Enhanced Electrochemical Performance of Vanadium Redox Flow Batteries Using Li4Ti5O12/TiO2 Nanocomposite‐Modified Graphite Felt Electrodes

Abstract

Abstract In this study, Li4Ti5O12 (LTO) and TiO2 nanocomposites uniformly were synthesized on the heat‐treated graphite felt through (HGF) hydrothermal and heat treatment methods, denoted by LTO/TiO2@HGF, which LTO/TiO2@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/TiO2@HGF show higher peak current densities and smaller peak separation than TiO2@HGF, HGF, and pristine graphite felt (PGF) for catalyzing V2+/V3+ and VO₂+/VO2+, indicating superior electrochemical activity of LTO/TiO2@HGF. The VRFB using LTO/TiO2@HGF as the positive and negative electrodes demonstrates an energy efficiency of 82.89 % at 80 mA cm−2. When the VRFB using LTO/TiO2@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/TiO2 nanowires on the surface of the graphite felt and the presence of oxygen vacancies on LTO/TiO2, which increased the number of active sites for vanadium ion absorption.

Keywords

• Energy storage system
• Vanadium redox flow battery
• Graphite felt
• Heat treatment
• Electrochemical activity
• Energy efficiency