Facilitating Polysulfide Conversion Kinetics via Multifunctional Solid-State Electrolytes under Lean Electrolyte Conditions for Lithium-Sulfur Batteries

Abstract

The sluggish redox kinetics of polysulfides under lean electrolyte conditions hinder practical applications of lithium-sulfur batteries. Herein, a polar solid-state electrolyte, Li10GeP2S12 (LGPS) whose ionic conductivity is higher than that of highly concentrated polysulfide electrolytes (or catholytes), could greatly alleviate the problem by providing pathways for lithium ions and attracting polysulfides to facilitate the conversion reactions. The affinity of polysulfides to LGPS and the catalytic effect enhancing kinetics were confirmed by density functional theory calculations and experimental results mainly from cyclic voltammetry and potentiostatic discharge. The LGPS inclusion in the cathode has significantly improved the performances of the cells showing a high areal capacity of 6.13 mAh cm-2 with an outstanding retention (70% at the 135th cycle) despite the extremely low electrolyte-to-sulfur ratio (E/S ratio of 2.9 µl mg-1), a high sulfur loading of 8.1 mg cm-2, and a low ratio of anode to cathode capacity (N/P ratio of 2). Further research and development could pave the way for practical and efficient energy storage solutions using multifunctional solid-state electrolyte approaches.