Tailoring storage capacity and ion kinetics in Ti2CO2/graphene heterostructures by functionalization of graphene

Using first-principles calculations, we evaluated the electrochemical performance of heterostructures made of Ti2CO2 and chemically modified graphene for Li batteries. We found that heteroatom doping and molecule intercalation have a large impact on storage capacity and Li migration barrier energies. While N and S doping do not improve the storage capacity, B doping together with molecule interaction make it possible to intercalate two layers of Li which stick separately to the surface of Ti2CO2 and B-doped graphene. The calculated diffusion barrier energies (E_diff), which are between 0.3 and 0.4 eV depending on Li concentration, are quite promising for fast charge/discharge rates. In addition, the predicted E_diff as much as 2 eV for the diffusion of Li from Ti2CO2 surface to B-doped graphene surface significantly suppress the interlayer Li migration, which diminishes the charge/discharge rates. The calculated volume and lattice parameter changes indicate that Ti2CO2/graphene hybrid structures exhibit cyclic stability against Li loading/unloading. Consequently, the performed first-principles calculations evidently highlight the favorable effect of molecular intercalation on the capacity improvement of ion batteries.