Role of PF
6
in the radiolytical and electrochemical degradation of
propylene carbonate solutions
Daniel Ortiz
a
, Isabel Jimenez Gordon
b
, Sol
ene Legand
c
, Vincent Dauvois
c
,
Jean-Pierre Baltaze
d
, Jean-Louis Marignier
e
, Jean-Fr
ed
eric Martin
b
, Jacqueline Belloni
e
,
Mehran Mostafavi
e
, Sophie Le Ca
€
er
a, *
a
LIONS, NIMBE, UMR 3685, CEA, CNRS, Universit e Paris-Saclay, CEA Saclay B^ at. 546, F-91191 Gif-sur-Yvette Cedex, France
b
CEA/LITEN/DEHT/SCGE, F-38000 Grenoble, France
c
CEA/DEN/DANS/DPC/SECR/LRMO, F-91191 Gif-sur-Yvette Cedex, France
d
Institut de Chimie Mol eculaire et des Mat eriaux d’Orsay, CNRS UMR 8182, B^ at. 410, F-91405 Orsay Cedex, France
e
Laboratoire de Chimie-Physique/ELYSE, UMR 8000 CNRS/UPS, Universit e Paris Sud, B^ at. 349, F-91405 Orsay Cedex, France
highlights graphical abstract
The presence of LiPF
6
in PC signifi-
cantly affects the decomposition
pathways.
CO
2
production is doubled in irradi-
ated PC/LiPF
6
1 M as compared to
irradiated PC.
This effect is specific of LiPF
6
and is
not observed in other salts such as
LiClO
4
.
A high reaction rate constant be-
tween the electron and PF
6
in PC is
measured.
Radiolysis accelerates aging and en-
ables the description of reaction
mechanisms.
article info
Article history:
Received 10 April 2016
Received in revised form
20 June 2016
Accepted 28 June 2016
Available online 9 July 2016
Keywords:
Propylene carbonate
Pulse radiolysis
Electrolysis
Li-ion battery
Anion effect
Degradation reaction mechanisms
abstract
The behavior under irradiation of neat propylene carbonate (PC), a co-solvent usually used in Li-ion
batteries (LIB), and also of Li salt solutions is investigated. The decomposition of neat PC is studied us-
ing radiolysis in the pulse and steady state regime and is assigned to the ultrafast formation, in the
reducing channel, of the radical anion PC
by electron attachment, followed by the ring cleavage, leading
to CO. In the oxidative channel, the PC(eH)
radical is formed, generating CO
2
. The CO
2
and CO yields are
both close to the ionization yield of PC. The CO
2
and CO productions in LiClO
4
, LiBF
4
and LiN(CF
3
)
2
(SO
2
)
2
solutions are similar as in neat PC. In contrast, in LiPF
6
/PC a strong impact on PC degradation is measured
with a doubling of the CO
2
yield due to the high reactivity of the electron towards PF
6
observed in the
picosecond range. A small number of oxide phosphine molecules are detected among the various
products of the irradiated solutions, suggesting that most of them, observed in carbonate mixtures used
in LIBs, arise from linear rather than from cyclical molecules. The similarity between the degradation by
radiolysis or electrolysis highlights the interest of radiolysis as an accelerated aging method.
© 2016 Elsevier B.V. All rights reserved.
* Corresponding author.
E-mail address: sophie.le-caer@cea.fr (S. Le Ca€ er).
Contents lists available at ScienceDirect
Journal of Power Sources
journal homepage: www.elsevier.com/locate/jpowsour
http://dx.doi.org/10.1016/j.jpowsour.2016.06.122
0378-7753/© 2016 Elsevier B.V. All rights reserved.
Journal of Power Sources 326 (2016) 285e295