Discharging Behavior of Hollandite α-MnO in a Hydrated Zinc-Ion Battery.

Hollandite, α-MnO, is of interest as a prospective cathode material for hydrated zinc-ion batteries (ZIBs); however, the mechanistic understanding of the discharge process remains limited. Herein, a systematic study on the initial discharge of an α-MnO cathode under a hydrated environment was reported using density functional theory (DFT) in combination with complementary experiments, where the DFT predictions well described the experimental measurements on discharge voltages and manganese oxidation states. According to the DFT calculations, both protons (H) and zinc ions (Zn) contribute to the discharging potentials of α-MnO observed experimentally, where the presence of water plays an essential role during the process. This study provides valuable insights into the mechanistic understanding of the discharge of α-MnO in hydrated ZIBs, emphasizing the crucial interplay among the HO molecules, the intercalated Zn or H ions, and the Mn ions on the tunnel wall to enhance the stability of discharged states and, thus, the electrochemical performances in hydrated ZIBs.