Micrometer-Sized, Dual-Conductive MoO₂ /β-MoO_{3- x} Mosaics for High Volumetric Capacity Li/Na-Ion Batteries

The transition metal oxides (TMOs) with high volumetric capacities are promising anodes for the future electronics, however, they usually suffer from severe capacity decay and poor rate capability. Carbon hybridization and nanosizing can resolve these challenges, yet these significantly compromise the volumetric capacity. Herein, both high capacity and long cycling stability are simultaneously achieved in the micrometer-sized Mo-based oxide particles by designing the dual conductive MoO₂ /β-MoO_{3- x} mosaics. The rational combination of the highly electronically conductive MoO₂ with the highly ionically conductive and open-structured β-MoO₃ achieves a promising volumetric capacity of 1742 mAh cm^-3 , which is four times higher than the commercial graphite. Simultaneously, both stable cycling performance (87% retention after 500 cycles) and excellent rate capability (outperformed a majority of the MoO₂ -based anodes reported in literature) are obtained in the lithium-ion batteries. For the sodium-ion batteries, the composite exhibits three times higher Na⁺ storage than pure MoO₂ . Moreover, the decisive role of the bond energy on the electrochemical performance of TMOs is also identified. This study may open up new perspectives for choosing and designing the TMO anodes with a high volumetric capacity for the practical applications.