隨著科技的發展，能源需求大增，作為大型儲能系統，全釩液流電池(Vanadium redox flow battery, VRFB)通常使用耐酸、具導電性的碳基材料作為電極，本研究以石墨氈當作電極，然而其表面疏水及電化學活性不足，降低了電池的效能表現。本研究提出利用水熱法，均勻合成觸媒於石墨氈電極上，提升電化學活性的同時，改善石墨氈活性位點、親水性不足的問題。鎳鈷硫化物，是由奈米管組合而成的海膽狀，可增加電極表面積，提升催化活性。接著引入缺陷，製造出的空位能夠產生更多的活性位點，從而增強導電性。電化學測試結果顯示，相較於沒有空位，具有空位的鎳鈷硫化物，能有效降低過電位，在單電池測試顯示，即使在200 mA/cm2的高電流密度下，仍可表現出71.02%的伏特效率及69.13%的能量效率，比熱處理石墨氈的表現分別高7.6%、7.5%。

This study proposes that the hydrothermal method successfully synthesized the urchin-like nickel-cobalt precursor composed of nanotubes on the graphite felt electrode by the hydrothermal method to increase the surface area of the electrode, and introduce defects. The vacancies can generate more active sites, thereby enhancing the electrical conductivity and improving the problems of graphite felt active sites and insufficient hydrophilicity. In the single-cell test, it can be confirmed that nickel-cobalt sulfide with sulfur vacancies (rNCS) can effectively reduce the overpotential. Even at a high current density of 200 mA/cm2, the cell assembled with rNCS-HGF exhibits a voltage efficiency of 71.02% and an energy efficiency of 69.13%, which are about 7.6% VE and 7.5% EE more efficient than heat-treated graphite felt (HGF), respectively.

[1] X. Fan, B. Liu, J. Liu, J. Ding, X. Han, Y. Deng, X. Lv, Y. Xie, B. Chen, W. Hu, Battery technologies for grid-level large-scale electrical energy storage. Transactions of Tianjin University, 26 (2020) 92-103.
[2] H. Chen, T.N. Cong, W. Yang, C. Tan, Y. Li, Y. Ding, Progress in electrical energy storage system: A critical review. Progress in natural science, 19 (2009) 291-312.
[3] 經濟部能源局111年度全國電力資源供需報告
[4] D. Rastler, Electricity energy storage technology options: a white paper primer on applications, costs and benefits, Electric Power Research Institute, 2010.
[5] M. Aneke, M. Wang, Energy storage technologies and real life applications – A state of the art review. Applied Energy, 179 (2016) 350-377.
[6] H.L. Ferreira, R. Garde, G. Fulli, W. Kling, J.P. Lopes, Characterisation of electrical energy storage technologies. Energy, 53 (2013) 288-298.
[7] M. Uddin, M.F. Romlie, M.F. Abdullah, C. Tan, G.M. Shafiullah, A.H.A. Bakar, A novel peak shaving algorithm for islanded microgrid using battery energy storage system. Energy, 196 (2020) 117084.
[8] M. Guarnieri, P. Mattavelli, G. Petrone, G. Spagnuolo, Vanadium Redox Flow Batteries: Potentials and Challenges of an Emerging Storage Technology. IEEE Industrial Electronics Magazine, 10 (2016) 20-31.
[9] K.J. Kim, M.-S. Park, Y.-J. Kim, J.H. Kim, S.X. Dou, M. Skyllas-Kazacos, A technology review of electrodes and reaction mechanisms in vanadium redox flow batteries. Journal of materials chemistry a, 3 (2015) 16913-16933.
[10] C. Yin, S. Guo, H. Fang, J. Liu, Y. Li, H. Tang, Numerical and experimental studies of stack shunt current for vanadium redox flow battery. Applied Energy, 151 (2015) 237-248.
[11] D. Lee, S. Ryu, S.-H. Shin, J.-H. Kim, S.-H. Moon, A model study on effects of vanadium ion diffusion through ion exchange membranes in a non-aqueous redox flow battery. Journal of Renewable and Sustainable Energy, 11 (2019) 034701.
[12] A. Hassan, T. Tzedakis, Enhancement of the electrochemical activity of a commercial graphite felt for vanadium redox flow battery (VRFB), by chemical treatment with acidic solution of K2Cr2O7. Journal of Energy Storage, 26 (2019) 100967.
[13] M. Gattrell, J. Qian, C. Stewart, P. Graham, B. MacDougall, The electrochemical reduction of VO2+ in acidic solution at high overpotentials. Electrochimica acta, 51 (2005) 395-407.
[14] A. Parasuraman, T.M. Lim, C. Menictas, M. Skyllas-Kazacos, Review of material research and development for vanadium redox flow battery applications. Electrochimica Acta, 101 (2013) 27-40.
[15] X. Qiu, T.A. Nguyen, J.D. Guggenberger, M.L. Crow, A.C. Elmore, A Field Validated Model of a Vanadium Redox Flow Battery for Microgrids. IEEE Transactions on Smart Grid, 5 (2014) 1592-1601.
[16] X.-Z. Yuan, C. Song, A. Platt, N. Zhao, H. Wang, H. Li, K. Fatih, D. Jang, A review of all-vanadium redox flow battery durability: Degradation mechanisms and mitigation strategies. International Journal of Energy Research, 43 (2019) 6599-6638.
[17] J. Xi, Z. Wu, X. Qiu, L. Chen, Nafion/SiO2 hybrid membrane for vanadium redox flow battery. Journal of Power Sources, 166 (2007) 531-536.
[18] M. Skyllas-Kazacos, M. Kazacos, State of charge monitoring methods for vanadium redox flow battery control. Journal of Power Sources, 196 (2011) 8822-8827.
[19]馬振基,謝曉峰,江仁吉,蕭閔謙,楊士賢,張立學新型儲能電池−全釩液流電池的原理與發展現況. 化學, 70(2012) 237-246, (2012).
[20] G. Oriji, Y. Katayama, T. Miura, Investigation on V (IV)/V (V) species in a vanadium redox flow battery. Electrochimica Acta, 49 (2004) 3091-3095.
[21] L. Li, S. Kim, W. Wang, M. Vijayakumar, Z. Nie, B. Chen, J. Zhang, G. Xia, J. Hu, G. Graff, J. Liu, Z. Yang, A Stable Vanadium Redox-Flow Battery with High Energy Density for Large-Scale Energy Storage. Advanced Energy Materials, 1 (2011) 394-400.
[22] B. Schwenzer, J. Zhang, S. Kim, L. Li, J. Liu, Z. Yang, Membrane Development for Vanadium Redox Flow Batteries. ChemSusChem, 4 (2011) 1388-1406.
[23] Q. Xu, T.S. Zhao, P.K. Leung, Numerical investigations of flow field designs for vanadium redox flow batteries. Applied Energy, 105 (2013) 47-56.
[24] K.H. Kim, B.G. Kim, D.G. Lee, Development of carbon composite bipolar plate (BP) for vanadium redox flow battery (VRFB). Composite Structures, 109 (2014) 253-259.
[25] K.J. Kim, Y.-J. Kim, J.-H. Kim, M.-S. Park, The effects of surface modification on carbon felt electrodes for use in vanadium redox flow batteries. Materials Chemistry and Physics, 131 (2011) 547-553.
[26] L. Cao, M. Skyllas-Kazacos, C. Menictas, J. Noack, A review of electrolyte additives and impurities in vanadium redox flow batteries. Journal of Energy Chemistry, 27 (2018) 1269-1291.
[27] D.M. Kabtamu, J.-Y. Chen, Y.-C. Chang, C.-H. Wang, Electrocatalytic activity of Nb-doped hexagonal WO3 nanowire-modified graphite felt as a positive electrode for vanadium redox flow batteries. Journal of Materials Chemistry A, 4 (2016) 11472-11480.
[28] A.W. Bayeh, D.M. Kabtamu, Y.-C. Chang, G.-C. Chen, H.-Y. Chen, G.-Y. Lin, T.-R. Liu, T.H. Wondimu, K.-C. Wang, C.-H. Wang, Ta2O5-nanoparticle-modified graphite felt as a high-performance electrode for a vanadium redox flow battery. ACS Sustainable Chemistry & Engineering, 6 (2018) 3019-3028.
[29] D.M. Kabtamu, A.W. Bayeh, T.-C. Chiang, Y.-C. Chang, G.-Y. Lin, T.H. Wondimu, S.-K. Su, C.-H. Wang, TiNb2O7 nanoparticle-decorated graphite felt as a high-performance electrode for vanadium redox flow batteries. Applied Surface Science, 462 (2018) 73-80.
[30] A.W. Bayeh, D.M. Kabtamu, Y.-C. Chang, G.-C. Chen, H.-Y. Chen, T.-R. Liu, T.H. Wondimu, K.-C. Wang, C.-H. Wang, Hydrogen-treated defect-rich W18O49 nanowire-modified graphite felt as high-performance electrode for vanadium redox flow battery. ACS Applied Energy Materials, 2 (2019) 2541-2551.
[31] A.W. Bayeh, G.-Y. Lin, Y.-C. Chang, D.M. Kabtamu, G.-C. Chen, H.-Y. Chen, K.-C. Wang, Y.-M. Wang, T.-C. Chiang, H.-C. Huang, Oxygen-Vacancy-rich cubic CeO2 nanowires as catalysts for vanadium redox flow batteries. ACS Sustainable Chemistry & Engineering, 8 (2020) 16757-16765.
[32] A.W. Bayeh, Y.-Y. Ou, Y.-T. Ou, Y.-C. Chang, H.-Y. Chen, K.-C. Wang, Y.-M. Wang, H.-C. Huang, T.-C. Chiang, D.M. Kabtamu, MoO2–graphene nanocomposite as an electrocatalyst for high-performance vanadium redox flow battery. Journal of Energy Storage, 40 (2021) 102795.
[33] D.M. Kabtamu, J.-Y. Chen, Y.-C. Chang, C.-H. Wang, Electrocatalytic activity of Nb-doped hexagonal WO 3 nanowire-modified graphite felt as a positive electrode for vanadium redox flow batteries. Journal of Materials Chemistry A, 4 (2016) 11472-11480.
[34] A. Di Blasi, O. Di Blasi, N. Briguglio, A.S. Aricò, D. Sebastián, M. Lázaro, G. Monforte, V. Antonucci, Investigation of several graphite-based electrodes for vanadium redox flow cell. Journal of Power Sources, 227 (2013) 15-23.
[35] X. Wu, H. Xu, P. Xu, Y. Shen, L. Lu, J. Shi, J. Fu, H. Zhao, Microwave-treated graphite felt as the positive electrode for all-vanadium redox flow battery. Journal of power sources, 263 (2014) 104-109.
[36] D.M. Kabtamu, J.-Y. Chen, Y.-C. Chang, C.-H. Wang, Water-activated graphite felt as a high-performance electrode for vanadium redox flow batteries. Journal of Power Sources, 341 (2017) 270-279.
[37] K. Zheng, G. Li, C. Xu, Advanced battery-supercapacitor hybrid device based on Co/Ni-ZIFs-derived NiCo2S4 ultrathin nanosheets electrode with high performance. Applied Surface Science, 490 (2019) 137-144.
[38] Y. Zhai, H. Mao, P. Liu, X. Ren, L. Xu, Y. Qian, Facile fabrication of hierarchical porous rose-like NiCo 2 O 4 nanoflake/MnCo 2 O 4 nanoparticle composites with enhanced electrochemical performance for energy storage. Journal of Materials Chemistry A, 3 (2015) 16142-16149.
[39] H. Chen, J. Jiang, L. Zhang, H. Wan, T. Qi, D. Xia, Highly conductive NiCo 2 S 4 urchin-like nanostructures for high-rate pseudocapacitors. Nanoscale, 5 (2013) 8879-8883.
[40] S. Hussain, T. Liu, N. Aslam, Y. Zhang, S. Zhao, Truncated NiCo2S4 cubohexa-octahedral nanostructures for high-performance supercapacitor. Materials Letters, 189 (2017) 21-24.
[41] D. Cai, D. Wang, C. Wang, B. Liu, L. Wang, Y. Liu, Q. Li, T. Wang, Construction of desirable NiCo2S4 nanotube arrays on nickel foam substrate for pseudocapacitors with enhanced performance. Electrochimica Acta, 151 (2015) 35-41.
[42] X. Dai, X. Wang, G. Lv, Z. Wu, Y. Liu, J. Sun, Y. Liu, Y. Chen, Defect-engineered Sulfur Vacancy Modified NiCo2S4-x Nanosheet Anchoring Polysulfide for Improved Lithium Sulfur Batteries. Small, n/a 2302267.
[43] J.C. Vickerman, I.S. Gilmore, Surface Analysis – The Principal Techniques, John Wiley & Sons, Ltd, 2009.
[44] D.Y. Kwok, A.W. Neumann, Contact angle measurement and contact angle interpretation. Advances in colloid and interface science, 81 (1999) 167-249.
[45] Y. Yuan, T.R. Lee, Contact angle and wetting properties, in: Surface science techniques, Springer, 2013, pp. 3-34.
[46] F. Lu, M. Zhou, W. Li, Q. Weng, C. Li, Y. Xue, X. Jiang, X. Zeng, Y. Bando, D. Golberg, Engineering sulfur vacancies and impurities in NiCo2S4 nanostructures toward optimal supercapacitive performance. Nano Energy, 26 (2016) 313-323.
[47] Y. Sun, Y. Wang, C. Wang, J. Wang, Z. Wang, M. Zhang, H. Zong, J. Xu, J. Liu, Construction of Co9S8@NiCo2S4 core–shell hetero-nanostructure with synergistic effect of abundant mesopores and multi-metallic elements for novel high-performance flexible hybrid supercapacitors. Chemical Engineering Journal, 469 (2023) 143812.
[48] R. Jia, F. Zhu, S. Sun, T. Zhai, H. Xia, Dual support ensuring high-energy supercapacitors via high-performance NiCo2S4@Fe2O3 anode and working potential enlarged MnO2 cathode. Journal of Power Sources, 341 (2017) 427-434.
[49] C. Han, T. Zhang, J. Li, B. Li, Z. Lin, Enabling flexible solid-state Zn batteries via tailoring sulfur deficiency in bimetallic sulfide nanotube arrays. Nano Energy, 77 (2020) 105165.
[50] J. Yang, M. Ma, C. Sun, Y. Zhang, W. Huang, X. Dong, Hybrid NiCo 2 S 4@ MnO 2 heterostructures for high-performance supercapacitor electrodes. Journal of Materials Chemistry A, 3 (2015) 1258-1264.
[51] L. Kang, M. Zhang, J. Zhang, S. Liu, N. Zhang, W. Yao, Y. Ye, C. Luo, Z. Gong, C. Wang, Dual-defect surface engineering of bimetallic sulfide nanotubes towards flexible asymmetric solid-state supercapacitors. Journal of Materials Chemistry A, 8 (2020) 24053-24064.
[52] C. Liu, S. Luo, H. Huang, Y. Zhai, Z. Wang, Direct growth of MoO2/reduced graphene oxide hollow sphere composites as advanced anode materials for potassium‐ion batteries. ChemSusChem, 12 (2019) 873-880.
[53] M. Kruk, M. Jaroniec, Gas Adsorption Characterization of Ordered Organic−Inorganic Nanocomposite Materials. Chemistry of Materials, 13 (2001) 3169-3183.
[54] R. Sun, Y. Bai, Z. Bai, L. Peng, M. Luo, M. Qu, Y. Gao, Z. Wang, W. Sun, K. Sun, Phosphorus Vacancies as Effective Polysulfide Promoter for High-Energy-Density Lithium–Sulfur Batteries. Advanced Energy Materials, 12 (2022) 2102739.