Solid polymeric electrolyte of poly(ethylene)oxide-50% epoxidized natural rubber-lithium triflate (PEO-ENR50-LiCF3SO3)

doi:10.4236/ns.2010.23029

Paper Menu >>

Journal Menu >>

Vol.2, No.3, 190-196 (2010) Natural Science

http://dx.doi.org/10.4236/ns.2010.23029

Solid polymeric electrolyte of poly(ethylene)oxide-50%

epoxidized natural rubber-lithium triflate

(PEO-ENR50-LiCF3SO3)

Siti Aminah bt. Mohd Noor1, Azizan Ahmad1, Mohd. Yusri bin Abd. Rahman2*, Ibrahim Abu Talib 3

1School of Chemical Science and Food Technology, Faculty of Science and Technology, National University of Malaysia, Selangor,

Malaysia; [email protected], [email protected]

2College of Engineering, Universiti Tenaga Nasional, Selangor, Malaysia; yusri@uni te n.ed u.my

3School of Applied Physics, Faculty of Science and Technology, National University of Malaysia, Selangor, Malaysia;

[email protected]

Received 19 November 2009; revised 28 December 2009; accepted 25 January 2010.

ABSTRACT

A solid polymer electrolyte (SPE) films consist-

ing of polyethylene oxide (PEO), 50% epoxi-

dized natural rubber (ENR50) and LiCF3SO3 with

various compositions of PEO-ENR50 and vari-

ous weight percentage of LiCF3SO3 were pre-

pared by solution casting technique. The poly-

mer electrolyte films were characterized using

DSC, XRD and AC impedance spectroscopy.

The SPE with the PEO-ENR50 composition of

70-30 shows the highest conductivity of 4.2 ×

10-5 Scm-1 at the 15 wt.% of LiCF3SO3 compared

with the other composition of PEO/ENR50. This

composition was then chosen to investigate the

effect of LiCF3SO3 on the thermal property,

structure and conductivity of the electrolyte.

The highest room temperature conductivity of

1.4 × 10-4 Scm-1 was achieved at 20 wt.% of

LiCF3SO3. The conductivity result is supported

by the DSC and XRD analysis which showed the

semi- crystalline nature of PEO turning to amor-

phous state due to the increase in LiCF3SO3

content.

Keywords: A. Polymers; C. Differential Scanning

Calorimetry (DSC); C. X-Ray Diffraction;

D. Electrical Conductivity; D. Electrical Properties

1. INTRODUCTION

Main application of polymer electrolytes lies in electro-

chemical device such as display, sensor, electrochemical

window, super-capacitor, rechargeable battery and photo-

electrochemical cell. However, the main attention of

many solid state researchers is the development of sec-

ondary lithium batteries [1-4]. Ionic conducting polymer

electrolytes were first suggested by Fenton et al. in 1973

[5], who reported that PEO-salt complexes are capable of

exhibiting ionic conductivity and subsequently substan-

tial activities were directed towards the development of a

wide variety of solid polymer electrolytes using different

combinations of polymer and salt. The most reported and

extensively studied polymer host for solid polymer elec-

trolyte is PEO [6-12]. This is due to a high electrochemi-

cal stability of PEO in comparison with other polyethers,

copolymers or PEO branched polymers [9]. Besides,

PEO has a good solubility for many salts such as LiTFSI,

Li2SO4, NH4ClO4 and LiCF3SO3. Even though PEO has a

good electrochemical stability, PEO exists in semi-crys-

talline state at room temperature and does not have an

excellent contact with the electrodes.

Solid polymer electrolytes (SPE) for lithium batter-

ies have many advantages over its counterpart liquid

electrolyte, such as mechanical stability and processing

flexibility. However, the conductivity at room tem-

perature is usually too low to be utilized in ionic device.

There are various techniques that can be employed to

enhance the conductivity of SPE at room temperature.

The recent technique developed for solid polymer elec-

trolytes is the dispersion of nanosize inorganic ceramic

filler particles such as Al2O3, SiO2, TiO2, SnO2, ZnO

and ZrO in the electrolyte systems [6-10]. Propylene

carbonate (PC), ethylene carbonate (EC) and dibutyl

phthalate (DBP) are also used as plasticizers for con-

ventional polymer electrolyte systems [11-13]. An al-

ternative to ceramic fillers or plasticizers is to employ a

complexing polymer such as modified natural rubber.

This is due to their distinctive characteristics such as

low glass transition temperature, soft elastomeric char-

acteristic at room temperature, good elasticity and ad-

hesion that makes them a suitable candidate as a filler

for polymeric electrolyte systems [1,11,12]. Figure 1

shows the structure of ENR50 dimmer.

S. A. M. Noor et al. / Natural Science 2 (2010) 190-196

191

Figure 1. Structure of ENR50 dimmer.

This work describes the effect of ENR50 content on

the conductivity of PEO-ENR50-LiCF3SO 3 electrolyte at

the fixed concentration of the LiCF3SO3 salt. The PEO-

ENR50 composition that gave the highest room tem-

perature conductivity was chosen to study the effect of

the salt content on the conductivity of the electrolyte.

The blended polymer of PEO-ENR50 as a polymer host

was doped with LiCF3SO3 using the solution casting

technique [14] to obtain a solid polymeric electrolyte

film. This work also reports the effect of LiCF3SO3 con-

tent on thermal property and structure of the electrolyte

fixed at PEO-ENR50 composition of 70/30.

2. EXPERIMENTAL

2.1. Sample Preparation

The SPE films were prepared by means of the solu-

tion-cast technique using a single solvent of THF. The

host materials, poly(ethylene oxide) (PEO) (MW =

600,000) was obtained from Sigma Aldrich, while 50%

epoxidized natural rubber (ENR50) (MW = 592,487) was

supplied by Malaysian Rubber Board. The required

amounts of PEO and ENR50 were dissolved in tetrahy-

drofuran (THF) that was obtained from SYSTERM

ChemAR. Lithium triflate (LiCF3SO3), obtained from

Fluka was used as the doping salt. All the materials were

used without further purification. Subsequently, the de-

sired amounts of PEO-ENR50 and various weight per-

centage of LiCF3SO3 were dissolved separately in THF,

mixed together and stirred efficiently for 24 hours in

order to achieve a homogeneous mixture. The solutions

obtained was cast on a teflon mould and was allowed to

evaporate completely at room temperature to produce an

electrolyte film. Then, the film was dried in a vacuum

oven at 60oC for 24 hours to remove the residual solvent.

This procedure provided a mechanically stable, free

standing and flexible films with the thickness ranging

from 150 to 250 μm. The preparation of SPE was carried

out in an atmosphere environment at room temperature

[12,14].

2.2. Sample Characterizations

The AC impedance measurement was carried out at

room temperature using a high frequency response ana-

lyzer (HFRA Solartron 1256, Schlumberger) in the fre-

quency range of 100 Hz-1 MHz with 30 mV amplitude.

The electrolyte was sandwiched between the stainless

steel ion-blocking electrodes with a surface contact area

of 2.0 cm2. The bulk resistance, (Rb) of the electrolyte

was determined from the equivalent circuit analysis as-

sisted with Z-View software. The conductivity, (σ) have

been calculated from the equation σ = (1/Rb)(t/A), where

t is the film thickness and A is the active area of the

electrode. The thermal property measurement was con-

ducted using a differential scanning calorimeter model

8822e Mettler Toledo from -60oC and + 150oC at a scan-

ning rate of 10oC min-1 under nitrogen atmosphere. Pre-

viously, a pure indium and tin were used for temperature

and enthalpy calibrations for DSC measurements. Ap-

proximately, 1 to 3 mg of the electrolyte film specimen

was used for each DSC measurement. The X-ray diffrac-

tion technique was performed on the electrolyte films at

room temperature using a Siemens model D5000

(Cu-Kα; α = 1.5418 Å). The diffraction angle, 2θ was

10o to 45o using a step size of 0.025o to determine the

crystallinity of the electrolyte samples. The Scherrer

length was then automatically calculated by evaluation

(EVA) software.

3. RESULTS AND DISCUSSION

3.1. Effect of ENR50 Content on

Conductivity of PEO- ENR50-LiCF3SO3

Electrolyte

The freestanding electrolyte films of PEO-ENR50-

LiCF3SO3 have been produced by using solution casting

technique. Table 1 shows the conductivity the electrolyte

with various compositions of PEO-ENR50 at the fixed

concentration of LiCF3SO3 (15 wt.%). The percentage

by weight of ENR50 was chosen up to 30% since after

this level, the electrolyte became a gel electrolyte and

was not a free standing film. It made the electrolyte film

Table 1. Room temperature conductivity for various com-

position of PEO-ENR50 at 15 wt.% LiCF3SO3.

Composition Ionic conductivity (Scm-1)

100-0 2.1 × 10-6

90-10 4.1 × 10-6

80-20 1.0 × 10-5

70-30 4.2 × 10-5

S. A. M. Noor et al. / Natural Science 2 (2010) 190-196

192

was difficult to peel off from the mould. From Table 1,

the conductivity of the electrolyte without ENR50 was

2.1 × 10-6 Scm-1. The conductivity was found to in-

crease with the increasing percentage of ENR50 in the

polymer host. The highest room temperature conduc-

tivity of 4.2 × 10-5 Scm-1 was achieved at 70-30 com-

position of PEO- ENR50. This observation shows that

the ENR50 content affected the conductivity of the

electrolyte. It shows that the elastomeric characteristic

of ENR50 reduced the glassy nature of PEO. This con-

dition will enhance the segmental motion of the poly-

mer host. The effect of segmental flexibility is respon-

sible for the formation of free volume which enhances

the ionic conductivity. The strong adhesive property

can give an efficient contact between the electrodes in

electrochemical contacts [12]. This behavior can be

seen in the electrolyte system which is due to a good

elasticity and adhesion property of ENR50. Razali et al.

[12] reported that ENR50-LiTf with 100% wt. of

EC/PC gave ionic conductivity of 4.0 × 10-5 Scm-1 at

room temperature. This conductivity value was almost

similar with our electrolyte system for 70-30 composi-

tion without any plasticizer. It shows that with the ab-

sence of a costly plasticizer, the conductivity of the

electrolyte has been improved by blending PEO with

ENR50. In addition, this electrolyte system produced a

low cost and an environmental friendly electrolyte.

Besides, the use of PC and EC can corrode the lithium

metal electrode in electrochemical cell [16]. Glasse et

al. [11] reported the incorporation of PEO with ENR50

can reduce the sticky property of ENR50 and made the

film could be peeled off easily from the mould.

3.2. Effect of LiCF3SO3 Salt on Thermal

Property, Structure and Conductivity of

PEO-ENR50-LiCF3SO3 Electrolyte

The effect of LiCF3SO3 salt on the above properties of a

PEO-ENR50-LiCF3SO3 electrolyte was investigated by

choosing the electrolyte with the 70-30 composition of

PEO-ENR50. This is because this composition has

shown the best performance in term of ionic conductiv-

ity as compared with the other compositions of

PEO-ENR50. The electrolytes were prepared by varying

the percentage by weight of LiCF3SO3 from 5% to 25%

at 5% interval. In order to investigate the effect of the

salt content on the thermal property of the electrolyte

such as melting point, DSC measurement was performed

on the prepared electrolyte samples. Figure 2 shows the

DSC thermographs for all samples. The sharp endother-

mic peak observed at 68oC, corresponds to the crystal-

line melting temperature (Tm) of the pure PEO [15]. The

endothermic peak for pure PEO showed the transition

from 68oC to 60oC by addition of 5 wt.% of the salt. The

Tm value decreases dramatically to 49oC with addition of

20 wt.% of the salt. This observation shows the reduc-

tion in Tm value by addition of the salt. The endothermic

curves also indicate a reduction of PEO crystallinity. The

relative percentage of crystallinity (λ) of PEO has been

calculated by using the relation, λ = (ΔHm/ΔHm

o) x 100%,

where, ΔHm is the melting enthalpy estimated experi-

mentally and ΔHm

o used as referenced is the melting

enthalpy for 100% crystalline PEO (213.7 Jg-1) [16]. The

calculated values of λ are summarized in Table 2. The

crystallinity degree of the electrolyte decreases with the

wt.% of the salt which causes an increase in the amor-

phous phase. The polymeric chain in the amorphous

phase is more flexible, which results in the enhancement

of segmental motion of the polymer [17]. The Tm and λ

values obtained from this work for polymer electrolyte

based on PEO closely agree with the values reported in

literature [8,18]. The reduction of Tm and λ suggest that

the interaction between the polymer host backbone and

LiCF3SO3 affects the dynamic main chain of the polymer.

This will promote the amorphous phase which is ex-

Figure 2. DSC thermograms of PEO,PEO-ENR50 (70-30) with different wt.% LiCF3SO3.

S. A. M. Noor et al. / Natural Science 2 (2010) 190-196

193

Table 2. O/Li mole ratio, crystallinity, (λ) and melting temperature, (Tm) of PEO-ENR50-LiCF3SO3 electrolyte.

LiCF3SO3 (wt%) to

PEO/ENR50 (70/30) O/Li Tm of PEO

(oC)

Relative percentage of

crystalline phase (λ)

(%)

Pure PEO - 68 78.5

Pure ENR - -

0% 0/1 67 49.9

5% 16/1 60 35.9

10% 8/1 53 31.6

15% 5/1 50 24.5

20% 4/1 49 19.1

25% 3/1 - -

2 theta

20 25 30 35 40

Intensity (a.u)

2 theta

20 2530 35 40

Intensity (a.u)

(b)

(e)

(d)

(c)

(g)

(f)

(h)

(a)

Figure 3. XRD patterns of PEO-ENR50 (70/30) with LiCF3SO3 with different weight ratios

(a) Pure salt (b) Pure PEO (c) 0% (d) 5% (e) 10% (f) 15% (g) 20% (h) 25%.

pected to favour ion transport, thus enhancing the elec-

trolyte conductivity [2]. DSC investigation confirmed

that PEO crystallinity is reduced with the addition of

ENR50 and the salt which has a plasticizing effect on the

polymeric chain.

The structure of the electrolyte samples was investi-

gated by XRD analysis. The XRD pattern of the electro-

lyte samples with various concentrations of LiCF3SO3,

and that for pure PEO and pure LiCF3SO3 salt are shown

in Figure 3. The indexing of the two PEO peaks are re-

ported to be (120) at 19.5o and (032) + (112) at 23.5o of

the monoclinic system [19]. The characteristic diffraction

peaks of crystalline PEO are apparent between 2θ = 15o –

40o [3,20]. The two prominent peaks for PEO at 2θ =

19.2o and 23.2o are present in all patterns, indicating the

presence of pure polymer. Nevertheless, the patterns

show that the intensities of the prominent peaks decrease

and become broader with the increasing wt.% of LiCF3SO3.

The broadening of sharp peaks of PEO could be due to the

disruption of the PEO crystalline structure by LiCF3SO3

and indicates that the complexation has taken place in the

amorphous phase [10]. These results confirm both the

decrease in degree of crystallinity and the lamellae size of

PEO with the presence of plasticizing LiCF3SO3 [15]. The

LiCF3SO3 peaks are not seen in any of the polymer-salt

complexes and this signifies that LiCF3SO3 solvates very

well in PEO-ENR50 matrix, resulting in the absence of

pure salt phase in the complexes. The main XRD peaks of

PEO are characterized by significant changes in the full

width at half maximum (FWHM) with the increasing salt

concentration. The peak broadening estimated in terms of

FWHM has been used to evaluate the Scherrer length (l)

S. A. M. Noor et al. / Natural Science 2 (2010) 190-196

194

of main PEO peak which was 22.90, 18.20, 18.12, 18.07,

15.84, 12.51 and 8.14 nm for the electrolytes shown in

Figure 3(b)-3(h), respectively. The length was automati-

cally calculated using evaluation (EVA) software with the

formula (l) = [0.9λ]/[BcosθB] where λ is the wavelength of

the X-rays used and B is FWHM in radians [21]. The l of

main PEO peak was 22.9 nm. This value was decreased to

18.20 nm when PEO was blended with ENR50 and be-

come 8.14 nm at 20 wt.% of LiCF3SO3. The Scherrer

length characterizes the crystallite size of PEO and it gives

a picture of changes in the PEO crystallinity as a polymer

host upon the salt addition. These results suggested that

the degree of crystallinity of PEO decreases with the

LiCF3SO3 content.

The ionic conductivity measurement was carried out

with the aim to observe the effect of LiCF3SO3 addi-

tion on the ionic conductivity of the electrolyte. The

AC spectra for two of the PEO-ENR50-LiCF3S03

electrolyte films are shown in Figure 4 in form of

Cole-Cole plot. The high frequency semicircle gives

the information about the bulk properties of the elec-

trolyte, such as bulk resistance (Rb) and bulk capaci-

tance (Cb) which arises from the migration of lithium

ions and the dielectric polarization of the electrolyte

film, respectively. In the low frequency response re-

gion, the appearance of a non vertical spike is attrib-

uted to the additional capacitance and resistance,

arising from dielectric relaxation and ion trapping in

PEO-ENR50-LiCF3SO3 electrolyte [13]. At room

temperature, the conductivity of the electrolyte with-

out LiCF3SO3 is 1.5 × 10-9 Scm-1. The ionic conduc-

tivity increases rapidly by two orders of magnitude

with addition of 5 wt.% of LiCF3SO3 as Li+ charge

carriers were added to the system. It was observed

that the conductivity increases gradually as the wt.%

of LiCF3SO3 increases to 20 wt.% of LiCF3SO3 and

began to decrease at 25 wt.% of LiCF3SO3. The maxi

Figure 4. Cole-cole plot for two PEO-ENR50 (70/30)-LiCF3SO3

electrolytes.

PEO-ENR 50-LiCF3SO3 (wt. % of LiCF3SO3)

   

log /Scm-1

















Figure 5. Room temperature conductivity of PEO-ENR50 (70/30)-LiCF3SO3

electrolyte a function of LiCF3SO3 concentration.

S. A. M. Noor et al. / Natural Science 2 (2010) 190-196

195

mum conductivity of 1.4 × 10-4 Scm-1 was achieved at 20

wt.% of LiCF3SO3 as presented in Figure 5. An addi-

tional factor that favoured the salt dissociation was that

the salt with a large monovalent anions such as LiCF3SO3

has a low lattice energy and as a result, it will easily dis-

solve in polyether [15]. The conductivity is reduced after

the maximum value due to an ever-increasing number of

transient crosslink in the system, thus reducing the chain

mobility. Besides, the formation of immobile aggregated

species will contribute to the fall in conductivity.

The conductivity increases with the lithium salt con-

centration due to the increase in charge carrier density and

also due to the plasticizing affects of the LiCF3SO3 which

decreases PEO crystallinity, thus increasing the pathway

for the polymer segmental motion [21]. Ramesh et al. [14]

reported that the highest conductivity achieved for

PEO-LiCF3SO3 electrolyte was 1.1 × 10-6 Scm-1 at room

temperature. However, the result is slightly lower than the

ionic conductivity obtained from this work. In conclusion,

the electrolyte based on PEO blended with modified natu-

ral rubber possess higher ionic conductivity than conven-

tional PEO-based electrolytes at ambient temperature

[11,12]. This result is due to the molecular structure of

ENR50. In term of molecular structure of the polymer,

ENR50 has active oxygen in the epoxy group attached to

the main chain as shown in Figure 1. It is assumed that the

ENR50 oxygen atom takes a role similar to the ether group

in the PEO polymer structure and provide co-ordination

sites for Li+ ion conduction [1,11,12]. Glasse et al. [11]

reported a gel electrolyte of PEO-ENR-LiTf-EC/PC and

found the highest conductivity around 10-4 Scm-1 at the

fixed salt concentration. This value was also in the range of

the electrolyte with 20 wt.% of LiCF3SO3. It shows that the

conductivity was influenced by the salt concentration.

However, the excessive of salt will increase the transient

crosslink in the electrolyte, thus reducing its chain mobility.

This observation also shows without using the EC/PC, high

room temperature conductivity can be achieved for solid

electrolyte system by increasing the wt.% of salt. The in-

crease in ionic conductivity with the wt.% of LiCF3SO3

clearly suggests that the major contribution to the conduc-

tivity enhancement is associated with structural modifica-

tion. This can be observed by the increase in amorphous

phase with Li salt content as observed from the DSC and

XRD results. According to Chandra & Chandra [20], there

is a correlation between Scherrer length and conductivity.

As the crystallite size decreases, the ionic conductivity in-

creases. Hence, it can be proven that the conductivity of our

electrolyte is greatly influenced by the wt.% of LiCF3SO3

through a consequential change in the crystallite size of the

host matrix.

4. CONCLUSIONS

A solid polymeric electrolyte of PEO-ENR50-LiCF3SO 3

has been successfully prepared by solution casting tech-

nique. The effect of ENR50 content on the conductivity

of the electrolyte was found to increase with the weight

percentage of ENR50. The highest room temperature

conductivity of 4.2 × 10-5 Scm-1 was achieved at 70-30

composition of PEO-ENR50 host and at 15 wt.%

LiCF3SO3 salt. The effect of the salt content on the ther-

mal property, structure and conductivity of the electro-

lyte was investigated for the electrolyte with 70-30 com-

position of PEO-ENR50. The maximum room tempera-

ture conductivity was 1.4 × 10-4 Scm-1 corresponding to

20 wt.% of LiCF3SO3. This result was supported by the

lowest relative percentage of crystalline phase and the

decrease in crystalline melting temperature of the elec-

trolyte. Also, XRD analysis showed that the semi-crys-

talline of the electrolyte became more amorphous with

the increase in LiCF3SO3 content.

5. ACKNOWLEDGEMENT

The authors would like to thank UKM and MOSTI for the provision of

grant 03-01-02-SF0423.

REFERENCES

[1] Latif, F., Madzlan, A., Nasir, K., Abd, M.M.A. and Muhd,

Z.Y. (2006) The role and impact of rubber in poly(methyl

metacrylate)/lithium triflate. Journal of Power Sources,

159, 1401-1404.

[2] Dissanayake, M.A.K.L., Bandara, L.R.A.K., Karaliyadda,

L.H., Jayathilaka, P.A.R.D. and Bokalawala, R.S.P. (2006)

Thermal and electrical properties for SPE PEO9Mg(ClO4)2

incoprating nano porous Al2O3 filler. Solid State Ionics,

177, 343-346.

[3] Reddy, V.S.C., Wu, G.P., Zhao, C.X., Jin, W., Zhu, Q.Y.,

Chen, W. and Sun-il, M. (2007) Mesoporous silica

(MCM-41) effect on PEO+LiAsF6 solid polymer elec-

trolyte. Current Applied Physics, 7, 655-661.

[4] Scrosati, B., Croce, F., and Panero, S. (2001) Progress in

lithium polymer battery R&D. Journal of Power Sources,

100, 93-100.

[5] Fenton, D.E., Parker, J.M. and Wright, P.V. (1973) Com-

plexes of alkali metal ions with poly (ethylene oxide).

Polymer, 14, 589.

[6] Kumar, B., Rodrigues, S.J. and Koka, S. (2002) The crys-

talline to amorphous transition in PEO-based composite

electrolytes: Role of lithium salts. Electrochimica Acta,

47, 4125-4131.

[7] Natesan, B., Karan, N.K., Rivera, M.B., Aliev, F.M. and

Katiyar, R.S. (2006) Segmental relaxation and ion trans-

port in polymer electrolyte films by dielectric spectros-

copy. Journal of Non-Crystalline Solids, 352, 5205-5209.

[8] Fan, L., Dang, Z., Wei, G., Ce-Wen, N. and Li, M. (2003)

Effect of nanosized ZnO on the electrical properties of

(PEO)16LiClO4 electrolytes. Material Science and Engi-

neering B, 99, 340-343.

[9] Mohapatra, S.R., Thakur, A.K. and Choudhary, R.N.P.,

(2008) Studies on PEO-based sodium ion conducting

S. A. M. Noor et al. / Natural Science 2 (2010) 190-196

196

composite polymer films. Ionics, 14, 255-262.

[10] Xiong, H.M., Zhao, K.K., Zhao, X., Wang, Y.W. and

Chen, J.S. (2003) Elucidating the conductivity enhance-

ment effect of nano sized SnO2 fillers in hybrid polymer

electrolyte PEO-SnO2-LiClO4. Solid State Ionics, 159,

89-95.

[11] Glasse, M.D., Idris, R., Latham, R.J., Linford, R.G. and

Schlindwein, W.S. (2002) Polymer electrolytes based on

modified natural rubber. Solid State Ionics, 147, 289-294.

[12] Idris, R., Glasse, M.D., Latham, R.J., Linford, R.G. and

Schlindwein, W.S. (2001) Polymer electrolytes based on

modified natural rubber for use in rechargeable lithium

batteries. Journal of Power Sources, 94, 206-211.

[13] Benedict, T.J. Banumathi, S. Veluchamy, A. Gangadharan,

R. Zulfihar, A.A. and Rajendran, S. (1998) Characteriza-

tion of plastisized solid polymer electrolyte by XRD and

AC Impedance methods. Journal of Power Sources, 75,

171-174.

[14] Ramesh, S., Tai, F.Y. and Chia, J.S. (2008) Conductivity

and FTIR studies on PEO-LiX [X: CF3SO3- , SO42-] poly-

mer electrolytes. Spectrocimica Acta: Part A, 69, 670-675.

[15] Pitawala, H.M.J.C., Dissanayake, M.A.K.L. and Senevi-

ratne, V.A. (2007) Combined effect of Al2O3 nano-fillers

and EC plasticizer on ionic conductivity enhancement in

solid polymer electrolyte (PEO)9 LiTf. Solid State Ionics,

178, 885-888.

[16] Ali, A.M.M., Subban, R.H.Y., Bahron, H., Winnie, T.,

Latif, F. and Yahya, M.Z. (2008) Grafted natural rubber

based polymer electrolytes: ATR-FTIR and conductivity

studies. Ionics, 14, 491-500.

[17] Lu, G., Li, Z.F., Li, S.D. and Xie, J. (2001) Blends of

natural rubber latex and methyl methacrylate-grafted

rubber latex. Journal of Polymer Science, 85, 1736-1741.

[18] Mihaylova, M.D., Krestev, V.P., Kresteva, M.N., Amzill,

A. and Berlinova, I.V. (2001) Amphiphilic graft copoly-

mers with poly(oxy ethylene) side chains: Supermolecu-

lar structure in solid state I. WAXS studies, European

Polymer Journal, 37, 233-239.

[19] Chu, P.P., Reddy, M.J. and Kao, H.M. (2003) Novel

composite polymer electrolyte comprising mesoporous

structured SiO2 and PEO/Li. Solid State Ionics, 156,

141-153.

[20] Chandra, A. and Chandra, S. (1994) Effect of alumina

dispersal on the conductivity and crystallite size of

polymer electrolyte. Proceeding of the 4th Asian Confer-

ence on Solid State Ionics, Kuala Lumpur,Malaysia, 2-6

August, 355-359.

[21] Ahn, J.H., Wang, G.X., Liu, H.K. and Duo, S.X. (2003)

Nanoparticle-dispersed PEO polymer electrolytes for Li

batteries. Journal of Power Sources, 119, 422-426.