First-principles Study Of Structure Modified Graphene As The Anode For Lithium-ion Batteries

With the development of society,people have higher requirements for lithium-ion batteries.Research on the traditional commercial electrodes that can replace lithium-ion batteries has been widely active among many researchers.Graphene is obtained as a new type of two-dimensional material.Widely concerned,it has high surface area,electrical conductivity,thermal conductivity,mechanical flexibility and excellent chemical properties.Therefore,even though the performance of lithium ions on graphene is not particularly good,graphene is still a good matrix for composite materials.This paper proposes three structural modification methods for graphene,they are graphene which construct heterojunction with Mo O₂and borophene and the wavy bending of its own,respectively.Through first-principles calculation methods to study the electronic properties,lithium adsorption and diffusion properties of three structurally modified graphenes as negative electrodes of lithium-ion batteries.First,the composite structure of graphene/Mo O₂ was studied which was constructed by Mo O₂and graphene with the smallest lattice mismatch,and studied its related properties.The results show that the composite structure is metallic before and after the adsorption of Li atoms.Li atoms adsorbed on the interlayer have good adsorption performance,small diffusion barrier and its theoretical capacity higher than 1682 m Ah/g,which make this structure a good anode material for lithium-ion batteries.Then studied the performance of the prepared graphene/borophene heterojunction in lithium-ion battery anode materials.By constructing a variety of structures to find the most stable structure of the heterojunction in its natural state,as well as the adsorption and diffusion properties of Li atoms on a variety of heterojunctions.The results show that due to the interaction of borophene and graphene,the adsorption energy of Li atoms are decreasing with the direction of graphene to borophene.The diffusion barrier of Li atoms in the direction of passing through the interface is partly lower than it on graphene,and other part is between the diffusion barriers of Li atoms on graphene and borophene.At the boundary of graphene and borophene,the adsorption and diffusion properties of Li atoms are also very good.Finally,the electronic properties of wavy graphene benging with different degrees in different directions were studied,as well as the adsorption and diffusion properties of Li atoms.The results show that the adsorption and diffusion of Li atoms are related to the bending direction.When bending along the Zigzag direction,the adsorption at the trough and peak will increase with the increase of the bending degree,and the band gap along this direction will gradually open;When bending along the Armchair direction,only the adsorption of the trough will increase with the increase of the degree of bending,and the adsorption energy of Li atoms at the peak changes little.With the change of the degree of bending,the stable adsorption position of Li atoms at the trough will change,thereby reducing the diffusion barrier of Li atoms at the trough,which is conducive to the diffusion of Li atoms.Through the research in this paper,graphene can be considered as an excellent composite material for lithium-ion anode,which can not only improve the deformation problems of other materials during charge and discharge,but also enhance the adsorption and diffusion properties of Li atoms.Through the research on the structure modification of graphene itself,it can also be found that the properties of curved graphene will change with the direction and degree of bending,therefore,the research on the structural modification of graphene will better promote the development of high-performance lithium-ion negative materials for ion batteries.