Investigation Of The Superior Diffusion Properties Of Li Ion On The Two-dimensional Zr₂B₂

Among the energy storage devices,lithium-ion batteries have stimulated great interests due to its high energy density and good cycle stability,which have been widely used in mobile devices,such as mobile phones.With the development of computational science,the theoretical calculation becomes more important in the field of searching for new materials.In this paper,we use the first-principles method based on density functional theory?DFT?to investigate the lithium ion diffusion properties of the Zr₂B₂.The details are as follows:1.The investigation of lithium ion diffusion property on two dimensional Zr₂B₂.Firstly,we use the Crystal structure Analysis by Particle Swarm Optimization?CALYPSO?package to predict a new material named Zr₂B₂ and then we select the relatively stable structures.Secondly,we calculate the electronic properties of the two dimensional Zr₂B₂ and find that the pristine Zr₂B₂ is metallic,which is beneficial for the diffusion of lithium ion on its surface.In the end,we compare the adsorption energy of different sites and we know that lithium ions are most stable when they are adsorbed above the B atom.After calculating the diffusion path of lithium ions,we find that lithium ions have a very low diffusion on Zr₂B₂?17 me V?.The ultralow diffusion barrier will greatly improve the charge-discharge rate.In addition,we also find that the theoretical specific capacity of lithium ion on Zr₂B₂ is quite high(526m Ah g^-1)and the average open circuit voltage is ultralow?0.236 V?.All these results propose the hexagonal two-dimensional Zr₂B₂ as an excellent anode material for lithium ion batteries.2.The effect of strain on the lithium ion diffusion property on two dimensional Zr₂B₂.With the development of flexible device,it is necessary to investigate the effect of strain on the properties of the material during the process of application.Therefore,we systematically calculate the influence of strain on the properties of Zr₂B₂ and its effect on the diffusion behavior of lithium ions on the surface of Zr₂B₂.The results show that strain will not obviously tune the electronic properties of the Zr₂B₂.The diffusion barrier of lithium ions on the surface of Zr₂B₂ will change with strain,while,the value of the diffusion is still extremely low.It can be proposed that the Zr₂B₂ still has good lithium ion diffusion performance within a certain strain range.In the present thesis,we explore the lithium ion diffusion paths and properties on Zr₂B₂ by performing the density functional theory method.We also calculate the effect of strain on its diffusion performance.This work can provide theoretical guidance on the design of novel lithium battery anode materials.