High-pressure in situ X-ray computed tomography and numerical simulation of sulfide solid electrolyte

High-pressure in situ three-dimensional structural measurements using X-ray computed tomography and electrochemical impedance spectroscopy measurement of a sulfide solid electrolyte are conducted to elucidate the influence of the nanoscale structure on its ionic conductivity. Computed tomography image-based three-dimensional numerical simulations are conducted to assess the ion-transportation phenomena. The results show that high-pressure in situ X-ray computed tomography can successfully enable visualization of crushing of the solid electrolyte particles and room-temperature pressure sintering. The ionic conductivity increases with an increase in applied pressure. The densified state achieved by room-temperature pressure sintering is maintained even after the applied pressure is decreased. The experimentally measured impedances are in close agreement with the computed tomography image-based numerical simulation results. This finding suggests that effects of internal stress on the contact resistance between sulfide solid electrolyte particles and their ionic conductivity are negligibly small. Furthermore, at small scale, ion-transportation characteristics can be estimated by the three-dimensional distribution of sulfide solid electrolyte and pores. The experiments and numerical simulations are conducted for various sulfide solid electrolytes, and these characteristics are found to be valid for all tested materials.