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

Abstract

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.

In situ Scanning Electron Microscopy of Silicon Anode Reactions in Lithium-Ion Batteries during Charge/Discharge Processes

“…The electrochemical experimental conditions were controlled with a potentiostat/galvanostat (VersaSTAT 4, Princeton Applied Research (USA)). All the electrochemical experiments were conducted in the chamber of the in situ SEM system, as described in our previous work30. Ex situ SEM of the Si anode after the charge/discharge experiments was conducted after rinsing with battery-grade DEC (Wako (Japan)) in an argon-filled glove box.…”

“…In situ scanning electron microscopy ( in situ SEM), while receiving less attention in the battery researches as compared to TEM, will be a powerful and user-friendly analytical tool, because it is easy access to the setup for the in situ observation and SEM itself is a common analysis equipment. Indeed, we have published several articles on in situ SEM of electrochemical reactions in ILs27282930.…”

Review of Recent Development of In Situ/Operando Characterization Techniques for Lithium Battery Research

“…Measurements in electron microscopes require high vacuum to maintain the stability of the electron source and to minimize the noise signals from background scattering. Therefore, samples must be prepared to fit the vacuum requirement, which for batteries can be achieved by using solid-state electrolytes [94][95][96][97][98][99][100] , polymer electrolytes [101,102] , and ionic liquid electrolytes that exhibit low vapor pressure [103][104][105][106][107][108][109][110] , or by using special carbonate solvents with high boiling points and low vapor pressure [111] . In certain experimental conditions, heating is needed to obtain the operating temperature of a polymer cell [101] .…”

Lithium-ion battery performance enhanced by the combination of Si thin flake anodes and binary ionic liquid systems

“…All the operando experiments were conducted in the vacuum chamber of the SEM system. 24 The variation in morphology in the Si anode during the charge-discharge processes in CC/CV mode was observed by a secondary electron image mode. The charge-discharge rate was 1/2C.…”