The ever-increasing need for energy-dense batteries with high safety is fuelling global research and innovations in new redox chemistry and device design. Here we show an aqueous battery employing highly concentrated hetero-halogen electrolytes that contain I⁻ and Br^-, resulting in a multielectron transfer process of I⁻/IO₃⁻. The intermediate bromide species IBr and Br₂, generated during the electrochemical process, enhances the reaction kinetics and alleviates the potential gap between oxidation and reduction. When using a 6 M I⁻ electrolyte to achieve over 30 M electron transfers, the I⁻/IO₃⁻ cathode displayed a high specific capacity of over 840 Ah l_catholyte⁻¹. A battery with Cd/Cd²⁺ as the anode demonstrated a high energy density of over 1,200 Wh l_catholyte⁻¹. Even at an exceptionally high current density of 120 mA cm⁻², an energy efficiency of 72% was obtained. Our work demonstrates that safe aqueous batteries with high energy density are possible, offering a development option for grid-scale energy storage and even electric vehicles.

对具有高安全性的能量密集型电池的需求不断增长，推动了全球在新型氧化还原化学和设备设计方面的研究和创新。在这里，我们展示了一种采用含有 I ^-和 Br ^-的高浓度杂卤素电解质的水系电池，从而产生 I ^- /IO ₃ ^-的多电子转移过程。电化学过程中产生的中间溴化物IBr和Br ₂增强了反应动力学并减轻了氧化和还原之间的电位差。当使用6 MI ^-电解质实现超过30 M的电子转移时，I ^- /IO ₃ ^{-阴极表现出超过840 Ah l}_{阴极电解质}^-1的高比容量。以Cd/Cd ²⁺作为阳极的电池表现出超过1,200 Wh l_{阴极电解液}^-1的高能量密度。即使在120mA cm ^-2的极高电流密度下，也获得了72%的能量效率。我们的工作表明，具有高能量密度的安全水性电池是可能的，为电网规模的储能甚至电动汽车提供了开发选择。