Long-Lasting, Reinforced Electrical Networking in High-Loading Li2S Cathode for High-Performance Lithium–Sulfur Batteries

Abstract

Realizing a Li2S cathode having both high energy density and long lifespan requires an innovative cathode design that maximizes electrochemical performance and resists electrode deterioration. Herein, a high-loading Li2S-based cathode that micrometric Li2S particles are composited with two-dimensional graphene (Gr) and one-dimensional carbon nanotubes (CNTs) in the compacted geometry is developed and the role of CNTs for stable cycling of high-capacity Li-S batteries is emphasized. In a dimensionally combined carbon matrix, CNTs embedded within the Gr sheets create robust and sustainable electron diffusion pathways while suppressing the passivation of the active carbon surface. As for a unique point, during the first charging process, the proposed cathode is fully activated through the direct conversion of Li2S to S8 without the extent of incurring lithium polysulfide formation. The direct conversion of Li2S to S8 in the composite cathode is ubiquitously investigated using the combined study of in situ Raman spectroscopy, in situ optical microscopy, and cryogenic transmission electron microscopy. The composite cathode demonstrates unprecedented electrochemical properties even with high Li2S loading of 10 mg cm–2; particularly, the practical and safe Li-S full cell coupled with graphite anode shows ultra-long-term cycling stability over 800 cycles.