Compilation and characterization of the visual appearance of alkali metal graphite intercalation compounds

Graphite intercalation compounds (GICs) have been extensively studied; however, their visual appearance has not been systematically documented. The appearance of GICs plays a crucial role in understanding their properties and potential applications. In this study, alkali metal GICs (Li-, Na-, K-, Rb-, and Cs-GICs), known for their vivid gold and blue colors, were synthesized using a common host graphite under standardized conditions. Photographs were taken under controlled settings to capture their visual appearance, and reflectance spectra were measured to provide objective optical data, contributing to a standardized color sample compilation. Additionally, their structures and electrical conductivities were evaluated. Furthermore, the relationship between the crystallinity of the host graphite and the perceived appearance of the GICs is discussed. This study provides a comprehensive reference dataset on GIC appearance and is expected to support future research on intercalation compounds.