First-principles Study Of PC₃ Based Anode Materials For Alkali-metal Ion Batteries

With the advent of the energy crisis,the study of energy storage and conversion has become a hot topic.Lithium-ion batteries have been widely concerned for their high safety,high operating voltage and good cycling performance.However,it is difficult to further improve the capacity and energy density of graphite electrodes for lithium-ion batteries,and lithium resources are in short supply.To overcome the current dilemma of lithium-ion batteries,the development of high-performance electrode materials and other types of alkali-metal ion batteries based on the high abundance of sodium and potassium elements in nature have been extensively researched and current research hotspot.two-dimensional materials with more ion embedding sites,high electron mobility,and good chemical stability are important candidates for high energy density electrode materials for lithium/sodium/potassium ion batteries.This paper predicts the performance of new two-dimensional materials PC₃-based monolayer as anode for alkali-metal ion batteries by means of first-principles calculations,aiming to provide guidance for the selection and performance optimization of anode materials for alkali-metal ion batteries.The main contents and conclusions are as follows:（1）The crystal structural,electronic structure,and mechanical properties of two-dimensional material PC₃ monolayer and its performance as the anode of alkali-metal ion batteries were investigated including atom adsorption performance,atom diffusion performance,capacity,open-circuit voltage,and volume change when ion insertion and extraction.The calculated results show that the PC₃ monolayer 2D material with the P3m1 space group has good stability at room temperature.PC₃ monolayers exhibit good diffusion properties（migration barriers of 0.11 e V,0.05 e V and 0.09 e V,respectively）,high theoretical capacities(1600 m A h g^-1,1200 m A h g^-1 and 1200 m A h g^-1),small volume expansions（1.37%,0.06%and 0.6%）,low open-circuit voltages（0.13 V,0.10 V and 0.34 V）and good electrical conductivity after adsorption of lithium,sodium and potassium atoms,respectively.However,its adsorption ability is high only for K atoms,and the adsorption of Li atoms and Na atoms is weak.（2）To improve the adsorption performance of alkali metal atoms,the performance of PC₃ monolayer two-dimensional material doping Si element for alkali-metal ion batteries anode was investigated.The calculated results show that the doping of Si elements can improve the adsorption ability of PC₃monolayer to Li atoms and Na atoms,and can avoid the generation of dendrites effectively.Little change in capacity and open circuit voltage occurs,while the diffusion energy barriers of Li and Na atoms are slightly increased.When the adsorption concentration is low,the conductivity of the doped PC₃ monolayer was not significantly improved.（3）Further,in order to improve the structural stability of the doped structure and to enhance the adsorption performance of the material,the effect of B-element doping on the performance of alkali metal battery anode of PC₃ monolayer two-dimensional material was investigated.The calculated results show that the doping formation energy of B-doped structures is lower than that of Si-doped ones,B-doping has less influence on the initial structure,and B-doped structure has better structural stability compared to Si-doped structures.Meanwhile,B doping also enhances the adsorption ability of PC₃ monolayer to Li,Na and K atoms.After adsorption,The B element-doped PC₃monolayer is highly conductive,which is beneficial to reduce the internal friction.