Can T-carbon serve as a Li storage material and a Li battery anode?

Abstract

Carbon can form a wide variety of bulk structures. The possibility of carbon-based materials to be utilized in future energy applications has attracted extensive attention. T-carbon is a newly discovered diamond-like phase with an acetylene-bond supported hollow structure. This feature inspires us to consider its possibility of serving as a high-capacity Li storage material and a Li battery anode. Density functional theory calculations are performed to investigate the structure evolution, energy spectrum, stability, and electrode potential of Li-loaded T-carbon. The adsorption of T-carbon to Li atoms originates from the valence electrons of Li filling into the antibonding π* orbitals of acetylene bonds. The maximum theoretical Li capacity is three times that of graphite (1116 mA h g⁻¹). At low Li density, too strong adsorption is disadvantageous to the release of Li and the discharge of the anode. At high Li density, Li atoms push against each other and fight against the adsorption of T-carbon. Such an advantageous issue leads to a decrease in anode potential. The significant difference of Li adsorption between low and high density makes a “dead zone” in which only half of the Li capacity could be useful for the discharge of the anode.