Probing Lithium Storage Mechanism of MoO2 Nanoflowers with Rich Oxygen-Vacancy Grown on Graphene Sheets

The search for new electrode materials is of paramount importance for the practical apply of lithium-ion batteries (LIBs). Herein, flower-like MoO2 microislands consist of MoO2 nanorods grown on both sides of graphene sheets were synthesized via a solvo-thermal method, followed by a simple thermal treatment in argon. Our EXAFS and ESR data suggest there oxygen-vacancies in MoO2 of the FMMGS hybrids. Besides, by tunning the ratio of glucose and CTAB, samples with different oxygen-vacancies content were synthesized. When used as anode materials for lithium-ion batteries, the oxygen vacancy-rich FMMGS hybrids exhibited obviously higher capacity, rate capability than any nonvacancy samples. Importantly, synchrotron-radiation-based X-ray absorption near-edge structure (XANES), extended X-ray absorption fine-structure (EXAFS) and ex situ X-ray diffraction (ex situ XRD) were employed to elucidate the Li-ion insertion and extraction processes in the MoO2 electrode. Our data clearly revealed that Li2MoO4 was generated during the Li uptake/removal process, which can be attributed to the existence of Abundant oxygen vacancies in MoO2 microislands. This provides us a useful insight for better understanding of dynamic cycling behavior in various Mo-based electrodes.