In situ SEM observation of the Si negative electrode reaction in an ionic-liquid-based lithium-ion secondary battery

• Published in: Microscopy Vol. 64; no. 3; p. 159
• Main Authors: Tsuda, Tetsuya, Kanetsuku, Tsukasa, Sano, Teruki, Oshima, Yoshifumi, Ui, Koichi, Yamagata, Masaki, Ishikawa, Masashi, Kuwabata, Susumu
• Format: Journal Article
• Language: English
• Published: England 01.06.2015
• Subjects: ionic liquid; negative electrode; silicon; scanning electron microscope; lithium-ion battery; in situ SEM observation
• ISSN: 2050-5701
• DOI: 10.1093/jmicro/dfv003

By exploiting characteristics such as negligible vapour pressure and ion-conductive nature of an ionic liquid (IL), we established an in situ scanning electron microscope (SEM) method to observe the electrode reaction in the IL-based Li-ion secondary battery (LIB). When 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)amide ([C2mim][FSA]) with lithium bis(trifluoromethanesulfonyl)amide (Li[TFSA]) was used as the electrolyte, the Si negative electrode exhibited a clear morphology change during the charge process, without any solid electrolyte interphase (SEI) layer formation, while in the discharge process, the appearance was slightly changed, suggesting that a morphology change is irreversible in the charge-discharge process. On the other hand, the use of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([C2mim][TFSA]) with Li[TFSA] did not induce a change in the Si negative electrode. It is interesting to note this distinct contrast, which could be attributed to SEI layer formation from the electrochemical breakdown of [C2mim](+) at the Si negative electrode|separator interface in the [C2mim][TFSA]-based LIB. This in situ SEM observation technique could reveal the effect of the IL species electron-microscopically on the Si negative electrode reaction.