An improved thin-film electrode for vanadium redox flow batteries enabled by a dual layered structure

Abstract The thin-film electrode has been regarded as one of the desirable options for the vanadium redox flow battery. However, most of the thin-film electrodes developed to date suffer from high mass transport resistance and deliver unsatisfactory performance. In this work, we proposed a dual-layer thin-film electrode, consisting of a backing layer and a catalyst layer, for flow batteries. The backing layer with larger pores is adapted to improve the concentration distribution as well as to provide mechanical support while the catalyst layer with smaller pores provides sufficient active sites. The electrospun fiber mat is adopted as catalyst layer and backing layers in the study include carbon paper, carbon cloth and graphite felt. It is showed that carbon cloth supported electrospun fiber mat electrode demonstrates an energy efficiency of 76.1% at the current density of 240 mA cm−2, which is much higher that achieved by conventional electrospun fiber mat electrodes (61.9%). After optimizations of flow field designs and key operational parameters, the energy efficiency of battery with dual-layer structured electrodes can reach as high as 80.2% at a current density of 240 mA cm−2. In addition, the present battery can stably operate for more than 800 cycles without obvious decay.