Quantification of Dead Lithium via In Situ Nuclear Magnetic Resonance Spectroscopy

Inhomogeneous lithium deposition or dendrite formation and occurrence of "dead lithium" fractions are challenging issues, hampering the commercial application of lithium metal batteries. Conditions and strategies for minimizing potential failure of lithium metal anodes are currently not fully understood, despite recent progress. We report a protocol utilizing in situ and ex situ 7Li solid-state NMR spectroscopy to quantify irreversible lithium losses in batteries, clearly distinguishing losses due to SEI formation and fractions of "dead lithium," revealing a distribution of different lithium metal microstructures on both working and counter electrodes upon plating and stripping. Estimates of dead lithium fractions of 3.3% ± 0.6% (with 5% FEC) and 9.4% ± 0.6% (without 5% FEC) are determined. The proposed protocol affords benchmarking of commercial cells, including future design of suitable strategies for effective development and tailoring of electrolyte formulations, fostering further advancement of high-performance energy storage applications.