Mechanistic Origins of Structural Failure in Deeply Lithiated Li x MoS 2

MoS 2 is a promising high capacity anode for Li-ion batteries due to its layered structure and theoretical capacity of ~670 mAh/g, but its practical performance is limited by structural degradation under deep lithiation. Here, we employ a combination of global optimization and ab initio molecular dynamics ( ai MD) to investigate the phase stability and structural failure mechanisms of Li-intercalated MoS 2 over a wide range of Li concentrations. Our results reveal that upon lithiation, MoS 2 undergoes a phase transformation from the 2H phase to a distorted 1T’ phase, with 1T’ Li x MoS 2 emerging as the most stable polymorph for x > 0.4. We further clarify how the initial Li distribution affects phase stability and structural fracture behavior. Through ai MD simulations, we find that pre-lithiated 1T’-Li x MoS 2 under the deep lithiation condition x > 1.0, exhibits enhanced structural integrity compared to a randomly lithiated (high energy) configuration. During ai MD simulation, our pre-lithiated Li x MoS 2 preserves the layered S-Mo-S framework up to higher Li concentrations (x ≈ 1.5), showing almost no S dislodgement while opening out-of-plane Li-ion diffusion channels via localized Mo-S bond cleavage. In contrast, dynamically-lithiated structures suffer from Mo-S bond breaking, early S dislodgement, and Li x S y cluster formation at the interfaces (notably around x ≈ 1.25). These findings suggest that controlling the initial Li intercalation geometry can significantly mitigate mechanical degradation in MoS 2 anodes, offering design guidelines for next-generation high-performance anodes with improved cycling stability and rate capability.