DFT investigation of capacious, ultrafast and highly conductive hexagonal Cr2C and V2C monolayers as anode materials for high-performance lithium-ion batteries.

Abstract

To assess the potential of hexagonal Cr2C and V2C monolayers as anode materials in lithium-ion batteries, first-principles calculations and AIMD simulations were carried out. AIMD simulations and phonon calculations revealed that the honeycomb structure of the hexagonal Cr2C and V2C monolayers is thermodynamically and dynamically stable. A single lithium atom is preferentially absorbed over the center of the honeycomb hollow. The full lithium storage phases of the hexagonal Cr2C and V2C monolayers correspond to Li6Cr2C and Li6V2C, with considerable theoretical specific capacities of 1386 and 1412 mA h g-1, respectively. Interestingly, lithium ion diffusion on the hexagonal Cr2C and V2C monolayers is extremely fast, with low energy barriers of 32 and 28 meV, respectively; these values are much lower than those of other widely investigated anode materials. Moreover, the lithiated hexagonal Cr2C and V2C monolayers show enhanced metallic characteristics and excellent electronic conductivity during the entire lithiation process; these values are superior to those of other anode materials with semiconducting characteristics. The findings in our study suggest that hexagonal Cr2C and V2C monolayers are promising anode materials with high capacities and high rate capabilities for next generation high-performance lithium-ion batteries.