Synergistic effect of morphology engineering and oxygen vacancies on enhancing the electrochemical performance of MgMn2O4 cathode for magnesium-ion batteries
摘要
The potential of spinel MgMn2O4 as a high-capacity cathode for magnesium-ion batteries is hindered by intrinsically sluggish Mg2+ ion diffusion and poor electronic conductivity. In this work, a porous cage-like MgMn2O4 cathode with moderate oxygen vacancies was fabricated via a glucose-assisted hydrothermal method. This material delivers a capacity of 239.3 mA h g−1 at 200 mA g−1, with 80% retention after 100 cycles, and exhibits superior rate capability (144.5 mA h g−1 at 500 mA g−1), outperforming sol–gel-derived microbars MgMn2O4 in cycling stability and rate performance. Density functional theory (DFT) calculations were performed on models with oxygen vacancy concentrations of 6.25% and 12.5%, corresponding to the hydrothermal and sol–gel samples, respectively. The results indicate that a 6.25% vacancy concentration enhances bulk electronic conductivity and facilitate Mg2+ ion extraction by weakening the interaction potential between Mg2+ ion and the host lattice at the (001) surface. Furthermore, the interconnected porous network enables rapid Mg2+ ion transport and efficient electrolyte infiltration. The enhanced electrochemical performance is therefore attributed to the synergistic combination of tailored porosity and optimized defect chemistry. This work underscores the importance of integrated structural and defect engineering in developing high-performance electrode materials for magnesium-ion batteries.