Vanadium flow battery (VFB) is one of the most promising energy storage technologies because of its superior safety, reliability and cycle life, but the poor electrochemical performance at high current density limits its commercial application. Herein, an advanced design of the dual-gradient carbon nanofibers/graphite felt (DG-CNFs/GF) composite electrode is firstly proposed for the next-generation VFB with high power density. Specifically, there is a macro gradient distribution of CNFs along the thickness direction of the electrode, meanwhile a micro gradient distribution of CNFs is also existed along the radial direction of a single fiber, and both the macro and micro gradient structure are verified through the physicochemical characterizations. In addition, the DG-CNFs/GF with a dual-gradient structure exhibits an excellent electrocatalytic activity and a fast mass transfer characteristic. It is worth noting that the energy conversion efficiencies, cycling stability in addition to power density of VFB with DG-CNFs/GF are much better than those with commercial GF, which make the dual-gradient DG-CNFs/GF to be a promising alternative. Most importantly, the accomplishment of this work will provide a promising development direction of the highly efficient electrode for the next-generation VFB with high power density.

钒液流电池（VFB）因其卓越的安全性、可靠性和循环寿命而成为最有前途的储能技术之一，但在高电流密度下较差的电化学性能限制了其商业应用。在此，首先提出了一种先进的双梯度碳纳米纤维/石墨毡（DG-CNFs/GF）复合电极设计，用于下一代高功率密度的VFB。具体而言，CNFs沿电极厚度方向存在宏观梯度分布，同时CNFs沿单根纤维径向也存在微观梯度分布，通过物理化学验证了宏观和微观梯度结构。表征。此外，具有双梯度结构的DG-CNFs/GF表现出优异的电催化活性和快速传质特性。值得注意的是，具有 DG-CNFs/GF 的 VFB 的能量转换效率、循环稳定性以及功率密度都远优于商业 GF，这使得双梯度 DG-CNFs/GF 成为一种很有前途的替代品. 最重要的是，这项工作的完成将为下一代高功率密度VFB的高效电极提供一个有前景的发展方向。