The safety concerns originating from the use of flammable organic liquid electrolytes have impeded widespread of conventional Li-ion batteries for the large-scale energy storage applications such as battery-driven electric vehicles and energy storage systems. In this regard, solidifying electrolytes with inorganic superionic conductors is considered as an ideal solution. Among various inorganic solid electrolyte (SE) candidates, sulfide materials are suitable to achieve high performance for all-solid-state batteries as the conductivities for the-state-of-the-art sulfide materials (e.g., Li9.54Si1.74P1.44S11.7Cl0.3: 25 mS cm-1) are comparable to that for liquid electrolytes and the sulfide materials are soft. The softness of sulfide materials allows surface contacts with active materials by simple pressing procedure at room temperature, avoiding deteriorating high-temperature sintering process which is the critical limitation for oxide SE materials.
Despite the extensive progresses in the SE materials, the test protocols for all-solid-state batteries are poorly developed. In most previous literatures, the performances of working electrodes for all-solid-state batteries have been assessed by using In or Li-In as reference and counter electrodes without any verification. Moreover, analysis of all-solid-state full-cells, which is crucial for practical applications, has been unprecedented so far. In this regard, development of all-solid-state three-electrode cells is of prime importance. Unfortunately, the unique fabrication protocol of all-solid-state batteries make the development of all-solid-state three-electrode cells extremely challenging.
In this presentation, our recent results on development of the first all-solid-state three-electrode cells and its application to diagnoses on failure modes of several battery systems.
 Y. S. Jung, D. Y. Oh, Y. J. Nam, K. H. Park, Israel J. Chem. 55 (2015) 472-485.