Spatial and Kinetic Regulation of Sulfur Electrochemistry on Semi‐Immobilized Redox Mediators in Working Batteries

Abstract Use of redox mediators (RMs) is an effective strategy to enhance reaction kinetics of multi‐electron sulfur electrochemistry. However, the soluble small‐molecule RMs usually aggravate the internal shuttle and thus further reduce the battery efficiency and cyclability. A semi‐immobilization strategy is now proposed for RM design to effectively regulate the sulfur electrochemistry while circumvent the inherent shuttle issue in a working battery. Small imide molecules as the model RMs were co‐polymerized with moderate‐chained polyether, rendering a semi‐immobilized RM (PIPE) that is spatially restrained yet kinetically active. A small amount of PIPE (5 % in cathode) extended the cyclability of sulfur cathode from 37 to 190 cycles with 80 % capacity retention at 0.5 C. The semi‐immobilization strategy helps to understand RM‐assisted sulfur electrochemistry in alkali metal batteries and enlightens the chemical design of active additives for advanced electrochemical energy storage devices.