Prediction of two-dimensional CP₃ as a promising electrode material with a record-high capacity for Na ions

Borophene with a maximum Li/Na capacity of 1984 mA h g^-1 (nanoscale 2016, 8, 15 340-15 347) has shown the highest capacity among two-dimensional (2-D) anode materials identified so far. Herein, we report the record break for Na-ion using a newly proposed 2-D material, namely, CP₃. We fully investigated Li- and Na-ion adsorption and diffusion processes on a CP₃ monolayer. We found that the material can enable stable Li/Na adsorption considering charge accumulation on CP₃ surfaces. The ion diffusion barriers for Li and Na were identified to be 98 meV and 356 meV, respectively. These values were comparable or smaller than those of the typical high-capacity electrode materials such as borophene. Most remarkably, the maximum Na capacity in CP₃ monolayer can reach up to 2298.9 mA h g^-1, which breaks the value recorded using borophene (1984 mA h g^-1). Our work highly promises that the 2-D CP₃ material could serve as an outstanding electrode material for Na-ion batteries with an extremely high storage capacity.