Operando Auger/XPS using an electron beam to reveal the dynamics/morphology of Li plating and interphase formation in solid-state batteries

Abstract

Interfaces and their understanding/control are the key to pave the way for the development of solid-state batteries. This work focuses on the development of operando Auger cycling using an electron beam to investigate the Li/solid electrolyte (SE) interphases. To do so, the fully tunable electron gun of the Auger was applied on top of a model Li/Li₆PS₅Cl(Arg) stack, allowing charge build up at the Arg surface and Li⁺ migration from the lithium electrode followed by SE interphase formation and Li plating. Overall, it is found that (i) Li₆PS₅Cl is first reduced to Li₂S, LiCl and Li₃P while (ii) Li plating occurs almost concomitantly and (iii) proceeds until the end of the operando cycling. These results were then confirmed by operando XPS using an electron beam. Importantly, this study highlights that operando Auger is more powerful than operando XPS as it provides visual observation of the dynamics/morphology of both Li/solid electrolyte interphase formation and Li plating together with reliable chemical information. This study thus opens the door for future development of operando Auger cycling using an electron beam as a powerful approach to better understand the interfaces in solid-state batteries.