A novel sulfurized polypyrrole composite for high-performance lithium-sulfur batteries based on solid-phase conversion

Sulfur polymers achieve a favorable stabilization of short-chain sulfurs for solid-phase conversion, but still suffer from the sluggish kinetics and ambiguous structural mechanisms. Herein, a typical conductive dopant polypyrrole (PPy) with ordered chain structure and exceptional electrical conductivity is novelly proposed to covalently bond short sulfur chains after the sulfurization at above 300 °C. Upon temperature regulation, the sulfurized polypyrrole (SPPy320V) cathode exhibits superior cycling stability at various current densities with decent reversible capacities. Even at a high rate of 2 C, an initial capacity of 803 mAh g−1 and a decay of as low as 0.022% per cycle during 700 cycles are presented. Theoretically, the existing form of sulfur chains and molecular structure are rationally proposed according to spectroscopy measurements and DFT calculations, as well as the semi-situ detections reveal the conversion mechanism of sulfur species. This systematic study provides an effective guide to the subsequent development of cathodic structure for Li-S batteries based on solid-phase conversion.