Operando Focused Ion Beam-Scanning Electron Microscope (FIB-SEM) Revealing Microstructural and Morphological Evolution in a Solid-State Battery

Thiophosphates have emerged as a promising solid electrolyte for the forthcoming solid-state battery technology only if transport properties, both electronic and ionic, can be controlled within the composite electrode. Unfortunately, during cycling, several chemo-mechanical degradations are occurring hindering the transport properties inside the batteries. Solutions could be provided if one could track the dynamics of such degradation processes. The development of a specific operando focused ion beam-scanning electron microscope (FIB-SEM) approach helps us to perform imaging during cycling and thus address the dynamic morphological investigation of a composite electrode LiNi0.6Mn0.2Co0.2O2 (NMC622 coupled to amorphous Li3PS4). This advanced methodology makes it possible to highlight the mechanical stress endured by the electroactive materials and by the electrolyte during cycling. In this study, polycrystalline NMC622 microstructural evolution was monitored during charge and discharge, showing that the polycrystalline morphology is poorly adapted to solid-state batteries and that the interface adhesion should be better controlled to enhance the electrochemical performance.