石墨烯表面Lin(n<10)团聚体沉积行为的第一性原理计算  

Deposition behavior of Li_(n)(n<10)aggregates on graphene based on first-principles calculations

作　　者：沈丁[1,2] 王来贵 唐树伟[1] 高思达 孙闻 董伟[1] 杨绍斌[1] SHEN Ding;WANG Lai-gui;TANG Shu-wei;GAO Si-da;SUN Wen;DONG Wei;YANG Shao-bin(College of Materials Science and Engineering,Liaoning Technical University,Fuxin 123000;School of Mechanics and Engineering,Liaoning Technical University,Fuxin 123000,China)

机构地区：[1]辽宁工程技术大学材料科学与工程学院,阜新123000 [2]辽宁工程技术大学力学与工程学院,阜新123000

出　　处：《中国有色金属学报》2022年第2期476-484,共9页The Chinese Journal of Nonferrous Metals

基　　金：国家自然科学基金资助项目(51874167,21808095);中国博士后基金资助项目(2018M641707)。

摘　　要：采用基于密度泛函的第一性原理,计算研究锂离子电池石墨烯负极表面Li原子或团聚体Li_(n)(n<10)的沉积行为,包括最低能量构型、吸附能、差分密度电荷和态密度等性质。结果表明:当n≤2时,Li原子以分散的形式,优先沉积在石墨烯碳六元环中心上方位置;随着Li原子数的增加,当n≥3时,Li原子优先聚集,以团聚体的形式沉积在石墨烯表面,在实际中有可能形成稳定的Li_(4)、Li_(7)和Li_(9)团聚体。这表明石墨烯的最大储锂容量可能超过石墨,但容易形成锂枝晶。电子结构分析表明,Li原子或Li_(n)团聚体的电子转移至临近石墨烯的反键π轨道,Li原子的2s轨道和C原子的2p轨道出现明显的杂化现象。随着Li原子数n的增多,体系的费米能级向石墨烯反键π轨道移动,金属性和电子导电性增强。Li_(n)团聚体底层的Li—Li键通常为离子键,最外层的Li—Li键通常为共价键;Li_(n)团聚体与石墨烯之间的Li—C键为具有部分共价键属性的离子键,并且Li—C键强度随着Li原子数量n的增多而逐渐减小。Deposition behavior of Li atoms or aggregates Li_(n)(n<10)on graphene negative electrodes for lithium-ion batteries was investigated by the first principles calculations based on density functional theory,including the lowest energy configuration,adsorption energy,charge density difference and density of states.The results show that Li atom preferentially deposits above the center of the carbon six-membered ring of graphene in a dispersed form when n≤2.As the number of Li atoms increases,Li atoms preferentially aggregate to reunite and deposit on graphene when n≥3.It is possible to form Li_(4),Li_(7)and Li_(9) stable agglomerates in the charging process of the lithium ion battery,which indicates that the maximum lithium storage capacity of graphene may exceed that of graphite.However,the lithium dendrites will form easily.The electronic structure analysis shows that the electrons of Li atom or Li_(n) aggregates transfer to the anti-bondedπorbital of graphene,and the 2s orbital of Li atom and the 2p orbital of C atom are obviously hybridized.The Fermi level of the system moves to the graphene anti-bondπorbital as the number of Li atoms n increases,which leads to the result that the metallicity and electronic conductivity increase.The Li—Li bond at the bottom of the Li_(n) agglomerate is usually an ionic bond and the outermost Li—Li bond is usually a covalent bond.The Li—C bond between the Li_(n)agglomerate and graphene is an ionic bond with partial covalent bond property and the strength of the Li—C bond gradually decreases as the number of Li atoms n increases.

关 键 词：锂离子电池 石墨烯 Li_(n)团聚体 第一性原理 沉积行为 

分 类 号：TM912.9[电气工程—电力电子与电力传动]