Multicycle Precursor Infiltration-Thermal Decomposition Achieves High In-Pore Li ₂ S Loading in Mesoporous Carbon for High-Performance Lithium Sulfide Batteries

Lithium sulfide (Li2S) is an attractive high-capacity cathode material for lithium–sulfur batteries (LSBs) that enables lithium-anode-free designs with improved safety and simpler manufacturing. However, conventional fabrication methods often yield poor Li2S confinement in mesoporous carbon host, restricting electrochemical performance. Here, we present a facile multicycle precursor infiltration-decomposition strategy to synthesize Li2S@C nanocomposites with high in-pore Li2S loading. Using mesoporous Super P (SP) as the conductive host and lithium trithiocarbonate (Li2CS3) as the precursor, sequential infiltration-decomposition cycles progressively increased the pore filling factor (FF) and in-pore Li2S loading (IPL), from FF = 38% and IPL = 30% for Li2S@SP-1 (one cycle) to FF = 91% and IPL = 73% for Li2S@SP-5 (five cycles), while maintaining a total Li2S loading of 70 wt %. Structural analyses of Li2S@SP-5 by XRD and SEM confirmed reduced crystallite size, suppressed external deposition, and more uniform Li2S distribution, contributing to significantly enhanced battery performance relative to Li2S@SP-1. Compared to a sulfur-based S@SP counterpart, Li2S@SP-5 showed superior performance due to the intrinsic volume contraction of Li2S upon charging, which confined sulfur species within the pores and mitigated shuttle effects. Furthermore, full cells paired with Si/C anodes achieved high reversible capacities, demonstrating the viability of lithium-anode-free configurations. This work establishes multicycle infiltration-decomposition as a broadly applicable and scalable strategy to achieve high in-pore Li2S loading, offering a promising pathway toward practical, high-energy-density Li2S-based batteries.