Effect of Cu-doping on the electrochemical performance of FeS2

FeS2 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 FeS2 and Ni-doping were adopted to modify the electrochemical properties of FeS2. Nevertheless, these approaches resulted only in limited improvements in the electrochemical properties. Therefore, in this study, we synthesized Cu-doped FeS2 via a solvothermal process, aiming at improved electrochemical properties. Systematic studies indicated that Cu doping changed the morphology of FeS2 from larger irregular particles to smaller spherical ones. The charge–discharge measurements indicated that the Cu-doped FeS2 exhibited two discharge plateaus, at 1.6 V and 1.4 V. The initial specific discharge capacity of Cu-doped FeS2 was about 866 mAh/g at a current density of 90 mA/g, which is approximately 11% higher than that of the undoped FeS2. The initial discharge capacity of the Cu-doped FeS2 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/FeS2 batteries.