Toward a deep understanding of the performances of bulk materials, the first step should be to study the structure and properties of their constituent molecules. Based on the analyses of the above research status, here we designed ten complexes M + @C18 of M + endohedral and exohedral C18, respectively denoted by M + @C18 in and M + @C18 out , and conducted in-depth studies of interaction of M + with C18 as well as optical properties of stable endohedral configurations. The purpose of this work is to investigate theoretically the utility of cyclocarbons for alkali-metal ion storage and the possibility of the formed complexes as optoelectronic functional materials.