Co₉S₈ Nanorods as an Electrocatalyst To Enhance Polysulfide Conversion and Alleviate Passivation in Li–S Batteries under Lean Electrolyte Conditions

As a result of the high theoretical energy density of lithium–sulfur (Li–S) batteries, they have been accepted as the next-generation energy storage system. Nevertheless, the current performance of Li–S batteries is still unsatisfactory under lean electrolyte conditions. It is because of sluggish deposition of Li2S2/Li2S passivating the sulfur/electrolyte interface, thus leading to lower sulfur use and bad rate performances of Li–S batteries. Herein, a novel Co9S8 nanorod-based catalytic interlayer placed between the cathode and separator is proposed. The interlayer possesses a three-dimensional open structure, which facilitates electrolyte infiltration but without trapping too much electrolyte. As a result, the electrocatalytic Co9S8 nanorods within the interlayer promote faster electrochemical kinetics and enhance the conversion of polysulfides, thus resulting in a higher specific discharge capacity and better rate and cycling performance. This work proves a feasible method in developing practical Li–S batteries.