Multilevel Coupled Hybrids Made of Porous Cobalt Oxides and Graphene for High-Performance Lithium Storage

Metal oxide coupling with carbon materials holds great promise for lithium storage. Herein, multilevel coupled cobalt oxide–graphene (CoO/CO ₃ O ₄ –G) hybrids were fabricated by in situ assembly of Co hydroxide precursors and a calcination process. The oxygen-containing functional groups on the graphene surface act as bridging sites and tend to bond with Co ²⁺ ions, effectively modifying the morphology and structure of the Co species. The as-obtained CoO/CO ₃ O ₄ –G hybrids are composed of unique CoO/CO ₃ O ₄ porous nanoparticles uniformly anchored on graphene sheets, as confirmed by a series of characterization analyses. Benefiting from these structural characteristics, the CoO/CO ₃ O ₄ –G hybrids used as an anode can deliver a high capacity of about 1080 mA h g ⁻¹ reversibly at 0.1 Ag ⁻¹ in the voltage range between 3.0 and 0.01 V, which is remarkably superior to that of the CoO hexagonal sheets in the absence of graphene. The high reversible capacity of the CoO/CO ₃ O ₄ –G hybrids is retained at elevated current densities, for example, a capacity of approximately 455 mA h g ⁻¹ can be achieved at a current rate as high as 4 A g ⁻¹ , indicative of its potential for high-performance lithium-ion batteries.