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.