Reconstruction of the Electric Double Layer for Long-Lasting Aqueous Manganese Metal Batteries.

Aqueous Mn metal batteries (AMMBs) have emerged as promising candidates for stationary energy storage owing to the natural abundance of Mn, their operational safety, and their high energy density. However, the high chemical reactivity of the Mn metal anode induces a severe hydrogen evolution reaction (HER), resulting in poor cycling reversibility. Fundamentally, HER is a parasitic cathodic reaction competing with Mn electrodeposition and may accompany Mn corrosion. Its kinetics are influenced by the interfacial water environment within the electric double layer (EDL). In this study, we propose a strategy for reconstructing the EDL by adding n-decyltrimethylammonium bromide (10-DTAB), a surfactant with a relatively high lowest unoccupied molecular orbital (LUMO), to the electrolyte to stabilize the Mn anode. The high LUMO energy level enhances its reduction stability, thus preventing continuous decomposition during cycling and enabling sustained interfacial protection. Consequently, the Mn anode exhibits a markedly enhanced Coulombic efficiency of 93%. This study demonstrates a durable EDL regulation paradigm based on high-LUMO additives, offering new insights into stabilizing Mn metal anodes and advancing AMMBs toward practical applications.