摘要
氟化铁由于Fe–F键的高离子性和大的理论容量,是发展大容量锂/钠电池的关键候选正极材料.开发其新型矿物相是改善氟化铁类材料本征离子/电子导电率、减少非电化学活性组分辅助、提高其在转换反应和大尺寸离子嵌入方面活性的最有力手段,也是难点所在.本文总结了近年来通过模块化学和开框架策略探索新型结构原型的储能氟化铁的研究进展,特别针对六方钨青铜(HTB)、四方钨青铜(TTB)、烧绿石相(pyrochlore)等进行了介绍,这些成果解决了长期困扰氟基材料的导电性差、掺碳量高、储锂功率密度小、储钠能量密度低等难题.
Iron fluoride is the key candidate of cathode materials for high capacity Li/Na based batteries, owing to high ionicity of Fe–F and large theoretical capacity of fluoride. Exploring novel mineral phases of iron fluoride enables the improvement of intrinsic ion/electron conductivity, decreasing the use of electrochemical non-active components. It can lead to the activation of fluorides in terms of conversion reaction and large-sized cation（e.g., Na＋） storage. This paper summarizes the recent progress on exploring novel structure prototypes of energy storage iron fluorides by module chemistry and open framework strategies, especially on hexagonal tungsten bronze（HTB）, tetragonal tungsten bronze（TTB） and pyrochlore phases. These results address the important issues of fluorides on their poor conductivity, high carbon wire content, low Li-insertion power density and low Na-storage energy density. The HTB iron fluoride（FeF3×0.33H2O） is of tunnel structure, which is beneficial for the kinetic improvement and high rate Li（de）insertion. Complete dehydration of HTB phase is enabled by enhancing the crystallinity of HTB and removing its surface coating species. Pyrochlore iron fluoride of microporous framework（FeF3×0.5H2O） is endowed with interconnected three-dimensional（3D） open ion channels, enabling high reversible capacity of Na storage even under the involvement of conversion reaction. In contrast to HTB phase, dehydrating more flexible pyrochlore phase would cause serious amorphization（i.e., from topotactic densification of pyrochlore） however with the preservation of short-range ordering. The dehydration of open framework fluorides remarkably improves the conversion capacity and its retention, especially with good maintenance of higher voltage intercalation region. Ionic liquid based synthesis methods, e.g., dissolution-precipitation fluorination, ionothermal fluorination and solid-solid topotactic transformation in a top-down way, are explored to prepare the HTB and pyrochlore
作者
曹敦平
尹从岭
张金仓
李驰麟
CAO DunPing YIN CongLing ZHANG JinCang LI ChiLin(Department of Physics, Shanghai University, Shanghai 200444, China State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences Shanghai 200050, China College of Material Science and Engineering, Jiangxi University of Science and Engineering, Ganzhou 341000, China Materials Genome Institute, Shanghai University, Shanghai 200444, China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2017年第9期897-907,共11页
Chinese Science Bulletin
基金
国家自然科学基金(51372263
21301077
11574194)
中国科学院"百人计划"
国家重点研发计划(2016YFB0901600)资助
关键词
氟化铁
开框架相
烧绿石相
钨青铜相
正极材料
锂/钠基电池
转换反应
iron fluoride
open framework
pyrochlore phase
bronze phase
cathode material
Li/Na batteries
conversion reaction
