Activation of Li2S Cathode by an Organoselenide Salt Mediator for All‐Solid‐State Lithium–Sulfur Batteries

Abstract

AbstractLithium sulfide (Li2S) is a promising electrode material with high specific capacity and can be paired with commercial anode materials such as graphite. However, bulk Li2S requires a high activation energy during the initial charge due to its inert electrochemical activity, resulting in high charge overpotential. Here, lithium phenyl selenide (PhSeLi) is proposed as a mediator that can effectively activate Li2S by altering the oxidation pathway in the initial charge process. It enables Li2S to release normal capacity over the general voltage range (1.5–3 V). The composite cathode with the Li2S:PhSeLi molar ratio of 4:1 exhibits a high reversible capacity of 615.9 mAh g−1 at 0.2 A g−1 after 400 cycles in all‐solid‐state batteries with Li7P3S11 sulfide electrolyte and In–Li anode (the corresponding capacity based on Li2S is 1016.6 mAh g−1). In a full cell with a partially pre‐lithiated silicon anode, it can still provide an average discharge capacity of 524 mAh g−1 at 0.1 A g−1 (the capacity based on Li2S is 844.2 mAh g−1). This work will contribute to the further development of Li2S‐based all‐solid‐state Li–S batteries.