Improving the capacity of zinc-ion batteries through composite defect engineering

Aqueous zinc-ion batteries (ZIB) are favored because of their low cost and high safety. However, as the most widely used cathodes, the rate performance and long-term cycle performance of manganese-based oxides are very worrying, which greatly affects their commercialization. Here, MnO₂ with composite defects of cation doping and oxygen vacancies was synthesized for the first time. Cation doping promoted the diffusion and transport of H⁺ and oxygen vacancies weakened the zinc-oxygen bond, allowing more electrons to be added to the charge and discharge process. The combination of these makes α-MnO₂ obtain a specific capacity of up to 346 mA h g^-1. This inspired us to use different combinations of defect engineering strategies on the materials which can be implemented as a potential method to improve performance for the modification of ZIB cathode materials, such as cation vacancies and anion doping.