N-doped graphitic carbon encapsulated cobalt oxide nanoparticles from ZIF-67 on ZIF-8 as an anode material for Li-ion batteries

Recently, cobalt (II, III) oxide (Co3O4) is considered as an alternative anode material for high-performance LIBs because of its high safety and theoretical capacity (890 mAh g−1). However, Co3O4 anode materials suffer from low conductivity and poor cycle life due to structural strain and huge volume change during lithiation/delithiation processes. In this work, porous N-doped graphitic carbon encapsulated Co3O4 structure (Co3O4 @PNGC) was synthesized by using mixed Zn and Co metal-organic frameworks templates (ZIF-67/ZIF-8) and coated with polydopamine as a nitrogen and carbon source. During the synthesis, Zn species was evaporated to form the structural pores, and the in-situ formation of Co(0) occurred that served as a catalyst in the graphitization of the carbon matrix. The Co3O4/PNGC exhibited an improved discharge capacity of 847.4 mAh g−1 after 500 cycles at 1 C when compared to the bare sample.