Stack pressure dependence on the three-dimensional structure of a composite electrode in an all-solid-state battery

An all-solid-state battery in which the organic liquid electrolyte of a lithium-ion battery (LIB) is replaced with an inorganic solid electrolyte is a candidate for next-generation rechargeable batteries. Although the solid electrolyte has high conductivity, the charge and discharge characteristics are inferior to those of conventional LIBs. To achieve the high performance of all-solid-state batteries, it is necessary to grasp the phenomena peculiar to the composite electrode that uses the solid electrolyte. This study analyses the three-dimensional structure of the composite electrode in an all-solid-state battery using a laboratory-built cell capable of performing electrochemical and X-ray computed tomography (CT) measurements while monitoring stack pressures. The dependencies of stack pressure on the porosity, contact area, and tortuosity of the composite electrodes are quantitatively analysed to evaluate their effects on the electrochemical properties. The CT observation reveals that there is insufficient contact between the active material and the solid electrolyte in a plane perpendicular to the pressure direction. The contact interface is found to be a key parameter for the charge/discharge characteristics.