Porous Co3O4@CoO composite nanosheets as improved anodes for lithium-ion batteries

We report a facile method to synthesise and modify porous Co3O4 nanosheets. The nanosheets are prepared by hydrothermal reaction and calcination, then reduced with an H2/Ar mixed gas at 250 °C within 1 min. The modification treatment generates oxygen vacancies and Co3O4/CoO interface structure. Electrochemical measurements show that the nanosheets (Co3O4-30) reduced for 30 s have excellent electrochemical performance. After the Co3O4-30 electrode was cycled 200 times under 0.5 Ag-1, the reversible capacity was 892 mAh g−1. A reversible capacity of 250 mAh g−1 can be achieved even at a higher current density of 5.0 Ag-1. The good lithium storage performance is attributed to oxygen vacancies and appropriate Co3O4/CoO interface structure. This study provides a facile strategy to construct improved transition metal oxide electrodes for energy storage and conversion.