Electrochemical Studies of Carbon Felt Electrode Modified Under Airless Conditions for Redox Flow Batteries

Abstract

Carbon felts were prepared under various thermal conditions to improve the electrochemical properties of vanadium redox flow batteries. The number of C-O and/or C-OH functional groups on the surface of the electrodes treated under airless conditions was much larger than that of the untreated and partially oxygen-treated electrodes. The carbon felt treated under airless conditions had the lowest surface area. The overall kinetic properties of the redox reaction were greatly improved for the carbon felt treated under airless conditions; i.e., the reversibility of the anodic and cathodic reactions associated with the VO 2 + /VO 2+ couple became more reversible. Single-cell tests indicated that the carbon felt exhibited an excellent discharge capacity of 3.1 Ahg -1 at 40 mAcm -2 , and the corresponding Coulombic, voltage, and energy efficiencies were 89.5%, 91.8%, and 82.2%, respectively.