Reversible Li-ion trade-off in ultrathick sulfur cathodes for practical lean Li–S batteries

Abstract

The use of low electrolyte volume is beneficial to improve energy density but severely limits access over obscured sulfur, along with sluggish ion kinetics and aggravated polarization, as the ion imbalance across the multicomponent interface of thick sulfur cathodes at a lean electrolyte viciously dominates the sulfur electrokinetics. Herein, we demonstrate that an ion imbalance at the interfaces of a thick electrode with a lean electrolyte can be compensated by the ion trade-off strategy utilizing a cationic ion conductive active binder. It ensures sustained lithium-ion donation/release over the vicinity of slow electrolyte percolation to realize an ion-enriched sulfur–binder–electrolyte interface. The in-situ evolved ionic interface essentially activates the inaccessible sulfur, bringing about additional capacity and low ion and charge transfer resistances. The active binder adopts sulfur cathodes housing 8.1 mg cm^–2 with an E/S ratio of 6 µL mg^–1 electrochemically utilized 60.89 % sulfur, corresponding to a 1020 mAh g^–1 capacity. The lean Li–S pouch cell delivers an energy density of 324 Wh kg^–1, demonstrating the efficacy of ion trade-off to ease the interfacial barrier. This study would open up a new paradigm in potentially designing thick electrodes for multiple high energy density batteries.