Hydrothermal Synthesis of SnO₂ Embedded MoO_3-x Nanocomposites and Their Synergistic Effects on Lithium Storage

We demonstrate a facile hydrothermal synthesis of SnO₂/MoO_3-x nanocomposites with ultrafine SnO₂ crystallites uniformly embedded into an amorphous MoO_3-x matrix, which demonstrate superior electrochemical performance as anodes for lithium ion batteries, including long-term cycling stability (953 mA h/g after 100 cycles at 200 mA/g), high rate capability (668.0 mA h/g after 1000 cycles at 1000 mA/g) and high initial Coulombic efficiency (81.3% at 200 mA/g). Synergistic effects of the both components SnO₂ and MoO_3-x on the lithium storage are revealed by electrochemical characterization and supported by TEM and XPS analysis performed at the different discharge/charge states of the respective electrodes. SnO₂ nanocrystallites confined within the amorphous MoO_3-x matrix efficiently buffer the volume changes of Li-Sn alloying-dealloying upon cycling, while the metallic Mo in situ generated by a conversion reaction of MoO_3-x promotes the reversible reaction SnO₂ + Li⁺ ↔ Sn + Li₂O. In addition, the amorphous MoO_3-x with bulk or surface defects allows for a better lithium insertion and thus enhanced capacity.