Layered carbon lattices and their influence on the nature of lithium bonding in lithium intercalated carbon anodes

Abstract

Ab initio molecular orbital calculations have been used to investigate the nature of lithium bonding in stage 1 lithium intercalated carbon anodes. This has been approximated by using layered carbon lattices such as coronene, (C24H12), anthracene, and anthracene substituted with boron. With two coronene carbon lattices forming a sandwich structure and intercalated with either two, three, four or six lithiums, it has been found that the predominant mode of bonding for the lithium is at the carbon edge sites as opposed to bonding at interior carbon hexagon sites. With a single planar coronene molecule approximating a graphene sheet, the bonding of four lithiums with this molecule is near the interior carbon hexagon sites. For anthracene and boron substituted anthracene, lithium bonding takes place within the carbon hexagon sites. The separation between lithiums in a sandwich type structure with two anthracenes in the eclipsed conformation is 5.36 Å. The effect of boron substitution is to increases lattice flexibility by allowing the lattice to twist and lithium to bond at adjacent hexagon sites.