Operando NMR characterization of a metal-air battery using a double-compartment cell design

Applying operando investigations is becoming essential for acquiring fundamental insights into the reaction mechanisms and phenomena at stake in batteries currently under development. The capability of a real-time characterization of the charge/discharge electrochemical pathways and the reactivity of the electrolyte is critical to decipher the underlying chemistries and improve the battery performance. Yet, adapting operando techniques for new chemistries such as metal-oxygen (i.e. metal-air) batteries introduces challenges in the cell design due notably to the requirements of an oxygen gas supply at the cathode. Herein a simple operando cell is presented with a two-compartment cylindrical cell design for NMR spectroscopy. The design is discussed and evaluated. Operando Li-7 static NMR characterization on a Li-O-2 battery was performed as a proof-of-concept. The productions of Li2O2, mossy Li/Li dendrites and other irreversible parasitic lithium compounds were captured in the charge/discharge processes, demonstrating the capability of tracking the evolution of the anodic and cathodic chemistry in metal-oxygen batteries.