Suppression of self-discharge in a non-flowing bromine battery via in situ generation of countercharged groups

Bromine is attractive for next-generation energy-storage systems because of its high capacity and natural abundance. However, because of 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 exploit bromine redox chemistry and demonstrate the feasibility of mitigating ion depletion in a stationary device. A cell using polyaniline vapor-grown carbon fiber (PANI-VGCF) as the electrode material exhibits close to 100% Coulombic efficiency at a low current density (50 mA/g). Electrochemical results, operando Raman spectroscopy, and theoretical analysis provide clues that the strong interaction between protonated PANI and Br⁻/ Br₃⁻ makes their decoupling unfavorable, thereby suppressing self-discharge processes. This strategy could be utilized for rational design of other conjugated materials/bromine systems without self-discharge issues.