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.

锂的不均匀沉积或枝晶的形成以及“死锂”馏分的出现是具有挑战性的问题，阻碍了锂金属电池的商业应用。尽管最近取得了进展，但对于将锂金属阳极的潜在故障降至最低的条件和策略目前仍未完全了解。我们报告了一种利用原位和异位 的协议⁷Li固态NMR光谱技术可量化电池中不可逆的锂损失，从而清楚地区分了SEI形成和“死锂”的分数所导致的损失，揭示了电镀和剥离过程中工作电极和对电极上不同锂金属微观结构的分布。确定了死锂分数的估计值，分别为3.3％±0.6％（使用5％FEC）和9.4％±0.6％（没有5％FEC）。拟议的协议提供了商用电池的基准测试，包括有效设计和定制电解质配方的合适策略的未来设计，从而促进了高性能储能应用的进一步发展。