A hybrid electrolyte with water-poor solvation structure for high-performance zinc-bromine battery

Due to the low cost and high safety, aqueous non-flow zinc-bromine battery have shown great potential. However, one of the difficulties hindering its practical application is the severe hydrogen evolution reactions (HER) and dendrites growth on zinc anodes. To address these issues, we propose a hybrid high concentrated electrolyte consisting of 7.5 M NaBr and 0.25 M ZnBr 2 with a nicotinamide (NAM) additive. The high concentration of bromide ions and NAM molecules demonstrate good ability to reconstruct the solvation structure of zinc ions, forming a water-poor solvation structure of [ZnBr 4.4 NAM 0.5 (H 2 O) 1.2 ] 2− in aqueous solution, which significantly retard the HER. Additionally, NAM adsorbs on the Zn anode surface to induce homogeneous Zn 2+ deposition, inhibit the dendrites growing. As a result, the Zn anode using the hybrid electrolyte achieved stable cycling over 2000 cycles with a high Coulombic efficiency (CE) of 99.8 %. Furthermore, the static Zn//Br 2 battery demonstrated a long cycling lifespan over 35,000 cycles with a capacity retention of 98 % at a low N/P ratio of 5. The energy density of this cell reaches 85.1 Wh kg −1 and the power density reaches 40800 W kg −1 . This work has provided new ideas for the optimization of electrolytes for zinc-based energy storage devices.