Zn-Doped Hollow Cubic MnO₂ as a High-Performance Cathode Material for Zn Ion Batteries

Manganese-based compounds have the characteristics of high theoretical capacity, low cost and stable performance, thus become a research hotspot for cathode materials of zinc-ion batteries (ZIBs). However, in the process of charging and discharging, it is accompanied by problems such as structural collapse and low conductivity, which resulted in severe capacity degration during cycles. In this paper, a kind of Zn²⁺ doped MnO₂ hollow cube cathode material (Zn-MnO₂) was prepared by self-sacrificing template method. The Zn²⁺ doped in MnO₂ crystals can induce oxygen vacancies in the structure, thereby improving the structural stability ion diffusion coefficient and electrical conductivity of the material. After 100 cycles at 0.3 A g^-1, the high specific capacity of 281.2 mA h g^-1 is still maintained. Through ex-situ XPS and ex-situ XRD tests, the mechanism of charge-discharge process was discussed. The results show that the storage mechanism of Zn-MnO₂ is H⁺ and Zn²⁺ insertion/removal and Mn³⁺/Mn²⁺ two-electron reaction pathway. The total state density (TDOS) and partial state density (PDOS) of Zn-MnO₂ and MnO₂ further demonstrated that the doping of Zn2+ enhanced the electron conductivity and is beneficial to the electron transfer during the electrochemical reaction.