Lithium fluoride/iron difluoride composite prepared by a fluorolytic sol-gel method: Its electrochemical behavior and charge-discharge mechanism as a cathode material for lithium secondary batteries

JOURNAL OF POWER SOURCES

卷:412

Article

Tawa, Shinya¹  Sato, Yuta²  Orikasa, Yuki³  Matsumoto, Kazuhiko¹  Hagiwara, Rika¹ 

[1] Kyoto Univ, Grad Sch Energy Sci, Sakyo Ku, Yoshida Honmachi, Kyoto 6068501, Japan

[2] Natl Inst Adv Ind Sci & Technol, Nanomat Res Inst, 1-1-1 Higashi, Tsukuba, Ibaraki 3058565, Japan

[3] Ritsumeikan Univ, Coll Life Sci, Dept Appl Chem, 1-1-1 Noji Higashi, Kusatsu, Shiga 5258577, Japan

关键词: Fluoride;    Reversal conversion;    Galvanostatic intermittent titration technique;    X-ray absorption spectroscopy;    Nanocomposite;   

DOI  :  10.1016/j.jpowsour.2018.11.046

来源: Elsevier

【 摘 要 】

Owing to their high theoretical capacity, metal fluorides have attracted significant interest as materials for fabricating the cathode of lithium secondary batteries. In the present study, a nanocomposite of LiF and FeF2 is prepared by a fluorolytic sol-gel method in an ethanol solution, for use as the cathode material of a lithium secondary battery. The produced LiF/FeF2 composite is characterized by broad X-ray diffraction peaks attributed to the nanosized (similar to 10 nm) LiF and FeF2 crystals, a large Brunauer-Emmett-Teller surface area of 119 m(2) g(-1), and adsorption-desorption hysteresis, attributed to the presence of mesopores. The results of charge-discharge tests indicates an initial discharge capacity of 225 mAh (g-LiF/FeF2)(-1) through reversal conversion at a current rate of 10 mA (g-LiF/FeF2)(-1). Based on a combination of galvanostatic intermittent titration, X-ray absorption, and X-ray diffraction investigations, a new reaction mechanism is developed, namely, the conversion of the local environment of an Fe atom from a rutile-type FeF2 structure to a rhenium trioxide-type FeF3 structure during charging, with the subsequent discharge resulting in the insertion of Li+ into the rhenium trioxide-type FeF3 structure, followed by the conversion reaction to LiF and FeF2.

【 授权许可】

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