Quasi-Homogeneous Bromine Phase in Zinc-Bromine Batteries with Advanced Energy Efficiency and Energy Density

Regarding energy density, kinetics, and reversibility, the zinc-bromine batteries (ZBBs) exhibit advantages comparable to the conventional metal hydride nickel batteries as aqueous systems. However, the development of ZBBs has been impeded by two critical challenges: the self-discharge of Br-Br species cross-over and the short circuit caused by zinc dendrites. Achieving high energy density necessitates a large areal capacity electrode and tight battery assembly, which introduces additional hurdles. Addressing these challenges, we have successfully implemented a novel quasi-homogeneous bromine phase. Our optimized approach has realized ZBBs with a remarkable energy efficiency (EE) of 92.7% based on an areal capacity of 12 mA h cm−2 in a period duration of 13 h, an energy density of whole battery (EDB) of 80 W h l−1 with average EE of 92.5% for an extended cycle life of approximately 500 cycles, and a maximum EDB of 186 W h l−1 without pre-added zinc metal. This innovative work holds practical significance for developing ZBBs and providing insights and solutions to critical challenges.