First-Principles Simulations for the Effect of Zinc Ions on MnO₂/water system

The aqueous zinc-ion battery (AZIB), with its excellent power density, high energy density, safety, and sustainability, is a potential energy storage device. Manganese dioxide (MnO2), as the cathode material of AZIB, has shown exceptional electrochemical performance due to its multiple valence states and outstanding ion storage performance. Nevertheless, the energy storage process of MnO2 remains controversial. In order to explain the energy storage process of MnO2 in AZIB, it is necessary to explore the effect of Zinc ions (Zn2+) on the structure of the MnO2/water interface at the atomic scale. The effect of Zn2+ on the structure of MnO2/water interface systems was examined in this work using molecular dynamics simulation. Two representative crystal phases of MnO2, including α-MnO2 and δ-MnO2, were considered. The results revealed that Zn2+ will affect the structural stability of the MnO2/water interface system, and the degree of structural deformation in MnO2 varies with its crystal phase. Moreover, Zn2+ for both the α-MnO2/water and δ-MnO2/water systems prefer to be stabilized at the interface near MnO2 and the water, forming a spinel-like product. These results offer a fresh understanding of the MnO2 energy storage process in AZIBs and can help in the development of high-performance cathode materials.