Synergistic Anion Regulation Inducing Fluoride‐Rich SEI and Defect‐Rich MnO ₂ for Stable Dual Electrode‐Free Zn‐MnO ₂ Batteries

ABSTRACT

Dual electrode‐free (DEF) Zn─MnO ₂ batteries based on dissolution‐deposition chemistry are promising candidates for large‐scale energy storage due to their lightweight architecture and high theoretical capacity (616 mAh g ⁻¹ ). However, poor interfacial reversibility and the accumulation of “dead manganese” significantly limit their lifespan. Here, we demonstrate a stable DEF battery enabled by an anion‐regulation strategy using a hybrid electrolyte (E‐OA) comprising trifluoromethanesulfonate (OTf ⁻ ) and acetate (Ac ⁻ ) ions. At the anode, OTf ⁻ facilitates the formation of a fluoride‐rich solid–electrolyte interphase (SEI), effectively suppressing dendrite growth and the hydrogen evolution reaction. At the cathode, the synergistic anionic environment elevates the MnO ₂ nucleation overpotential, shifting the electrocrystallization pathway to an instantaneous nucleation mode. The kinetically driven growth process traps abundant structural defects, identified as proton‐compensated manganese vacancies (Ruetschi defects). These vacancies lower the thermodynamic energy barrier for Mn─O bond cleavage, thereby ensuring highly reversible dissolution. Consequently, the E‐OA‐based DEF battery achieves exceptional stability for over 7500 cycles at 0.5 mAh cm ⁻² and sustains 600 cycles at 2 mAh cm ⁻² (10 mA cm ⁻² ), demonstrating superior rate capability and versatility in both flow and gel battery configurations. This work provides a transformative strategy for high‐energy aqueous batteries via tailored anion chemistry and kinetics‐driven defect engineering.