Alkali metal bilayer intercalation in graphene

• Published in: Nature communications Vol. 15; no. 1; pp. 425 - 9
• Main Authors: Lin, Yung-Chang, Matsumoto, Rika, Liu, Qiunan, Solís-Fernández, Pablo, Siao, Ming-Deng, Chiu, Po-Wen, Ago, Hiroki, Suenaga, Kazu
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 24.01.2024; Nature Publishing Group; Nature Portfolio
• Subjects: 119/118; 140/133; 147/137; 639/301/357/918/1053; 639/925/357/1018; Alkali metals; Atomic structure; Bilayers; Cesium; Charge transfer; Electric potential; Electron energy loss spectroscopy; Energy loss; Energy storage; Graphene; Graphite; Heavy metals; Humanities and Social Sciences; Intercalation; Monolayers; multidisciplinary; Rubidium; Scanning electron microscopy; Scanning transmission electron microscopy; Science; Science (multidisciplinary); Spectroscopy; Transmission electron microscopy; Voltage
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-023-44602-3

Alkali metal (AM) intercalation between graphene layers holds promise for electronic manipulation and energy storage, yet the underlying mechanism remains challenging to fully comprehend despite extensive research. In this study, we employ low-voltage scanning transmission electron microscopy (LV-STEM) to visualize the atomic structure of intercalated AMs (potassium, rubidium, and cesium) in bilayer graphene (BLG). Our findings reveal that the intercalated AMs adopt bilayer structures with hcp stacking, and specifically a C 6 M 2 C 6 composition. These structures closely resemble the bilayer form of fcc (111) structure observed in AMs under high-pressure conditions. A negative charge transferred from bilayer AMs to graphene layers of approximately 1~1.5×10 14  e − /cm −2 was determined by electron energy loss spectroscopy (EELS), Raman, and electrical transport. The bilayer AM is stable in BLG and graphite superficial layers but absent in the graphite interior, primarily dominated by single-layer AM intercalation. This hints at enhancing AM intercalation capacity by thinning the graphite material. Here, the authors report a study of the structural properties of intercalated alkali metals in bilayer graphene and graphite via low-voltage scanning transmission electron microscopy, providing mechanistic insights for the development of energy storage applications.