Thursday, 2 June 2022: 10:20
West Meeting Room 110 (Vancouver Convention Center)
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 materials already widely used. Presently, revamped interest in anode materials is observed -- primarily graphite electrodes for lithium-ion batteries. Here, we use HOPG as a model system to investigate lithium ion intercalation, providing nuclear magnetic resonance (NMR) reference data from a system as well-defined as possible for further in operando studies of LIBs. To exclude any external influence on the intercalation process, we opted for an infiltration technique under ambient pressure using lithium metal and HOPG as precursors[1]. We focus on the upper limit of lithium intercalation in the morphologically quasi-ideal highly oriented pyrolytic graphite (HOPG), with a LiC6 stoichiometry corresponding to 100 % state of charge (SOC). We resolved unexpected signatures of superdense intercalation compounds, LiC{6-x} [2]. These have been ruled out for decades, since the highest geometrically accessible composition, LiC2, can only be prepared under high pressure [3,4].
We monitored the sample upon calendaric aging and assessed the plausibility of such an assignment of spectral features by ab initio calculations. The computed relative stabilities of different superdense configurations reveal that non-negligible overintercalation does proceed spontaneously beyond the currently accepted capacity limit [1].
[1] Grosu et al., https://arxiv.org/abs/2107.11137v2
[2] Guerard et al., Carbon 1975, 13, 337–345
[3] Nalimova et al., Carbon 1995, 33, 177–181
[4] Rabii et al., Journal of Physics and Chemistry of Solids 2008, 69, 1165–1167