Hydrothermal-template synthesis and electrochemical properties of Co 3 O 4 /nitrogen-doped hemisphere-porous graphene composites with 3D heterogeneous structure.

Despite the high capacity of Co 3 O 4 employed in lithium-ion battery anodes, the reduced conductivity and grievous volume change of Co 3 O 4 during long cycling of insertion/extraction of lithium-ions remain a challenge. Herein, an optimized nanocomposite, Co 3 O 4 /nitrogen-doped hemisphere-porous graphene composite (Co 3 O 4 /N-HPGC), is synthesized by a facile hydrothermal-template approach with polystyrene (PS) microspheres as a template. The characterization results demonstrate that Co 3 O 4 nanoparticles are densely anchored onto graphene layers, nitrogen elements are successfully introduced by carbamide and the nanocomposites maintain the hemispherical porous structure. As an anode material for lithium-ion batteries, the composite material not only maintains a relatively high lithium storage capacity (the first discharge specific capacity can reach 2696 mA h g -1 ), but also shows significantly improved rate performance (1188 mA h g -1 at 0.1 A g -1 , 344 mA h g -1 at 5 A g -1 ) and enhanced cycling stability (683 mA h g -1 after 500 cycles at 1 A g -1 ). The enhanced electrochemical properties of Co 3 O 4 /N-HPGC nanocomposites can be ascribed to the synergistic effects of Co 3 O 4 nanoparticles, novel hierarchical structure with hemisphere-pores and nitrogen-containing functional groups of the nanomaterials. Therefore, the developed strategy can be extended as a universal and scalable approach for integrating various metal oxides into graphene-based materials for energy storage and conversion applications.