Poly(ionic liquid) binders as Li+ conducting mediators for enhanced electrochemical performance

Article abstract of DOI:10.1039/c5ra16535k

A series of poly(ionic liquid)s (PILs) were used as binders for lithium-ion battery (LIB) with a LiFePO₄ cathode to explore their role and benefits in a model electrochemical energy storage system. The PILs are imidazolium-based and bear differ

Full text of DOI:10.1039/c5ra16535k

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Poly(ionic liquid) binders as Li+ conducting
mediators for enhanced electrochemical
Cite this: RSC Adv., 2015, 5, 85517
performance†
a
ab
a
a
*
*
Markus Antonietti and Jiayin Yuan
Jung-Soo Lee,‡ Ken Sakaushi,
A series of poly(ionic liquid)s (PILs) were used as binders for lithium-ion battery (LIB) with a LiFePO4 cathode
to explore their role and benefits in a model electrochemical energy storage system. The PILs are
imidazolium-based and bear different main chain structures and alkyl substituents. The results nicely
show that PILs both improve the cycling stability and specific capacity. When carefully designed, they
especially exhibited a usually high electrochemical stability against oxidative conditions (¼4.0 vs. Li/Li+). It
is found that the PIL binders together with carbon additive form very effective Li+ and electron
conducting pathways in the electrode. These finding illustrate that binder with carefully designed
chemical structures can have a high potential to improve the electrochemical performance even of
current rechargeable battery systems. A better Li+ and electron conduction is however of general
importance for a wide spectrum of electrochemical devices.
Received 17th August 2015
Accepted 30th September 2015
DOI: 10.1039/c5ra16535k
www.rsc.org/advances
endure the operation conditions.5 The direct and indirect
benets of an improved binder thereby sum up easily to 10%
1. Introduction
efficiency and a longer lifetime, an apparently small improve-
ment which however has to be multiplied with the some billion
battery systems produced and thrown away every year.
Electrochemical energy storage and conversion devices, such as
batteries, fuel cells, supercapacitors, but also liquid solar cells
and articial photosynthesis are attracting tremendous atten-
tion due to their active role in solving global challenges such as
the change towards sustainable energy and the coupled avoid-
ance of pollution and climate change.1 As a model, rechargeable
lithium-ion batteries (LIBs) have gained extensive utilization
in consumer electronics owing to their high power,
energy density and low weight.2 Expansion of LIBs for next-
generation technology, such as electric vehicles and large-
scale-electrochemical-energy-storage however relies on further
developments towards higher energy density, but also longer
life-time.3,4 Adding to the current focus on design of new elec-
trode materials and stable electrolytes at harsh conditions in
batteries, only little effort has been directed to polymer binder
so far. Such binder material accounts for typically 10 wt% of the
electrode mass, but it effectively “glues” all powderous
components, such as electrochemically active species and
conductive additives, into a mechanically stable electrode to
Through very limited but inspiring primary studies,6–12 it is
well known that even huger effects of polymer binders on the
overall performance of many electrochemical devices can be
expected, particularly with respect to the resulting mechanical
properties and interactions with electrolytes and active mate-
rial. PVDF has been extensively utilized as a standard choice for
electrodes of, among many, LIBs due to its electrochemical
inertness, especially for cathodes. The disadvantages of PVDF
binders are its insulating character and a relatively large
amount of electrolyte swelling. As a result, the adhesion of
PVDF to electrode materials deteriorates under long operational
run, and an increase in contact resistance between the active
material and carbon material is found.12 As lifetime enters
directly the costs per stored kWh of a practical large-scale
energy storage system, any lifetime improvement is valuable,
and a stable operation for more than a decade is desired.13 To
overcome these drawbacks, newly designed binder materials are
necessary. In our opinion, next-generation binders participating
in the main electrochemical reactions, but being at same time
electrochemically at least as stable as PVDF, can help address
those problems.
aMax Planck Institute of Colloids and Interfaces, Colloid Chemistry Department, Am
¨
Muhlenberg 1 OT Golm, D-14476 Potsdam, Germany. E-mail: jiayin.yuan@mpikg.
mpg.de
bNational Institute for Materials Science, International Center for Materials
Nanoarchitectonics (MANA), 1-1 Namiki, Tsukuba, 305-0044 Ibaraki, Japan. E-mail:
sakaushi.ken@nims.go.jp
Ionic liquids (ILs) are for a long time investigated for use in
several electrochemical energy storage/conversion devices, due
to their favorable physical properties such as negligible vapor
pressure, high ion conductivity, chemical inertness and a broad
electrochemical stability.14–21 Recently, the interest on poly(ionic
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c5ra16535k
‡ Present address: Chosun University, Department of Bio-chemical and polymer
engineering, 309 Pilmun-daero, Dong-gu, Gwangju 501-759, Korea.
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liquid)s (PILs) were found to be a highly attractive class of stir for 24 h at room temperature. Then, the oil was taken up in
functional polymers.22–27 To our knowledge, only in a recent ethyl acetate and washed with D.I. water several times. Excess
paper a PIL copolymer in nanoparticulate form have been solvent was removed in vacuum to give a very viscous liquid.
examined as binder for electrode of LIBs.28 In spite of the
1-(4-Vinylbenzyl)-2,3-dimethylimidazolium
TFSI
(M3).
exciting and encouraging progress reported when applied to the 4-Vinylbenzyl chloride (22 g, 0.14 M), 1,2-dimethylimidazole
cathode, these nanoparticle binders were nevertheless claimed (15 g, 0.154 M), and acetonitrile (100 mL) were mixed. This
to decompose under operation. It should however be possible to monomer synthesis follow the same method as mentioned
avoid this degradation when the binders are correctly designed above.
by polymer chemistry. In our recent attempt, via modifying the
building unit of PIL nanoparticles, we were able to extend the 2.3 Polymer synthesis
cycling stability of LIBs far beyond that based on PVDF binder.
Nevertheless, the complicated synthetic chemistry to PIL
Poly(1-vinyl-3-ethylimidazolium TFSI) (P1). The puried
monomer product M1 (50 g) was transferred in D.I. water
nanoparticles not only makes the large-scale production
(500 mL). 2.5 wt% VA86 (1.25 g) was then added. The mixture
unconventional but also restricts a deep insight in the electro-
was degassed with argon for 30 min and then stirred at 85 ꢀC for
chemical process of how these binders improve the electrode
24 h. Aer cooling down, the mixture was precipitated into ice
cooled THF (200 mL). The beige solid was ltered off and
performance.29
Here, we demonstrate the good performance and high
washed with THF several times (400 mL in total). The product
stability of more easy-to-synthesize linear chain PIL binders,
was dried at 80 ꢀC under high vacuum. The anion exchange was
while trying to describe mechanistically how they assist the
then performed by adding an aqueous solution of LiTFSI into
electrochemical reactions in LIBs. The data can be described by
an aqueous solution of the polymer to replace Brꢂ by TFSIꢂ. The
formation of a favorable Li+ conducting polymer interface
ꢀ
glass transition temperature is measured to be ꢃ90 C.
which acts as a heterojunction at the storage material grains. At
the same time, while stabilizing and connecting the carbon
additives, it forms a convenient electron conductive network.
Poly(1-(4-vinylbenzyl)-3-methylimidazolium TFSI) (P2). The
puried monomer product M2 (10 g) was transferred in DMF
(15 mL). 2 wt% AIBN (50 mg) was then added. The mixture was
ꢀ
degassed with argon for 30 min and then stirred at 85 C for
24 h. Aer cooling down, the mixture was precipitated into ice
2. Experimental
2.1 Materials
cooled water/MeOH (v/v ¼ 6 : 1). The beige solid was ltered off
and washed with water/MeOH several times (400 mL in total).
The product was dried at 80 ꢀC under high vacuum. This
monomer based-binder is anion exchanged aer polymeriza-
tion with same method.
Poly(1-(4-vinylbenzyl)-2,3-dimethylimidazolium TFSI) (P3).
This polymer synthesis from monomer M3 follows the same
method as P2 mentioned above.
1-Vinylimidazole, methylimidazole, 1,2-dimethylimidazole,
ethylbromide, 4-vinylbenzyl chloride, water-soluble nonionic
azo-initiator VA86 (Wake Chemicals), a,a0-azobisiso-
butyrobitrile (AIBN; Aldrich 99%), and lithium bis(tri-
uoromethylsulfonyl)imide (TFSI; Aldrich 97%) were used as
received without further purications. All solvents used were of
analytic grade.
2.4 Characterization methods
2.2 Monomer synthesis
Thermal gravimetric analyses (TGA) were performed on
a Netzsch TG209-F1 apparatus at a heating rate of 10 ꢀC minꢂ1
.
1-Vinyl-3-ethylimidazolium bromide (M1). 1-Vinylimidazole
(47.3 g, 0.5 M), ethylbromide (63.9 g, 0.57 M), and MeOH
(50 mL) were mixed. The mixture was stirred at 40 C for 24 h.
Aer cooling down, the mixture was precipitated into diethyl-
ether (4 L). The solid product was ltered off and washed with
diethyl-ether several times. Subsequently the product was dried
at room temperature under high vacuum (1 ꢁ 10ꢂ3 mbar) till
constant weight.
FT-IR spectra were recorded on a Varian1000 FT-IR spectrom-
eter. Gel permeation chromatography (GPC) was performed in
a NOVEMA-column using a mixture of 80% of aqueous acetate
ꢀ
buffer solution and 20% of methanol (ow rate 1.00 mL minꢂ1
,
PEO standards) and using RI detector-Optilab-DSP-
Interferometric Refractometer (Wyatt-Technology). P1 paired
with Br as counter anion was measured directly by GPC, while
P2 and P3 bearing TFSI as counter anion underwent an anion
exchange to replace TFSI with Br counter anion before
measurements by GPC. For the anion exchange reaction,
a solution of P2 and P3 bearing TFSI as counter anion was
added dropwise into a 1 M solution of tetrabutylammonium
bromide in acetone. The precipitate was soluble in water for
GPC measurements.
1-(4-Vinylbenzyl)-3-methylimidazolium TFSI (M2). 4-Vinyl-
benzyl chloride (40 g, 0.26 M), methylimidazole (21.34 g,
0.28 M), and acetonitrile (100 mL) were mixed. The mixture was
ꢀ
stirred at 45 C for 24 h. Aer cooling down, the product was
precipitated and washed with an excess of diethyl ether and
dried in vacuum at room temperature to give a viscous liquid of
1-(4-vinylbenzyl)-3-methylimidazolium chloride (VBmMCl). The
product VBmMCl (54 g) was dissolved in D.I. water (400 mL).
Lithium bis(triuoromethylsulfonyl)imide (61.26 g, 0.2 M) was
2.5 Electrochemical analysis
added to the aqueous solution, and an oily liquid was instantly The electrodes were prepared by spreading on aluminium foil
visible at the bottom of the ask. The reaction was allowed to current collector with slurry of acetylene black (AB), PILs
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binders and lithium iron phosphate (LiFePO4) in N-methyl- to determine the number-average apparent molecular weight of
pyrrolidone (NMP). The ratio was kept constant in all 80% the PILs, which are 130, 85 and 37 kDa, respectively (Fig. S3†).
LiFePO4, 10% AB and 10% binder material. The electrodes were These PILs feature a high density of IL species, i.e. one per unit,
dried at 80 ꢀC for 3 h and 120 ꢀC for 24 h. The loading of mixture as well as a multivalent binding power via the linear connection
was controlled at ꢃ2.5 mg. The electrodes were assembled in of the IL species into a polymer backbone. The polymers are
two-electrode Swagelok-type cells in an argon lled glove box expected to possess a broad electrochemical window and
(MBraun). Lithium foil was used counter electrode and glass enhanced surface activity, two of the key requirements for binder
ber membrane was used as separator. The electrolyte solution materials. In the specic design of this work, 3 different PILs in
was 1 M lithium hexauorophosphate (LiPF6) in mixture of terms of the backbone structure and substitution pattern on the
ethylene carbonate (EC) and dimethyl carbonate (DMC) (1 : 1 v/v). imidazolium ring were chosen and are denoted as P1, P2, and
The cells were cycled in potential window between 2.0 and 4.0 V P3, respectively. P1 has a polyvinylimidazolium-based backbone
vs. Li/Li+ using multichannel potentiostatic/galvanostatic system while P2 and P3 have a polystyrene-based one. Additionally, P2
(Bio-Logic). The C-rate was calculated on the basis of LiFePO4 and P3 differentiate in terms of blocking the alkalinity of the C2
assuming a theoretical specic capacity of 170 mA h gꢂ1. The position with a methyl unit.
corrosion test for PILs binders was performed at constant
The electrochemical properties of the PIL binders were
potential of 4.0 V Li/Li+ for 2 weeks using ꢃ2 mg of binders. investigated by several electrochemical techniques. First of all,
Electrochemical impedance spectroscopy (EIS) measurements we examined our binders using LiFePO4 as a model cathode
were carried out with a frequency range from 100 mHz to 20 kHz material (a redox potential at 3.4 V vs. Li/Li+; a theoretical
with an amplitude of 25 mV. The t of the experimental EIS data specic capacity of 170 mA h gꢂ1) with a current density of 1C,
was carried out by using EC-Lab.
which will assumes fully charge or discharge in one hour
(¼170 mA gꢂ1).30–32 The charge–discharge curves show that PIL
binders P1, P2 and P3 favorably delivered a higher specic
capacity of 126, 132 and 137 mA h gꢂ1, respectively, higher than
the PVDF binder with 120 mA h gꢂ1. This result indicates that
PILs can make a higher specic capacity of the material acces-
sible. In parallel, the electrodes with P1, P2 and P3 were proven
stable until 100 cycles at the same current density (Fig. 2B).
Further investigations on the PIL binders were executed by
a higher current density of 5C (¼850 mA gꢂ1), which is harsh
and provides accelerated ageing of all involved materials
(Fig. 2C). The cathodes using PVDF, P1, P2 and P3 show at these
high currents initial discharge capacities of 85, 90, 96 and 101
mA h gꢂ1, respectively. P1 exhibits the lowest specic capacity,
while P3 presents both a highest specic capacity and the best
3. Results and discussion
The chemical structures of linear PIL binders tested in this study
are shown in Fig. 1 and the synthetic details were given in the
ESI.† P1 was prepared via conventional free radical polymeriza-
tion of an ionic liquid monomer (M1) with Brꢂ as counter anion,
followed by an anion exchange reaction of the polymer to replace
Brꢂ with an electrochemically inert anion, bis(triuoromethane
sulfonyl)imide (TFSI). P2 and P3 were directly obtained via
conventional free radical polymerization of the corresponding
imidazolium ionic liquid monomers (M2 and M3) with TFSI as
counter anion. TFSI was also chosen to match the applied
conduction salt of the testing set-up. Since the free radical
polymerization method is widely employed in industry for
production of commercial polymers, the synthetic route chosen
for these binder polymers thus advantageously allows for large-
scale synthesis for their potential commercialization.
The success in the monomer and PIL synthesis was
conrmed by proton nuclear magnetic resonance (1H-NMR)
spectra and Fourier transform infrared spectroscopy (FT-IR) in
Fig. S1 and S2.† Gel permeation chromatography was performed
Fig.
2 Electrochemical properties of LiFePO4 electrodes using
different PIL binders. (A) Charge–discharge curves at a current density
of 1C (¼170 mA gꢂ1). (B) Cycling performance up to 100 cycles at 1C.
(C) Cycling performance up to 1000 cycles at 5C (¼850 mA gꢂ1). (D)
Rate capability for PIL binders and PVDF. The rate capability data of
Fig. 1 Chemical structures of three PIL binders used in this study. TFSI PVDF (the black line in (A), (B) and (C)) was taken from ref. 29 (active
denotes the counter anion, bis(trifluoromethane sulfonyl)imide.
materials loading 2.5 mg).
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cycling stability, with around 86% retention of the initial P1, though delivers a high specic capacity in the initial runs
specic capacity aer 1000 cycles (Fig. 3C). This is the highest (Fig. 2B), is intrinsically unstable during the long term
value of the tested binders in this work. Also the rate capability charging–recharging process. In the case of P2 (Fig. 3C), less
suggests that P3 is the best structure among the three tested PIL changes were observed in the 1H-NMR spectra. The change in a-
binders (Fig. 3D).
H signal was nevertheless spotted by a slight shi from 9.2 to
To track the chemical alterations being potentially respon- 9.5 ppm, a sign that a-H elimination takes place only partially.
sible for the different behaviors of these binders in the electrode Affected by this side reaction, the other 2 imidazolium protons
1
operation, H-NMR (Fig. 3) and FT-IR (Fig. S5†) spectroscopies deform their signals around 7.5 ppm. The two FTIR spectra did
were employed to analyze the chemical structure for all binders not present detectable variation before and aer the corrosion
before and aer a 2 week corrosion test at 4.0 V vs. Li/Li+ (see tests. A close view on the chemical structures of P1 and P2
ESI† for details). In Fig. 3A, the 1H-NMR spectra of PVDF appear implies that the large phenyl ring attached to the imidazolium
identical before and aer the test, indicating that PVDF is inert unit via a methylene bridge exerts a positive effect, which is
during this well-dene process. In comparison in Fig. 3B of P1, possibly related to the sterical hindrance that minimizes the
peaks between 7 and 9.5 ppm assigned to the imidazolium attack to the imidazolium ring. In the case of P3, the basic C2
protons have changed signicantly. The protic a-H (marked in position was blocked by a methyl group. No change was iden-
red) at C2 position vanished aer the test. It is known that the tied at all in both 1H-NMR and FTIR spectra (Fig. 3D and S5C
a-H due to its acidity may become invisible due to proton and D†). P3 is intrinsically the most inert among the three PILs
exchange with protic NMR solvents. In the current case, a non- in a harsh electrochemical environment and maintains its
protic NMR solvent, DMSO-d6 was used for these two samples glueing and conducting power.
under identical conditions, and the signal of a-H in P1 dis-
Further investigations were carried out to explain the exact
appeared only in the sample aer the corrosion test. This functions of PIL binders to deliver higher specic capacities
comparison thus supports unambiguously the occurrence of than PVDF. In our previous report, the PIL nanoparticle binders
side reactions at the C2 position. Additionally, in the FT-IR were discussed to reduce the interfacial charge transfer resis-
spectrum of the P1 binder, the bands at 2950 cmꢂ1 assigned tance, being a major part of resistance in Li+ intercalation
to –CH3 stretching models (Fig. S5B†) disappeared completely mechanism.29 In order to give a deeper insight in this
at their original position and a set of new bands were observed phenomenon of the current linear PIL system, we build up the
at 3150 cmꢂ1, implying that the a-H elimination may form the cathodes made of only binders (the cell conguration is PIL/
imidazol-2-ylidene persistent carbene under the electro- liquid electrolyte/Li) and measured cyclic voltammograms
chemical condition.33 Furthermore, the appearance of multiple (CVs) and electrochemical impedance spectra (EIS) at room
peaks from 1600 to 1725 cmꢂ1 in P1 aer the corrosion test is temperature (Fig. 4). We applied an equivalent circuit based on
indicative of the oxidation of the ethyl substituent into several half-blocking cell to t the EIS which is constituted of an elec-
types of carbonyl functions, such as aldehyde, ketone or trolyte resistance (Rs), charge transfer resistance (R1 and R2),
carboxylic acids, which cannot be specically distinguished at constant phase element (CPE1 and CPE2), and capacitance at
present. Bearing this observation in mind, we concluded that the blocking electrode (C1). For PVDF, P2, and P3, the CVs
exhibited similar specic capacitance and showed no redox
peak for all samples, which means that there is no electro-
chemical transition/energy storage function for the PIL binders
(Fig. 4A). Only P1 shows small anodic peak suggesting forma-
tion of decomposition as shown by the 1H-NMR spectrum
(Fig. 3B). However, the EIS show that the PIL binders are Li+
conductors in the presence of electrolyte (LiPF6 in EC/DMC)
while PVDF is not (Fig. 4B and S6, and Table S1†). A high Li+
conductivity of PILs is found in general in the presence of Li
Fig. 3 1H-NMR spectra of PVDF and 3 PIL binders to track changes of
the chemical structure before and after the electrochemical corrosion
test. (A) PVDF, (B) P1, (C) P2 and (D) P3. The black arrow in a point out
a peak assigned to a grease residue involved in all samples.
Fig. 4 Electrochemical characterization for the PIL binders and PVDF.
(A) Cyclic voltammograms, and (B) electrochemical impedance
spectra at room temperature.
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salts, which was also well studied by Ohno and other in any case an undesired choice, as it forms an insulation layer,
researchers.23,34,35 The pristine PIL phase doesn't contain any Li+ independent of the presence of electrolyte (Fig. 5 and S6†).
and is not a Li+ conductor. The Li+ conductivity in the cell
Also for interaction with the conductive carbon additive, the
occurred aer a formation of PIL/liquid electrolyte swollen layer formation of interfacial space Li+ charging layer will promote
phase, where the lithium salt starts to diffuse into the PIL phase ionic character and conduction. The well-known charge transfer
and turns it into a Li+ conductor. Worth mentioning, the binder interaction between PILs to carbons making them perfect
P3 outperforms all other systems already in this short term nanocarbon stabilizers42,43 is not only creating a favourable
experiment, i.e. it provides the lowest ion and current ux structural electron pathway due to a strong interaction between
resistance.
carbon and PILs, but at the same time will also increase the
Considering these results, we can propose an overall mech- number of charge carriers by charge transfer effects.
anism for high electrochemical performance where the PIL
binders do not only glue the particles, but actively contribute to
the high ion conductivity in a two-phase nano-heterojunction 4. Conclusions
system.36,37 The PIL binders absorb the organic electrolyte in
In conclusion, our results, using a LiFePO4-cathode of a LIB as
their chain structures, building up a nanometer thick layer with
a higher concentration of Li+ at the interface to the active
a model electrochemical system, show that already linear PIL
binders following specic structure designs can signicantly
battery material (here LiFePO4) of PIL binder and bulk electro-
improve the electrochemical performance of even current daily
lyte (Fig. 5). It must be underlined that the build-up of an
systems. This could be related to improved charge transfer
(inhibitive) Maxwell–Wagner polarization sensitively depends
on the charge concentrations at the interface. The applied
processes between solvent/salt and binder and binder/salt and
active material, while the creation of a new inter-phase
equivalent circuit model for the Li+-cathode containing two
improves both the ion and electron conductions. To our
semi-circles to t the experimentally obtained impedance signal
opinion, the use of such functional binder with adopted
mediator function is a new strategy to impact electrochemical
heterophase reactions in general, tackling both a slightly higher
(Fig. 4B inset): the rst semi-circle is related to Li+ transfer
resistance from a bulk liquid electrolyte to the heterophase
associated with the desolvation process (R1), and the second
capacity, but essentially a better rate behavior and longer life-
semi-circle described the Li+ transfer resistance in the LiFePO4
times of the resulting overall systems. We believe that different
heterophase (R2).38–40 From a view of chemistry, the data
choices of polymer moieties would give more stable binders in
describe an enhanced electrochemical reactions via high ion
high voltage region in order to apply to cathode materials such
conductivity and high electrochemical stability of an enriched
as LiCoPO4.
electrolyte nanophase, as the concentration of Li+ in the PIL-
stabilization layer is higher than in the bulk because the PILs
are favorably polarized media.
Acknowledgements
In the EIS measurements P3 showed both the lowest R1 and
R2 among the three PILs (Fig. 4B and Table S1†). We can only
speculate why P3 is most favourable, but it is to be assumed that
The authors would like to thank the Max-Planck Society (MAX-
NET Energy program) for the nancial support, and M & T
the 3 solvophilic substituents on the charged imidazolium ring
Olivine Co., Ltd for providing high-quality LiFePO4.
prohibit the known interface packing41 and thereby give the
space to embed mobile Li-ions. From this point of view, PVDF is
References
1 M. Armand and J. M. Tarascon, Nature, 2008, 451, 652–657.
2 J.-M. Tarascon, Philos. Trans. R. Soc., A, 2010, 368, 3227–3241.
3 Y.-C. Lu, B. M. Gallant, D. G. Kwabi, J. R. Harding,
R. R. Mitchell, M. S. Whittingham and Y. Shao-Horn,
Energy Environ. Sci., 2013, 6, 750.
4 N. Yabuuchi, K. Kubota, M. Dahbi and S. Komaba, Chem.
Rev., 2014, 114, 11636.
5 M. Winter and R. J. Brodd, Chem. Rev., 2004, 104, 4245.
6 J. Li, R. B. Lewis and J. R. Dahn, Electrochem. Solid-State Lett.,
2007, 10, A17.
7 I. Kovalenko, B. Zdyrko, A. Magasinski, B. Hertzberg,
Z. Milicev, R. Burtovyy, I. Luzinov and G. Yushin, Science,
2011, 334, 75.
Fig. 5 Hypothetic schematic illustration of effect on PIL/electrolyte
heterophase for high Li+ conductivity (left). On the other hand, PVDF
8 S. Komaba, Y. Matsuura, T. Ishikawa, N. Yabuuchi,
blocks the Li+ transport (right), therefore, it shows a higher resistance
W. Murata and S. Kuze, Electrochem. Commun., 2012, 21, 65.
(¼low Li+ flux) compared to the cathode composed with the PIL
9 C. V. Amanchukwu, J. R. Harding, Y. Shao-Horn and
binders. For the simplification, carbon additives are not described in
the figure.
P. T. Hammond, Chem. Mater., 2014, 27, 550.
This journal is © The Royal Society of Chemistry 2015
RSC Adv., 2015, 5, 85517–85522 | 85521

View Article Online
RSC Advances
Paper
10 S.-J. Park, H. Zhao, G. Ai, C. Wang, X. Song, N. Yuca, 26 H. Hu, W. Yuan, L. Lu, H. Zhao, Z. Jia and G. L. Baker, J.
V. S. Battaglia, W. Yang and G. Liu, J. Am. Chem. Soc.,
2015, 137, 2565.
11 M. Wu, X. Xiao, N. Vukmirovic, S. Xun, P. K. Das, X. Song,
Polym. Sci., Part A: Polym. Chem., 2014, 52, 2104.
27 Z. Jia, W. Yuan, C. Sheng, H. Zhao, H. Hu and G. L. Baker, J.
Polym. Sci., Part A: Polym. Chem., 2015, 53, 1339.
P. Olalde-Velasco, D. Wang, A. Z. Weber, L.-W. Wang, 28 J. von Zamory, M. Bedu, S. Fantini, S. Passerini and
V. S. Battaglia, W. Yang and G. Liu, J. Am. Chem. Soc.,
2013, 135, 12048.
12 S. S. Zhang and T. R. Jow, J. Power Sources, 2002, 109, 422–
426.
E. Paillard, J. Power Sources, 2013, 240, 745.
29 J. Yuan, S. Prescher, K. Sakaushi and M. Antonietti, J. Mater.
Chem. A, 2015, 3, 7229.
30 A. K. Padhi, K. S. Nanjundaswamy and J. B. Goodenough, J.
Electrochem. Soc., 1997, 144, 1188.
13 IEA, World Energy Outlook, IEA, 2014.
14 J. Yuan and M. Antonietti, Polymer, 2011, 52, 1469–1482.
15 M. Armand, F. Endres, D. R. MacFarlane, H. Ohno and
B. Scrosati, Nat. Mater., 2009, 8, 621.
16 G. Gebresilassie Eshetu, M. Armand, B. Scrosati and
S. Passerini, Angew. Chem., Int. Ed., 2014, 53, 13342.
17 K. Sakaushi and M. Antonietti, Bull. Chem. Soc. Jpn., 2015,
88, 386.
31 A. Yamada, S. C. Chung and K. Hinokuma, J. Electrochem.
Soc., 2001, 148, A224.
32 Y. Wang, Y. Wang, E. Hosono, K. Wang and H. Zhou, Angew.
Chem., Int. Ed., 2008, 47, 7461.
33 A. J. Arduengo, H. V. R. Dias, R. L. Harlow and M. Kline, J.
Am. Chem. Soc., 1992, 114, 5530.
34 H. Sakaebe, H. Matsumoto and K. Tatsumi, J. Power Sources,
2005, 146, 693.
18 K. Kishimoto, M. Yoshio, T. Mukai, M. Yoshizawa, H. Ohno
and T. Kato, J. Am. Chem. Soc., 2003, 125, 3196.
35 A. Fernicola, B. Scrosati and H. Ohno, Ionics, 2006, 12, 95.
¨
19 J. Ranke, S. Stolte, R. Stormann, J. Arning and B. Jastorff, 36 J. Maier, Prog. Solid State Chem., 1995, 23, 171.
Chem. Rev., 2007, 107, 2183. 37 J. Maier, Nat. Mater., 2005, 4, 805.
20 A. Fernicola, F. Croce, B. Scrosati, T. Watanabe and H. Ohno, 38 P. G. Bruce and M. Y. Saidi, J. Electroanal. Chem., 1992, 332,
J. Power Sources, 2007, 174, 342. 93.
21 K. Sakaushi, T.-P. Fellinger and M. Antonietti, 39 K. Sakaushi, G. Nickerl, F. M. Wisser, D. Nishio-Hamane,
ChemSusChem, 2015, 8, 1156.
22 J. Yuan and M. Antonietti, Macromolecules, 2011, 44, 744–
750.
E. Hosono, H. S. Zhou, S. Kaskel and J. Eckert, Angew.
Chem., Int. Ed., 2012, 51, 7850.
40 K. Sakaushi, E. Hosono, G. Nickerl, T. Gemming, H. S. Zhou,
S. Kaskel and J. Eckert, Nat. Commun., 2013, 4, 1485.
23 H. Ohno, Electrochim. Acta, 2001, 46, 1407.
24 G. B. Appetecchi, G. T. Kim, M. Montanino, M. Carewska, 41 Y. Zhou and M. Antonietti, Chem. Mater., 2004, 16, 544.
R. Marcilla, D. Mecerreyes and I. de Meatza, J. Power 42 D. Kuzmicz, S. Prescher, F. Polzer, S. Soll, C. Seitz,
Sources, 2010, 195, 3668.
M. Antonietti and J. Yuan, Angew. Chem., Int. Ed., 2014, 53,
25 H. Hu, W. Yuan, Z. Jia and G. L. Baker, RSC Adv., 2015, 5,
1062.
3135.
43 Y. Men, X.-H. Li, M. Antonietti and J. Yuan, Poly. Chem.,
2012, 3, 871–873.
85522 | RSC Adv., 2015, 5, 85517–85522
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