Quantifying inactive lithium in lithium metal batteries

Abstract

Lithium metal anodes offer high theoretical capacities (3,860 milliampere-hours per gram)¹, but rechargeable batteries built with such anodes suffer from dendrite growth and low Coulombic efficiency (the ratio of charge output to charge input), preventing their commercial adoption^2,3. The formation of inactive (‘dead’) lithium— which consists of both (electro)chemically formed Li⁺ compounds in the solid electrolyte interphase and electrically isolated unreacted metallic Li⁰ (refs ^4,5)—causes capacity loss and safety hazards. Quantitatively distinguishing between Li⁺ in components of the solid electrolyte interphase and unreacted metallic Li⁰ has not been possible, owing to the lack of effective diagnostic tools. Optical microscopy⁶, in situ environmental transmission electron microscopy^7,8, X-ray microtomography⁹ and magnetic resonance imaging¹⁰ provide a morphological perspective with little chemical information. Nuclear magnetic resonance¹¹, X-ray photoelectron spectroscopy¹² and cryogenic transmission electron microscopy^{<a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 13" title="Li, Y. et al. Atomic structure of sensitive battery materials and interfaces revealed by cryo-electron microscopy. Science 358, 506–510 (2017)."...}