Effect of Polyaniline on Sulfur/Sepiolite Composite Cathode for Lithium-Sulfur Batteries

Composite materials with a stable network structure consisting of natural sepiolite (Sp) powders (both sieved sepiolite and post-treated sepiolite), sulfur(S), and conductive polymer Polyaniline (PAni) have been successfully synthesized using a simple heat treatment. The morphology of composites illustrates that the sepiolite is composed of many needle-like fibrous clusters. The initial discharge capacity of the post-treated sepiolite/sulfur/PAni composite is about 1230 mA h g(−1) at 0.1 C, and it remains at 826 mA h g(−1) even after 40 cycles with the corresponding coulombic efficiency above 97%. Such performance is attributed to the specific porous structure, outstanding adsorption characteristics, and excellent ion exchange capability of sepiolite, as well as the excellent conductivity of PAni. In addition, the PAni coating has a pinning effect on sulfur, which influences the consumption of the active mass and enhances the cycling constancy and the coulombic efficiency of the composite material at elevated current rates.