Facile Synthesis of Lithium Sulfide@Carbon Nanocomposite via Precursor Solution Infiltration-Decomposition for High-Performance Lithium Sulfide Batteries

Lithium–sulfur batteries (LSBs) based on lithium sulfide (Li2S), or Li2S-LSBs, are promising candidates for next-generation energy storage due to their high theoretical capacity, lower costs, and environmental benefits compared to lithium-ion batteries. However, synthesizing Li2S-infiltrated mesoporous carbon nanocomposites (Li2S@C) to mitigate the low conductivity of Li2S has been challenging because of its high melting point and poor solubility. To address this, we developed an efficient synthesis method for Li2S@C nanocomposites under mild conditions. Li2S was first reacted with carbon disulfide (CS2) in ethanol at ambient temperature, forming a highly soluble lithium trithiocarbonate (Li2CS3) solution, which was easily infiltrated into mesoporous Super P carbon (SP) to form a Li2CS3@C nanocomposite. Thermal decomposition of Li2CS3 at 400 °C produced Li2S@SP-400 nanocomposites with finely dispersed Li2S particles (∼11 nm) confined within the SP matrix. The Li2S-LSBs exhibited a high discharge capacity of 821 mA h g–1 (Li2S) (equivalent to 1190 mA h g–1 (S) based on sulfur content) and demonstrated superior rate and cycling performance compared to commercial Li2S, noninfiltrated Li2S-400 nanoparticles, and sulfur nanocomposites (S@SP) prepared by melt infiltration. This simple, scalable method offers a promising route for commercializing high-energy-density Li2S-LSBs.