Quantitatively analyzing the failure processes of rechargeable Li metal batteries

Practical use of lithium (Li) metal for high-energy density lithium metal batteries has been prevented by the continuous formation of Li dendrites, electrochemically isolated Li metal, and the irreversible formation of solid electrolyte interphases (SEIs). Differentiating and quantifying these inactive Li species are key to understand the failure mode. Here, using operando nuclear magnetic resonance (NMR) spectroscopy together with ex situ titration gas chromatography (TGC) and mass spectrometry titration (MST) techniques, we established a solid foundation for quantifying the evolution of dead Li metal and SEI separately. The existence of LiH is identified, which causes deviation in the quantification results of dead Li metal obtained by these three techniques. The formation of inactive Li under various operating conditions has been studied quantitatively, which revealed a general two-stage failure process for the Li metal. The combined techniques presented here establish a benchmark to unravel the complex failure mechanism of Li metal.

Automated summary

The practical use of lithium metal in high-energy density lithium metal batteries is hindered by the continuous formation of lithium dendrites and irreversibly formed solid electrolyte interfaces (SEIs). By combining operando nuclear magnetic resonance (NMR) spectroscopy with ex situ titration gas chromatography (TGC) and mass spectrometry titration (MST) techniques, a solid foundation for quantifying the evolution of dead lithium metal and SEI separately has been established. The existence of LiH has been identified, causing deviations in the quantification results of dead lithium metal obtained by these techniques. Quantitative studies on the formation of inactive lithium under different operating conditions have revealed a general two-stage failure process for lithium metal.