Consolidating Lithiothermic-Ready Transition Metals for Li₂ S-Based Cathodes.

Abstract

Li₂ S 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 Li₂ S 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 Li₂ S/transition metal (TM) nanocomposites are synthesized via a lithiothermic reduction reaction, and it is realized that the presence of TMs in Li₂ S matrix can transform electrochemical behaviors of Li₂ S. On the one hand, the incorporation of W, Mo, or Ti greatly increases electronic and ionic conductivity of Li₂ S composites and inhibits the polysulfide dissolution via the TMS bond, effectively addressing the drawbacks of Li₂ S cathodes. In particular, Li₂ S/W and Li₂ S/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 Li₂ S into a prelithiation agent, forming metal sulfides rather than S₈ after the full charge. These interesting findings may shed light on the design of Li₂ S-based cathode materials.