In Situ Dilatometric Study of the Binder Influence on the Electrochemical Intercalation of Bis(trifluoromethanesulfonyl) imide Anions into Graphite

Huesker, Jessica; Kwade, Arno; Froböse, Linus; Winter, Martin; Placke, Tobias

doi:10.1016/j.electacta.2017.10.042

Journal Article

FZJ-2018-04840

In Situ Dilatometric Study of the Binder Influence on the Electrochemical Intercalation of Bis(trifluoromethanesulfonyl) imide Anions into Graphite

Huesker, J. ; Froböse, L. ; Kwade, A. ; Winter, M. (Corresponding author)FZJ* ; Placke, T. (Corresponding author)

2017
Elsevier New York, NY [u.a.]

Electrochimica acta 257, 423 - 435 (2017) [10.1016/j.electacta.2017.10.042]

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Abstract: Dual-ion or dual-graphite batteries based on the mechanism of electrochemical anion intercalation into a graphite cathode have become attractive as an alternative storage technology in recent years. Due to large volume changes of the graphite particles during electrochemical anion intercalation, an appropriate electrode binder is required to sustain the mechanical integrity of the composite electrode and a stable and highly reversible charge/discharge cycling. Therefore, the expansion and contraction behavior of graphite positive electrodes containing different binders, including Na-carboxymethyl cellulose (CMC), poly(vinylidene)difluoride (PVdF) and a CMC/styrene butadiene rubber (SBR) mixture, during anion intercalation/de-intercalation was investigated by in situ electrochemical dilatometry (ECD). These measurements give insights into reversible and irreversible relative height changes at different cycling conditions and, thus, into the long-term cycling stability of the composite electrodes.Long-term cycling measurements reveal that the maximum and minimum electrode thicknesses of PVdF-based electrodes remain constant during anion intercalation/de-intercalation, while the CMC-containing electrodes exhibit a thickness increase in the first cycles and subsequent decrease after reaching a maximum electrode thickness. This instability can most likely be correlated with the mechanical instability of the electrode due to the high stiffness of the CMC binder compared to PVdF and an active material contact loss during cycling. If CMC is applied as binder mixture in combination with SBR, which shows a high flexibility, the thickness decay can be decreased. Our results give new insights into the optimization potentials of composite electrodes for carbon-based cathodes in dual-ion cells that experience large volume expansion during cycling.

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