Recent advances in Li₂S@C nanocomposites for lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) are considered as promising next-generation energy-storage systems because of their high theoretical energy density, low cost, material abundance, and environmental compatibility. Over the past decade, intensive research has substantially mitigated key sulfur-cathode limitations, including poor electronic/ionic transport, large volume changes, and the polysulfide shuttle, enabling near-commercial performance in selected studies. These advances have been achieved predominantly in elemental sulfur-based LSBs (S-LSBs), but practical deployment remains largely constrained by reliance on lithium-metal anodes. Lithium sulfide (Li₂S)-based LSBs (Li₂S-LSBs) offer an attractive alternative because they can eliminate lithium-metal anodes while retaining the same overall sulfur redox chemistry. However, Li₂S-LSBs face distinct challenges, most notably the moisture sensitivity of Li₂S and the high first-charge activation overpotential, which often reduces accessible capacity and compromises cycling stability. The central barrier is the preparation of well-defined Li₂S@C nanocomposites with Li₂S uniformly embedded within nanoscale porous carbon hosts, a performance-dictating architecture that is readily achieved for S@C via melt infiltration but is difficult for Li₂S because of its high melting point and limited processability. This review summarizes the current state of Li₂S@C synthesis, critically comparing major physical and chemical routes (e.g., ball milling, carbothermal methods, lithiation of S@C, sulfuration strategies, solution infiltration, and precursor infiltration-decomposition), and evaluates their advantages, limitations, and scalability. Emerging developments in Li₂S@C nanocomposites for all-solid-state Li₂S batteries are also discussed, with emphasis on design strategies for addressing sluggish solid-state reaction kinetics. Finally, we outline complementary directions needed to advance Li₂S-LSBs toward practical implementation, including Li₂S-compatible binders and additives that couple shuttle suppression with kinetic promotion, lean-electrolyte cell designs, lithium-free full-cell configurations, and opportunities enabled by integrating Li₂S@C nanocomposites with solid-state electrolytes.