掺杂FeF3·0.33H2O的结构设计及其电化学反应机理的第一性原理研究

Among metal fluorides,FeF3·0.33H2O is promising next generation of cathode material as Li-ion battery. However, the poor conductivty of FeF3·0.33H2O has prevented its practical application.Although cation doping is an effective method to improve material conductivity, the problems of complextion and random in selection of doping cation exist,which lacks systemic theoretical guidance. Moreover, the reaction machanism between FeF3·0.33H2O with Li requirs deep discussion.In this project,first principles calculations will be firstly carried out to clarify mechanism how to improve conductivity of FeF3·0.33H2O by cation doping in microscale and build quantitative relationship between doped cation and conductivity. It will be helpful to design MxFe1-xF3·0.33H2O with good conductivity .On the other hand,the MxFe1-xF3·0.33H2O (hkl) surface can be obtained, which can make fast charging and discharging possible. And the key scientific problem about perpendicular orientation of graphite crystallites on the surface of MxFe1-xF3·0.33H2O(hkl) will be studied. As a result, ionic and electronic conductivity of MxFe1-xF3·0.33H2O(hkl) can be improved furtherly. Lastly,models of ion transport and interfacial reaction will be built,which can uncover the inner law of interaction between cation doped FeF3·0.33H2O and Li ion. Our project will offer important theoretical guidance and scientific evidence for application of FeF3·0.33H2O and metal fluorides in Li-ion battery.

FeF3·0.33H2O是金属氟化物中最具有代表性的新一代锂电池正极材料，但较差的导电性阻碍了其实际应用。阳离子掺杂是改善材料导电性的有效方法，但存在着掺杂离子选择的复杂性和随机性等问题，尚缺乏系统的理论指导，而且其与锂的反应机理有待深入探讨。本项目采用第一性原理方法首先从微观尺度上阐明阳离子掺杂改善FeF3·0.33H2O导电性的机制，构建掺杂阳离子与导电性的定量关系，设计具有优良导电性的MxFe1-xF3·0.33H2O；优化并确定能快速充放电的晶面(hkl)，解决石墨烯在晶面(hkl)上垂直吸附等关键科学问题，进一步提高其离子和电子导电性；最后建立锂离子在掺杂FeF3·0.33H2O中的离子传输及界面反应模型，揭示锂离子在其中发生扩散及化学转换反应的内在规律，为FeF3·0.33H2O及金属氟化物在锂离子电池中的应用提供理论指导和科学依据。

氟化铁是金属氟化物中最具有代表性的新一代Li/Na/K 电池正极材料，但较差的导电性阻碍了其实际应用。阳离子掺杂是改善材料导电性的有效方法，但存在着掺杂离子选择的复杂性和随机性等问题，尚缺乏系统的理论指导，而且其与锂的反应机理有待深入探讨。本项目采用第一性原理方法首先分别从微观尺度上分别阐明Co、Ti离子掺杂改善氟化铁导电性的机制，构建Co、Ti离子掺杂离子与导电性的定量关系，设计出具有优良导电性的离子掺杂化合物Co0.17Fe0.83F3和Ti0.25Fe0.75F3·0.33H2O；然后探讨石墨烯在FeF3·0.33H2O晶面上垂直吸附等关键科学问题，通过掺杂离子筛选，发现Hf能最显著增强石墨烯在FeF3·0.33H2O（002）表面上的垂直吸附作用,进一步提高其离子和电子导电性；最后建立Li/Na/K离子在氟化铁表面的离子传输及界面反应模型，揭示Li/Na/K离子在其中发生扩散及化学转换反应的内在规律，为氟化铁在Li/Na/K离子电池中的应用提供理论指导和科学依据。