Copper-induced formation of heterostructured Co3O4/CuO hollow nanospheres towards greatly enhanced lithium storage performance

We report a facile template-free fabrication of heterostructured Co3O4/CuO hollow nanospheres using pre-synthesized Co/Cu-glycerate as conformal precursor. The introduction of copper nitrate in the solvothermal reaction system of glycerol/isopropanol/cobalt nitrate readily induces the conversion from solid Co-glycerate to hollow Co/Cu-glycerate nanospheres, and the effect of the Co/Cu atomic ratio on the structure evolution of the metal glycerates as well as their corresponding oxides were investigated. When examined as anode materials for lithium-ion batteries, the well-defined Co3O4/CuO hollow nanospheres with Co/Cu molar ratio of 2.0 demonstrate excellent lithium storage performance, delivering a high reversible capacity of 930 mAh/g after 300 cycles at a current density of 0.5 A/g and a stable capacity of 650 mAh/g after 500 cycles even at a higher current density of 2.0 A/g, which are much better than their counterparts of bare CuO and Co3O4. The enhanced lithium storage performance can be attributed to the synergistic effect of the CuO and Co3O4 heterostructure with hollow spherical morphology, which greatly enhances the charge/electrolyte transfer and effectively buffers the volume changes upon lithiation/delithiation cycling.