Recent Development of Co3O4 and Its Composites as Anode Materials of Lithium-ion Batteries

The depletion of non-renewable fossil fuels and environmental issues force us to explore substitutes for fossil fuels, such as solar energy, hydroelectricity, thermal enegy, wind power etc., which are the potential global energy sources in the future. However, most of the renewable energy are typically periodic or intermittent and need to equip with appropriate electrical energy storage devices, such as lithium-ion batteries (LIBs). Novel and advanced anode and cathode materials are the key technologies for high performance LIBs, so various electrode materials with high energy density have been extensively investigated. Cobaltosic oxide (Co3O4), commonly used as the anode materials for LIBs, has attracted extensive interest due to its high theoretical specific capacity (890 mAh.g(-1)), high tap density and stable chemical properties. However, its practical use is hindered because of the large volume change during repeated lithium uptake and removal reactions, low electronic conductivity, rapid capacity fading upon extended cycling and poor rate capability. To overcome these problems, it is an effective way to prepare nanometer-sized materials with nano-/micrometer-sized structures, which can buffer huge volume changes during the lithium insertion/extraction process and offer extra space for the lithium storage. Up to now, various morphologies of Co3O4 have been synthesized, such as nanoparticles, nanospheres, nanorods, nanowires, nanotubes, nanosheets, nanoplatelets, nanocubes, hierarchical nanoflowers and some other more complex structures. Another method is to composite with other materials such as carbon or graphene, which has large surface area, open porous structure, great flexibility, chemical stability, high electrical conductivity and the ability to facilitate electron transport within the active sites and effectively alleviate the strain from the volume expansion. In this paper, the recent advances of Co3O4 and its composites as anode materials of LIBs are reviewed. The researches are classified by the characteristics and morphologies of materials. Their advantages and disadvantages are summarized and the possible reaction mechanisms are explained. In addition, it is also discussed how to improve the electrochemical performance of Co3O4.