Experimental verification of electrode activation for improved performance in vanadium redox flow batteries

Abstract

Vanadium redox flow batteries (VRFBs) have held significant promise in large-scale energy storage applications due to their advantages, including long cycle life, high safety, and the ability to independently design power and capacity. However, the relatively low power density has remained a critical bottleneck for further development. As a key material in VRFB power units, enhancing the performance of graphite felt electrodes has represented an effective strategy for achieving high-power battery technology. To improve the activity of graphite felt electrodes, this study has employed an experimental verification approach to investigate battery performance parameters under various activation temperatures and durations, thereby identifying the optimal activation conditions. In contrast to prior studies that exclusively targeted 400°C without systematically optimizing activation duration, this study has systematically evaluated five activation temperatures and four activation durations to clarify the synergistic influence of these parameters on VRFB performance. Specifically, experiments have been conducted at room temperature using activation temperatures of 300, 350, 400, 450, and 500°C, as well as activation durations of 24, 11, 7, and 3 h. The results have indicated that an activation temperature of 400°C yielded notable improvements in charge/discharge performance, internal resistance, efficiency, and capacity retention. Notably, energy efficiency has increased by 5.06%, 5.94%, 3.67%, and 4.72% under these conditions. This study has identified the optimal activation conditions of “400°C for 7 h” and has provided the corresponding performance data, which can help reduce research costs associated with electrode activation in future investigations. This study has provided valuable insights into electrode activation and has offered guidance for enhancing VRFB performance.

Keywords

Vanadium redox flow battery / Graphite felt electrode / Thermal activation / Cell performance

CRediT authorship contribution statement

Zhi Zhuge: Writing - review & editing, Writing - original draft, Investigation. Zebo Huang: Writing - review & editing, Writing - original draft, Supervision, Methodology, Investigation. Osamah Ibrahim Khalaf: Writing - review & editing, Conceptualization. Longxing Wu: Writing - review & editing, Visualization.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work is supported by Natural Science Foundation of Guangxi Zhuang Autonomous Region (Grant No. 2025GXNSFAA069724) and Project for Enhancing Young and Middle-aged Teacher's Research Basis Ability in Colleges of Guangxi (Grant No.2024KY0211). We extend our gratitude to Wuhan Zhisheng New Energy Co., Ltd. for their provision of experimental equipment and guidance the experiment.

Data availability

The authors do not have permission to share data.

References

[1] Arenas, L.F., de Leön, C.P., Walsh, F.C., 2019. Redox flow batteries for energy storage: their promise, achievements and challenges. Curr. Opin. Electrochem. 16, 117-126.

[2] Ashok, A., Kumar, A., 2024. A comprehensive review of metal-based redox flow batteries: progress and perspectives. Green Chem. Lett. Rev. 17 (1), 2302834.

[3] Amini, K., Shocron, A.N., Suss, M.E., Aziz, M.J., 2023. Pathways to high-power-density redox flow batteries. ACS Energy Lett 8 (8), 3526-3535.

[4] Al-Yasiri, M., Park, J., 2018. A novel cell design of vanadium redox flow batteries for enhancing energy and power performance. Appl. Energy 222, 530-539.

[5] Barranco, J.E., Cherkaoui, A., Montiel, M., Gonzalez-Espinosa, A., Lozano, A., Barreras, F., 2023. Analysis of the electrochemical performance of carbon felt electrodes for vanadium redox flow batteries. Electrochim. Acta 470, 143281.

[6] Cheng, D., Zhu, W., Gao, J., Li, J., Yang, Y., Dai, L., Wang, L., He, Z., 2022. High- graphitization, large-surface area, and porous carbon nanofiber: a superior bi- functional electrode for vanadium redox flow battery. Appl. Surf. Sci. 599, 153919.

[7] Caiado, A.A., Chaurasia, S., Aravamuthan, S.R., Howell, B.R., Inalpolat, M., Gallaway, J. W., Agar, E., 2023. Exploring the effectiveness of carbon cloth electrodes for all- vanadium redox flow batteries. J. Electrochem. Soc. 170 (11), 110525.

[8] Cheng, T., Qi, S., Jiang, Y., Wang, L., Zhu, Q., Zhu, J., Dai, L., He, Z., 2024. Carbon structure regulation strategy for the electrode of vanadium redox flow battery. Small 20 (37), 2400496.

[9] Chen, Z., Gao, Y., Zhang, C., Zeng, X., Wu, X., 2019. Surface-wrinkle-modified graphite felt with high effectiveness for vanadium redox flow batteries. Adv. Electron. Mater. 5 (7), 1900036.

[10] Dai, G., Huang, Y., Chu, F., Jin, C., Liu, H., 2024. Analysis of the effect of thermal treatment and catalyst introduction on electrode performance in vanadium redox flow battery. Heliyon 10 (13), e33561.

[11] Dai, L., Chen, X., Cheng, T., Qi, S., Zhu, J., Feng, Z., Wang, L., Jiang, Y., Li, Y., He, Z., 2024. Major obstacles and optimization strategies for the electrode of vanadium redox flow battery. ACS Mater. Lett. 6 (7), 2816-2836.

[12] Devi, N., Mishra, J.N., Singh, P., Chen, Y., 2024. Physiochemical and electrochemical properties of a heat-treated electrode for all-iron redox flow batteries. Nanomaterials 14 (9), 800.

[13] Faggiano, L., Lacarbonara, G., Badenhorst, W.D., Murtomäki, L., Sanz, L., Arbizzani, C., 2022. Short thermal treatment of carbon felts for copper-based redox flow batteries. J. Power Sources 520, 230846.

[14] Fetyan, A., Bamgbopa, M.O., Andisetiawan, A., Alhammadi, A., Susantyoko, R.A., 2023. Evaluation of asymmetric flow rates for better performance vanadium redox flow battery. Batter. Supercaps 6 (11), e202300301.

[15] Greco, K.V., Bonesteel, J.K., Chanut, N., Tai-Chieh, W.C., Chiang, Y.M., Brushett, F.R., 2021. Limited accessibility to surface area generated by thermal pretreatment of electrodes reduces its impact on redox flow battery performance. ACS Appl. Energy Mater. 4 (12), 13516-13527.

[16] Guo, J., Pan, L., Sun, J., Wei, D.B., Dai, Q.X., Xu, J.H., Li, Q.L., Han, M.S., Wei, L., Zhao, T.S., 2024. Metal-free fabrication of nitrogen-doped vertical graphene on graphite felt electrodes with enhanced reaction kinetics and mass transport for high- performance redox flow batteries. Adv. Energy Mater. 14 (1), 2302521.

[17] Hou, Z., Chen, X., Liu, J., Huang, Z., Chen, Y., Zhou, M., Liu, W., Zhou, H., 2024. Towards a high efficiency and low-cost aqueous redox flow battery: a short review. J. Power Sources 601, 234242.

[18] Huang, X., Wang, H., Zhou, W., Deng, Q., Liu, Z., Zeng, X., Wu, X., Ling, W., 2024. In situ growth of amorphous MnO₂ on graphite felt via mild etching engineering as a powerful catalyst for advanced vanadium redox flow batteries. ACS Appl. Mater. Interfaces 16 (25), 32189-32197.

[19] Huang, Z., Mu, A., Wu, L., Yang, B., Qian, Y., Wang, J., 2022. Comprehensive analysis of critical issues in all-vanadium redox flow battery. ACS Sustain. Chem. Eng. 10 (24), 7786-7810.

[20] Huang, Z., Liu, Y., Xie, X., Wu, J., Deng, Y., Xiong, Z., Wu, L., Li, Z., Huang, Q., Liu, Y., Luo, Y., Zhang, C., 2025a. Design and optimization of a novel flow field structure to improve the comprehensive performance of vanadium redox flow batteries. J. Power Sources 640, 236736.

[21] He, Z., Lv, Y., Zhang, T., Zhu, Y., Dai, L., Yao, S., Zhu, W., Wang, L., 2022. Electrode materials for vanadium redox flow batteries: intrinsic treatment and introducing catalyst. Chem. Eng. J. 427, 131680.

[22] Huang, Z., Li, K., Wu, J., Xiao, Z., Liu, Y., Xie, X., Deng, Y, Xiong, Z., Huang, Q., Liu, Y., Zhuguo, Z., Zhang, C., 2025b. Performance evaluation of vanadium redox flow battery based on asymmetric flow rate design. Electrochim. Acta 524, 146046.

[23] Jiang, Q., Ren, Y., Yang, Y., Wang, L., Dai, L., He, Z., 2022. Recent advances in carbon- based electrocatalysts for vanadium redox flow battery: mechanisms, properties, and perspectives. Compos. B Eng. 242, 110094.

[24] Köble, K., Jaugstetter, M., Schilling, M., Braig, M., Diemant, T., Tschulik, K., Zeis, R., 2023a. Multimodal characterization of carbon electrodes' thermal activation for vanadium redox flow batteries. J. Power Sources 569, 233010.

[25] Köble, K., Schilling, M., Eifert, L., Bevilacqua, N., Fahy, K.F., Atanassov, P., Bazylak, A., Zeis, R., 2023b. Revealing the multifaceted impacts of electrode modifications for vanadium redox flow battery electrodes. ACS Appl. Mater. Interfaces 15 (40), 46775-46789.

[26] Liu, Y., Zhang, B., Huang, Z., Xie, X., Liu, Y., Xiong, Z., Luo, Y., Li, Z., Wu, J., Wu, L., Huang, Q., 2024a. Redox flow batteries: asymmetric design analysis and research methods. J. Energy Storage 104, 114455.

[27] Liu, Y., Huang, Z., Xie, X., et al., 2024b. Redox flow battery: flow field design based on bionic mechanism with different obstructions. Chem. Eng. J. 498, 155663.

[28] Li, Q., Dong, Q., Zhang, T., Xue, Z., Li, J., Wang, Z., Sun, H., 2022. Performance of room- temperature activated tubular polypyrrole modified graphite felt composite electrode in vanadium redox flow battery. Electrochim. Acta 409, 139970.

[29] Lv, Y., Yang, Y., Gao, J., Li, J., Zhu, W., Dai, L., Liu, Y., Wang, L., He, Z., et al., 2022. Controlled synthesis of carbon nanonetwork wrapped graphite felt electrodes for high-performance vanadium redox flow battery. Electrochim. Acta 431, 141135.

[30] Myures, X.M., Midhun, V.C., Arthanareeswaran, G., Mohamed, S.N., Suresh, S., 2025. Optimization of formation charging process based on energy conservation in vanadium redox flow battery. Electrochim. Acta 513, 145579.

[31] Niu, Y., Yuan, S., Liu, Z., Heydari, A., Liu, Y., Qiu, W., Xu, C., Xu, Q., 2025. Research and optimization of slit issues in the kW-scale redox flow batteries stack. J. Energy Storage 106, 114703.

[32] Oreiro, S.N., Jacquemond, R.R., Boz, E.B., Forner-Cuenca, A., Bentien, A., 2025. Investigation of the positive electrode and bipolar plate degradation in vanadium redox flow batteries. J. Energy Storage 132, 117689.

[33] Prasanna, M.M., Jayanti, S., 2025. Effect of electrode thickness and compression on the performance of a flow-through mode vanadium redox flow battery cell. J. Power Sources 631, 236203.

[34] Sharma, H., Kumar, M., 2021. Enhancing power density of a vanadium redox flow battery using modified serpentine channels. J. Power Sources 494, 229753.

[35] Shi, M., Dai, Q., Li, F., Li, T., Hou, G., Zhang, H., Li, X., 2020. Membranes with well- defined selective layer regulated by controlled solvent diffusion for high power density flow battery. Energy Mater 10, 2001382.

[36] Sun, B., Skyllas-Kazacos, M., 1992a. Chemical modification of graphite electrode materials for vanadium redox flow battery application—part II. Acid treatments. Electrochim. Acta 37 (13), 2459-2465.

[37] Sun, B., Skyllas-Kazacos, M., 1992b. Modification of graphite electrode materials for vanadium redox flow battery application—I. Thermal treatment. Electrochim. Acta 37 (7), 1253-1260.

[38] Sun, J., Wu, M.C., Fan, X.Z., Wan, Y., Chao, C., Zhao, T., 2021. Aligned microfibers interweaved with highly porous carbon nanofibers: a novel electrode for high-power vanadium redox flow batteries. Energy Storage Mater. 43, 30-41.

[39] Su, R., Wang, Z., Cai, Y., Ying, J., Li, H., Zhao, T., Jiang, H., 2024. Scaling up flow fields from lab-scale to stack-scale for redox flow batteries. Chem. Eng. J. 486, 149946.

[40] Wu, L., Wei, X., Lin, C., Huang, Z., Fan, Y., Liu, C., Fang, S., 2025. Battery SOC estimation with physics-constrained BiLSTM under different external pressures and temperatures. J. Energy Storage 117, 116205.

[41] Wan, S., Jiang, H., Guo, Z., He, C., Liang, X., Djilali, N., Zhao, T., 2022. Machine learning-assisted design of flow fields for redox flow batteries. J. Energy Environ. 15, 2874-2888.

[42] Wang, R., Li, Y., Wang, Y., Fang, Z., 2020. Phosphorus-doped graphite felt allowing stabilized electrochemical interface and hierarchical pore structure for redox flow battery. Appl. Energy 261, 114369.

[43] Xu, Z., Zhu, M., Zhang, K., Zhang, X., Xu, L., Liu, J., Liu, T., Yan, C., 2021. Inspired by “quenching-cracking” strategy: structure-based design of sulfur-doped graphite felts for ultrahigh-rate vanadium redox flow batteries. Energy Storage Mater. 39, 166-175.

[44] Yao, Y., Lei, J., Shi, Y., Ai, F., Lu, Y., 2021. Assessment methods and performance metrics for redox flow batteries. Nat. Energy 6 (6), 582-588.

[45] Zhang, K., Yan, C., Tang, A., 2021. Oxygen-induced electrode activation and modulation essence towards enhanced anode redox chemistry for vanadium flow batteries. Energy Storage Mater. 34, 301-310.

[46] Zhong, S., Padeste, C., Kazacos, M., Skyllas-Kazacos, M., 1993. Comparison of the physical, chemical and electrochemical properties of rayon- and polyacrylonitrile- based graphite felt electrodes. J. Power Sources 45 (1), 29-41.

[47] Zhou, A., Li, D., Shao, X., Du, Y., Zhang, Y., Li, B., Cao, L., Yang, J., 2024. Synchronized dual-modified graphite felt electrodes for all-vanadium redox flow batteries with high power density and ultra-long lifespan. J. Energy Storage 81, 110501.