MXenes/Graphene Heterostructures for Li Battery Applications: A Frist Principles Study*

There is a large demand for high-performance batteries with higher C-rate and larger capacity. In recent years, MXenes as a new class of two-dimensional materials have been shown promising features for Li battery applications [1-2]. Here, we propose vertical heterostructures made of graphene and MXenes, which have a larger volumetric energy density than monolayer MXenes and a larger gravimetric energy density than the multi-layer MXenes. In addition, graphene and MXenes are both good electrical conductors, which is essential for a good battery. It is shown that in these systems the binding energies of Li atoms are high even at full coverage. The stability of the materials under lithiation is confirmed through small lattice variations, i.e, <1%. Among the materials that we investigated, those are M₂CX₂ where M=Sc, Ti, V and X=OH, O, Ti₂CO₂/graphene and V₂CO₂/graphene exhibit well-balanced relationships between the capacity and kinetics of Li atoms, and therefore they are expected to deliver better performance for Li battery applications.

[1] J. Am. Chem. Soc. 135, 15966 (2013).
[2] J. Phys. Chem. C 117, 25409 (2013).