Thermo-mechanical stress analysis and critical condition estimation in lithium lanthanum niobate (LiLaNbO) thin electrolyte plate of all-solid-state battery

Abstract

This study analyzes the thermo-mechanical stress fields within a LiLaNbO electrolyte in all-solid-state batteries, considering various temperature gradients, boundary conditions, and material properties. Using advanced plate theory, an infinitesimally thin electrolyte plate integrated into a planar battery system was modeled. The stress distributions were computed analytically and verified with simulations using ANSYS Workbench under four distinct boundary conditions: FR (Free to expand and bend), NB (No bending, free to expand), NE (No expansion, free to bend), and NBE (No bending or expansion). For uniform temperature conditions (T1 = T2 = 350 K), compressive stresses of up to 70 MPa were observed for NBE, while FR and NB conditions yielded negligible stresses. Under temperature gradients (e.g., T1 = 300 K, T2 = 250 K to 350 K), stress profiles varied linearly along the z-axis for theoretical predictions, while simulated results showed slight deviations, with maximum stresses of approximately -60 MPa. Material properties such as Young's modulus (97–106 GPa) and thermal expansion coefficients (6 × 10⁻⁶ K⁻¹) were considered temperature-dependent, revealing their limited impact on stress distributions within 200–400 K. A novel estimation method for identifying critical operational conditions is proposed, ensuring mechanical stability by limiting stress to below 150 MPa. The findings provide actionable insights for enhancing the safety and reliability of all-solid-state batteries.