Effects of Si, B doping on PC3 monolayer as anode for Na-ion batteries

Abstract

Two-dimensional phosphorus carbides are predicted to be promising anode materials for Na-ion batteries due to their high theoretical capacity, low diffusion barrier, low volume expansion rate and excellent electronic conductivity. However, previous theoretical calculations show that most phosphorus carbides have weak adsorption for Na atoms, which may lead to the fact that Na atoms are prone to aggregate to form Na dendrites during the charging and discharging process. Here, the effects of Si and B doping on the structural stability, and the adsorption and diffusion behaviors of Na atom of PC3 were investigated using first-principles calculations. The results show that single Si and B atom doping has more negative formation energy at the P site. Si and B doping enhances the adsorption properties of PC3 for Na atom, and the maximum adsorption energy of Na on the Si-doped system is decreased to −1.87 eV. B-doped PC3 monolayer has more Na atom adsorption sites than the undoped ones. Therefore, it can be concluded that Si and B doping is a feasible way to improve the weak Na adsorption in the PC3 monolayer. This work provides guidance for improving the electrochemical performance of phosphorus carbides.