Stable aqueous redox flow battery assembled in air atmosphere employing an anionic terpolymer as active cathode material

Abstract

Polymer-based aqueous redox flow batteries (RFBs) have emerged as a promising technology for large-scale energy storage. The development of novel polymeric electrode materials with high aqueous solubility to enhance the capacity and stability of batteries is the foremost concern of this area, yet remains challenging. Here we describe a stable polymer-based aqueous RFB assembled in air atmosphere, which uses a low-cost anionic terpolymer (P4) as the active cathode material, N,N′-dimethyl-4,4′-bipyridinium dichloride (MV) as the anode material, and environmentally benign aqueous NaCl solution (NaClaq) as the electrolyte. P4 exhibits high solubility (28.8 Ah L−1) and low viscosity in 1.5 M NaClaq. The theoretical storage capacity of such stable RFB is as high as 12 Ah L−1. At the current density of 10 mA cm−2 and over 170 consecutive cycles in air atmosphere at room temperature, the P4/MV RFB exhibits the actual energy density of 6.43 Wh L−1, the material utilization of 71.3%, Coulombic efficiency over 95%, and the average attenuation per cycle of 0.12%.