摘要
采用密度泛函理论平面波赝势的方法,计算了LiFeSO_4F和LiTi_(0.25)Fe_(0.75)SO_4F正极材料的电子结构。计算结果表明:当锂嵌入材料后,S、O和F的原子布居变化较小,电子主要填充在过渡金属的3d轨道,导致过渡金属被还原,成为电化学反应的活性中心。在嵌锂态中,锂和氧(氟)之间形成了离子键,而过渡金属(Ti和Fe)与氧(氟)之间则形成了共价键,S-O键的共价性最强。态密度的计算结果则表明:Ti和Fe均保持高自旋排列结构;LiFeSO_4F的两个自旋通道的带隙分别为2.88和2.29 e V,其导电性很差;Ti掺杂使体系的带隙消失,显著地提高了正极材料的导电性;LiTi_(0.25)Fe_(0.75)SO_4F系统中Ti-O和Ti-F键均比纯相中的Fe-O和Fe-F键的共价性更强,因此Ti掺杂材料具有更好的结构稳定性。
By using density functional theory plane-wave pseudo-potential technique(DFT-PW-PS), the electronic structures of LiFeSO4 F and LiTi(0.25)Fe(0.75)SO4 F cathode materials were calculated.The computational results indicated that after lithium was intercalated into the materials, the atomic populations of S, O and F atoms are changed slightly, and that the electrons are mainly filled on the 3d orbits of the transition metals, leading to the reduction of the transition metals and making the transition metals being as redox centers.In the intercalation states, ionic bonds were formed between lithium and oxygen(fluorine), while covalent bonds were formed between the transi-tion metals(Ti and Fe) and oxygen(fluorine),and the covalency of the S-O bonds is the strongest.The results from the density of states(DOSs) suggested that both titanium and iron take a high spin arrangement; the band gaps for the two spin channels of LiFeSO4 F are 2.88 and 2.29 e V, implying a rather poor electric conductivity; Ti doing will result in the disappearance of the band gap, enhancing significantly the electric conductivity of the cathode materials; As Ti-O and Ti-F bonds in LiTi(0.25)Fe(0.75)SO4 F system are stronger than Fe-O and Fe-F bonds in pure phase, Ti doping cathode materials would have a much better structural stability.
作者
陶伟
黄云
伊廷锋
谢颖
TAO Wei HUANG Yun YI Ting-Feng XIE Ying(School of Chemistry and Chemical Engineering, Anhui University of Technology, Maanshan, Anhui 243002, China Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, School of Chemistry and Materials science, Heilongjiang University, Harbin 150080, China)
出处
《无机化学学报》
SCIE
CAS
CSCD
北大核心
2017年第3期429-434,共6页
Chinese Journal of Inorganic Chemistry
基金
国家自然科学基金(No.51274002)
黑龙江省自然科学基金项目(No.E2016056)
安徽省自然科学基金项目(No.1508085MB25)
高校优秀青年人才支持计划重点项目(No.gxyq ZD2016066)
黑龙江大学功能无机材料化学教育部重点实验室开放基金
安徽省大学生创新创业训练计划资助项目(No.201610360163)
关键词
锂离子电池
正极材料
氟硫酸盐
电子结构
密度泛函
lithium-ion battery
cathode material
fluorosulfate
electronic structure
density functional theory