Chemo-Mechanical Failure Mechanisms in Solid-State Li-S Batteries: Stress Evolution, Fracture Toughness, and Mitigation Strategies

The transition from liquid-electrolyte lithium-sulfur (Li-S) systems to solid-state Li-S (SS-Li-S) architectures represents a pivotal advancement in the pursuit of high-energy-density storage, offering theoretical specific energies exceeding ۲۶۰۰ Wh kg⁻¹. However, the practical realization of these systems is fundamentally impeded by severe chemo-mechanical incompatibilities between the active sulfur cathode and the rigid solid electrolyte (SE). This critical review delineates the mechanical degradation mechanisms driven by the drastic volumetric oscillation of sulfur (~۸۰%) expansion upon lithiation to Li۲S and the consequent stress fields that propagate through brittle ceramic interfaces. We structure the analysis into two distinct chronological phases: Phase ۱ (۲۰۱۰-۲۰۲۱), which established the foundational understanding of stress accumulation, interface delamination (breathing fatigue), and catastrophic fracture modes in oxide (LLZO, LATP) and sulfide electrolytes; and Phase ۲ (۲۰۲۲-۲۰۲۶), characterized by the emergence of advanced toughening strategies, including soft polymer buffers, ۳D porous scaffolds, and self-healing molecular crystals. Central to this discourse is the application of Griffith fracture theory to solid electrolytes, where low fracture toughness (Kic < ۱ Mpa m¹/²) renders materials susceptible to dendrite-induced transgranular and intergranular cracking. Furthermore, we evaluate advanced characterization techniques—specifically Acoustic Emission (AE) and in-situ Transmission Electron Microscopy (TEM)—for their utility in distinguishing mechanical fracture from electrochemical noise. The report concludes with a synthesis of recent Finite Element Method (FEM) studies and proposes that the future of SS-Li-S lies in functionally graded, chemo-mechanically compliant interfaces that decouple ionic transport from mechanical stress.

کلیدواژه ها:

Solid-State Li-S Batteries ، Chemo-Mechanical Failure ، Fracture Toughness ، Volume Expansion ، Stress Mitigation