Sulfur/polythiophene with a core/shell structure: Synthesis and electrochemical properties of the cathode for rechargeable lithium batteries

Novel sulfur/polythiophene composites with core/shell structure composites were synthesized via an in situ chemical oxidative polymerization method with chloroform as a solvent, thiophene as a reagent, and iron chloride as an oxidant at 0 °C. Different ratios of the sulfur/polythiophene composites were characterized by elemental analysis, FTIR, XRD, SEM, TEM, and electrochemical methods. A suitable ratio for the composites was found to be 71.9% sulfur and 18.1% polythiophene as determined by CV and EIS results. Conductive polythiophene acts as a conducting additive and a porous adsorbing agent. It was uniformly coated onto the surface of the sulfur powder to form a core/shell structure, which effectively enhances the electrochemical performance and cycle life of the sulfur cells. The initial discharge capacity of the active material was 1119.3 mA h g^-1, sulfur and the remaining capacity was 830.2 mA h g^-1 sulfur after 80 cycles. After a rate test from 100 to 1600 mA g^-1 sulfur, the cell remained at 811 mA h g^-1 sulfur after 60 cycles when the current density returned to 100 mA g^-1 sulfur. The sulfur utilization, the cycle life, and the rate performance of the S-PTh core/shell electrode in a lithium-sulfur battery improved significantly compared to that of the pure sulfur electrode. The pore and thickness of the shell affected the battery performance of the lithium ion diffusion channels.