Interconnected core-shell MoO ₂ microcapsules with nanorod-assembled shells as high-performance lithium-ion battery anodes

In this paper, a facile and template-free one-step strategy has been developed to synthesize interconnected core-shell MoO ₂ hierarchical microcapsules via a solvothermal route. The as-synthesized MoO ₂ microcapsules exhibit a core-shell hierarchical architecture, which integrates four beneficial features: carbon-free, hollow cavity, porous shell, and interconnected wall. Due to their unique nanostructure, when evaluated for lithium-storage properties, they exhibit a high specific capacity of 749.3 mA h g ^-1 in the first discharge at a rate of 1 C and high reversible capacity of 623.8 mA h g ^-1 after 50 cycles. Meanwhile, higher rate (2 C and 5 C) measurements show that the carbon-free, core-shell MoO ₂ microcapsules exhibit much better rate capacity even compared to MoO ₂-C nanocomposites tested under the same conditions. This superior electrochemical performance of the as-synthesized microcapsules could be ascribed to, on the one hand, their inherently metallic electrical resistivity, and on the other hand, their special structure, which not only provides short Li ion pathways and high electronic and ionic conductivity, and but also be able to accommodate large volume variation.