Outstanding electrochemical performance of a graphene-modified graphite felt for vanadium redox flow battery application

The development of more efficient electrode materials is essential to obtain vanadium redox flow batteries (VRFBs) with enhanced energy densities and to make these electrochemical energy storage devices more competitive. A graphene-modified graphite felt synthesized from a raw graphite felt and a graphene oxide water suspension by means of electrophoretic deposition (EPD) is investigated as a suitable electrode material in the positive side of a VRFB cell by means of cyclic voltammetry, impedance spectroscopy and charge/discharge experiments. The remarkably enhanced performance of the resultant hybrid material, in terms of electrochemical activity and kinetic reversibility towards the VO2+/VO2+, and mainly the markedly high energy efficiency of the VRFB cell (c.a. 95.8% at 25 mA cm−2) can be ascribed to the exceptional morphological and chemical characteristics of this tailored material. The 3D-architecture consisting of fibers interconnected by graphene-like sheets positively contributes to the proper development of the vanadium redox reactions and so represents a significant advance in the design of effective electrode materials.The authors thank MINECO (projects MAT2013-48107-C3-1-R, INNPACTO IPT-2011- 1690-920000 and NANO-EN-ESTO MAT2010-2015), Principado de Asturias (Fondo Europeo de Desarrollo Regional: GRUPIN 14-118) and the European Regional Development Funds (ERDF, FEDER Programa Competitivitat de Catalunya 2007-2013) for their financial support.Peer reviewe