The most important feature for the batteries used in various measures aimed at achieving carbon neutrality is high reliability. Batteries used in electric vehicles and energy storage from renewables are large-scale, and thus safety issues originating from the flammable organic electrolytes used in lithium-ion batteries become serious. Furthermore, batteries in these applications are required to have durability incomparable to that of consumer applications. Because solid-state batteries do not use flammable electrolytes, battery safety is dramatically enhanced; moreover, since the diffusing species in the solid electrolyte is limited solely to lithium ions, any other species are not transported to the electrode surface to cause side reactions, resulting in a long battery life.
To realize solid-state batteries with these characteristics, not only solid electrolytes with highionic conductivity, but also processing technologies for bonding battery materials at interfaces that do not interfere ionic conduction, as well as the understanding and control of anomalous ionic conduction phenomena at the interfaces, are necessary. We are tackling these challenges together with computational and measurement researchers.