High Mobility and High Storage Capacity of Lithium in sp-sp2 Hybridized Carbon Network: The Case of Graphyne

We have carried out first-principles calculations to explore the energetics and dynamics of Li in graphyne, a novel carbon allotrope consisting of sp-sp(2) hybridized carbon atoms, relevant for anode lithium intercalation in rechargeable Li-ion batteries. In contrast to graphite where Li diffusion is confined in the interlayer space (in-plane diffusion), the unique atomic arrangement and electronic structures enable both in-plane and out-plane diffusion of Li ions in graphyne with moderate barriers, 0.53-0.57 eV. The highest Li intercalation density in graphyne can be LiC4, exceeding the up limit of LiC6 in the commonly used graphite. The high lithium mobility and high storage capacity make graphyne a promising candidate for the anode material in battery applications.