Facile synthesis of Li2S–polypyrrole composite structures for high-performance Li2S cathodes

Li2S is an attractive prelithiated cathode material with a high theoretical capacity of 1166 mA h g−1, which is far above that of its transition metal oxide/phosphate counterparts. Here, we demonstrate facile, in situ synthesis of Li2S–polypyrrole composites for use as high-performance Li2S cathodes. The N atoms in polypyrrole were found to possess favorable Li–N interaction with Li2S, which enables polypyrrole to bind strongly onto and cover the surface of Li2S to constrain intermediate polysulfides during cycling. Polypyrrole, being a conducting polymer, also helps to facilitate electronic conduction. Using the Li2S–polypyrrole composites as a cathode material, we demonstrate a high discharge capacity of 785 mA h g−1 of Li2S (∼1126 mA h g−1 of S) with stable cycling over prolonged 400 charge/discharge cycles.