Space-Confined Synthesis of Yolk–Shell Structured Co₃O₄/Nitrogen-Doped Carbon Nanocomposites with Hollow Mesoporous Carbon Nanocages as Advanced Functional Anodes for Lithium-Ion Batteries

Despite the high theoretical capacity as the anode material of lithium-ion batteries (LIBs), Co3O4 is subjected to rapid capacity decline and poor rate performance owing to its severe volume expansion and poor electronic conductivity. Herein, a yolk–shell structured Co3O4 nanocomposite with double carbon shells (Co3O4@NC@CNC) was fabricated as an electrode material to improve the properties of LIBs. The Co3O4@NC@CNC was derived from ZIF-67 within carbon nanocages (CNC) by carbonization. The hollow CNC acted as nanoreactors, which could effectively control the growth of ZIF-67 within the CNC and reduce the particle size of Co3O4@nitrogen-doped carbon (Co3O4@NC) nanocomposite derived from ZIF-67. When assessed as an LIBs anode material, the optimized Co3O4@NC@CNC material exhibited outstanding properties with high capacity, superior cycling stability, and rate performance (960 mAh g–1 at 0.5 A g–1 and 772 mAh g–1 at 2 A g–1 after 100 cycles). The electrochemical properties were ascribed to the yolk–shell structure and the synergistic effect of the nanoscale Co3O4@NC and CNC, which improved the electronic conductivity, alleviated the volume expansion effect, shortened the diffusion distance of Li+, and accelerated Li+ transport kinetics. Moreover, the large specific surface and mesoporous structure were beneficial to the diffusion of electrolyte as well as capacitive contribution.