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RSC Advances
Table 1 1H NMR data (300 MHz, D2O) for EMImCl$1.5AlCl3 and
EMImCl (300 MHz, CDCl3) before and after electrochemical and/or
thermal treatment
pyrolysis chromatography coupled with mass spectrometry
incorporated and headspace gas chromatography-mass spec-
trometry enables the identication of decomposition products
of ionic liquids. Thermal degradation of EMImCl$1.5AlCl3
produces chloromethane, dichloromethane, hydrochloric acid,
imidazole, alkylimidazole and 1-ethyl-3-methylimidazole based
on the formation of a reactive carbene intermediate. ClÀ ions are
irreversibly consumed and the obtained data can be explained by
an equilibrium, shis from excess of reducible Al-species
[Al2Cl7]À to excess of the not reducible Al-compound [AlCl4]À.
Another consideration that has to be taken into account is the
potential dri to more negative potentials during electroplating,
until the limit of the electrochemical stability window of IL is
exceeded. All these factors will contribute to irreversible
decomposition of ionic liquid and damage of the plating bath.
Sample
t, 3H
s
s
s, 3H q, 2H s, 1H s, 1H s, 1H
1a
2b
3c
4d
5e
6f
ppm 1.03
ppm 0.91 2.12
ppm 1.08
ppm 1.01 2.30 2.91 3.39 3.71
ppm 1.01 2.29 2.58 3.40 3.71
ppm 1.30
—
—
—
3.42 3.73
3.30 3.62
6.83 6.87
6.71 6.76
6.88 6.92
6.81 6.85
6.81 6.86
7.85
7.73
7.89
7.82
7.83
—
3.00 3.46 3.78
—
—
3.82 4.13
7.44 7.44 10.16
a
b
EMImCl$1.5AlCl3 before treatment. EMImCl$1.5AlCl3 aer thermal
c
treatment at 368 K. EMImCl$1.5AlCl3 aer electrochemical and
thermal treatment at 368
d
K
for 10 h.
EMImCl$1.5AlCl3 aer
for 50 h.
electrochemical and thermal treatment at 368
K
e
EMImCl$1.5AlCl3 aer electrochemical and thermal treatment at 368
f
K for 100 h. EMImCl aer thermal treatment at 368 K for 100 h.
Acknowledgements
EMImCl$1.5AlCl3 (before treatment). 13C NMR, (D2O): d
14.81 (s, CH3), 36.53 (s, CH3), 45.11 (s, CH2), 121.84 (s, 1C),
123.53 (s, 1C), 134.11 (s, 1C) ppm.
The authors acknowledge the Austrian Research Promotion
Agency (FFG) for the nancial support under contract 821964
(Neue Energien 2020, Neuartige Lithium Ionen Batterie
Elektroden).
Although EMIm halides (ClÀ, BrÀ or IÀ) exhibit temperatures
for onset decomposition between 553 K and 583 K,28 we have
found additional peaks in the 1H-spectra of the thermally
treated sample at 368 K. A possible explanation could be the
thermal decomposition of the complexed ionic liquid indi-
cating the presence of alkyl chlorides and HCl in the thermal
stressed sample. On the other hand the 13C-NMR spectra don't
show additional peaks, but this could be due to a less sensi-
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