Study On The Regulation Of Electrode Performance Of Two-dimensional Lithium Ion Battery By Edge Modification

With the development of society and the progress of technology,the demand for energy in modern society is increasing.Common fossil energy reserves are limited and unevenly distributed,making development difficult.Compared with traditional fossil energy sources,new energy sources such as wind power and photovoltaic are inexhaustible.However,wind power and photovoltaic power generation are non-continuous and unstable,and the power generation performance will change with the external environment.So a high-performance power storage link is crucial.Lithium-ion batteries are very suitable for new energy storage power due to their high specific energy,no memory effect,high operating voltage,long life and good cycling performance,etc.In addition to applications in the power generation industry,many products,such as electric cars,cell phones,etc.are also gradually powered by lithium-ion batteries.It is a real green energy.In recent years,as the research on the cathode and anode materials of lithium-ion batteries has become more and more advanced,the development of cheap and high performance electrode materials has become the focus of research on lithium-ion batteries.The study of two-dimensional materials starting with graphene has been the focus of modern materials science research.Two-dimensional materials such as phosphorene and graphene have also shown excellent electrical conductivity and ultra-thin mechanical properties for lithium-ion battery applications.So researchers have also focused their attention on the application of two-dimensional materials for lithium-ion battery electrode materials.In this paper,the properties of two-dimensional materials Cr₂N and h-BN were studied by first-principles calculations to modulate the properties through edge modifications,and the feasibility of suitable materials after modulation was theoretically evaluated as lithium-ion electrode materials,with the following main studies:（1）The geometric structure,magnetic and electronic properties of Cr₂N monolayers and edge-modified derivatives（Cr₂NF₂,Cr₂N（OH）₂and Cr₂NO₂monolayers）in two-dimensional carbon-nitrogen MXenes were investigated.We found that intrinsic two-dimensional Cr₂N is an antiferromagnetic metal,and Cr₂NF₂,Cr₂N（OH）₂after modification by-F and-OH functional groups retains antiferromagnetic metal properties.while Cr₂NO₂modified by-O functional group changes its properties and transforms into a ferromagnetic semimetal.The structural stability of Cr₂NF₂and Cr₂NO₂monolayers was further verified by molecular dynamics simulations at 300 K.The adsorption energy,electronic properties,diffusion energy barrier,open circuit voltage and theoretical capacity of Cr₂NF₂and Cr₂NO₂monolayers after lithium adsorption were subsequently Capacity calculations were carried out,and lower lithium diffusion energy barriers were obtained,which were about 0.18 eV and 0.58 eV on Cr₂NF₂and Cr₂NO₂monolayers,which ensured excellent charge and discharge rates as LIBs electrodes,and also higher theoretical capacities were obtained,which were about 583 m Ahg^-1and 556m Ahg^-1for Cr₂NF₂and Cr₂NO₂monolayers,thus Cr₂NF₂and Cr₂NO₂monolayers can be used as excellent materials for fast-charging Li-ion batteries.（2）The feasibility of BNF materials as electrode materials for Li-ion batteries was explored.We performed energy band and density of states calculations for semiconductor h-BN monolayers with large intrinsic band gap.And modulated the band gap and magnetic properties of h-BN by one-sided modification of fluorine atoms,which transformed BNF monolayers into ferromagnetic semimetallic materials with good electronic conductivity.And we investigated the structure,electronic properties,lithium atom,adsorption properties,diffusion energy barrier,open-circuit voltage and lithium storage capacity of BNF materials were investigated.It was found that BNF materials possess multiple diffusion paths,low diffusion energy barrier（0.18eV）and very high theoretical capacity(1243 m Ahg^-1),which are favorable for the detachment and embedding of lithium atoms on BNF materials and storage,and have high value for lithium applications.