A strategy for local anion substitution in MnO2 for alkaline manganese secondary batteries

Alkaline‑manganese batteries, with their high energy density and long shelf life, have become ubiquitous and are often used in a variety of electronic devices. However, the instability of MnO₂ in alkaline solutions has emerged as a significant factor limiting the development of rechargeable alkaline manganese batteries. In this study, fluorine, a highly electronegative element from the same group, is partially substituted for oxygen atoms in MnO₂. Both theoretical calculations and experimental characterizations reveal that surface F coordination effectively adjusts the adsorption capacity of the cathode for Zn(OH)₄²⁻, thereby suppressing byproduct formation and enhancing reaction kinetics. Furthermore, owing to the presence of robust MnF bonds, the irreversible structural phase transition of the cathode during cycling is mitigated. Incorporating 5 mol% Hexafluoroisopropanol (HFIP) to MnO₂ (MnO₂@F-5) results in maximum capacity retention (97.22 %) after 300 cycles, accompanied by a significant average specific discharge capacity enhancement (189.4mAh g⁻¹). This modification strategy provides a new prospect for the design of alkaline manganese secondary batteries.