Strain-Enhanced Li Storage and Diffusion on the Graphyne as the Anode Material in the Li-Ion Battery

The density functional theory is used to study the effect of the external biaxial strain on the adsorption and diffusion of Li on the graphyne as an anode material in the Li-ion battery (LIB). The increasing adsorption energy of Li on graphyne appears with the larger external biaxial strain. The Li capacity of the Li6C6 configuration for graphyne reaches 2233 mA h/g under the 12% strain, which is six times that of graphite (372 mA h/g) and two times that of graphyne without strain (1117 mA h/g). The average open-circuit voltage is 0.50 V, which is about 0.14 eV lowered by the 12% strain and is ideal for LIBs. Li on the graphyne can diffuse easier under the 12% strain than that without strain. Furthermore, the diffusion coefficient for Li on the multilayer graphyne under the 12% strain at 300 K is fivefold of the value without strain. Excellent performances of Li capacity and Li diffusion make graphyne under the 12% strain a promising anode material for LIBs.