Mechanistic Origins of Structural Failure in Deeply‐Lithiated L i x M o S 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 −1 , 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 (aiMD) 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 aiMD simulations, we find that pre‐lithiated (ground‐state) 1T′‐Li x MoS 2 under the deep lithiation condition x > 1.0 exhibits enhanced structural integrity compared with a randomly‐lithiated (high‐energy) configuration. During aiMD simulation, the 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. By 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 in Li x MoS 2 ≃ 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.