Invited: Solid-State Lithium Thin-Film Batteries Capable of Fast Charging

Solid-state Li batteries are promising energy storage devices owing to their high-energy densities with improved safety. However, the large resistance at the interface of solid-electrolytes and electrodes hinders the fast charging and discharge of solid-state Li batteries. Accordingly, understanding electronic and ionic transport properties across interfaces is crucial for designing high-performance solid-state lithium batteries. Here, we introduced the semiconductor technology and their knowledge into battery research. The model solid-electrolyte/electrode interfaces were fabricated using epitaxial thin film growth techniques. We succeeded in demonstrating the interface resistance below 5 Ωcm2(Li3PO4/LiCoO2interface [1], [2], Li3PO4/LiNi0.5Mn1.5O4interface [3]); the value is smaller than that of liquid-electrolyte-based Li-ion batteries. Furthermore, we found that the deteriorated interfaces improve by annealing the model interfaces. These studies strongly encourage solid-state Li battery research by demonstrating a very low interface resistance leading to fast charging and discharging.