Cobalt Carbonate/ and Cobalt Oxide/Graphene Aerogel Composite Anodes for High Performance Li-Ion Batteries

Nanocomposites consisting of ultrafine, cobalt carbonate nanoneedles and 3D porous graphene aerogel (CoCO3/GA) are in situ synthesized based on a one-step hydrothermal route followed by freeze-drying. A further heat treatment produces cobalt oxide nanoparticles embedded in the conductive GA matrix (Co3O4/GA). Both the composite anodes deliver excellent specific capacities depending on current density employed: the CoCO3/GA anode outperforms the Co3O4/GA anode at low current densities, and vice versa at current densities higher than 500 mA g–1. Their electrochemical performances are considered among the best of similar composite anodes consisting of CoCO3 or Co3O4 active particles embedded in a graphene substrate. The stable multistep electrochemical reactions of the carbonate compound with a unique nanoneedle structure contribute to the excellent cyclic stability of the CoCO3/GA electrode, whereas the highly conductive networks along with low charge transfer resistance are responsible for the high rate performance of the Co3O4/GA electrode.