Stress distribution in the composite electrodes of sulfide all-solid-state lithium-ion batteries

Pressurization of all-solid-state lithium-ion batteries is expected to increase the efficiency of ion transport between solid electrolyte particles. Here, we show the practicality of considering internal stress distribution to explain the ion transport behavior inside a composite electrode containing a sulfide solid electrolyte. Considering internal stress distribution allows for an accurate evaluation in microscale, and phenomenon stemming from nanoscale features is explained. To independently analyze the effect of ohmic overpotential on ion transport, undesired electrochemical reactions are eliminated by replacing active materials in a composite electrode by zirconia. The ionic conductivity of the zirconia composite at different pressures is measured and its three-dimensional structure is visualized by X-ray computed tomography. Graphics processing unit-based large-scale voxel finite element method stress analysis and an electric field numerical calculation are conducted to analyze the effect of stress distribution on the ion transport characteristics of the composite electrode. Experimentally, the ionic conductivity of the zirconia composite decreases drastically as the volume fraction of zirconia increases. The degree to which the ionic conductivity decreases exceeds that expected when considering the volume fraction and tortuosity of zirconia. When stress distribution is also considered, the discrepancy between experimental and numerical results decreases greatly.