First Principles Study Of Sodium Storage Properties Of Graphene-like MoS₂

With the rapid development of new energy technologies such as electric vehicles and energy storage power stations,the demand for large-scale energy storage is increasing day by day.However,the existing energy storage technology is difficult to meet the requirements of large-scale energy storage.Therefore,in recent years,people have extended their vision to the alkali metal Na element with abundant resources and low cost,so as to build a new system of low-cost and high-performance secondary battery by using the embedding reaction of such ions.This article mainly with MoS2 as the research object to construct the surface defects and graphene composite build reasonable geometric structure,by first principles calculation method,systematically studied the structure characteristics of sodium atoms under different system properties,electrical properties and density of states,as a class graphene MoS2 in the preparation of sodium ion battery electrode materials and modification to provide effective theoretical guidance.The following conclusions are obtained:First,when Na atoms are adsorbed at different adsorption positions of single layer MoS2,the adsorption energy at the top position of Mo is the smallest,the structure is the most stable and the material has the best safety performance.As the number of embedded sodium atoms increased from 1 to 4,the adsorption energy increased and the adsorption became more unstable.Moreover,the average embedding voltage does not change with the number of sodium ions embedded,but maintains at about 0.299 V,with good cycling performance.Second,The single vacancy defect of sulfur in a single layer MoS2 is easier to form.The imbedding of sodium atoms will make the system have metal characteristics and better electrical conductivity.With the increase of vacancy concentration,the average sod ium embedding voltage decreased,and the average sodium-embedding voltage was the lowest when adsorbed at the sulfur top.Finally,When graphene was compounded with molybdenum disulfide,it was found that the structure was most stable when the interval d was 3.2?.under the structure of sodium atoms adsorbed on different position find only in molybdenum disulfide/graphene layer containing adsorption for physical adsorption of vacancy in other place for chemical adsorption,Moreover,the infiltration of sodium atoms will enhance the metallic properties of molybdenum disulfide/graphene system,and the chemical bond between sodium ions and the system is mainly ionic bond with a small number of covalent bonds.