Enhanced H+ Storage of a MnO2 Cathode via a MnO2 Nanolayer Interphase Transformed from Manganese Phosphate

The MnO2 cathode has attracted extensive attention in aqueous zinc ion battery research due to its environmental benignity, low cost, and high capacity. However, sluggish kinetics of hydrated zinc ion and manganese dissolution lead to insufficient rate and cycle performances. In this study, a manganese phosphate nanolayer synthesized in situ on a MnO2 cathode can be transformed into a δ-MnO2 nanolayer interphase after activation upon cycling, endowing the interphase with abundant interlayer water. As a result, the δ-MnO2 nanolayer interphase with the function of H+ topochemistry significantly enhances H+ (de)insertion in the MnO2 cathode, which leads to a kinetics conversion from Zn2+-dominated (de)insertion to H+-dominated (de)insertion, thus endowing the MnO2 cathode with superior rate and cycle performances (85.9% capacity retention after 1000 cycles at 10 A g-1). This strategy can be highly scalable for other manganese-based cathodes and provides an insight for developing high-performance aqueous zinc ion batteries.