用于锂离子电池的氟化铁和FeFx/C纳米复合电极的电子能量损失谱学

EELS spectroscopy of iron fluorides and FeFx/C nanocomposite electrodes used in Li-ion batteries.

作者信息

Cosandey Frederic, Al-Sharab Jafar F, Badway Fadwa, Amatucci Glenn G, Stadelmann Pierre

机构信息

Department of Materials Science and Engineering, Rutgers, The State University of New Jersey, Piscataway, NJ 08854-8065, USA.

出版信息

Microsc Microanal. 2007 Apr;13(2):87-95. doi: 10.1017/S1431927607070183.

DOI:10.1017/S1431927607070183

PMID:17367548

Abstract

A new type of positive electrode for Li-ion batteries has been developed recently based on FeF3/C and FeF2/C nanocomposites. The microstructural and redox evolution during discharge and recharge processes was followed by electron energy loss spectroscopy (EELS) to determine the valence state of Fe by measuring the Fe L3 line energy shift and from Fe L3/L2 line intensity ratios. In addition, transition metal fluorides were found to be electron beam sensitive, and the effect of beam exposure on EELS spectra was also investigated. The EELS results indicate that for both FeF3/C and FeF2/C nanocomposite systems, a complete reduction of iron to FeO is observed upon discharge to 1.5 V with the formation of a finer FeO/LiF subnanocomposite ( approximately 7 nm). Upon complete recharging to 4.5 V, EELS data reveal a reoxidation process to a Fe2+ state with the formation of a carbon metal fluoride nanocomposite related to the FeF2 structure.

摘要

最近基于FeF3/C和FeF2/C纳米复合材料开发出了一种新型锂离子电池正极。通过电子能量损失谱（EELS）跟踪充放电过程中的微观结构和氧化还原演变，通过测量Fe L3线能量位移和Fe L3/L2线强度比来确定Fe的价态。此外，发现过渡金属氟化物对电子束敏感，还研究了束流曝光对EELS光谱的影响。EELS结果表明，对于FeF3/C和FeF2/C纳米复合体系，在放电至1.5 V时观察到铁完全还原为FeO，并形成更细的FeO/LiF亚纳米复合材料（约7 nm）。在完全充电至4.5 V时，EELS数据显示重新氧化为Fe2+状态，并形成与FeF2结构相关的碳金属氟化物纳米复合材料。