Electrochemical mechanism for FeS₂/C composite in lithium ion batteries with enhanced reversible capacity

Abstract

Nanoscale FeS2 was synthesized via a simple hydrothermal method and was decorated by hydrothermal carbonization (FeS2@C). The structural properties of the synthesized materials detected by X-ray diffraction (XRD), together with the morphologies characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that the hydrothermal carbonization only had an impact on the morphology of pyrite. Additionally, the electrochemical performance of the coated pyrite in Li/FeS2 batteries was evaluated by galvanostatic discharge-charge tests and electrochemical impedance spectroscopy (EIS). The results showed that the initial capacity of FeS2@C was 799.2 mAh·g−1 (90% of theoretical capacity of FeS2) and that of uncoated FeS2 was only 574.6 mAh·g−1. XRD and ultraviolet (UV) visible spectroscopy results at different depths of discharge-charge for FeS2 were discussed to clarify the electrochemical mechanism, which play an important part in Li/FeS2 batteries.