Anode-free lithium metal cells store 60% more energy per volume than conventional lithium-ion cells. Such high energy density can increase the range of electric vehicles by approximately 280 km or even enable electrified urban aviation. However, these cells tend to experience rapid capacity loss and short cycle life. Furthermore, safety issues concerning metallic lithium often remain unaddressed in the literature. Recently, we demonstrated long-lifetime anode-free cells using a dual-salt carbonate electrolyte. Here we characterize the degradation of anode-free cells with this lean (2.6 g Ah−1) liquid electrolyte. We observe deterioration of the pristine lithium morphology using scanning electron microscopy and X-ray tomography, and diagnose the cause as electrolyte degradation and depletion using nuclear magnetic resonance spectroscopy and ultrasonic transmission mapping. For the safety characterization tests, we measure the cell temperature during nail penetration. Finally, we use the insights gained in this work to develop an optimized electrolyte, extending the lifetime of anode-free cells to 200 cycles.
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This research was financially supported by Tesla Canada and NSERC under the Industrial Research Chairs Program. A.J.L. and A.E. thank NSERC, the Killam Foundation and the Nova Scotia Graduate Scholarship programmes for financial support. M.G. thanks the NSERC PDF Program. We acknowledge J. Li (formerly of BASF) and D. J. Xiong (formerly of Capchem) for providing the chemicals used in the electrolytes. We also acknowledge P. Scallion for SEM support, as well as S. Trussler for expert fabrication of the parts used in this work.
R.W., R.P., S.H. and S.J.H.C. are employed by Tesla Canada R&D. R.T.W., J.L. and T.R. are employed by Carl Zeiss Microscopy.
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Supplementary Table 1, Figs. 1–16 and discussion.
Submerge and observe qualitative reactivity test pictured in Fig. 6. Charged negative electrode (graphite and plated lithium) samples retrieved from cycled pouch cells at the top of charge are submerged into water to observe their reactivity. The electrolyte chemistries used in the pouch cells from which these samples were retrieved are indicated in the video titles before each submersion.
Nail test videos pictured in Fig. 6. Anode-free pouch cells at the top of charge after being cycled 50 times were penetrated with nail. The electrolyte chemistries used in each pouch cell nailed are indicated in the video titles before each experiment.
Source data for Supplementary Figs. 1 and 2.
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Louli, A.J., Eldesoky, A., Weber, R. et al. Diagnosing and correcting anode-free cell failure via electrolyte and morphological analysis. Nat Energy 5, 693–702 (2020). https://doi.org/10.1038/s41560-020-0668-8
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