Direct Electrophoretic Deposition of Binder-Free Co3O4/Graphene Sandwich-Like Hybrid Electrode as Remarkable Lithium Ion Battery Anode.

Co3O4 is emerging as a promising anode candidate for lithium ion batteries (LIBs) with high theoretical capacity (890 mAh g-1) but suffers from poor electrochemical cycling stability resulting from the inferior intrinsic electronic conductivity and large volume changes during electrochemical cycling. Here, a new electrophoretic deposition Co3O4/graphene (EPD Co3O4/G) hybrid electrode is developed to improve the electrochemical performance. Through EPD, Co3O4 nanocubes can be homogeneously embedded between graphene sheets to form a sandwich-like structure. Owing to the excellent flexibility of graphene and a large number of voids in this sandwich-like structure, the structural integrity and unobstructed conductive network can be maintained during cycling. Moreover, the electrode kinetics has proved to be a fast surface-controlled lithium storage process. As a result, the Co3O4/G hybrid electrode exhibits high specific capacity and excellent electrochemical cycling performance. The Co3O4/G hybrid electrode was also further studied by in situ electrochemical XRD to understand the relationship of its structure and performance: (1) The observed LixCo3O4 indicates an intermediate of possible small volume change in the first discharging. (2) The theoretical capacity achievement of the Co3O4 in hybrid electrode was evidenced. (3) The correlation between the electrochemical performance and the structural evolution of the Co3O4/G hybrid electrode was discussed detailedly.