PVP-assisted synthesis of shape-controlled CuFeS2 nanocrystals for Li-ion batteries

In this paper, chalcopyrite CuFeS2 with sheet-like or rod-like morphology has been synthesized by solvothermal reaction route in the presence of poly(vinylpyrrolidone) (PVP). The concentration of PVP has significant influences on the morphology of CuFeS2 nanocrystals. With the increasing concentrations of PVP, the sheet morphology of CuFeS2 becomes more uniform. Meanwhile, the average dimensions of CuFeS2 sheets are reduced and small CuFeS2 nanoparticles are clearly decreased. When the molar ratio of CuFeS2 to PVP is 1:2, the shape of CuFeS2 changes to rod-like, which is composed of CuFeS2 sheets. Considering the influence of uniformity and shape of CuFeS2 nanocrystals, the CuFeS2 nanocrystals with different molar ratios of PVP have been used as active component to prepare anode for Li-ion batteries. The Li-ion battery using CuFeS2 nanocrystals with the molar ratio of 1:2 to PVP shows the highest reversible specific capacity of ~519 mAh/g after 50 cycles at a current density of 100 mA/g and maintains a specific capacity of ~400 mAh/g at a density of 1000 mA/g. The results demonstrate that the PVP-assisted CuFeS2 electrodes are promising candidates for use as Li-ion batteries.