High-Energy Aqueous S-MnO₂ Batteries with Redox Charge Carriers

The energy densities of conventional aqueous batteries are often unsatisfactory due to the limited capacities of electrode materials. Therefore, the design of creative aqueous batteries has to be considered. Herein, aqueous S-MnO₂ batteries are constructed by matching S/Cu₂S redox couples and MnO₂ deposition/dissolution. In such batteries, S/Cu₂S redox couples undergo the solid-solid conversion reaction with four-electron transfer, ensuring a high specific capacity of 2220 mAh g^-1 in S anodes. Furthermore, the conversion reaction of S/Cu₂S redox couples can take place stably in acidic electrolyte that is essential for the MnO₂ deposition/dissolution. As a result, the S/Cu₂S redox couples can match MnO₂ deposition/dissolution well, which endow the batteries with a membrane-free configuration. As a proof of concept, Ah-level prismatic and single-flow batteries were assembled and could operate stably for over 1000 h, demonstrating their great potential for large-scale energy storage. This work broadens the horizons of aqueous batteries beyond metal-manganese chemistry.