Solid electrolytes and solid-state batteries

Solid-state batteries are regarded as reliable battery systems that overcome some issues in current lithium-ion batteries originated from the organic-solvent electrolytes; however, their power densities have not been high enough to practical use. Intensive studies aiming at the improvement of the rate capability have provided solid electrolytes with high ionic conductivities, in which lithium-ion transport properties are comparable or superior to those in the liquid electrolytes. However, there are further resistances still remaining at interfaces, which are rate-determining; high-power solid-state batteries will not be realized without reducing the interfacial resistances. This paper reviews such highly-resistive interfaces in some solid-state systems and some attempts made to reduce the interfacial resistances.