Colloidal Electrolyte Enables Bulk-to-Interface Stabilization for Aqueous Manganese Metal Batteries

Abstract Aqueous Mn metal batteries combine the potential for high safety and energy density, yet are limited by high water activity, sluggish Mn2+ desolvation, and severe interfacial parasitic reactions, which cannot be resolved by isolated strategies. Here we develop an ether-oxygen-rich colloidal electrolyte (EORC) whose nanoscale units couple bulk solvation regulation with interfacial stabilization. EORC disrupts the water hydrogen-bond network, partially replaces Mn2+ solvated waters, and enriches ether-oxygen species to reconstruct the electrical double layer. This continuous bulk-to-interface regulation reduces free water activity, lowers desolvation and nucleation barriers, promotes uniform Mn deposition, and suppresses interfacial parasitic reactions, e.g., corrosion and byproducts accumulation. Consequently, Mn∥Mn symmetric cells operate stably for over 3000 h and Mn∥AgVO full cells achieve over 11000 cycles with 93% capacity retention, along with enhanced low-temperature and pouch cell performance. This work offers a transformative strategy that bridges bulk electrolyte chemistry and interfacial electrochemistry for stable aqueous Mn anodes.