃; the drying time is 12 h.
[0008] A modified graphite felt electrode for use in a fully alkaline manganese-based open-circuit flow battery is prepared by the aforementioned method; the electrode area ranges from 1 to 9 cm². 2 .
[0009] A fully alkaline manganese-based open-circuit flow battery includes a modified graphite felt electrode prepared by the aforementioned method; the positive electrode electrolyte of the fully alkaline manganese-based open-circuit flow battery includes MnO4 under alkaline conditions. - / MnO4 2- The negative electrode electrolyte includes ethylene glycol (EG), and the pH of the positive and negative electrode electrolytes is the same, with a pH range of 12~14.
[0010] The beneficial effects of this invention are: This invention provides a modified graphite felt electrode with hydrophilicity, large electrochemical active area, and low mass transfer resistance, as well as its preparation method. The modified graphite felt electrode is applied to an all-alkaline manganese-based open-circuit flow battery. The electrode preparation method is simple, and the performance is significantly improved. It can improve the electrochemical activity and surface wettability of ordinary graphite felt, thereby improving the rate performance of the open-circuit flow battery. By conducting a long-term electrochemical reaction between ordinary graphite felt and modified graphite felt, the modified graphite felt can also improve the stability of the open-circuit flow battery electrode.
[0011] This invention proposes a highly efficient electrochemical activation method that significantly improves the performance of all-alkaline manganese-based open-circuit flow batteries at high current densities. This method utilizes 0.5 mol L... -1 Modified graphite felt electrode materials were successfully prepared by treating raw graphite felt in Na2SO4 solution using cyclic voltammetry. Electrochemical activation technology generated abundant oxygen-containing functional groups (such as carboxyl, hydroxyl, and carbonyl groups) on the surface of the graphite felt electrode material. The introduction of these oxygen-containing functional groups improved the hydrophilicity of the graphite felt material, allowing the electrolyte solution to better wet the internal pores of the electrode, achieving more complete solid-liquid contact and reducing ion transport resistance. Simultaneously, electrochemical activation using sodium sulfate solution roughened the surface of the graphite felt electrode through electrochemical corrosion, resulting in a larger active area and improved electrochemical activity. This further confirmed that electrochemically activated graphite felt possesses excellent mass transfer and charge transport properties. The modification method of this invention has advantages such as short processing time, simple operation, low cost, and environmental friendliness, providing a new approach for the preparation of high-performance all-alkaline manganese-based open-circuit flow battery electrodes. Attached Figure Description
[0012] Figure 1 This is a SEM image of the modified graphite felt in Embodiment 1 of the present invention; Figure 2 This is a polarization curve diagram of modified graphite felt and ordinary graphite felt used in a fully alkaline manganese-based open-circuit flow battery in Example 1 of the present invention. Figure 3 These are EIS diagrams of modified graphite felt and ordinary graphite felt used in a fully alkaline manganese-based open-circuit flow battery in Example 1 of this invention. Figure 4 These are the cyclic voltammetry curves of the modified graphite felt and ordinary graphite felt used in the fully alkaline manganese-based open-circuit flow battery in Example 1 of this invention. Figure 5 This is a capacitance diagram of the modified graphite felt and ordinary graphite felt in Embodiment 1 of the present invention; Figure 6 This is a test diagram of the wettability contact angle of modified graphite felt and ordinary graphite felt in Embodiment 1 of the present invention; Figure 7This is a Raman diagram comparing the modified graphite felt and ordinary graphite felt in Embodiment 1 of the present invention; Figure 8 This is a SEM image of the modified graphite felt in Embodiment 2 of the present invention; Figure 9 This is a SEM image of the modified graphite felt in Embodiment 3 of the present invention.
[0013] For those skilled in the art, other related figures can be obtained from the above figures without any creative effort. Detailed Implementation
[0014] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.
[0015] The chemicals used in the embodiments and comparative examples of this invention were all purchased from Aladdin Reagent Company, and all were of analytical grade.
[0016] A method for preparing a modified graphite felt electrode for a fully alkaline manganese-based open-circuit flow battery includes the following steps: S1. Take a 2 cm × 3 cm graphite felt (CF), immerse it in a 0.5 M KMnO4 solution for 30 min, rinse it clean after immersion, and then place it in deionized water for ultrasonic treatment for 30 min at an ultrasonic frequency of 40 kHz to remove surface oil and other impurities; then vacuum dry it at 60℃ for 2 h. S2. Preparation of electrolyte solution: Na2SO4 is used as the electrolyte with a concentration of 71 g / L; deionized water is used as the solvent. S3. Using the treated graphite felt as the working electrode, it is placed together with the platinum counter electrode and the calomel reference electrode in the electrolyte solution prepared in step S2. The electrochemical activation is carried out for 10 h in the potential range of -1.1 V to 1.3 V (vs. calomel) using cyclic voltammetry. During this process, abundant oxygen-containing functional groups are introduced into the surface of the graphite felt fibers, fundamentally changing its surface chemical properties. S4. Thoroughly clean the electrochemically activated graphite felt with deionized water to remove residual electrolyte solution from the surface, and then dry it in an oven at 60°C.
[0017] from Figure 1 The scanning electron microscope image shown clearly demonstrates that the overall fiber skeleton of the prepared modified graphite felt electrode remains intact, but etched areas are formed on its surface, exhibiting a uniformly distributed microcrack structure.
[0018] from Figure 2The polarization curves of the modified graphite felt electrode and the ordinary graphite felt electrode used in an all-alkaline manganese-based open-circuit flow battery clearly show that, compared with the ordinary graphite felt electrode, the modified graphite felt electrode significantly increases the rate performance of the system at high current densities, thereby improving the stability of the all-alkaline manganese-based open-circuit flow battery at high current densities.
[0019] from Figure 3 In the EIS diagrams of the modified graphite felt electrode and the ordinary graphite felt electrode used in an all-alkaline manganese-based open-circuit flow battery, it can be observed that the modified graphite felt electrode has lower internal resistance and better mass transfer than the ordinary graphite felt electrode, thereby improving the reaction kinetics activity of the all-alkaline manganese-based open-circuit flow battery.
[0020] from Figure 4 The cyclic voltammetry diagrams shown for the modified graphite felt electrode and the ordinary graphite felt electrode in a fully alkaline manganese-based open-circuit flow battery demonstrate that the modified graphite felt electrode in MnO4… - / MnO4 2- The redox peak current is larger, indicating better electrochemical activity.
[0021] from Figure 5 The capacitance comparison diagram of the modified graphite felt electrode and the ordinary graphite felt electrode shows that the modified graphite felt electrode has a larger capacitance than the ordinary graphite felt electrode, that is, its surface active area is larger and its electrochemical reaction kinetics are faster.
[0022] from Figure 6 The wettability contact angle test diagram of the modified graphite felt electrode and the ordinary graphite felt electrode shown shows that the contact angle of the modified graphite felt is 138°, which is smaller than that of the ordinary graphite felt (143°), indicating that its hydrophilicity is improved.
[0023] from Figure 7 The Raman graph comparing the modified graphite felt and the ordinary graphite felt shown can be seen in the comparison at 1350 cm⁻¹. -1 (D band) and approximately 1590 cm -1 A characteristic peak was observed at (G band), in ordinary graphite felt I. D / I G The ratio is approximately 1.25, indicating that it has a low defect density and high crystal integrity; after electrochemical activation, I D / I G The ratio increased to 1.44, indicating that the activation process effectively induced structural disorder on the carbon felt surface, and... Figure 5 Combined, it is evident that this structural defect exposes more electrochemically active sites and enhances the electron transport capability of the carbon felt.
[0024] A method for preparing a modified graphite felt electrode for a fully alkaline manganese-based open-circuit flow battery includes the following steps: S1. Take a 2 cm × 3 cm graphite felt (CF), immerse it in a 0.5 M KMnO4 solution for 30 min, rinse it clean after immersion, and then place it in deionized water for ultrasonic treatment for 30 min at an ultrasonic frequency of 40 kHz to remove surface oil and other impurities; then vacuum dry it at 60℃ for 2 h. S2. Preparation of electrolyte solution: KOH is used as the electrolyte with a concentration of 336 g / L; deionized water is used as the solvent. S3. Using the treated graphite felt as the working electrode, it is placed together with the platinum counter electrode and the calomel reference electrode in the electrolyte solution prepared in step S2. Electrochemical activation is performed for 10 h in the potential range of -1.3 V to 0.6 V (vs. Hg / HgO) using cyclic voltammetry. During this process, abundant oxygen-containing functional groups are introduced into the surface of the graphite felt fibers, fundamentally changing its surface chemical properties. S4. Thoroughly clean the electrochemically activated graphite felt with deionized water to remove residual electrolyte solution from the surface, and then dry it in an oven at 60°C.
[0025] Figure 8 The scanning electron microscope image shown can be seen that the surface of the graphite felt is rougher than that of ordinary graphite felt, forming etched areas.
[0026] A method for preparing a modified graphite felt electrode for a fully alkaline manganese-based open-circuit flow battery includes the following steps: S1. Take a 2 cm × 3 cm graphite felt (CF), immerse it in a 0.5 M KMnO4 solution for 30 min, rinse it clean after immersion, and then place it in deionized water for ultrasonic treatment for 30 min at an ultrasonic frequency of 40 kHz to remove surface oil and other impurities; then vacuum dry it at 60℃ for 2 h. S3. Using the treated graphite felt as the working electrode, it is placed together with the platinum counter electrode and the calomel reference electrode in the electrolyte solution prepared in step S2. Electrochemical activation is performed for 10 h using cyclic voltammetry in the potential range of -1.4 V to 0.6 V (vs. calomel). During this process, abundant oxygen-containing functional groups are introduced into the surface of the graphite felt fibers, fundamentally changing its surface chemical properties. S4. Thoroughly clean the electrochemically activated graphite felt with deionized water to remove residual electrolyte solution from the surface, and then dry it in an oven at 60°C.
[0027] from Figure 9The scanning electron microscope image shown shows that the graphite felt surface after electrochemical activation with Na3PO4 has an etched area, a rougher surface, and a larger active area compared to ordinary graphite felt.
[0028] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.
[0029] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.
Claims
1. A method for preparing a modified graphite felt electrode for a fully alkaline manganese-based open-circuit flow battery, characterized in that: Includes the following steps: (I) Pretreatment of the graphite felt matrix; (II) The graphite felt matrix pretreated in step (I) is placed in an electrolyte solution for electrochemical activation treatment: (III) The graphite felt after electrochemical activation treatment in step (II) is cleaned and then dried to obtain a modified graphite felt electrode for use in a fully alkaline manganese-based open-circuit flow battery.
2. The method for preparing the modified graphite felt electrode for a fully alkaline manganese-based open-circuit flow battery according to claim 1, characterized in that: The pretreatment in step (I) specifically involves immersing the graphite felt substrate in a KMnO4 solution, rinsing it clean after immersion, and then subjecting it to ultrasonic treatment in deionized water.
3. The method for preparing the modified graphite felt electrode for a fully alkaline manganese-based open-circuit flow battery according to claim 2, characterized in that: The concentration of the KMnO4 solution is 0.1 M to 0.5 M; the soaking time in the KMnO4 solution is 30 min to 45 min; the ultrasonic cleaning time is 30 min to 45 min, and the frequency is 40 kHz.
4. The method for preparing the modified graphite felt electrode for a fully alkaline manganese-based open-circuit flow battery according to claim 1, characterized in that: The specific method of electrochemical activation treatment in step (II) is as follows: the pretreated graphite felt substrate is used as the working electrode, and together with the counter electrode and the reference electrode, it is placed in the electrolyte for electrochemical activation treatment.
5. The method for preparing the modified graphite felt electrode for a fully alkaline manganese-based open-circuit flow battery according to claim 4, characterized in that: The counter electrode is a platinum sheet; the reference electrode is a calomel electrode; the electrolyte is a salt solution or an alkaline solution; the electrochemical activation potential is -1.1 V to 1.3 V; and the electrochemical activation treatment time is 10 h to 15 h.
6. The method for preparing the modified graphite felt electrode for a fully alkaline manganese-based open-circuit flow battery according to claim 5, characterized in that: The salt solution is at least one of sodium sulfate solution, potassium sulfate solution, or sodium phosphate solution; the alkaline solution is potassium hydroxide solution or sodium hydroxide solution.
7. The method for preparing the modified graphite felt electrode for a fully alkaline manganese-based open-circuit flow battery according to claim 6, characterized in that: The concentration of the salt solution is 50 g / L to 200 g / L; the concentration of the alkali solution is 0.1 g / L to 100 g / L.
8. The method for preparing the modified graphite felt electrode for a fully alkaline manganese-based open-circuit flow battery according to claim 1, characterized in that: The drying temperature in step (Ⅲ) is 50~80℃.
9. A modified graphite felt electrode for a fully alkaline manganese-based open-circuit flow battery, characterized in that: Prepared by the method described in any one of claims 1 to 8.
10. A fully alkaline manganese-based open-circuit flow battery, characterized in that: Including the modified graphite felt electrode prepared by the method described in any one of claims 1 to 8.