Synthesis of a Novel Cobalt Selenide/Carbon Composites with Polyacrylonitrile Coating and Application in Li-Ion Battery

Cobalt selenide is an ideal anode material for lithium-ion batteries because of its good lithium-ion insertion or extraction capability. However, the battery performance of cobalt selenide is limited by the large volumetric expansion upon cycling and its insulating nature. In this study, we produced CoSe₂-C/c-PAN by coating CoSe₂-C polyhedrons with polyacrylonitrile (PAN) in N₂ atmosphere. The CoSe₂-C polyhedrons were successfully synthesized using Co-based zeolitic imidazolate framework (ZIF-67) as precursor through a two-step method, which includes carbonization of ZIF-67 and a subsequent selenization. The resultant CoSe₂-C/c-PAN showed high specific capacity and excellent cycling stability with an initial discharge capacity of 1 440 mA·h/g at 0.2 A/g and a reversible capacity of 653 mA·h/g at 1.0 A/g after 200 cycles as anode material of Li-ion battery. The excellent battery performance of CoSe₂-C/c-PAN could be attributed to the synergistic effect of nanostructured CoSe₂ and carbon materials, in which the nanostructured CoSe₂ possesses high reactivity towards lithium-ions and the carbon can provide a continuous conductive matrix to facilitate the charge transfer and an effective buffering to mitigate the structural variation of CoSe₂ during cycling. The significantly enhanced electrochemical performance of the composite could be ascribed to the improved electrical conductivity and structural stability of c-PAN.