锂离子电池LiTi0.25Fe0.75SO4F正极材料的电子结构
Electronic Structure of LiTi0.25Fe0.75SO4F Positive-Electrode Material for Lithium-Ion Battery
作者单位E-mail
陶伟 安徽工业大学化学与化工学院, 马鞍山 243002  
黄云 安徽工业大学化学与化工学院, 马鞍山 243002  
伊廷锋 安徽工业大学化学与化工学院, 马鞍山 243002;黑龙江大学功能无机材料化学教育部重点实验室, 哈尔滨 150080 tfyihit@163.com 
谢颖 黑龙江大学功能无机材料化学教育部重点实验室, 哈尔滨 150080 xieying@hlju.edu.cn 
摘要: 采用密度泛函理论平面波赝势的方法,计算了LiFeSO4F和LiTi0.25Fe0.75SO4F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;LiFeSO4F的两个自旋通道的带隙分别为2.88和2.29 eV,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;LiTi0.25Fe0.75SO4F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。
关键词: 锂离子电池  正极材料  氟硫酸盐  电子结构  密度泛函
基金项目: 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.gxyqZD2016066)、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和安徽省大学生创新创业训练计划资助项目(No.201610360163)。
Abstract: By using density functional theory plane-wave pseudo-potential technique (DFT-PW-PS), the electronic structures of LiFeSO4F and LiTi0.25Fe0.75SO4F 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 transition 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 LiFeSO4F are 2.88 and 2.29 eV, 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 LiTi0.25Fe0.75SO4F system are stronger than Fe-O and Fe-F bonds in pure phase, Ti doping cathode materials would have a much better structural stability.
Keywords: lithium-ion battery  cathode material  fluorosulfate  electronic structure  density functional theory
投稿时间:2016-09-14 修订日期:2016-11-02
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陶伟,黄云,伊廷锋,谢颖.锂离子电池LiTi0.25Fe0.75SO4F正极材料的电子结构[J].无机化学学报,2017,33(3):429-434.
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