Hierarchical CuFeS2 spheres hybridized with N-doped carbon for efficient anodic lithium storage: Synthetic optimization, electrochemical analysis and in situ XRD characterization

Due to its high availability, low cost, and outstanding electrochemical capabilities, CuFeS2 is a viable electrode material for lithium-ion batteries (LIBs). Its actual application is constrained, nonetheless, by substantial capacity fading and polysulfide production during the electrochemical process. To enhance the electrochemical characteristics and the chemical dissolution stability of the electrolyte, we present an optimal solvothermal synthesis of CuFeS2 with spherical morphology and high phase purify. The subsequent thermal pyrolysis with dopamine hydrochloride forms a uniform coating of N-doped carbon (NC) on the surface of CuFeS2 spheres. The successful NC coating increases the electronic conductivity of CuFeS2 and Li+ ion diffusion kinetics, and thus dramatically improves the rate and cycle performances of the constructed half cells and full LIBs. The ideal CuFeS2@NC with a 10 wt% NC anode demonstrates a reversible capacity of 878.6 mAh·g-1 at a current density of 0.5 C after 300 cycles, which is 93.4% of the initial capacity, and the coulombic efficiency remains above 98%. The fundamental charge and discharge mechanisms of CuFeS2@NC anodes are clarified by in situ electrochemical XRD analysis, and their primary mechanism for storing lithium is the “insertion-conversion” reaction.