Operando Observation of Inter-Particle Li⁺ Transport in Layered Bimetallic Sulfides for High-Rate Lithium-Sulfur Batteries.

Abstract

The slow reaction kinetics, particularly at high rates, hinder the practical use of lithium-sulfur batteries (LSBs). To overcome the inadequate ion transport in conventional electrodes, a two-dimensional layered bimetallic sulfide (FeMo₂S₄) as a sulfur host, creating fast ion-conduction pathways is developed. Using a free-standing FeMo₂S₄/carbon cloth cathode with a Li₂S₆ catholyte, high-rate performance is achieved. Crucially, in situ high-resolution TEM directly visualized rapid inter-particle lithium ion transport between the layered FeMo₂S₄ flakes, offering direct evidence of enhanced kinetics. This phenomenon, combined with strong polysulfide adsorption and high catalytic activity, boosts reaction rates. The Li₂S₆-based battery delivered a high initial capacity of 1516 mAh g^- ¹ and outstanding stability with only 0.028% decay per cycle at 3C. This work highlights the effectiveness of layered hosts with fast ion channels and bimetallic catalysis for durable, high-rate LSBs.