Effect of Cu-doping on the electrochemical performance of FeS2

Abstract FeS 2 reportedly has a high specific capacity of 893 mAh/g; however, its poor cyclic performance limits its commercialization. To circumvent this limitation, strategies such as preparation of high-purity FeS 2 and Ni-doping were adopted to modify the electrochemical properties of FeS 2 . Nevertheless, these approaches resulted only in limited improvements in the electrochemical properties. Therefore, in this study, we synthesized Cu-doped FeS 2 via a solvothermal process, aiming at improved electrochemical properties. Systematic studies indicated that Cu doping changed the morphology of FeS 2 from larger irregular particles to smaller spherical ones. The charge–discharge measurements indicated that the Cu-doped FeS 2 exhibited two discharge plateaus, at 1.6 V and 1.4 V. The initial specific discharge capacity of Cu-doped FeS 2 was about 866 mAh/g at a current density of 90 mA/g, which is approximately 11% higher than that of the undoped FeS 2 . The initial discharge capacity of the Cu-doped FeS 2 at a current density of 2700 mA/g was 518 mAh/g, and its cyclic discharge capacity exceeded 105 mAh/g at the 20th cycle. Cyclic voltammetry and resistance measurements revealed that Cu-doping reduces both the internal resistance and polarization of Li/FeS 2 batteries.