Investigation of Lithium Migration Pathway in Ti2CY2 /Graphene (Y = O,
S) van der Waals Heterostructure as Potential Anode Material for
Lithium-Ion Batteries: A First-Principle Study
Abstract
In this work, we have performed first-principle calculations to
investigate the electronic properties, structural stability, and lithium
migration pathway of 2D Ti 2CY
2/Graphene (Y = O, S) van der Waals (vdW)
Heterostructure. The heterostructure formed by O and S functionalized
MXene and graphene layers are separated by 3.04 and 3.40 Å exhibiting
weak vdW interaction. It is found that the intercalation of lithium (Li)
atoms in between the Ti 2CY 2/Graphene
layers is thermodynamically more favorable in comparison with
intercalation on the top or below the heterostructures. The Bader charge
transfer analysis confirms that O atoms gain less charge -0.13 e during
Li intercalation compared to S atoms with charge transfer of -0.47 e due
to the larger size of the 3p orbital of S atoms. Each Li atom
contributes ~0.88-0.89 e during the intercalation process.
As O is more negatively charged in comparison with S atoms in the
heterostructures, Li atoms are more localized on the Ti
2CO 2 layers with a tendency to form
chemical bonds with Ti 2CO 2 layers
while they are less localized on the Ti 2CS
2 layers creating lesser chemical bonds. The diffusion
energy barrier is lower for Ti 2CS
2/graphene than Ti 2CO
2/graphene during Li intercalation. The NEB study also
confirms that the activation energy barrier decreases with the increase
of intercalated Li atoms for both the heterostructures indicating that
Li atoms exhibit weak repulsive interaction causing weak Li binding with
the heterostructures as they increase in number. Both the Ti
2CO 2/graphene and Ti
2CS 2/graphene heterostructures can be
considered promising anode materials for Li-ion batteries due to their
structural stability, and lower diffusion energy barrier.