In situ synthesis of hierarchical CoFe2O4 nanoclusters/graphene aerogels and their high performance for lithium-ion batteries.

In this article, we demonstrate a simple solvothermal method towards in situ growth of hierarchical CoFe2O4 nanoclusters on graphene aerogels (GAs). SEM and TEM results confirm that CoFe2O4 nanoclusters are well wrapped by the graphene skeleton. As an anode material for lithium-ion batteries, the CoFe2O4/GAs composite displays a stable cycling performance with a reversible capacity of over 100 discharge/charge cycles at the current density of 0.1 A g(-1), considerably higher than that of CoFe2O4 nanoclusters. Moreover, the reversible capacity of the CoFe2O4/GAs composite exhibits 966 mA h g(-1) after 300 cycles even at a high current density of 0.5 A g(-1). Most important of all, a new CoFe2O4/GAs//LiCoO2 full cell was successfully assembled, and this exhibited excellent electrochemical performance. The superior electrochemical performance of the CoFe2O4/GAs composite in half and full cells can be attributed to the synergistic interaction between the uniform CoFe2O4 nanoclusters and GAs, the high electrical conductivity, and the three-dimensional hierarchically porous structure, which can not only facilitate the diffusion of Li ions and electrolyte into the electrodes, but also prevent volume expansion/contraction upon prolonged discharge/charge cycling.