Polymer Interface Enables Reversible Quasi-Solid Sulfur Conversion in Sodium-Sulfur Batteries

Abstract

Room-temperature sodium–sulfur (Na─S) batteries are appealing candidates for large-scale energy storage owing to their high theoretical capacity and the use of earth-abundant, low-cost active materials. The quasi-solid conversion in Na─S batteries was proposed as a promising mechanism, lying between solid-liquid-solid and solid-solid mechanisms, with suppressed polysulfide dissolution while retaining faster kinetics, enabling stable, high-performance Na─S batteries. To realize the quasi-solid conversions, the rational design of the cathode-electrolyte interphase is the key; however, the study is at an early stage. Herein, a multifunctional cross-linked polymer (MCP) is first introduced as an artificial interface for the quasi-solid sulfur conversions in Na-S batteries with enhanced stability, faster kinetics, mechanical robustness, and improved chemical confinement. The MCP interfaces demonstrate significantly improved electrochemical performances for various nanocarbon hosts with a one-step quasi-solid sulfur reversible conversion mechanism, even under high sulfur loading. Our study offers new insights and design guidelines for artificial interfaces enabling quasi-solid conversion in Na─S batteries.