Rechargeable Aqueous Mn-Metal Battery Enabled by Inorganic-Organic Interfaces

Aqueous batteries that use metal anodes exhibit maximum anodic capacity, whereas the energy density is still unsatisfactory partially due to the high redox potential of the metal anode. Current metal anodes are plagued by the dilemma that the redox potential of Zn is not low enough, whereas Al, Mg, and others with excessively low redox potential cannot work properly in aqueous electrolytes. Mn metal with a suitably low redox potential is a promising candidate, which was rarely explored before. Here, we report a rechargeable aqueous Mn-metal battery enabled by a well-designed electrolyte and robust inorganic-organic interfaces. The inorganic Sn-based interface with a bottom-up microstructure was constructed to preliminarily suppress water decomposition. With this bubble-free interface, the organic interface can be formed via an esterification reaction of sucrose triggered by acyl chloride in the electrolyte, generating a dense physical shield that isolates water while permitting Mn²⁺ diffusion. Hence, a Mn symmetric cell achieves a superior plating/stripping stability for 200 hours, and a Mn||V₂ O₅ battery maintains approximately 100 % capacity after 200 cycles. Moreover, the Mn||V₂ O₅ battery realizes a much higher output voltage than that of the Zn||V₂ O₅ battery, evidencing the possibility of increasing the energy density through using a Mn anode. This work develops a systematic strategy to stabilize a Mn-metal anode for Mn-metal batteries, opening a new door towards enhanced voltage of aqueous batteries.