Suppressing Self-Discharge in a Non-Flowing Bromine Battery via the in situ Generation of Countercharged Groups

Bromine is attractive for next-generation energy storage systems due to its high capacity and natural abundance. However, because of the issues relating to self-discharging processes, prototypes involving bromide/ bromine redox couples are largely limited to the design of flow cells. Here, we propose a method to take advantage of bromine redox chemistry and demonstrate the feasibility of mitigating ion depletion in a stationary device. A cell using polyaniline-vapor grown carbon fibre (PANI-VGCF) as the electrode material exhibits close to 100% Coulombic efficiency at a low current density (50 mA/ g). Electrochemical results, operando Raman and theorectical analysis provide clues that the strong interaction between protonated PANI and Br-/Br3- makes their decoupling unfavourable, thereby suppressing self-discharge processes. This strategy could be utilized for the rational design of other conjugated materials/ bromine systems without self-discharge issues.