Synergistic effect of electrolyte additives on the suppression of dendrite growth in a flowless membraneless Zn–Br2 battery

Aqueous ZnBr2 batteries (ZBBs), particularly in flowless and membraneless form (FLML-ZBB), offer a cost-effective and promising large-scale energy storage system. Unfortunately, these batteries suffer from unavoidable Zn dendrite growth and inherent cross-diffusion of volatile and corrosive soluble Br3− species, which can eventually lead to a short circuit and serious self-discharge of the battery, respectively. To address these challenges, a single chamber FLML-ZBB is demonstrated in which the synergic effect of various metal ions (Li+, Na+, K+, Mn2+, and Cr3+) suppresses Zn dendritic growth. In addition, the use of a bromine complexing agent (BCA), 1-ethylpyridinium bromide (1-EPBr), efficiently inhibits cross-diffusion and induces reversible complexation of Br2/Br3−. The experimental results reveal that a battery with both Mn2+ ions and 1-EPBr electrolyte additives shows stable operation and exhibits a high Coulombic efficiency of 98.5% over 700 charge/discharge cycles at a high current density of 20 mA cm−2 and a long cycle life (1600 cycles) of over 3200 h at 1 mA cm−2.