High-valence molybdenum promoted proton migration and inhibited dissolution for long-life aqueous Zn-MnO₂ batteries

The disproportionation reaction and irreversible phase transition of MnO2 cathode during charge/discharge seriously limit the cycle life of Zn-MnO2 batteries. Herein, we introduce high valence doping of Mo into the [MnO6] octahedral structure of alpha-MnO2 nanowires (Mo-MnO2) to inhibit the disproportionation reaction of Mn3+. The Mo-MnO2 exhibits the high specific capacities of 222.8 mAh g(-1) at 100 mA g(-1) and 65.8 mAh g(-1) at 5.0 A g(-1), as well as the excellent cycling stability with the retention of 82.6% at 2 A g(-1) after 1000 cycles, which is 60.0% higher than that of pure MnO2. The EX-situ characterization technologies indicate that doping high valence Mo can effectively inhibit the dissolution of Mn3+ to improve cycle stability, and provide additional capacity due to multivalent transition of Mo. Meanwhile, the doped Mo also significantly promotes the proton migration, which won't cause lattice distortion during the proton insertion/extraction process and further improved cyclic stability. The first principle calculation shows that Mo-doped could effectively promote the proton transport and structural stability of discharge product MnOOH, which verifies the source of stability. This work provides new ideas for the design of highly reversible manganese-based oxide cathode materials for zinc-ion batteries.