Aqueous all-manganese batteries

Aqueous batteries are the next-generation energy storage systems because of their low cost and high safety, but their low output voltages limit their widespread applications. The development of high voltage aqueous batteries with metal anodes at low redox potentials and metal oxide cathodes at high redox potentials is expected to increase their energy density. In this study, we propose and develop a proof-of-concept aqueous all-manganese battery (AAMB) with a high theoretical voltage of 2.42 V and theoretical energy density of 900 W h kg⁻¹, which is achieved on the basis of plating/stripping reactions on both the Mn metal anode and the MnO₂ cathode in an optimized electrolyte. We verify the feasibility of the Mn metal anode at a low redox potential of −1.19 V vs. SHE by achieving a low overpotential of 20 mV through an electrolyte engineering strategy. It has been revealed by a series of characterization studies that the SeO₂ additive in the electrolyte helps to form Se and MnSe during the nucleation stage of metallic Mn, thereby reducing the overpotential of Mn plating and stripping. As a result, the designed AAMB achieves a high discharge platform of 2.28 V and stability for 300 cycles. Furthermore, we summarize the challenges and opportunities of the AAMB and call for the development of high performance Mn metal anodes and AAMB. This work is expected to promote the future development of Mn-ion batteries.