MXenes/graphene heterostructures for Li battery applications: a first principles study

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2018, Vol.6 (5), p.2337-2345
• Main Authors: Aierken, Yierpan, Sevik, Cem, Gülseren, Oğuz, Peeters, François M., Çakır, Deniz
• Format: Article
• Language: English
• Subjects: Battery cycles; Binding energy; Diffusion barriers; Electrical conductivity; Electrical resistivity; Electronic devices; Electronic equipment; Energy storage; First principles; Graphene; Heterostructures; Intercalation; Interlayers; Kinetics; Lattice parameters; Lithium; Lithium-ion batteries; Mathematical analysis; Monolayers; MXenes; Nanotubes; Phase separation; Rechargeable batteries; Stacking; Storage capacity; Thermodynamics; Thermoelectric materials
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/C7TA09001C

MXenes are the newest class of two-dimensional (2D) materials, and they offer great potential in a wide range of applications including electronic devices, sensors, and thermoelectric and energy storage materials. In this work, we combined the outstanding electrical conductivity, that is essential for battery applications, of graphene with MXene monolayers (M 2 CX 2 where M = Sc, Ti, V and X = OH, O) to explore its potential in Li battery applications. Through first principles calculations, we determined the stable stacking configurations of M 2 CX 2 /graphene bilayer heterostructures and their Li atom intercalation by calculating the Li binding energy, diffusion barrier and voltage. We found that: (1) for the ground state stacking, the interlayer binding is strong, yet the interlayer friction is small; (2) Li binds more strongly to the O-terminated monolayer, bilayer and heterostructure MXene systems when compared with the OH-terminated MXenes due to the H + induced repulsion to the Li atoms. The binding energy of Li decreases as the Li concentration increases due to enhanced repulsive interaction between the positively charged Li ions; (3) Ti 2 CO 2 /graphene and V 2 CO 2 /graphene heterostructures exhibit large Li atom binding energies making them the most promising candidates for battery applications. When fully loaded with Li atoms, the binding energy is −1.43 eV per Li atom and −1.78 eV per Li atom for Ti 2 CO 2 /graphene and V 2 CO 2 /graphene, respectively. These two heterostructures exhibit a nice compromise between storage capacity and kinetics. For example, the diffusion barrier of Li in Ti 2 CO 2 /graphene is around 0.3 eV which is comparable to that of graphite. Additionally, the calculated average voltages are 1.49 V and 1.93 V for Ti 2 CO 2 /graphene and V 2 CO 2 /graphene structures, respectively; (4) a small change in the in-plane lattice parameters (