Porous structures of carbon-doped Co3O4 with tunable morphologies from microflowers to cubes as anodes for high performance lithium/sodium-ion batteries

Abstract

Co3O4 microflowers and size controllable porous cubes are synthesized through a facile solvothermal process followed by annealing. The Co3O4 microflowers and porous cubes range in size from 3 to 10 µm, which consist of Co3O4 particles of a few tens of nanometers, can be obtained by adjusting the amount of urea precursor during the preparation. The porous structure of Co3O4 cubes can provide abundant diffusion paths for lithium or sodium ions and void space to accommodate volume variation during the repeated ion insertion/extraction process significantly. In addition, the uniform carbon-doping could effectively enhance the conductivity of the composites. As a result, the CC-3 sample exhibits a high specific capacity of 539.2 mAh g−1 after 500 cycles at a current density of 1000 mA g−1 as an anode for LIBs and 176.1 mAh g−1 after 1000 cycles at 2000 mA g−1 for SIBs. Meanwhile, the sample delivers an excellent cycle performance of 130.2 mAh g−1 after 160 cycles at 500 mA g−1 when used as an anode for the full cell of a sodium-ion battery. The superior electrochemical performance can be attributed to the unique cube shape with a porous structure, appropriate sample size, and carbon-doping, which have been discussed based on the morphology, construction, phase, and electrochemical properties.