  Employing two-dimensional (2D) materials as anodes for lithium-ion batteries
(LIBs) is believed to be an effective approach to meet the growing demands of
high-capacity next-generation LIBs. In this work, the first-principles density
functional theory (DFT) calculations are employed to evaluate the potential
application of two-dimensional phosphorus carbide (2D PCx, x=2, 5, and 6)
monolayers as anode materials for lithium-ion batteries. The 2D PCx systems are
predicted to show outstanding structural stability and electronic properties.
From the nudge elastic band calculations, the Li atoms show extreme high
diffusivities on the PCx monolayer with low energy barriers of 0.18 eV for PC2,
0.47 eV for PC5, and 0.44 eV for PC6. We further demonstrate that the
theoretical specific capacity of monolayer PC5 and PC6 can reach up to 1251.7
and 1235.9 mAh g-1, respectively, several times that of graphite anode used in
commercial LIBs. These results suggest that both PC5 and PC6 monolayer are
promising anode materials for LIBs. Our work opens a new avenue to explore
novel 2D materials in energy applications, where phosphorus carbides could be
used as high-performance anode in LIBs.
