Effect of Particle Size and Pressure on the Transport Properties of the Fast Ion Conductor t-Li_7SiPS_8

摘要

All-solid-state batteries promise higher energy and power densities as well asincreased safety compared to lithium-ion batteries by using non-flammablesolid electrolytes and metallic lithium as the anode. Ensuring permanentand close contact between the components and individual particles iscrucial for long-term operation of a solid-state cell. This study investigatesthe particle size dependent compression mechanics and ionic conductivityof the mechanically soft thiophosphate solid electrolyte tetragonal Li_7SiPS_8(t-LiSiPS) under pressure. The effect of stack and pelletizing pressure is demonstratedas a powerful tool to influence the microstructure and, hence, ionicconductivity of t-LiSiPS. Heckel analysis for granular powder compressionreveals distinct pressure regimes, which differently impact the Li ion conductivity.The pelletizing process is simulated using the discrete element methodfollowed by finite volume analysis to disentangle the effects of pressuredependentmicrostructure evolution from atomistic activation volume effects.Furthermore, it is found that the relative density of a tablet is a weakerdescriptor for the sample’s impedance compared to the particle size distribution.The multiscale experimental and theoretical study thus captures bothatomistic and microstructural effects of pressure on the ionic conductivity,thus emphasizing the importance of microstructure, particle size distributionand pressure control in solid electrolytes.