Consolidating Lithiothermic-Ready Transition Metals for Li₂S-Based Cathodes

Li₂S holds a promising role as a high-capacity Li-containing cathode, circumventing use of metallic lithium in constructing next-generation batteries to replace current Li-ion batteries. However, progress of Li₂S cathode has been plagued by its intrinsic drawbacks, including high activation potentials, poor rate performance, and rapid capacity fading during long cycling. Herein, a series of Li₂S/transition metal (TM) nanocomposites are synthesized via a lithiothermic reduction reaction, and it is realized that the presence of TMs in Li₂S matrix can transform electrochemical behaviors of Li₂S. On the one hand, the incorporation of W, Mo, or Ti greatly increases electronic and ionic conductivity of Li₂S composites and inhibits the polysulfide dissolution via the TM-S bond, effectively addressing the drawbacks of Li₂S cathodes. In particular, Li₂S/W and Li₂S/Mo exhibit the highest ionic conductivity of solid-phase Li-ion conductors ever-reported: 5.44 × 10⁻² and 3.62 × 10⁻² S m⁻¹, respectively. On the other hand, integrating Co, Mn, and Zn turns Li₂S into a prelithiation agent, forming metal sulfides rather than S₈ after the full charge. These interesting findings may shed light on the design of Li₂S-based cathode materials.