Effect of Young's modulus of active materials on ion transport through solid electrolyte in all-solid-state lithium-ion battery

Abstract

An all-solid-state lithium-ion battery with sulfide solid electrolyte is expected to be operated and fabricated under pressure to achieve high ionic conductivity. However, the varying mechanical properties of the constituent materials of composite electrodes generate a non-uniform stress distribution, which affects the ionic conductivity. Moreover, because of the presence of various active materials with different Young's moduli, the correlation between the Young's modulus of the active material and ion-conduction characteristics of a composite electrode is considered. In this study, to elucidate the effect of the Young's modulus of the active material on the ionic conductivity of a composite electrode, electrochemical impedance spectroscopy measurements and finite element method stress simulations based on X-ray computed tomography images are performed for model composite electrodes. The model composite electrodes are fabricated by mixing the solid electrolyte with zirconia or nylon in different volumetric fractions. The experimental results demonstrate that a composite electrode containing an active material with lower Young's modulus exhibits a higher ionic conductivity and lower saturation pressure. The finite element method stress simulation indicates that the change in the ion-conduction characteristics originates from the stress concentration induced by the active material's Young's modulus and volumetric fraction.