氧缺陷TiO_2-B作为可充电锂离子电池负极材料的第一性原理研究(英文)

First-Principles Study on TiO_2-B with Oxygen Vacancies as a Negative Material of Rechargeable Lithium-Ion Batteries

利用对氧缺陷的TiO_2-B材料进行密度泛函理论的计算,阐述了氧空穴对于TiO_2-B材料的电化学性质的影响。计算研究主要聚焦于缺陷材料的锂离子迁移和电子导电性等基本问题。计算结果表明在低锂离子浓度下(x(Li/Ti)≤0.25),相比于无缺陷的TiO_2-B,氧缺陷TiO_2-B有着更高的插入电压和更低的b轴方向迁移活化能,意味着锂离子的嵌入也更容易,这对于可充电电池的充电过程是有利的。而在高浓度下(x(Li/Ti)=1),锂饱和的氧缺陷TiO_2-B相较于无缺陷的TiO_2-B有着较低的插入电压,更有利于锂离子的脱嵌过程,这对于可充电电池的放电过程也是有利的。电子结构计算表明缺陷材料的禁带宽度在1.0-2.0 e V之间,低于无缺陷的材料的3.0 e V。主要态密度贡献者是Ti-Ov-3d,并且随着氧空穴的增加它的强度也变得更强。这就表明氧缺陷TiO_2-B有更好的电子导电性。

Density functional theory calculations were carried out on oxygen-deficient TiO_2-B to evaluate the effect of oxygen vacancies on its electrochemical properties. The computational studies focused on the lithium（Li）-ion transport and electronic conductivity of this defect-containing material. Calculations on TiO_2-B with low Li-ion concentration（x（Li/Ti）≤0.25） suggest that compared with defect-free TiO_2-B, oxygen-deficient TiO_2-B has a higher intercalation voltage and lower migration activation energy along the b-axis channel. This facilitates Li-ion intercalation, which is beneficial for the charge process of rechargeable batteries. Meanwhile, for TiO_2-B with high Li-ion concentration（x（Li/Ti） = 1）, saturated oxygen-deficient TiO_2-B with lower insertion voltage favors Li-ion deintercalation, which aids the discharge process. Electronic structure calculations suggest that the band gap of this defect-containing material is within 1.0-2.0 e V, which is narrower than that of defect-free TiO_2-B（3.0 e V）. The main contributor to the band-gap narrowing is the density of the Ti-Ov-3d state, which becomes much higher as the oxygen vacancy content increases, which increases electronic conductivity.