Preparation And Application Of Greenish Phosphorus For Lithium Metal Anode

Phosphorus has color-rich allotropes（white phosphorus,red phosphorus,violet phosphorus,black phosphorus,and blue phosphorus）.As a layered material,black phosphorus possesses the unique properties,such as layer-dependent band gap and high carrier mobility.Black phosphorus has been attracted much attention in the fields of field-effect transistors,phototransistors,catalysts and sensors.The research boom of black phosphorus has promoted the exploration of new phosphorus allotropes.In this work,a new phosphorus allotrope,greenish phosphorus,was synthesized for the first time by chemical vapor deposition method.We have studied the key factors for growth mechanism of greenish phosphorus,such as P₄ vapour pressure and substrate.In addition,we applied greenish phosphorus as the active material for electrochemical lithiation and the functional material for inducing Li-metal deposition.The main results are as follows:（1）The new phosphorus allotrope named greenish phosphorus was successfully synthesized by a simple chemical vapor deposition method.It was found that the greenish phosphorus was deposited on the glassy carbon substrate in the form of particles with the diameter of 100～700 nm.In comparison with red phosphorus and black phosphorus,XRD and Raman results showed that greenish phosphorus has a distinct crystal structure.The greenish phosphorus can grow on the carbon substrates with edge carbon structure at P₄ vapour pressure of～210 k Pa.The DFT results shows that there is a strong adsorption between the edge carbon and P₄ molecules.This strong adsorption can activate P₄ molecules to polymerize and form greenish phosphorus.The lithium storage mechanism of greenish phosphorus was investigated by cyclic voltammetry,in which,the lithiation potential of greenish phosphorus was lower than that of red phosphorus and black phosphorus,indicating its distinct crystal structure and chemical properties.（2）Based on the phenomenon that greenish phosphorus can grow on carbon substrates with abundant edge carbon atoms,greenish phosphorus nanoparticles were successfully loaded on carbon fiber paper（CP）by chemical vapor deposition method.The greenish phosphorus nanoparticles on CP（greenish P@CP with 7.36 wt%greenish P）can be electrochemically lithiated into Li₃P particles at 0.40 V.Li₃P improves the lithophilicity of the carbon paper and reduces the nucleation overpotential of metallic lithium deposition.The impedance test after 50 cycles showed that the greenish P@CP electrode had lower interfacial impedance and charge transfer impedance than that in the CP electrode,indicating that the SEI formed at the greenish P@CP electrode was more stable than that in the CP electrode.In addition,the affinity of greenish P@CP for lithium was improved well.The uniform distribution of Li₃P as the nucleation sites for Li-metal deposition suppressed the generation of lithium dendrites,resulting in a coulombic efficiency of the greenish P@CP electrode higher than 91%after 100 cycles at a current density of 1 m A cm^-2 and a capacity of 1 m Ah cm^-2 in half-cell,much higher than that of CP electrode（66%）.