ZIF-67-Derived N-Doped Co/C Nanocubes as High-Performance Anode Materials for Lithium-Ion Batteries

Co nanoparticles embedded in nitrogen-doped carbon nanocubes (Co/NCs) for applications as anode materials in rechargeable lithium-ion batteries were synthesized by calcining Co-based metal-organic framework. Sizes of Co nanoparticles were ∼15 nm according to X-ray diffraction (XRD) and transmission electron microscopy. Electrochemical performances of the as-prepared anode nanocube composite at 700 °C showed a high initial capacity of 1375.1 mAh g^-1 in the voltage range of 0.01-3.0 V at the current rate of 0.1 A g^-1. After 100 cycles, capacity remained at 688.6 mAh g^-1. Thereinto, the role of Co nanoparticles in electrochemical reaction was also elucidated by in situ XRD experiment. Capacity increase of Co/NCs at the high currents was observed, which are potentially caused by the activation of electrode and pseudocapacitance during cycling. High surface area and abundant mesopores contributed to the improved electrochemical performances of the anode, providing numerous pathways and sites for Li⁺ transfer and storage and accordingly contributing to pseudocapacitance capacity.