A Novel Approach for Post-Mortem Analysis in All-Solid-State Batteries: Isolating Solid Polymer Electrolytes from Lithium Anodes

Polymeric electrolytes are currently at the forefront of research for the next generation of lithium all-solid-state batteries. Polyethylene oxide (PEO), a commonly used polymer for these batteries, operates at elevated temperatures at which it reacts with active metal electrodes (e.g., lithium). Rich surface chemistry is developed at the Li-PEO interfaces, thereby controlling these batteries’ electrochemical behavior. Interfacial studies are essential to comprehend batteries’ stabilization or capacity fading mechanisms. For that, post-mortem analysis with an emphasis on interfaces is a necessary approach to underpinning these mechanisms. While it can be readily done with liquid electrolytes, post-mortem characterization of similar interfaces with solid electrolytes is hampered by the Li-PEO stack firm adhesion, which is impossible to separate. Here, various methods were attempted to separate polymer electrolytes from metallic anodes after Li symmetric cells’ operation, which is a necessary step for solid-state NMR characterization. By a simple method involving exposure to N_2(g) atmosphere, PEO-based solid electrolyte samples were successfully isolated from lithium anodes while preserving their morphology and chemical characteristics to enable their direct analysis. This method’s concept was approved by Solid-state NMR spectroscopy. This work opens the door for post-operative analysis of many kinds of solid-state Li batteries.