▎ 摘　　要

The electron excitation spectra of the Li-intercalated graphene (LiC2) are obtained using a high-accuracy ab initio density function theory calculation within the random phase approximation. The low-energy parts of the spectra are analyzed to predict the existence of two quasi-two-dimensional collective modes: a Dirac plasmon similar to the one in the doped graphene but significantly stronger, and an acoustic plasmon.