Probing the Superconductivity Limit of Li‐Doped Graphene

Abstract The introduction of superconductivity in graphene systems is highly desirable from both fundamental physics and application perspectives. In this article, a superlattice strategy to develop a series of Li‐doped graphene is reported: deposition type‐I (Li 2 C 6 , Li 2 C 8 , LiC 6 , Li 3 C 24 , LiC 12 , LiC 16 , Li 2 C 36 , LiC 24 ), intercalation type‐II (LiC 4 , Li 2 C 12 , LiC 8 , LiC 12 , LiC 16 ), and coexisting deposition and intercalation type‐III (Li 3 C 12 ). With increasing concentration of Li atoms, both metallicity, and electron–phonon coupling (EPC) has dramatically increased, which is favorable for the emergence of superconductivity in the screened Li–C compounds. Notably, graphene superlattice structures with intercalated Li2 atoms have higher stability, while Li1‐deposited graphene at the same concentration produces higher T c . Among them, type‐I‐Li 2 C 6 , type‐I‐Li 2 C 8 , type‐II‐LiC 4 , and type‐III‐Li 3 C 12 are phonon‐mediated superconductors with high transition temperatures ( T c ) of 18, 12, 3.4, and 14 K, respectively. The EPC of type‐I‐Li 2 C 6 , type‐I‐Li 2 C 8 , and type‐III‐Li 3 C 12 mainly arises from the coupling of the C‐2 p z electron states with the low‐frequency (0–800 cm −1 ) deposition‐Li xy /Li z , and out‐of‐plane‐C z vibrations. In contrast, the high‐frequency (800–1600 cm −1 ) vibration modes of in‐plane‐C xy atoms are mainly responsible for the T c of type‐II‐LiC 4 . The findings provide comprehensive insights into the superconductivity limit of Li‐doped graphene.