Enhanced Electrochemical Performance of Vanadium Redox Flow Batteries Using Li 4 Ti 5 O 12 /TiO 2 Nanocomposite‐Modified Graphite Felt Electrodes

In this study, Li 4 Ti 5 O 12 (LTO) and TiO 2 nanocomposites uniformly were synthesized on the heat‐treated graphite felt through (HGF) hydrothermal and heat treatment methods, denoted by LTO/TiO 2 @HGF, which LTO/TiO 2 @HGF acts as effective electrocatalysts to enhance the electrochemical activity in vanadium redox flow battery (VRFB) systems. The cyclic voltammetry (CV) curves of the LTO/TiO 2 @HGF show higher peak current densities and smaller peak separation than TiO 2 @HGF, HGF, and pristine graphite felt (PGF) for catalyzing V 2+ /V 3+ and VO₂ + /VO 2+ , indicating superior electrochemical activity of LTO/TiO 2 @HGF. The VRFB using LTO/TiO 2 @HGF as the positive and negative electrodes demonstrates an energy efficiency of 82.89 % at 80 mA cm −2 . When the VRFB using LTO/TiO 2 @HGF is applied by a high current density of 200 mA cm −2 , it still shows an energy efficiency of 62.22 %. However, the VRFB using PGF cannot perform any performance, and the VRFB using HGF only performs 51.94 %. This improvement can be attributed to the uniform distribution of LTO/TiO 2 nanowires on the surface of the graphite felt and the presence of oxygen vacancies on LTO/TiO 2 , which increased the number of active sites for vanadium ion absorption.