中文摘要：

采用基于密度泛函理论的第一性原理研究了含空位和杂质缺陷的LiFePO4电子结构,通过能带、态密度、布居分布分析,阐明缺陷及阴离子掺杂对材料电化学性能的影响,为LiFePO4的结构设计和实验研究提供理论基础。结果表明,Li、Fe和O空位型缺陷对LiFePO4的带型变化影响较小,禁带中无新的导带,禁带宽度有一定程度缩小,有利于电子的传导,但总能量上升,造成结构的不稳定性,在实际高温制备过程中,可能产生少量杂相,影响LiFePO4正极材料的电化学性能;P空位缺陷对LiFePO4的带型影响同样较小,但在禁带中产生了两条新的导带,禁带宽度明显变窄,有利于电子的传导,虽然总能量上升,造成结构的不稳定性,但在实际高温制备过程中,可能产生微量有利于电化学性能的杂相;F掺杂LiFePO4的带型出现了明显的变化,半导体类型由p型转变为n型,极大地促进了电子的导电性,总能量下降,结构稳定,对LiFePO4正极材料的电化学性能有正面的影响。

英文摘要：

The electronic structures of LiFePO4 crystal with various vacancy defects and anion doping were studied by the first-principles method based on DFT. To providing theoretical basis for the studies of LiFePO4 modification experiments,the effects of defects on the electrochemical performance were illustrated by the analysis of the band structure,the density of states and the population distribution. The results showed that Li,Fe and O-site vacancy defects almost have no effect on the band structure of LiFePO4,no new conduction band appears in the band gap though the forbidden band width decreases,and the rise in total energy indicates the instability of structure; P-site vacancy defects introduce two new conduction bands in the band gap,the decrease in forbidden band width is obviously in favor of the electronic conductivity,the increased total energy results in the instability of structure,however,it may be work to get high performance LiFePO4,due to the small amount of impurity phase produced during annealing; F-doping defects show significant effect on the band structure of LiFePO4 which makes the transform from n-type semiconductor into p-type semiconductor, indicating of tremendous improvement in the electronic conductivity. Besides, the improvement in the stability of structure can also be deduced according to the declined total energy.