隨著全球綠能的發展，對大型儲能系統的需求不斷增加。其中，全釩液流電池（Vanadium redox flow battery, VRFB）因其具有許多優勢，成為大型儲能系統中受到關注的一種技術。然而，儘管VRFB在儲能方面表現出色，其電極材料通常使用導電性石墨，但這些材料存在導電性不足、電化學活性差等缺點，這些問題可能導致VRFB的效能不佳。因此，本研究將作為電極的石墨氈進行改質，將高熵氧化物(HEO)修飾石墨氈，利用高熵氧化物中大量的氧空位，作為釩離子進行氧化還原的活性位點，進而達到提升全釩液流電池效能的目的。
在循環伏安法與電化學阻抗分析之中，無論是HEO或是將HEO修飾於熱處理石墨氈在正極，皆展現出優異的電化學表現。最終的全電池測試中，一開始在電流密度為80 mA/cm2的條件下，HEO修飾於熱處理石墨氈作為正極電極，表現出89.19%的伏特效率及86.90%的能量效率，相較於其它樣品，伏特效率與能量效率皆有提升。隨著電流密度增加至160 mA/cm2的條件下，相比於其它樣品，伏特效率與能量效率皆大幅度提升。經過100圈循環充、放電後，效率皆沒有明顯的衰退，並與第一次充放電循環相比，仍具備65.4%的放電電容，這代表利用HEO修飾石墨氈電極在長時間充、放電仍相當穩定。由以上結果象徵著經由高熵氧化物所改質的石墨氈電極，不僅僅可以有效提升全釩液流電池的效能，其還展現出可以長時間使用的穩定性。

With the global development of green energy, the demand for large-scale energy storage systems continues to increase. Among them, the Vanadium redox flow battery (VRFB) has attracted attention as a technology with many advantages in large-scale energy storage systems. However, despite the excellent energy storage performance of VRFB, its electrode materials typically use conductive graphite, which has shortcomings such as inadequate conductivity and poor electrochemical activity. These issues may result in suboptimal performance of VRFB. Therefore, this study aimed to modify the graphite felt used as the electrode by high-entropy oxides (HEO). By modifying the graphite felt with high-entropy oxides, the abundant oxygen vacancies in high-entropy oxides can serve as active sites for the oxidation-reduction of vanadium ions, thereby enhancing the performance of the VRFB.
In cyclic voltammetry and electrochemical impedance analysis, both HEO and HEO-modified heat-treated graphite felt at the positive electrode exhibited excellent electrochemical performance. In the final full-cell testing, initially under a current density of 80 mA/cm2, using HEO-modified heat-treated graphite felt as the positive electrode showed a voltage efficiency of 89.19% and an energy efficiency of 86.90%. Compared to other samples, both the voltage efficiency and energy efficiency were improved. With an increase in current density to 160 mA/cm2, both the voltage efficiency and energy efficiency showed a significant improvement compared to other samples. After 100 cycles of charge and discharge, there was no significant degradation in efficiency, and it still retained 65.4% of its discharge capacity compared to the first charge and discharge cycle. This indicates that utilizing HEO-modified graphite felt electrode remains highly stable during long-term charge and discharge. The results above signify that the graphite felt electrode modified by high-entropy oxides not only effectively enhances the performance of the VRFB but also demonstrates long-term stability.

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