Anion-Assisted Regulation of Solvation Structure for High-Performance Manganese-Organic Batteries

Rechargeable manganese metal batteries (MMBs) have recently gained attention owing to the high abundance, large theoretical capacity, and low redox potential (-1.19 V vs SHE) of Mn compared with Zn. However, Mn anodes suffer from severe hydrogen evolution in aqueous electrolytes, while in nonaqueous systems, corrosion suppression is accompanied by sluggish Mn²⁺ desolvation and high polarization. Moreover, the limited availability of cathodes capable of reversible Mn²⁺ storage further hinders the MMB development. Herein, we design a propylene carbonate (PC)-based electrolyte containing 0.5 M MnBr₂ and 0.25 M EMIMBF₄, enabling highly reversible Mn plating/stripping. The cooperative incorporation of Br^- and BF₄^- into the Mn²⁺ solvation sheath reduces the PC coordination number, accelerating the Mn²⁺ desolvation kinetics. Consequently, the Mn deposition overpotential drops from ∼1 to 0.15 V, while the Coulombic efficiency exceeds 95%. The Mn||Mn symmetric cell exhibits outstanding stability over 3000 h at 0.2 mA cm^-2 with a low overpotential (∼0.15 V). A full cell pairing a polyimide cathode (PNTCDA) with the Mn anode delivers excellent rate capability and 80% capacity retention after 500 cycles. This solvation-structure regulation strategy offers an effective route toward high-performance MMBs.