Postmortem Lithium-7 NMR Analysis to Evaluate the Reversibility of Lithium Metal Electrodes and the Behavior of Li+ in Lithium Metal Batteries

Solid-state 7 Li NMR spectroscopy is highly effective in monitoring the physical and chemical states of Li metal electrodes. In this study, we employed postmortem 7 Li NMR spectroscopy with an ordinary magic angle spinning (MAS) probe to evaluate the reversibility of lithium metal electrodes and the behavior of Li + in lithium metal batteries(LMBs). Through contrasting NMR spectra of a protective layer(PL)-coated Li metal and LiAg alloy electrodes against bare Li electrodes before and after cycling, we identified alterations in Li 0 and Li + signals attributable to the degradation of the Li metal electrode and efficacy of the protective layer in mitigating dendrite and the solid electrolyte interphase formation. Investigation on Li electrodes after different number of electrochemical cycles revealed the more dendritic Li metal formation through the more number of cycles. In addition, our investigation showed that rinsing and drying the electrode-separator-electrode assemblies extracted from LMBs altered the physical and chemical states of the battery constituents. This study provides valuable insights and practical guidelines for characterizing distinct lithium states in LMBs using 7 Li NMR spectroscopy.