Lithium-Induced Oxygen Vacancies in MnO2@MXene for High-Performance Zinc–Air Batteries

The traditional methods for creating oxygen vacancies in materials present several challenges and limitations, such as high preparation temperatures, limited oxygen vacancy generation, and morphological destruction, which hinder the application of transition metal oxides in the field of zinc-air batteries (ZABs). In order to address these limitations, we have introduced a pioneering lithium reduction strategy for generating oxygen vacancies in δ-MnO2@MXene composite materials. This strategy stands out for its simplicity of implementation, applicability at room temperature, and preservation of the material's structural integrity. This research demonstrates that aqueous Ov-MnO2@MXene-5, with introduced oxygen vacancies, exhibits an outstanding oxygen reduction reaction (ORR) activity with an ORR half-wave potential reaching 0.787 V. DFT calculations have demonstrated that the enhanced activity could be attributed to adjustments in the electronic structure and alterations in adsorption bond lengths. These adjustments result from the introduction of oxygen vacancies, which in turn promote electron transport and catalytic activity. In the context of zinc-air batteries, cells with Ov-MnO2@MXene-5 as the air cathode exhibit outstanding performance, featuring a significantly improved maximum power density (198.3 mW cm-2) and long-term cycling stability. Through the innovative strategy of introducing oxygen vacancies, this study has successfully enhanced the electrochemical catalytic performance of MnO2, overcoming the limitations associated with traditional methods for creating oxygen vacancies. Consequently, this research opens up new avenues and directions for nonprecious metal catalyst application in ZABs.