Mechanical regulation of lithium intrusion probability in garnet solid electrolytes

Abstract

Solid electrolytes in rechargeable lithium-metal batteries are susceptible to lithium-metal short circuiting during plating, and the root cause is under debate. In this work, we investigated statistically the effect of locally and globally applied stress on lithium penetration initiation in Li6.6La3Ta0.4Zr1.6O12 (LLZO) via operando microprobe scanning electron microscopy. Statistical analysis revealed that the cumulative probability of intrusion as a function of lithium-metal diameter follows a Weibull distribution. Upon increasing the microprobe–LLZO contact force, the characteristic failure diameter of lithium metal decreases significantly. In addition, we control the direction of intrusion propagation by applying a 0.070% compressive strain via operando cantilever beam-bending experiments. Overall, we find that the root cause of lithium intrusion into the electrolyte is a combination of current focusing and the presence of nanoscale cracks, rather than electronic leakage or electrochemical reduction. These insights highlight the mechanical tunability of electrochemical plating reactions in brittle solid electrolytes.