A high-energy efficiency static membrane-free zinc–bromine battery enabled by a high concentration hybrid electrolyte

Abstract

As a promising energy storage system, aqueous zinc–bromine batteries (ZBBs) provide high voltage and reversibility. However, they generally suffer from serious self-discharge and corrosion of the zinc anode caused by the diffusion of corrosive bromine species. In this work, high concentration ZnBr₂ (20 M) with LiCl additive was for the first time developed as a new electrolyte for static membrane-free zinc–bromine batteries. The cross diffusion of Br₃⁻ is effectively restricted by the high viscosity of the electrolyte, and the low water content further reduces the self-discharge rate caused by the zinc–bromine reaction. The introduction of LiCl additive not only offsets the conductivity reduction caused by high electrolyte viscosity, but also inhibits the growth of zinc dendrites through regulating the electric field intensity on the zinc protrusion. The zinc–bromine battery with 20 M ZnBr₂ and LiCl additive exhibits a high coulombic efficiency of 98% and a high energy efficiency of 88%, which are higher than those of most reported static membrane-free ZBBs. The stabilization of the zinc anode endows the battery with high stability of more than 2500 cycles, corresponding to continuous 1000 hours working. Our cell design provides an economical, efficient and easy manufacturing way to popularize zinc–bromine batteries for practical applications.