Electrochemical and mechanical properties of nanochitin

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Ionics (2011) 17:407–414
DOI 10.1007/s11581-010-0517-z
ORIGINAL PAPER
Electrochemical and mechanical properties
of nanochitin-incorporated PVDF-HFP-based
polymer electrolytes for lithium batteries
N. Angulakshmi & Sabu Thomas & K. S. Nahm &
A. Manuel Stephan & R. Nimma Elizabeth
Received: 24 June 2010 / Revised: 19 November 2010 / Accepted: 28 December 2010 / Published online: 12 February 2011
# Springer-Verlag 2011
Abstract Nanocomposite polymer electrolytes (NCPE)
composed of poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) and chitin for different concentrations of
LiClO4 have been prepared by a hot-press technique. The
prepared NCPE films were subjected to XRD, SEM, FTIR
and tensile analyses. The thermal stability of NCPE
membrane was investigated by TG-DTA. Ionic conductivity
studies have also been made as a function of lithium salt
concentration for different temperatures ranging from 0 to
80 °C. The polymeric membrane comprising PVDF-HFP/
chitin/LiClO4 of ratio 75:20:5 (wt.%) offered maximum
ionic conductivity. Thermal study reveals that these
membranes are stable up to 260 °C.
Keywords Batteries . Electrochemical characterizations .
Polymer electrolyte . Nanocomposite electrolytes . XRD .
Mechanical properties . Thermal stability .
Ionic conductivity
N. Angulakshmi : R. N. Elizabeth
Department of Physics, Lady Doak College,
Madurai 652 002, India
S. Thomas
School of Chemistry, Mahatma Gandhi University,
Kottayam, India
K. S. Nahm
School of Chemical Engineering and Technology, Chonbuk
National University,
Chonju, Chonbuk 561-756, South Korea
A. M. Stephan (*)
Central Electrochemical Research Institute,
Karaikudi 630 006, India
e-mail: [email protected]
Introduction
More than three decades, polymer electrolytes have drawn
the attention of many researchers as they find applications
in not only lithium batteries but also in other electrochemical devices which include supercapacitors and electrochromic devices, etc. Unlike the liquid electrolytes, these
polymer electrolytes have a number of advantages like
high-energy density, no leakage of electrolytes and absence
of non-combustible reaction products at the electrode
surfaces [1–5].
The polymer electrolytes have gone through different
developmental stages namely (1) dry polymer electrolytes,
(2) gel polymer electrolytes and (3) composite polymer
electrolytes. Dry solid polymer electrolytes do not possess
any organic liquids, and the polymer host along with the Li
salt acts as solid solvent. The ionic conductivity of these
dry polymer electrolytes (PEO-LiX) have been found to be
very low (of the order of 10−8 S/cm at ambient temperature)
which excludes it from practical applications [6, 7]. On the
other hand, the gel polymer electrolytes composed of low
molecular weight liquid plasticizers (e.g. PC, DMC, DEC
etc.) along with polymer hosts offer high ionic conductivity
at ambient temperature. However, gel polymer electrolytes
lose their mechanical robustness upon plasticization. Furthermore, the lithium metal undergoes severe passivation
upon contact with gel polymer electrolytes. This phenomenon eventually leads the battery systems for poor safety
aspects. In the case of composite electrolytes, the ionic
conductivity has been enhanced by the incorporation suitable
fillers that prevent recrystallization process [8–11]. In a
sparking pioneer research, Weston and Steele [12] have
successfully incorporated Al2O3 in the poly(ethylene oxide)
PEO-matrix. By virtue of its appealing properties like low
cost, high electrochemical stability and helical structure the
408
PEO has drawn the attention of many researchers and has
been intensively studied.
Recent studies revealed that the composite polymer
electrolytes (CPE) alone can offer improved electrolytes/
electrode compatibility and prevent safety for Li-polymer
batteries [13–15]. The addition of fillers dramatically
improves the morphological and electrochemical properties
of polymer electrolytes [13–16]. Investigations have also
been carried out on highly conducting ceramic fillers
ionites [17], zeolites [18] as well as electrically neutral
ceramic fillers [19]. Results reveal that the addition of
ceramic filler improves the conductivity of polymer hosts
and their interfacial properties in contact with Li electrode
[15]. Kumar et al. [20] have shown that nanosized ceramic
fillers have better compatibility with Li metal than micronsized fillers. Extensive studies have been made with fillers
like SiO2, TiO2, γ-Al2O3 and α-Al2O3 [4].
In the recent past, poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) has been identified as a potential
candidate due to its appealing properties; the polymer host
itself has a dielectric constant of 8.4 which aids higher
dissociation ionic species. Also, the PVDF crystalline phase
acts as mechanical support while HFP amorphous phase
facilitates for higher ionic conduction [21].
In the present study [20], chitin, one the most
abundant polymers, poly(β-(1-4)-N-acetyl-D-glucosamine
is used as inert filler which is biodegradable, antibacterial
and is less toxic. It is also reinforced to strengthen
polymeric materials due to its crystalline micro-fibrils
form [22]. Shin et al. [23] have shown that membranes
prepared by conventional solvent casting method lead to
poor interfacial properties, at the Li-polymer interfaces
and the traces of solvent are trapped in the nanosized inert
fillers due to their high surface area even after prolonged
drying. Hence in the present study the hot-press technique
is employed for preparation of nanocomposite polymer
electrolyte.
Ionics (2011) 17:407–414
20 min and hydrolyzed with 3 N HCl under stirring for 1.5 h.
After hydrolysis, the suspension was transferred to a dialysis
bag and dialyzed for 24 h until its pH reached a value of 6. The
pH of the suspension was adjusted to 3.5 with HCl. The
dispersed whiskers were treated ultrasonically and were
filtered to remove residual aggregates. The resulting
nanochitin was preserved in a refrigerator with sodium
azoture as a protectant against microorganisms. The
prepared nanochitin particles were of size between 400
and 500 nm of length and diameter of 1 nm, and its
AFM picture is displayed in Fig. 1.
Preparation of nanocomposite polymer electrolyte
PVDF-HFP (Aldrich, USA) and LiClO4 (Merck, Germany)
were dried under vacuum for 2 days at 80 and 100 °C,
respectively. Nanochitin was also dried under vacuum at
50 °C for 5 days before use. Nanocomposite polymer
electrolytes were prepared by dispersing appropriate amounts
of chitin in (PVDF-HFP) LiClO4 as displayed (Table 1) and
hot-pressing into films as described elsewhere [23, 24].
The nanocomposite electrolyte films had an average
thickness of 30–50 μm. This procedure yielded homogenous and mechanically strong membranes, which were
dried under vacuum at 50 °C for 24 h for further
characterization.
Electrochemical characterization
The prepared films were sandwiched between the two
stainless steel blocking electrodes of diameter 1 cm and the
ionic conductivity of the membranes was measured using
an electrochemical impedance analyzer (IM6 Bioanalytical
Experimental
Synthesis of nanochitin
The chitin precursor was purchased from local sources in
India and was boiled and stirred with a 5% aqueous
solution of KOH for 6 h in order to remove most of the
proteins. Subsequently, it was washed with distilled water
and dried. This process was repeated three times. The
sample was then bleached with 17 g of NaCl in 1 L of
water containing 0.3 M sodium acetate buffer for 6 h at
80 °C. The bleaching solution was changed every 2 h. The
chitin suspension was then kept in 5% KOH for 72 h to
remove any residual protein, centrifuged at 3,000 rpm/min for
Fig. 1 AFM image of nanochitin
Ionics (2011) 17:407–414
409
Table 1 Compositions of polymer, chitin and LiClO4
Sample
Results and discussion
Polymer (wt.%)
Chitin (wt.%)
LiClO4 (wt.%)
S1
S2
S3
S4
S5
S6
S7
S8
95
90
85
75
70
94
93
92
0
5
10
17
20
5
5
5
5
5
5
8
10
1
2
3
S9
91
5
4
System, USA) in the 50 mHz to 100 kHz frequency and ac
amplitude was 10 mV at various temperature viz., 0, 15, 30,
45, 60, 70 and 80 °C. The bulk resistance of polymer
electrolyte was found from the impedance spectrum. Thus,
the ionic conductivity was calculated based on the equation:
s ¼ ‘=A 1=Rb
Where σ is the ionic conductivity, Rb the bulk resistance; ℓ and
A are the thickness and area of the specimen, respectively.
Morphological study of the films was made by a
scanning electron microscopy (SEM; Hitachi S-4700 FESEM) under a vacuum condition (10−1 Pa) after sputtering
gold on one side of the films. The thermal property of the
nanocomposite polymer electrolytes (NCPE) film was
investigated with SDT Q 600 instrument. Differential
scanning calorimetry (DSC) measurements were performed
at a rate of 10 °C/min between 20 and 250 °C, and in
thermogravimmetry-differential thermal analysis (TG-DTA)
the temperature range was 20–500 °C.
The lithium/polymer electrolyte interface was analysed
using Fourier transform infrared (FTIR; Thermo NICOLET
Corporation, Nexus model 670) by using single internal
reflection mode. The infrared spectra were obtained at
ambient temperature with an 8 cm−1 resolution.
The mechanical strength of the NCPE was determined
using a tensile machine (Tinius Olsen) with a constant
cross-head speed of 10 mm/min. The sample dimensions
were 20×50×0.1 mm. X-ray diffraction (XRD) measurements were conducted on a Bruker D8 X-ray diffractometer with Cu-Kα radiation (λ=1.54178 Å) at 50 kV and
250 mA with a scanning rate of 2 °/min. LiFePO4 was
synthesised by a simple sol–gel method as described
earlier [24]. The composite cathode was prepared by
blending LiFePO4 active material (70%) with super-P
carbon electronic conductor (20%) and PVDF binder
(10%). All preparations were performed in an argonfilled glove box (MBRAUN, Germany) having a humidity
content below 10 ppm.
XRD analysis
X-ray diffraction analysis is very useful in determining the
structure of materials. Figure 2(a–d) shows the X-ray
diffraction patterns of samples PVDF-HFP, chitin, PVDFHFP+LiClO4 (S1) and PVDF-HFP+LiClO4 +chitin (S5),
respectively. The diffraction peaks at 2θ=18.4, 20 and 26.6
correspond to (1 0 0), (0 2 0) and (1 1 0) reflections of
crystalline PVDF [25].This confirms partial crystallisation of
the PVDF units in the copolymer to give an over-all semicrystalline morphology for PVDF-HFP [26]. Since LiClO4 is
complexed in the polymer matrix, peaks corresponding to
LiClO4 are not observed which also indicate that the lithium
salt is completely dissolved in the polymer matrix (Fig. 2(c)).
Figure 2(d) shows that the intensity of crystalline peaks
decreased and broadened upon incorporation of chitin.
However the chitin peaks remain unaltered. These observations apparently reveal that the polymer undergoes significant structural reorganisation while adding inert fillers and
salts. Upon the addition of nanochitin and lithium salt, the
crystallinity of the polymer has been considerably reduced.
This reduction in crystallinity is attributed to small particles
of inert filler, which changes the chain reorganisation and
facilitates higher ionic conduction [27].
Thermal analysis
Figure 3 shows the DSC thermograms of samples PVDFHFP+LiClO4 (S1) and PVDF-HFP+chitin+LiClO4 (S5),
(e)
(d)
(c)
(b)
(a)
10
20
30
40
50
60
70
80
2 Theta (Degree)
Fig. 2 XRD spectra of polymer membranes: a PVDF-HFP, b chitin, c
PVDF-HFP+LiClO4+5% chitin, d PVDF-HFP+LiClO4+17% chitin
and e PVDF-HFP+LiClO4+20% chitin
Ionics (2011) 17:407–414
Endo
410
(a) 0% Chitin
(b) 5% Chitin
(c) 17% Chitin
(d) 20% Chitin
Heat Flow (mW)
14
S5
12
S1
50
100
150
Stress (MPa)
10
200
8
(a)
6
4
Temperature (ºC)
2
Fig. 3 DSC thermograms of PVDF-HFP+LiClO4 (S1), PVDF-HFP+
chitin+LiClO4 (S5)
(b)
0
0
respectively. The melting endotherm peak of PVDF-HFP+
LiClO4 (S1) (140 °C) gets broadened, and the melting
temperature gets reduced upon incorporation of nanochitin and lithium salt in the polymer matrix (S5). The
broadening of the endotherm also takes place with an
apparent decrease in the heat of fusion (ΔHf) with
increasing concentration of filler [28]. In order to evaluate
the thermal stability of polymer electrolytes, the thermogravimetric analysis of the NCPE was performed under
nitrogen atmosphere. The TG-DTA traces of PVDF-HFP+
LiClO4 (S1) and a PVDF-HFP + chitin + LiClO4 (S5)
membranes are displayed in Fig. 4a, b, respectively. A
weight loss of about 3% was observed about 116 °C for
sample (S1) and is attributed to the release of water
absorbed at the time of loading the sample [29, 30].
Furthermore, no weight loss was observed up to 304 °C
which indicates that no decomposition was induced by the
thermal steps of the hot-press process [24]. A peak
exhibited in DTA curve at about 140 °C is attributed to
the eutectic transition in the electrolytes [28]. Upon
addition of chitin in the polymer matrix (Fig. 4b), the
5
10
20
25
30
35
40
Fig. 5 Stress vs Strain curves of polymer electrolytes PVDF-HFP+
LiClO4+ x% chitin: (a) x=0, (b) x=5, (c) x=17 and (d) x=20
decomposition temperature is reduced to 260 °C which is
attributed to the decomposition of chitin.
Tensile measurements
In order to quantify the mechanical strength, the stress–strain
properties have been measured and are shown in Fig. 5. The
stress–strain behaviour gives fundamental information about
the load Vs deformation characteristics of polymer
composites. In the case of unfilled system (0% chitin),
the sample shows two distinct regions: the initial linear
region reflects the elastic characteristic and then nonlinear region shows the plastic deformation. As expected,
the neat sample (sample S1) has high elongation at break
(21%) and low tensile strength (12 MPa) as compared
with the filled nanocomposites [31]. Upon the addition of
chitin, we can see that the moduli and tensile strength
0.8
1.4
90
0.8
0.6
85
0.4
0.6
95
Weight (%)
1.0
Temperature Difference (oC)
1.2
TGA
100
90
0.4
85
0.2
80
DTA
DTA
0
50
100
150
200
250
300
350
400
0.2
450
75
0
o
Temperature ( C)
Fig. 4 TG-DTA traces of a PVDF-HFP+LiCIO4 and b PVDF-HFP+chitin+LiCIO4
100
200
300
o
Temperature ( C)
400
0.0
500
Temperature Difference (oC)
TGA
80
45
S5-Kynar+chitin+LiClO 4
95
Weight (%)
15
Strain (%)
S1 -Kynar+LiClO4
100
(d)
(c)
Ionics (2011) 17:407–414
411
Fig. 6 SEM images of a PVDFHFP+LiClO4, PVDF-HFP+
LiClO4+chitin, b 5% chitin
and c, d 20% chitin
increases (to 13 MPa) with dramatic decrease in strain at
break (4.2%). The maximum tensile strength and moduli
are obtained at 5% addition of chitin. At higher concentration of chitin, the decrease in tensile strength is
attributed to the aggregation of chitin particles in the
polymeric membrane.
Scanning electron microscope analysis
Figure 6a–d shows typical SEM images of samples S1, S3
and S5, respectively. Figure 6a shows a smooth surface
with different pore sizes. According to Chu et al. [32, 33],
the morphology of the electrolyte surface can be modified/
tailored by the incorporation of both ionic salts and fillers.
The SEM image (Fig. 6b) of PVDF-HFP+5% chitin+
LiClO4 (sample S3) shows a relatively smooth surface with
inhomogeneous morphology. Although it was intended to
prepare a uniform distribution of nanochitin in PVDF
matrix, the aggregation of nanoparticles with increasing
concentration of nanochitin could not be achieved in the
a
Figure 7a, b shows the variation of ionic conductivity as a
function of temperature for different concentrations of
lithium salt and nanochitin, respectively. It is well known
that Li ions migrate in two ways: (a) move along the
molecular chains of polymer, and (b) move in the amorphous
phase of polymer electrolyte [34]. The former is slow
transport where as the latter is fast. Figure 7a illustrates that
the ionic conductivity increases with the increase of
temperature and salt concentration. The ionic conductivity
S1
S2
S3
S4
S5
1E -6
Ionic Conductivity (S/cm)
Ionic Conductivity (S/cm)
Ionic conductivity
b
S1
S6
S7
S8
S9
1E -6
porous PVDF-HFP-based electrolytes, as evidenced in
Fig. 6c (PVDF-HFP+LiClO4 +20% chitin, sample S5).
This relatively smooth morphology (sample S1, Fig. 6a) is
attributed to a reduction in the crystallinity of PVDF-HFP
due to cross-linking with cations [32]. However at high
contents of nanochitin (20%), the membrane is seen to have
a rough surface with an inhomogeneous morphology with
islands of aggregated particles [31].
1E -7
1E -8
1E -9
1E -7
1E -8
1E -9
1E -10
1E -10
2.8
3.0
3.2
3.4
-1
1000/ T ( K )
3.6
3.8
2. 8
3.0
3. 2
3.4
3. 6
-1
1000/ T ( K )
Fig. 7 Ionic Conductivity as a function of temperature for the various a lithium salt concentrations and b chitin concentrations
3.8
412
Ionics (2011) 17:407–414
Fig. 8 FTIR spectra of a
PVDF-HFP, b chitin, c PVDFHFP+LiClO4 and d PVDFHFP+LiClO4+chitin
d
d
d
Transmittance (%)
c
c
c
b
b
b
a
a
a
4000 3800 3600 3400 3200 3000 1800
1700
1600
1500
1400
1300
1200
1000
800
600
400
Wavenumber (cm -1 )
gradually increases from 1.0×10−9 to 4.8×10−9 S/cm with
the increase in LiClO4 content for the samples S6 and S9,
respectively at 30 °C. Similarly, it increases from 3.2×10−7
to 3.5×10−5 S/cm respectively for the samples S6 and S9.
Apparently, at 80 °C the ionic conductivity of S6, S7 and S8
are lower than the S1 but S9 is higher than the S1. These
results are in accordance with those reported on PEO-based
polymer electrolytes with SiO2 lithium imide anion system
[35]. The ionic conductivity increases with the rise of
amount of nanochitin in the polymer film can be seen in
Fig. 7b. The volume of the interfacial layers, which
possesses a higher ionic conductivity, increases with the
amount of nanochitin filling in the polymer film so the
number of tunnels for lithium ions migration enhances. On
(c)
the other hand, the competition between nanochitin and F
atoms with respect to lithium ions facilitates the migration
for lithium ions in polymer electrolyte. So, the ionic
conductivity of polymer electrolyte increases with the
addition of nanochitin into polymer matrix.
According to Scrosati and co-workers [36], the Lewis
acid groups of the added inert filler may compete with the
Lewis acid lithium cations for the formation of complexes
with the PEO chains as well as the anions of the added
lithium salt. In the present study, the Lewis acid group of
the added filler (e.g. –OH group of chitin) may quite likely
compete with the Lewis acid lithium cation for the
formation of complexes in the PVDF-HFP chains as well
as with the anion of the LiX salts. This in turn results in
structural modifications and promotes “free” ions and this
accounts for the observed enhancement in ionic conductivity.
100
90
1491
405
1579
(b)
938
(a)
4000
3500
3000
2500
2000
1500
1000
500
Wave number (cm -1 )
Discharge Capacity (mA-h/g)
% Transmittance
1754
80
70
60
50
40
30
20
10
0
0
2
4
6
8
10
12
14
16
18
20
Cycle number
Fig. 9 FTIR spectrum of a sample S5; in situ from a lithium surface
in contact with b PVDF-HFP+LiClO4 and c PVDF-HFP+LiClO4+
chitin (S5)
Fig. 10 Discharge capacity as a function of cycle number for Li/
NCPE/LiFePO4 at 80 °C (C/10 rate)
Ionics (2011) 17:407–414
FTIR analysis
FTIR has been used as a powerful to characterise the
molecular and structural changes in the polymer electrolyte
systems. Figure 8(a–d) shows the FTIR spectra of pure
PVDF-HFP, chitin, PVDF-HFP+LiClO4 and PVDF-HFP+
LiClO4 +chitin. The vibrational bands at 490 cm−1 (Fig. 8a)
are assigned to the wagging vibrations of CF2 group. The
frequencies of 1,071,759 and 607 cm−1 belongs to the
vibration of crystalline phase of (PVDF-HFP) whereas
the frequencies of 883 and 841 cm−1 are assigned to the
vibration of amorphous phase of (PVDF-HFP) [26]. The CH2
ring and CH groups absorb in the regions of 3,100–
2,990 cm−1. The peaks appearing at 1,192 and 2,923 cm−1
are assigned to the asymmetrical stretching vibrations of CF2
and CH2 groups, respectively [37]. The deformation vibration
of CH2 group which appears at the frequency 1,402 cm−1
[38] will move to a higher frequency/position with the
weakening of interaction between H atoms of CH2 groups
and F atoms of CF2 groups. The vibration bands at 1,647 and
3,418 cm−1 can be assigned to the stretching and bending
vibrations of OH bonds of the absorbed water. Several IR
spectral studies have been made on chitin [37, 38]. The
amide I band is split into two at 1,659 and 1,626 cm−1. The
band at 1,659 cm−1 is commonly assigned to stretching of the
C=O group hydrogen bonded to N–H of the neighbouring
intra-sheet chain of (polyamides) and proteins [35].The band
at 1,626 cm−1 is attributed to a specific hydrogen bond of C=
O in the hydroxyl methyl group of the next chitin residue of
the same chain [39].
Upon incorporation of LiClO4 in polymer host, the peak
at 758 cm−1 shift to 748 cm−1 attributed to wagging band of
CH2Cl. Frequencies 840–560 cm−1 are assigned to C–Cl
stretching vibrations. The characteristic absorption vibrations of LiClO4: 1,150–1,080 cm−1, 941 cm−1 are assigned
to symmetrical vibration of ionic pairs between Li+ and ClO4−
[39], 624 cm−1 is stretching vibration of ClO4− and the sharp
peaks 3,597 and 1,637 cm−1 are stretching and bending
vibrations of OH bonds of the absorbed water. The absorption
peaks at 2,983 and 3,025 cm−1, which are assigned to the
symmetrical and non-symmetrical stretching vibration of CH2
groups, appear after addition of LiClO4 to polymer film,
because of the interaction between lithium ions and F atoms.
It is found that the intensity of these two absorptions decreases
with the addition of nanochitin (Fig. 8(d)) in polymer matrix.
Figure 8(d) shows that the deformed vibration of CH2 group
moves to 1,407 cm−1 after addition of nanochitin into polymer
matrix from 1,402 cm−1 (Fig. 8(c)).
Interfacial property of Li/NCPE
Figure 9(a) shows the FTIR spectrum of NCPE (sample S5)
consisting PVDF-HFP+LiClO4 +chitin. The FTIR spectra
413
obtained on a lithium electrode in contact with PVDF-HFP+
LiClO4 and PVDF-HFP+LiClO4 +chitin polymer membranes (through KBr window) are displayed in Fig. 9(b)
and (c), respectively. In Fig. 9(c), the original features
belonging to the polymer electrolytes not only disappeared,
but new peaks have arisen. When a nanochitin-incorporated
composite electrolyte comes in contact with the lithium
metal anode, new peaks appear at 1,754, 1,579, 1,492,938
and 405 cm−1. The peak that appears at 405 cm−1 is
attributed to Li–N and 938 cm−1 is assigned to unconjugated
cyclic anhydrides. The peaks at 1,754, 1,579 and 1,491 cm−1
are attributed to C=O, CH2 stretching and C–C skeletal
vibrations. [40, 41] It is significant that no predominant peak
appears around 1,100 cm−1 and is attributed to the fact that
LiClO4 is reduced to LiClOy species thus confirming its
presence [42].
Charge–discharge studies
The discharge capacity as a function of cycle number of the
polymer cell composed of Li/NCPE (sample S5)/LiFePO4
performed at C/10 rate is depicted in Fig. 10. The cell
delivered an initial discharge capacity of 80 mAh/g during
its first three cycles and decreased to 68 and 43 mAh/g at
its 10th and 20th cycle, respectively. The fade in capacity
has been calculated as 0.54 mAh per cycle. Possibly, this
fade in capacity is due to a composition of cathode which
has not been optimised [24]. A similar study has been
reported by Appetecchi et al. [24] where the authors
reported the cycling behaviour of PEO-based nanocomposite electrolytes for different temperatures and C rates.
Conclusions
PVDF-HFP-based NCPE electrolytes were prepared for
various concentrations of nanochitin and lithium salts. The
nanocomposite polymer electrolytes with a composition of
PVdF-HFP/chitin/LiClO4 (80:15:5) exhibited maximum
ionic conductivity at 80 °C. The maximum tensile strength
and moduli are obtained at 5% nanochitin-added polymer
electrolytes. These electrolytes are found to be stable
thermally up to 260 °C which is much higher than the
operating temperature of normal lithium batteries.
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