Suppressing Dendrite-Induced Cracking in Solid-State Electrolytes: Pressure Constraints and Mechanical Properties

To address the critical challenge of solid-state electrolyte (SSE) cracking triggered by lithium dendrite penetration in Li-metal solid-state batteries, we develop a coupled electrochemical-mechanical-phase-field cracking (EMPC) model. We systematically reveal the synergistic regulation mechanism of biaxial pressure (stack pressure and lateral pressure) and intrinsic mechanical properties (Young's modulus and fracture toughness) on the failure behavior. Under zero external pressure, lithium dendrites preferentially fill pre-existing cracks, inducing a localized tensile stress concentration and accumulating tensile strain energy density at the crack tip. The crack evolution drives into three stages: filling, synchronous propagation, and asynchronous propagation, ultimately forming dendrite-free "dry cracks" that cause penetration failure. While stack pressure delays cracking initiation, 100 MPa is required for complete suppression. Moreover, an excessively high stack pressure tends to induce short circuits via lithium creep and penetration. In contrast, lateral pressure efficiently dampens the crack-driving force by directionally suppressing tensile strain along the y-axis, achieving complete crack suppression at a mere 15 MPa, demonstrating significant advantages. Fracture toughness analysis confirms that enhancing fracture toughness disrupts the dendrite-crack positive feedback loop. Young's modulus exhibits a nonlinear regulatory effect. SSEs within a high-risk window of 100-120 GPa suffer exacerbated failures due to competing mechanisms: intensified stress concentration versus strain energy accumulation inhibition. A developed pressure-failure coefficient contour map quantifies the synergistic strategy of stack and lateral pressures, enabling concurrent crack suppression and dendrite penetration protection. Furthermore, customized pressure loading strategies are further proposed for SSEs with distinct mechanical properties. This work establishes fundamental insights for developing highly stable solid-state batteries from the dual perspectives of mechanical constraint design and intrinsic material optimization.