Preparation method and application of ion-electron coupled high-activity graphite felt electrode
By loading modified carbon nanotubes onto graphite felt to form an ion-electron coupling environment, the problem of poor conductivity of graphite felt was solved, and the electrochemical performance was significantly improved, making it suitable for large-scale industrial production.
Patent Information
- Application Number
- CN202511418901.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-30
- Publication Date
- 2026-01-06
AI Technical Summary
Existing graphite felt exhibits poor conductivity in viologen-based aqueous organic flow batteries, necessitating improvements in the battery's electrochemical performance. Furthermore, existing modification methods are complex and unsuitable for large-scale industrial production.
By loading modified carbon nanotubes onto graphite felt, PDDA was used to modify CNTs, and an ion-electron coupling environment was formed on the surface of the graphite felt, thereby increasing the electrochemical active area.
It significantly improves the electrochemical active area and electrocatalytic activity of graphite felt, promotes the electrochemical reaction of electroactive ions on the electrode surface, and enhances battery efficiency.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrochemical energy storage technology, specifically relating to a method for preparing and applying a highly active graphite felt electrode with ion-electron coupling. Background Technology
[0002] With the advancement of modern technology and industry, fossil fuels are facing increasing scrutiny and resistance due to their inherent limitations and environmental pollution. Against this backdrop, renewable energy, as an environmentally friendly and efficient new energy source, has gained widespread attention. However, renewable energy is characterized by intermittency and volatility, necessitating stable and controllable large-scale energy storage devices to ensure sustainable energy utilization. Flow batteries, with their high safety and stability, strong controllability, long cycle life, and environmental friendliness, are considered one of the preferred technologies for large-scale energy storage devices.
[0003] Vanadium redox flow batteries (VRFBs), developed since the 1980s, are the most integrated technology in flow batteries, but they still face several limitations hindering their industrial application. A major issue is the toxicity and environmental impact of vanadium and its compounds. The limited supply of vanadium also raises sustainability concerns. The corrosiveness of vanadium electrolytes is another key limitation. The acidic environment required to achieve optimal performance leads to degradation of materials used in battery components, resulting in increased maintenance costs and reduced lifespan.
[0004] Aqueous organic redox flow batteries (AORFBs) using aqueous organic electrolytes offer solutions to the shortcomings of VRFBs, including improved safety, reduced maintenance requirements, and environmental potential. Furthermore, the variable electrochemical performance of organic active materials composed of readily available and affordable elements such as C, N, and O due to their structural tunability makes AORFBs a highly promising energy storage device.
[0005] Viologen has emerged as a promising candidate for anodes in AORFBs (Automatic Orifice Redox Fuses). Viologens can undergo two-electron transfer reactions, making them suitable for high-capacity energy storage applications; however, their second redox process is typically only partially reversible, and the resulting products exhibit low solubility and poor stability. Advances in research may address these challenges, enabling full utilization of the redox capabilities of these molecules. Water-soluble viologen derivatives have been used in neutral AORFBs, demonstrating high performance and good stability. Among these, the viologen derivative BTMAP-Vi (with two positively charged quaternary ammonium groups grafted to both ends of the viologen bipyridine molecule) increases the electrostatic repulsion between BTMAP-Vi molecules, thereby preventing disproportionation of free radical cations and other bimolecular side reactions during battery cycling. This derivative exhibits superior electrochemical activity and is the most widely used.
[0006] Currently, graphite felt is widely used as an electrode in viologen-based AORFBs. As a three-dimensional carbon fiber material, graphite felt has a large specific surface area, which can provide a site for redox reactions in BTMAP-Vi. However, the conductivity of graphite felt in viologen-based AORFBs is poor, and further optimization is needed to improve the electrochemical performance of the battery and reduce side reactions.
[0007] Currently, methods for increasing the electrochemical surface area of graphite felt mainly include etching, chemical in-situ growth, and carbon nanotube loading. Etching requires using lasers or metal ions to etch the graphite felt fibers at high temperatures, creating nanoscale or microscale pores on the fiber surface. While this method increases the number of active sites for the BTMAP-Vi molecular reaction by increasing the specific surface area of the graphite felt, the process is complex and technically challenging, making it unsuitable for large-scale industrial production of graphite felt electrodes. Chemical in-situ growth generally requires high-temperature and high-pressure treatment of the graphite felt, making the process complex and dangerous. Carbon nanotube loading methods for modifying graphite felt typically require additional binders, increasing costs; furthermore, the modification methods for carbon nanotubes are complex and not conducive to large-scale industrial production. Therefore, there is an urgent need to develop a simple preparation method for modified graphite felt electrodes that can significantly optimize the electrochemical performance of viologen-based AORFBs. Summary of the Invention
[0008] To address the shortcomings of existing technologies, this invention provides a method for preparing a highly active ion-electron coupled graphite felt electrode and its application as an electrode material in aqueous flow batteries. By loading PDDA-modified carbon nanotubes onto graphite felt, the bonding strength between the carbon nanotubes and the graphite felt fiber surface is enhanced. The composite of PDDA ions and carbon nanotubes provides an ion-electron coupling environment, which helps to improve the electrocatalytic activity of the electrode. Furthermore, it increases the electrochemical active area of the graphite felt, further promoting the electrochemical reaction process of electroactive ions on the electrode surface.
[0009] The technical solution of the present invention is as follows:
[0010] A method for preparing a highly active graphite felt electrode with ion-electron coupling includes the following steps:
[0011] 1) Carbon nanotubes (CNTs) were immersed in a mixed solution of ethanol and water, ultrasonically cleaned, filtered and dried to obtain pre-purified carbon nanotubes.
[0012] 2) Immerse the pre-purified carbon nanotubes obtained in step 1) in hydrochloric acid solution, filter, wash until neutral, and then dry to obtain purified carbon nanotubes.
[0013] 3) The purified carbon nanotubes obtained in step 2) were immersed in an aqueous solution of polydiallyldimethylammonium chloride (PDDA), ultrasonically vibrated, centrifuged and dried to obtain polydiallyldimethylammonium chloride modified carbon nanotubes (PDDA-CNTs).
[0014] 4) The graphite felt is pre-activated with ozone to obtain ozone-modified graphite felt with a hydrophilic surface.
[0015] 5) Disperse the PDDA-CNTs prepared in step 3) in deionized water to obtain an aqueous dispersion of PDDA-CNTs; immerse the ozone-modified graphite felt obtained in step 4) in the aqueous dispersion of PDDA-CNTs, and sonicate it to make the PDDA-CNTs uniformly distributed on the surface of the ozone-modified graphite felt fibers. After drying, the highly active graphite felt electrode PDDA-CNTs-GF with ion-electron coupling is obtained.
[0016] Furthermore, in the above preparation method, in step 1), the volume ratio of ethanol to water is 1:1 to 1:2.
[0017] Furthermore, in the above preparation method, in step 1), the ultrasonic cleaning time is 0.5 h to 1 h.
[0018] Furthermore, in the above preparation method, in step 2), the concentration of the hydrochloric acid solution is 0.1 M to 0.5 M, and the soaking time is 1 h to 3 h.
[0019] Furthermore, in the above preparation method, in step 3), the volume fraction of the PDDA aqueous solution is 0.1% to 0.5%, the concentration of the purified carbon nanotubes in the PDDA aqueous solution is 1 mg / mL to 5 mg / mL, and the ultrasonic oscillation time is 0.5 h to 1 h.
[0020] Furthermore, in the above preparation method, step 4), the specific method of ozone pre-activation treatment is as follows: the original graphite felt is placed in a tube furnace, and ozone is continuously introduced into the tube furnace using an ozone generator at an ozone generation rate of 2-10 g / h. The tube furnace is heated to 180-220°C at a heating rate of 2-5°C / min and kept at a constant temperature for 5-15 min. Under the condition of continuous ozone supply, it is cooled to room temperature to obtain ozone-modified graphite felt.
[0021] Furthermore, in the above preparation method, in step 5), the concentration of the PDDA-CNTs aqueous dispersion is 0.5 mg / mL to 2 mg / mL, and the ultrasonic treatment time is 10 min to 30 min.
[0022] Application of the highly active ion-electron coupled graphite felt electrode obtained by any of the above preparation methods in flow batteries.
[0023] Furthermore, in the above application, the flow battery is a viologen-based aqueous organic flow battery.
[0024] Technical features and beneficial effects of the present invention:
[0025] 1. This invention uses PDDA to modify CNTs, and then loads the modified carbon nanotubes onto graphite felt, which can significantly increase the electrochemical active area of the graphite felt and effectively improve the redox reaction intensity of BTMAP-Vi. Therefore, the carbon nanotube-modified graphite felt provided by this invention can be used as an electrode for viologen-based organic flow batteries, promoting the redox reaction of organic molecules and improving battery efficiency.
[0026] 2. Compared with existing methods of modification by etching and carbon nanotube loading, the carbon nanotube-modified graphite felt preparation method provided by this invention uses a suspension of PDDA-CNTs to directly load the modified carbon nanotubes onto the graphite felt. The manufacturing process is simpler, the operation is safer, and no additional binder is required, thus saving costs. Attached Figure Description
[0027] Figure 1 The images show the SEM morphology of the ion-electron coupled highly active graphite felt electrode (PDDA-CNTs-GF) (a) prepared in Example 1 of this invention and the blank graphite felt (GF) (b) of Comparative Example 1.
[0028] Figure 2 This is a multi-cycle cyclic voltammetry test result of the ion-electron coupled highly active graphite felt electrode (PDDA-CNTs-GF) prepared in Example 1 of this invention.
[0029] Figure 3 This is a comparison graph of cyclic voltammetry tests between the ion-electron coupled highly active graphite felt electrode (PDDA-CNTs-GF) prepared in Example 1 of this invention and the blank graphite felt (GF) in Comparative Example 1.
[0030] Figure 4 This is a comparison diagram of the electrochemical active area (ECSA) of the ion-electron coupled highly active graphite felt electrode (PDDA-CNTs-GF) prepared in Example 1 of the present invention and the blank graphite felt (GF) of Comparative Example 1.
[0031] Figure 5 This is a comparison of the electrochemical impedance spectroscopy (EIS) of the ion-electron coupled highly active graphite felt electrode (PDDA-CNTs-GF) prepared in Example 1 of this invention and the blank graphite felt (GF) of Comparative Example 1. Detailed Implementation
[0032] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.
[0033] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.
[0034] Example 1
[0035] A method for preparing a highly active graphite felt electrode with ion-electron coupling includes the following steps:
[0036] (1) 0.3 g of carbon nanotubes (CNTs) were soaked in a 50 mL mixture of ethanol and water (volume ratio = 1:1), ultrasonically cleaned for 1 h, filtered, and dried in an oven at 60 °C for 12 h to obtain pre-purified carbon nanotubes.
[0037] (2) The pre-purified carbon nanotubes were soaked in 100 mL of 0.1 M hydrochloric acid solution for 2 h, filtered and washed until neutral, and then dried in an oven at 60 °C for 12 h to obtain purified carbon nanotubes.
[0038] (3) 0.2 g of purified carbon nanotubes were soaked in 200 mL of polydiallyldimethylammonium chloride (PDDA) (volume fraction of 0.2%) aqueous dispersion, ultrasonically vibrated for 0.5 h, centrifuged, and dried in an oven at 60 °C for 12 h to obtain modified carbon nanotubes (PDDA-CNTs).
[0039] (4) Place the original graphite felt in a tube furnace and continuously supply ozone into the tube furnace using an ozone generator. The ozone generation rate is 8 g / h. The tube furnace is heated to 200 ℃ at a heating rate of 5 ℃ / min and kept at a constant temperature for 10 min. Under the condition of continuous ozone supply, it is cooled to room temperature to obtain ozone-modified graphite felt.
[0040] (5) A 3 cm × 3 cm ozone-modified graphite felt was soaked in 15 mL of an aqueous solution containing 15 mg PDDA-CNTs, sonicated for 10 min, and dried in an oven at 60 °C for 12 h to obtain the modified graphite felt (PDDA-CNTs-GF).
[0041] Comparative Example 1
[0042] An untreated, raw blank graphite felt (GF).
[0043] Experimental Example 1
[0044] The highly active ion-electron coupled graphite felt electrode (PDDA-CNTs-GF) prepared in Example 1 and the blank graphite felt (GF) in Comparative Example 1 were tested by scanning electron microscopy.
[0045] The PDDA-CNTs-GF prepared in Example 1 is shown in the scanning electron microscope. Figure 1 As shown in (a), the GF scanning electron microscope of Comparative Example 1 is as follows: Figure 1 As shown in (b), the GF surface is smooth, while the PDDA-CNTs-GF surface has relatively uniform modified carbon nanotubes. This indicates that the addition of modified carbon nanotubes increases the electrochemical active area and provides more reaction sites without changing the three-dimensional pore structure of the graphite felt, which is beneficial to the BTMAP-Vi redox reaction.
[0046] Experimental Example 2
[0047] The highly active ion-electron coupled graphite felt electrode (PDDA-CNTs-GF) prepared in Example 1 was subjected to multi-cycle cyclic voltammetry testing. Specifically, the test was conducted in a three-electrode electrolytic cell consisting of PDDA-CNTs-GF, Pt sheet, and silver-silver chloride electrode as the working electrode, counter electrode, and reference electrode, respectively. The electrolyte solution was a 2.5 mM BTMAP-Vi + 1 M NaCl mixed solution.
[0048] The multi-cycle cyclic voltammetry curves of PDDA-CNTs-GF prepared in Example 1 are as follows: Figure 2 As shown.
[0049] Depend on Figure 2 It can be seen that the multi-cycle cyclic voltammetry test patterns of PDDA-CNTs-GF at high scan rate in Example 1 have good overlap and good electrochemical stability.
[0050] Experimental Example 3
[0051] Cyclic voltammetry was performed on the ion-electron coupled highly active graphite felt electrode (PDDA-CNTs-GF) prepared in Example 1 and the blank graphite felt (GF) in Comparative Example 1. Specifically, the test was conducted in a three-electrode electrolytic cell with PDDA-CNTs-GF and GF from Example 1 as working electrodes, Pt sheet as counter electrode, and silver-silver chloride electrode as reference electrode. The electrolyte solution was a 2.5 mM BTMAP-Vi + 1 M NaCl mixed solution.
[0052] The cyclic voltammetry curves of the PDDA-CNTs-GF prepared in Example 1 and the GF in Comparative Example 1 are shown below. Figure 3 As shown.
[0053] Depend on Figure 3It can be seen that both untreated GF and PDDA-CNTs-GF showed good electrochemical reversibility for viologen electrolyte. However, compared with the original GF, the electrochemical redox peak measured on PDDA-CNTs-GF was significantly larger, indicating that the composite electrode effectively enhanced the electrochemical redox reaction process of viologen.
[0054] Test Example 4
[0055] ECSA tests were performed on the ion-electron coupled highly active graphite felt electrode (PDDA-CNTs-GF) prepared in Example 1 and GF in Comparative Example 1. Specifically, the tests were conducted in a three-electrode electrolytic cell consisting of PDDA-CNTs-GF and GF from Example 1 as working electrodes, Pt sheet as counter electrode, and silver-silver chloride electrode as reference electrode. The electrolyte solution was a 1 M NaCl mixed solution.
[0056] ECSA diagrams of PDDA-CNTs-GF prepared in Example 1 and GF in Comparative Example 1 are shown below. Figure 4 As shown.
[0057] Depend on Figure 4 It can be seen that, compared with untreated GF, PDDA-CNTs-GF has a larger electrochemical active area, providing more reaction sites for the BTMAP-Vi redox reaction.
[0058] Experimental Example 5
[0059] Electrochemical impedance spectroscopy (EIS) tests were performed on the ion-electron coupled highly active graphite felt electrode (PDDA-CNTs-GF) prepared in Example 1 and the blank graphite felt electrode (GF) in Comparative Example 1. Specifically, the tests were conducted in a three-electrode electrolytic cell with PDDA-CNTs-GF and GF from Example 1 as working electrodes, Pt sheet as counter electrode, and silver-silver chloride electrode as reference electrode. The electrolyte solution was a 1 M NaCl mixed solution.
[0060] The EIS chromatograms of PDDA-CNTs-GF prepared in Example 1 and GF in Comparative Example 1 are shown below. Figure 5 As shown.
[0061] Depend on Figure 5 It can be seen that the EIS spectra of both materials contain a semicircular arc and a linear portion, indicating that the electrochemical reaction of BTMAP-Vi on each electrode surface is controlled by a mixture of charge transfer and diffusion processes. Compared with Comparative Example 1 GF, Example 1 PDDA-CNTs-GF has a smaller semicircular arc, indicating that it has a lower charge transfer resistance, which is consistent with the CV test results.
Claims
1. A method for preparing an ion-electron coupled high activity graphite felt electrode, characterized by, The method comprises the following steps: 1) soaking carbon nanotubes (CNTs) in a mixed solution of ethanol and water, ultrasonic cleaning, filtering and drying to obtain primary purified carbon nanotubes; 2) soaking the primary purified carbon nanotubes obtained in step 1) in a hydrochloric acid solution, filtering, washing to neutral and drying to obtain purified carbon nanotubes; 3) soaking the purified carbon nanotubes obtained in step 2) in a polydiallyldimethylammonium chloride (PDDA) aqueous solution, ultrasonic oscillation, centrifugation and drying to obtain PDDA-modified carbon nanotubes (PDDA-CNTs); 4) ozone pre-activation treatment of graphite felt to obtain ozone-modified graphite felt with a hydrophilic surface; 5) dispersing the PDDA-CNTs prepared in step 3) in deionized water to obtain a PDDA-CNTs aqueous dispersion; soaking the ozone-modified graphite felt prepared in step 4) in the PDDA-CNTs aqueous dispersion, ultrasonic treatment, making the PDDA-CNTs uniformly distributed on the surface of the ozone-modified graphite felt fibers, and drying to obtain an ion-electron coupled high-activity graphite felt electrode (PDDA-CNTs-GF).
2. The production method according to claim 1, characterized by, In step 1), the volume ratio of ethanol to water is 1:1-1:
2.
3. The preparation method according to claim 1, characterized in that, In step 1), the ultrasonic cleaning time is 0.5-1 h.
4. The method of claim 1, wherein, In step 2), the concentration of the hydrochloric acid solution is 0.1-0.5 M, and the soaking time is 1-3 h.
5. The preparation method according to claim 1, characterized in that, In step 3), the volume fraction of the PDDA aqueous solution is 0.1-0.5 %, the concentration of the purified carbon nanotubes in the PDDA aqueous solution is 1-5 mg / mL, and the ultrasonic oscillation time is 0.5-1 h.
6. The method of claim 1, wherein, In step 4), the specific method of ozone pre-activation treatment is as follows: the original graphite felt is placed in a tube furnace, an ozone generator is used to continuously supply ozone into the tube furnace, the ozone generation amount is 2-10 g / h, the tube furnace is heated to 180-220 °C at a heating rate of 2-5 °C / min, and the temperature is kept constant for 5-15 min; cooling to room temperature under the condition of continuous ozone supply, and ozone-modified graphite felt is obtained.
7. The preparation method according to claim 1, characterized in that, In step 5), the concentration of the PDDA-CNTs aqueous dispersion is 0.5-2 mg / mL, and the ultrasonic treatment time is 10-30 min.
8. The use of the ion-electron coupled high-activity graphite felt electrode prepared by the method of any one of claims 1-7 in a flow battery.
9. Use according to claim 8, characterized in that, The flow battery is a viologen-based aqueous organic flow battery.