Modified Carbon As Anode Material For Lithium-Ion Batteries:A First-Principles Study

With the development of novel energy,the popularity of new energy vehicles and portable electronic devices,the social demand for energy storage equipment has increased sharply.As a kind of energy storage battery with a broad prospect,the highest market share and the most mature technology,lithium ions batteries（LIBs）are expected to solve the problem of large-scale storage of electric energy.Carbonbased anode materials have been widely used in lithium ions batteries with a bright future.Among the various anode materials,graphite anode materials are the most commercially successful,which account for the major portion of shipment market.Nevertheless,with the increasing desire for higher-capacity batteries,traditional graphite materials with lower capacity and limited promotion space have been gradually phased out.Novel anode materials have been intensively investigated,such as graphite derivatives like carbon nanotubes,graphene,graphyne.In this paper,first-principles calculations based on density functional theory is used to systematically study the lithium storage mechanism of modified graphdiyne and modified graphene,helping to establish a clear and intuitive link between the microscopic geometric changes of anode materials and the macroscopic performance of LIBs,thus providing novel insights into future design of high-capacity carbon anode materials for LIBs and contributing to further optimization of realistic energy storage devices.We firstly systematically studied the lithium storage mechanism and properties of group-15 elements doped graphdiyne（GDY）.We have found that:1.The doping of group-15 elements at the benzene ring sites would result in significant changes in GDY configuration,of which the aperture between the adjacent benzene rings varies from triangle to a six-times larger hexagon,providing more adsorption sites for Li.2.CBM and VBM of the doped graphdiyne are mainly contributed by the Pz orbital of carbon,leading to the in-plane distribution of most of the adsorption sites of lithium ions.3.Considering both electronegativity and pore size,P-GDY can hold the largest amount of lithium atoms in formation of Li₂₄C₂₂M₂H₄,with storage capacity of 1949mA·h·g^-1,which is 2.6 times higher than that of undoped graphdiyne,and the migration barrier of lithium ions on P-GDY is also significantly reduced.In addition,the lithium storage mechanism and performance of graphene/silicon dioxide and graphene/MXene nanocomposites were also systematically investigated.It was found that the formation of nanocomposite materials could significantly improve the stability and the storage capacity of the anode material due to interfacial quantum effect.In this paper,the lithium storage properties of modified graphdiyne and graphene were systematically studied at atomic scale using first-principles simulations.By directly comparing the geometric structures,electronic structures,adsorption behaviors,lithium storage capacities,migration barriers and other properties of the anode materials before and after modification,we found that element doping and formation of nanocomposites can dramatically improve the lithium storage performance of carbon-based anode materials.Our approach provides novel insights into the Li ions storage properties of modified graphdiyne and graphene from aspect of theoretical calculations,which would be useful to guide the future design of high-capacity carbon anode materials for LIB.