Regensburg 2022 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 8: Materials for Storage and Conversion of Energy
MM 8.8: Vortrag
Montag, 5. September 2022, 17:45–18:00, H46
Revisiting the storage capacity limit of graphite battery anodes: spontaneous lithium overintercalation at ambient pressure — Cristina Grosu1,2, •Chiara Panosetti1, Steffen Merz2, Peter Jakes2, Sebastian Matera1, Rüdiger-A. Eichel2, Josef Granwehr2, and Christoph Scheurer1 — 1Fritz-Haber-Institut, Berlin, Germany — 2IEK-9, Forschungszentrum Jülich, Germany
The market quest for fast-charging, safe, long-lasting, and performant batteries drives the exploration of new energy storage materials, but also promotes fundamental investigations of those already widely used. Presently, revamped interest in anode materials is observed – primarily graphite electrodes for Li-ion batteries. We focus on the upper intercalation limit in the morphologically quasi-ideal highly oriented pyrolytic graphite (HOPG), with a LiC6 stoichiometry corresponding to 100% state of charge (SOC). We prepared a sample by immersion in liquid lithium at ambient pressure. Investigation by static 7Li nuclear magnetic resonance (NMR) resolves unexpected signatures of superdense intercalation compounds, LiC6−x. These were ruled out for decades, since the highest geometrically accessible composition, LiC2, can only be prepared under high pressure. We thus challenge the widespread notion that any additional intercalation beyond LiC6 is not possible under ambient conditions. We monitored the sample upon calendaric aging and employed ab initio calculations to rationalise the NMR results. The computed relative stabilities of different superdense configurations reveal that non-negligible overintercalation does proceed spontaneously beyond the currently accepted capacity limit.