Electrochemical Performance of Nitrogen-Doped Graphene/Silicene Composite as a Pseudocapacitive Anode for Lithium-ion Battery

摘要

Silicene,as a two-dimensional(2D)nanostructure of silicon with many active sites for charge distribution,suitable space to control the volumetric strain,and an adjustable bandgap has attracted more attention as an anode for lithium-ion batteries.Nitrogen,with a small radius and high electronegativity,is pretty good to form an n-type configuration of silicene.Herein,single-crystal silicene with adjusting nitrogen atoms at pyrrolic and graphitic sites in the graphene layer is identified by XRD,XPS,and Raman analyses for nitrogen-doped graphene/silicene(NG/SNS)composite.Electrochemical performance of silicene exhibits the first intercalation/deintercalation capacity of 1030/768 mAh/g with 74% Columbic efficiency(CE)at a current density of 10 mA/g,whereas NG3-SNS with 0.3 g NG precursor shows the first intercalation/deintercalation capacity of 795/600 mAh/g with 75.4% CE.Interestingly,NG3-SNS indicates a stable specific capacity of ~600 mAh/g at 200th cycle with 100% CE and a second volumetric capacity of 3352 mAh/cm3 with 80% retention after 200 cycles at a current density of 100 mA/g.Subsequently,the high electronegativity of nitrogen results in lone pair in both hybridized configurations of graphitic-NG and pyrrolic-NG;which may cause effortless adsorption/desorption of Li+-ion at the nitrogen sites,as well as,pyrrolic sites help to develop diffusion of Li+-ion and graphitic sites help to accelerate the kinetics and surfacecontrolled contributions.