Studies On Surface Properties Of Low Dimensional C₃N Based Anode Materials For Li Ion Batteries

In recent years,low-dimensional materials have attracted extensive attention in the field of energy storage due to their large specific surface area,specific crystal structure,and human-controllable characteristics.Two-dimensional(2D)C₃N,with appropriate band gap,high stiffness,and high thermal conductivity shows great potential for the application in lithium ion batteries(LIBs).In this paper,the surface characteristics of2D C₃N,C₃N/P heterostructure,C₃N allotropes,and C₃N nanoribbon for LIBs anode materials are systematically studied by first principles calculations.The specific contents and innovations are as follows:(1)The surface properties of 2D C₃N and defect-containing 2D C₃N as anode materials for LIBs were systematically studied by first principles calculations.The calculated results show that pristine C₃N possess excellent stiffness(Young's modulus is 364.33 N/m),high storage capacity(1071.56 mAh/g),good electronic conductivity(bandgap is 0.39 eV),and good lithium migration capability(energy barrier is 0.27 eV),which indicate that C₃N is apromising anode material for LIBs.Besides,our research further proves that the defects of C₃N arise from the experimental preparation will reduce the properties of the LIBs.Our research provides a guidance for the application of C₃N in LIBs and enhances the understanding of 2D C-N based materials.(2)The structure,electronic properties,mechanical properties,surface lithium adsorption and migration properties of C₃N/P heterostructure have been systematically investigated through first principles calculations.The calculated results show that compared to 2D C₃N and phosphorene,C₃N/P heterostructure have better mechanical properties,electronic conductivity and bond strength of lithium.Besides,the migration properties of Li are also improved.These improvements are mainly due to the interfacial synergy effect in heterostructures.Our research demonstrates the great potential of the C₃N/P heterostructure as an anode material in the application of LIBs.(3)Three new 2D C₃N allotropes were predicted by structure search method.Electronic properties,mechanical properties,surface lithium adsorption and migration properties of the C₃N allotropes were further investigated by first principles calculations.It is found that the metallic property was caused by the continuous C-C chain in the surface structure.Moreover,compared to the pristine C₃N,its allotropes not only have high mechanical properties,but also have better conductivity and surface lithium ion migration ability.(4)The surface characteristics of C₃N nanoribbons used as anode material for lithium ion batteries have been systematically investigated through first-principle calculations.The results suggest that C₃N nanoribbons not only have excellent mechanical properties,good electronic conductivity and Li mobility,but also have high Li insertion capacity and significantly enhanced Li binding strength.Besides,the mechanism of edge saturation on ion diffusion property of C₃N nanoribbon was revealed.