In situ observations of interfacial evolutions in solid-state lithium battery with sulfide-based solid electrolyte

Solid electrolytes provide for safe rechargeable lithium batteries and allow the batteries with lithium metal anodes to possess higher energy densities than those of traditional liquid electrolyte based batteries. However, the structural evolution-induced interfacial failures during the electrochemical cycling have not been explored at a fundamental level. In this report, a practical setup is developed for in situ detection of the electrochemical reaction- induced micro and nanoscale morphological changes along the battery’s interface. We have focused on the anode interface with lithium metal as the electrode and solid sulfide as the electrolyte, while monitoring an inflating phenomenon in the electrolyte during the lithium plating. This observation suggests that the lithium dendrite formation as well as the lithium deposition in the porous structures drives the volume expansion of the solid electrolyte. This rare finding offers a fresh perspective, indicating a new impact of the lithium plating in sulfide electrolyte, which does not accord with the conventional structural evolution model at the electrode-solid electrolyte interface. This study contributes significant insights into the mechanism of the interfacial phenomena in sulfide solid-state battery and paves the way for their advanced engineering.