Activation of MnO hexagonal nanoplates via in situ electrochemical charging toward high-capacity and durable Zn-ion batteries

Rechargeable aqueous Zn-MnO2 batteries hold great promise in grid-scale energy storage owing to their merits of high specific energy, inexpensiveness, environmental benignity, and high safety. However, MnO2 cathodes suffer from extremely poor cycling stability in pure ZnSO4 electrolyte. In this work, MnO hexagonal nanoplates constructed by porous nanocrystals are reported to show superior zinc-ion storage performance in pure ZnSO4 electrolyte. Mechanistic investigation reveals that the MnO cathode experiences an in situ gradual oxidation during electrochemical charging to form active MnO2 ultrathin nanosheets, which subsequently allow for a reversible and consecutive insertion of H+ and Zn2+. Notably, a high specific capacity of 292 mAh g−1 can be obtained in the activated cathode at a current density of 0.1 A g−1. In particular, the cathode could sustain a long 1000-cycling operation without noticeable capacity degradation, which is comparable to the reported MnO2 cathodes in an electrolyte containing MnSO4 additive. The present study will shed light on the development of low-valence Mn-oxides by in situ electrochemical charging toward high-capacity and durable zinc-ion batteries.