MOF-derived high-entropy oxide-modified graphite felt for enhanced electrochemical performance in vanadium redox flow batteries

Abstract

This study employs a MOF-induced strategy to synthesize high-entropy oxide (HEO)-modified graphite felt (GF) electrodes and systematically investigates their electrochemical performance in vanadium redox flow batteries (VRFBs). The spatial confinement effect of the MOF precursor ensures the homogeneous distribution of Zn, Mo, La, Ni, and Co multi-metallic ions, while the high-entropy stabilization effect strengthens the structural stability of the material, offering significant advantages for electronic structure tuning and oxygen vacancy introduction. Experimental results demonstrate that compared to medium-entropy oxide (MEO) electrodes, HEO electrodes exhibit superior redox kinetics, lower interfacial impedance, and enhanced electron transport capability. XPS analysis reveals that oxygen vacancies in the HEO structure serve as additional active sites for V species, accelerating the redox reaction and reducing polarization during charge-discharge processes. In VRFB single-cell tests, the electrode maintained high energy efficiencies of 87.05% at 100 mA cm⁻² and 82.40% at 200 mA cm⁻², while retaining 76.16% of its capacity after 500 cycles, demonstrating excellent cycling stability and high-rate cycling performance. This study demonstrates that the MOF-induced high-entropy oxide strategy enhances the electrochemical performance of VRFB electrodes, offering valuable insights for the design of advanced energy storage materials.