Low-temperature synthesis of two-dimensional nanostructured Co₃O₄ and improved electrochemical properties for lithium-ion batteries

Urea as a cheap reagent is very useful in preparation two-dimensional metal oxides with tunable crystal morphologies, while refluxing method is a simple route to control the decomposition of urea. Here, a low temperature refluxing in the presence of urea is developed to prepare porous Co₃O₄ as anode material for lithium-ion batteries. The self-assembly cobalt hydrotalcite-like compounds (Co-HLC) is firstly synthesized through refluxing the mixture of cobaltous nitrate and urea. After pyrolysis, the flower-like morphology of Co-HLC is successfully maintained in the final product of Co₃O₄. The ordered two-dimensional Co₃O₄ nanosheets provide good contact with electrolyte and stable porous structure during lithiation/delithiation. Co₃O₄-120 synthesized under refluxing temperature of 120 °C shows the initial charge capacities of 722 and 741 mAh g⁻¹ at the 2nd and 100th cycle under 100 mA g⁻¹. Moreover, Co₃O₄-120 as electrode for a supercapacitor presents excellent capacitance, 167 F g⁻¹ after 3000 cycles at 1 A g⁻¹. Under 5, 10 and 20 A g⁻¹, Co₃O₄-120 electrode delivers 128, 104 and 90 F g⁻¹, respectively. The porous structure in Co₃O₄ with enhanced electrochemical performance indicates low temperature refluxing preparation is an applicable and energy-saved method to synthesize transitional metal oxide with tunable crystal morphologies.