DFT investigation of capacious, ultrafast and highly conductive hexagonal Cr₂C and V₂C monolayers as anode materials...

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.