Preparation of FeS2/CNT/S composite and application as the cathode material of lithium-sulfur batteries

Abstract

Metal sulfide pyrite (FeS₂) has received much attention in energy storage because of its structural diversity, abundant resources, and low cost. However, the volume expansion and poor electrical conductivity during the cycle are the main reasons for the low specific capacity. Therefore, in this study, carbon nanotubes (CNT) are introduced into FeS₂ by the organic solvothermal method to prepare FeS₂/CNT composite as the S carrier material. The FeS₂ nanoparticle ball serves as a “connecting unit” that forms a three-dimensional (3D) interconnected conductive network structure by connecting with CNT. Adding CNT can effectively change the problem of insufficient conductivity of FeS₂ to sulfur electrode, providing a large specific surface area and abundant reaction sites, which promotes the electrode reaction transformation. In addition, the porous structure of the FeS₂/CNT composite ensures the electrode’s structural integrity during the reaction process and effectively avoids volume expansion. As a result, the discharge specific capacity of FeS₂/CNT/S reaches 1352.4 mAh·g⁻¹ at 0.1C. And after 200 cycles at 0.5C, the capacity retention is 75.9%, and the capacity decay rate is only 0.12% per cycle. This work provides a new way to develop highly efficient cathode composites.