Advancing bromine-ion batteries: A breakthrough in “Water-in-Salt” electrolyte for safe and sustainable energy storage

In this study, we introduce a novel “water-in-salt” electrolyte for Bromine-ion batteries (BIBs) for the first time: 3M AlCl 3  + 1M NH 4 Br. The 3M AlCl 3 establishes the “water-in-salt” system, while 1M NH 4 Br supplies Br- ions. Employing flexible graphite paper as the cathode, during charging, Br- cooperates with AlCl 3 , forming AlCl 3 Br - ions that embed into the graphite paper, resulting in reversible reactions during discharge. The anode utilizes various metals such as Zn, Cu, Pb, In 2 O 3 , undergoing reversible redox reactions in the charge–discharge process. The designed electrolyte effectively prevents elemental bromine generation, presenting a safe, green, and environmentally friendly aqueous electrolyte suitable for BIBs.