Origin of charge storage in cobalt oxide - Anchored graphene nanocomposites

Prospects of transition metal oxide (TMO) anodes in practical Li-ion batteries are limited despite their high capacity, owing to conversion reaction-driven inefficiencies and poor cycle life. Size confinement of TMOs and compositing them with carbon architectures is an established approach to realize high-performance electrodes. Here, we report cobalt oxide nanoparticles anchored on graphene (CoG) nanocomposite for Li-ion batteries; the anode exhibits a reversible capacity of 1270 mA h g−1 at 2 C rate and delivers 770 mA h g−1 even at a high rate of 50 C (44.5 Ag-1) of which >99% is retained at the end of 1000 cycles. Although many papers have reported exorbitant high capacity and rate performance for graphene-3d metal oxide composites, the nature of charge storage in these nanocomposites remains unidentified particularly in the voltage region of conversion reaction. By using cobalt oxide-anchored graphene as a model system, we reveal that the charge storage is a collective response from conversion/intercalation and pseudocapacitive processes. In addition, the CoG composite anode reported here provides excellent chemical stability and high durability as witnessed in terms of high capacity, impressive rate performance, and long cycle life. This study illustrates the benefits of nanoarchitecturing toward designing high-performance electrodes.

Graphical abstractThe origin of charge storage in Co3O4-graphene nanocomposite is uncovered: the superior electrochemical performance of the nanocomposite is a combined response of diffusion controlled conversion and non-diffusion controlled pseudocapacitive processes.Download high-res image (258KB)Download full-size image