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Progress Report No. 2

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Project ID: 2069

Project Type: Young research grant

Project Title: Magnesium battery based on solid acid membrane

Principal Investigator: Eslam Mohamed Sheha

Affiliation: Benha University

Project Start Date: 20/10/2010

Project End Date: 20/10/2012

Project Duration: 2 years

Reporting period: From: 20/1/2011

To: 20/10/2011

Date of submission: 15/10/2011

Signature of Principal Investigator:


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Table of Contents

1. Overview……………………………………….………..….…3

2. Objective(s) of the reporting period…………………………3

3. Former achievements through this contract………………..4

4. Activities conducted since the project start date…………....5

4.1 Abstract………………………………………...….5

4.2 Introduction……………………………………..…6

4.3 Experimental Section…………………………..….8

4.4 Results and Discussion…………………………....11

5. Conclusion……………………………………………………..22

6. References……………………………………………………..23

7. Outcomes ………………………………..…………………....25

8. Planning for the next reporting period …………………….26

9. International Cooperation……………………………….….27

10. Conferences………………………………………………….28

11. Problems Encountered and Resolutions…………………...30

12. Implementing team(s)………………………………………..31

13. Brief monetary report……….……………………….…..…32

14. Appendices……………………………………………………34

15. Grant Chart………..…………………………………………52

16. Logical frame work (LFM)………………………………….53


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1. Overview

This document is the progress report number 2 prepared for the project

number 2069. This report covers months 4-12 (January 2011- October 2011) of

the project. The purpose of this document is to provide a report of the activities

undertaken in this reporting period. A descriptive form and a spreadsheet with

experimental reporting data are provided. This report outlines future plans for the

rest of the project.

2. Objective(s) of the reporting period, as given in the submitted grant

application.

The key objectives of this reporting area were:-

Synthesize and characterize second phase of solid acid membrane,

PVA(1-x)(MgBr2)x/2(PWA)x/2.

Conduct impedance and dielectric analysis of PVA(1-

x)(MgBr2)x/2(PWA)x/2 membrane to determine the optimum

membrane.

Conduct surface characterization and diffraction analysis of PVA(1-

x)(MgBr2)x/2(PWA)x/2 membrane.

Demonstrate magnesium cells utilizing optimized membranes.

Demonstrate an article to be published in an international peer

reviewed journal.

Finalize the second progress report.


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3. Former achievements through this contract:

Data reviewing and sample preparation.

Preparation phase 1 of PVA /solid acid films with uniform well-mixed

matrix.

Surface characterization and diffraction analysis.

Performance tests to show that the novel PVA /solid acid membrane has

comparable or higher ionic conductivity than others.

Finalize the first progress report.


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4. Technical/scientific accomplishment/activities

4.1 Abstract

In the present work, Mg acid salt membrane using poly (vinyl alcohol)

(PVA), magnesium bromide (MgBr2) and phosphotungstic acid (PWA) in

different compositions has been prepared by the solution-casting technique.

Surface feature of films was characterized by scanning electron microscopy

(SEM) measurement. X-ray diffraction (XRD) was used to determine the

complexation of the polymer with Mg acid salt. The electro-physical

characteristics were measured and analyzed as dependent on the concentration

and nature of the Mg acid salt component and ambient temperature. The optimum

ionic conductivity value 8.63×10-6

S/cm at 303 K is obtained for PVA(0.5)

(MgBr2)0.25(PWA)0.25 membrane. The ionic transference number of mobile ions

has been estimated by a dc polarization method and the results reveal that the

conducting species are predominately ions. The dc polarization of Mg/electrolyte/

Mg cell using the polymeric electrolyte proved that Mg2+

is mobile in the present

polymeric system. The applicability of the present film to a rechargeable battery

system was examined by a prototype cell consisting of Mg and TiO2 as the

negative and the positive electrodes, respectively.


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4.2 Introduction

Recently, the magnesium-based rechargeable battery system has attracted

attention due to its performance capabilities, which are expected to be close to

those of lithium-based rechargeable batteries [1,2]. Magnesium is one of the ideal

materials for the negative electrode for practical batteries because it has low

electrochemical equivalence (12.15geq−1

), considerably negative electrode

potential (−2.3V vs. SHE), low cost due to natural abundance, and greater safer

than lithium. Aurbach et al.[3] have developed a prototype high-capacity

rechargeable magnesium battery using electrolyte solutions based on Mg

organohaloaluminate salts. The same group reported that Chevrel phases Mo6T8

(T = S, Se) can insert Mg ions reversibly and can be used as practical cathode

materials for rechargeable Mg-batteries [4]. Despite these studies, however,

development of rechargeable Mg-batteries has not be accelerated mainly due to

the lower reversibility of the Mg electrode/electrolyte charge transfer and the lack

of suitable Mg2+

ion conducting non-aqueous electrolytes [5,6]. Recently, the

development of solid-state Mg2+

ion-conducting electrolytes has become one of

the important issues to realize rechargeable, solid-state Mg-batteries.

Polymer electrolytes, an excellent substitute for liquid electrolytes,

continue to attract research interest due to properties which make them suitable

for application in solid-state electrochemical devices, e.g., rechargeable batteries,

super capacitors, etc.. Such electrolytes are examined mostly for use in lithium

systems. Mg2+

ion-conducting polymer electrolytes are not widely reported except

a few systems [7,8]. Few solid-state rechargeable magnesium batteries using

polymer electrolytes have been reported in literature[9]. Polymer electrolytes have


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some important advantages over liquid electrolytes in that the risk of leakage is

reduced, and electrode interfacial contact can be maintained during volumetric

changes associated with charge and discharge cycling of the battery. The ability

of polymer electrolytes to act as both the separator and the electrolyte leads to

easy fabrication and allows the possibility of miniaturized devices.

PVA has high glass transition temperature (Tg) (358 K) and good

mechanical properties. And despite being a tactic, PVA can crystallize, especially

if highly hydrolyzed, since the hydroxyl group can be accommodated in place of a

hydrogen atom in the crystal lattice of heteropolyacids shows remarkable [9]

chemical and electrochemical stability. So with these two components, we can

prepare Mg-conducting SPEs containing ion conduction mechanism decoupled

from the polymer segmental motion.

Heteropolyacids (HPAs) are one of the most attractive inorganic modifiers

because these inorganic materials in crystalline form have been demonstrated to

be highly conductive and structural stable. Phosphotungstic acid is one of the

strongest Keggin-type heteropolyacids and is considered to have strong Bronsted

acidity to be used as proton donor [10], meanwhile, bromine salts compresses the

diffusive electric double layers and hence reduces the repulsion between ions.

Owing to these merits, the strategy in the development of Mg ion

conducting polymer electrolytes for rechargeable magnesium batteries was

determined by the intention to study an intermediate phase between PWA and

MgBr2 (Mg acid salt). In this work, the effect of Mg acid salt in structural,

morphological, and electrical properties in PVA have been evaluated. To achieve

the stated objectives, various common analyzes such as x-ray diffraction (XRD),


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scanning electron microscopy, dc polarization and AC impedance spectroscopy

are used. In order to determine the capability of the highest conducting sample as

an electrolyte, it was used in the fabrication of Mg/electrolyte/TiO2 cells. TiO2

cathode material for reversible accommodation of Mg ions were investigated.

using optical microscope and x-ray diffraction.

4.3 Experimental Section

Preparation of electrolyte materials

Poly (vinyl alcohol), PVA (degree of hydrolization ≥98%, Mw=72,000),

magnesium bromide MgBr2 and phosphotungstic acid (PWA) were received from

Sigma. The complex electrolytes were prepared by mixing of 0.4%(w/v)

hydroquinone[11], 1%(w/v) ethylene carbonate, PVA, MgBr2 and PWA at several

stoichiometric ratios in distilled water to get PVA(1-x)(MgBr2)x/2(PWA)x/2 complex

electrolytes, where x is 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5 gm. Solution with variable

ratio was stirred vigorously and casted in Petri dish following solution cast

technique at room temperature. Six different polymer electrolytes were produced.

Compositional and structural characterization

The crystalline structures of all the PVA(1-x)(MgBr2)x/2(PWA)x/2

membranes were examined using a Philips X’Pert X-ray diffractometer (XRD)

with a Cu Kα radiation of wavelength λ = 1.54056 Å for 2 angles between 4 and

60o. The cross-sectional view and top surface morphologies and microstructures

of all the complex electrolytes were examined with a S-2600H scanning electron

microscope (Hitachi Co. Ltd.).


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Conductivity measurement

Conductivity measurements were made for PVA(1-x)(MgBr2)x/2(PWA)x/2

composite polymer membrane by an ac impedance method. Samples of diameter

0.5 cm were sandwiched between the two similar brass electrodes of a spring-

loaded sample holder. The whole assembly was placed in a furnace monitored by

a temperature controller. The rate of heating was adjusted to be 2 K/min.

Impedance measurements were performed on PM 6304 programmable automatic

RCL (Philips) meter in the frequency ranging from 100 Hz to 100 kHz at different

temperatures.

Total ionic transport number tion was evaluated by the polarization

technique. In this technique, the cell Cu/electrolyte/Cu was polarized by applying

a step potential of 1.5 V and the resulting potentiostatic current was monitored as

a function of time. The copper electrode act as a blocking electrodes for the above

cell. The tion was evaluated using the formula[12]:

i

fi

ionI

IIt

1

Where Ii is the initial current and If is the final residual current.

Magnesium transference number (tMg+2) was measured by the steady-state

technique which involved a combination of ac and dc measurements. The ac

complex impedance response of the Mg/electrolyte/Mg cell was first measured to

determine the cell resistances. It was followed by the dc polarization run, in which

a small voltage pulse (ΔV=0.33V) was applied to the cell until the polarization

current reached the steady-state Is. Finally, the ac impedance response of the cell


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was measured a gain to determine the cell resistance after dc polarization. Then

tMg+2 could be calculated with the following equation[12]:

)(

)(2

sso

oos

mgIRVI

IRVIt

2

Where Io and Is are the initial and final steady-state currents and R0 and Rs are the

cell resistances before and after the polarization, respectively.

Fabrication and characterization of batteries

Batteries test were performed by using two-electrode Swagelok type cells,

Fig. 1.a. The test cell assembly of Mg/Electrolyte/TiO2.xwt.%electrolyte is

schematically shown in Fig. 1b. The highest conducting sample in the PVA(1-

x)(MgBr2)x/2(PWA)x/2 system was used as an electrolyte for battery fabrication. To

make an anode pellet for the battery, 0.2 gm magnesium ribbon were pressed at 3

tons.cm-2

for 15 minutes. To make the cathode pellet composed of 70 wt.% TiO2,

30 wt.% graphite powder (QualiKems) and electrolyte (0, 10, 20, 30, 40 wt.%)

were grounded and pressed at 3 tons.cm-2

for 5 minutes. The diameter of the

pellets equals 13mm.

The discharge/charge cycling was performed within a voltage range of

0.01-4.0 V at ambient temperature. Several cells were assembled for the purpose

of different experiments to ensure reproducibility. Current drains ranging from 0

to 0.2 mA were used to plot the current–voltage (I–V) and current density–power

density (J–P) curves. The average of each battery’s voltage was monitored for


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each current drain after 10 sec of operation. The internal resistance of the cell was

then calculated by using equation:

IrEV

where V is the voltage, E is the electromotive force, I is the current and r is the

internal resistance.

The room temperature X-ray diffraction patterns for battery cathodes after

discharge were recorded on Bruker X-ray diffraction system with Cu tube anode

of wave length K1= 1.5460 Å and K2= 1.54439 Å. The start angle (2 ) was 4o

and the end angle was 60o. The patterns subsequently analyzed using the JCPDS

file data. The surface morphology of the samples were characterized by optical

microscope.

3.3 Results and discussion

Scanning electron microscopy

Depending on the type and amount of Mg acid salt present in the polymer

matrix, the morphology of the polymer electrolyte will vary and greatly influence

its properties. Morphological examination of this study is carried out to study the

phase morphology changes of the pure polymer and the resulting Mg acid salt

polymer-electrolyte films, after the addition of Mg acid salt. Scanning electron

micrographs of pure PVA and 0.2 acid salt have been presented in Fig.2. Very

distinguishable changes can be observed from pure PVA and high concentrations

of Mg acid salt. Pure PVA shows smooth surface. The morphology changes, as

soon as 20 wt % of Mg acid salt is incorporated into the polymer. The

morphology changes drastically to become significantly more layered and even


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greater pore size. An open pore structure of the polymer electrolyte matrix is

essential for ionic conductivity across the thin film. This type of open porous

structure provides enough channels for the migration of ions, accounting for better

ionic conductivity[13].

X-ray diffraction

The X-ray diffraction patterns of pure PVA and complexed with Mg acid

salt are shown in Fig. 3. From the figure, it is clear that the pure PVA shows a

remarkable peak for an orthorhombic lattice centered at 200 indicating its semi-

crystalline nature. In addition, this peak becomes less intense as the Mg acid salt

content is increased and increase of full-width half maximum of this peak has also

been observed. This increase in broadness of the peak reveals the amorphous

nature of the complex system. These results can be interpreted in terms of the

Hodge et al. [14] criterion, which has established a correlation between the height

of the peak and the degree of crystallinity. This could be due to the disruption of

the PVA crystalline structure by Mg acid salt. No peaks pertaining Mg acid salt

appeared in the complexes, which indicate the complete dissolution of Mg acid

salt in the polymer matrices. No sharp peaks were observed for higher contents of

Mg acid salt in the polymer, suggesting the dominant presence of amorphous

phase. This amorphous nature results in greater ionic diffusivity with high-ionic

conductivity, which can be obtained in amorphous polymers that have flexible

backbone. Similar type of Mg acid salt complexed polymer electrolytes films

were observed in the literature [15,16].


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Ionic conductivity

Impedance spectroscopy is used to establish the conduction mechanism,

observing the participation of the polymeric chain, the mobility and carrier-

generation processes[14]. Fig.4 shows Cole Cole plots for PVA(1-x)(MgBr2)x/2(

PWA)x/2 films. The typical Nyquist plot of the samples shows a semicircular arc

which is related to conduction in the bulk of the complex. The diameter of the

semicircle varies with the concentration of Mg acid salt ( MgBr2)(x/2)(PWA)(x/2),

where Mg acid salt at x=0.5 yield the smallest diameter. The intercept of this

semicircle with the real axis (z') gives estimate of the bulk resistance to be used

subsequently for evaluation of bulk conductivity. The bulk conductivity is

calculated using the relation

A

L

Rb

b 1

3

Where A is the known area of the electrolyte film and L is the thickness. In order

to explain the observed features, the measured impedance can be modeled by the

equivalent circuit as shown in the inset of Fig. 4. The data are fitted well with a

single semicircle that gives a simple equivalent circuit consisting of the parallel

resistance (bulk resistance, Rb) and the capacitance (bulk capacitance, Cb)

network in series. Fig.5 shows the dependence of bulk conductivity on

concentration for the polymer electrolyte at room temperature. The conductivity

of based (x=0) PVA is low, about 8.8510-10

S.cm-1

. It is observed that the

conductivity increases with the increase in concentration of Mg acid salt and

reaches 61063.8 S.cm−1

for x=0.5 gm. This may be attributed to the increase in

the number of mobile charge carriers and also to the increase in the amorphous


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nature of the polymer electrolyte, which reduces the energy barrier thereby

facilitating the fast ion transport, as the relation:

e n 4

Where n is the total ion concentration, e is the elementary charge and µ is the

mobility.

Fig.6 presents the temperature dependence of ionic conductivities for

PVA(1-x) (MgBr2)x/2(PWA)x/2 films at a frequency of 1 kHz. The plot shows that as

temperature increases, the conductivity increases. This indicates that the plots

obey Arrhenius rule;

)/exp( KTEao 5

Where σo is the pre-exponential factor, Ea is activation energy, K is Boltzmann

constant and T is absolute temperature. There is no sudden change in the value of

conductivity with temperature it may be inferred that these complexes do not

undergo any phase transitions within the temperature rang investigated. Druger et

al [16], have attributed the change in conductivity with temperature in solid

polymer electrolyte to segmental (i.e., polymer chain) motion, which results in an

increase in the free volume of the system. Thus, the segmental motion either

permits the ions to hop from one site to another or provides a pathway for ions to

move. In other words, the segmental movement of the polymer facilitated the

translational ionic motion. From this, it is clear that the ionic motion is due to

translational motion/ hopping facilitated by the dynamic segmental motion of the

polymer. As the amorphous region increases, however, the polymer chain

acquires faster internal modes in which bond rotation produce segmental motion

to favor inter-and intra-chain ion hopping, and thus the degree of conductivity


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becomes high. The activation energy, Ea (combination of the energy of defect

formation and the energy of migration) is calculated for all prepared polymer

electrolytes by linear fit of the Arrhenius plot. The calculated activation energy

values have been listed in table 1. Table 1 listed the activation energy values in

region 1 range from (0.884 to 0.5453), and Ea in region 2 range from (0.374255 to

-0.42456). The negative value of Ea can be attributed to, the excess amount of mg

acid salt beyond x=0.2 is found to result in mere loss of ion mobility at relatively

high temperature, which would inhibit the fast ionic transport, as is evident from

the present conductivity data

AC conductivity studies were carried out on all samples, synthesized with

different concentrations of Mg acid salt over a frequency range of 100 Hz to 100

kHz. It is observed that ac conductivity spectra, Fig. 7, show two distinct regions,

within the measured frequency, (i) plateau and (ii) dispersion region. The plateau

region corresponds to frequency independent conductivity dc and is obtained by

extrapolating the conductivity value to the zero frequency. AC conductivity

dispersion with frequency were fitted using Jonscher’s [17] power law (JPL) by

non-linear least square fit analysis of:

n

dcac A 6

where dc is the zero frequency limit of ac, A is a constant and n is the

power law exponent 0 < n<1. The value of n for different Mg acid salt

concentration is listed in table 1. The n value obtained from JPL fit for polymer

electrolytes synthesized with various concentrations of Mg acid salt is from 0.2 to

1.


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Generally the low values of power law exponents (n) at high Mg acid salt

concentration , x= 0.4 and 0.5, can be attributed to the ideal long range pathway

and diffusion limited hopping (tortuous pathway) respectively. The frequency

response of the conductivity is interpreted in terms of jump relaxation model [18],

where the conduction is due to translation and localized hopping. In jump

relaxation, the charge carrier (ion) hops in atomic scales in both space and time.

When an ion at time t=0 hops from site A to a vacant neighboring site B, there are

competing relaxation process to consider. First the ion may go back to site A,

which constitutes the forward– backward hop. It is possible that before the ion

decides to hop back, the surroundings of the new site relax in such a way that the

ion finds the site as its new quasi-permanent address. The overall behavior of ac

conductivity follows a universal dynamic process, which has been widely

observed in disordered materials like ion conducting polymers and glasses.

Dielectric properties

The study of dielectric relaxation in solid polymer electrolytes is a

powerful approach for obtaining information about the characteristics of ionic and

molecular interactions. The dielectric parameters associated with relaxation

processes are of particular significance in ion-conducting polymers where the

dielectric constant plays a fundamental role which shows the ability of a polymer

material to dissolve salts. The frequency-dependent conductivity and dielectric

relaxation are both sensitive to the motion of charged species and dipoles of

polymer electrolytes. The complex dielectric constant of a system is defined by;

'''* i 7


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Where ' is the real part of the dielectric constant of the material and '' is

the imaginary part. Also, these real and imaginary parts of the dielectric constants

are expressed as;

A

Cl

o ' 8

and tan''' 9

Where ' is the permittivity in free space, C is parallel capacitance and L and A

are the thickness and known area of the sample [20].

The frequency dependent dielectric constant and loss (' and '') at room

temperature for pure and Mg acid salt added PVA are shown in Figs. 8a and b. It

is evident from the figure that the values of ' and '' are significantly high in the

low frequency region. This indicates that the electrode polarization and space

charge effects are prevalent confirming the non-Debye type behavior. At higher

frequencies, periodic reversal of the field takes place so rapidly that the charge

carriers will hardly be able to orient themselves in the field direction resulting in

the observed decrease of dielectric constant and dielectric loss.

The temperature dependent dielectric constant and loss for pure and Mg

acid salt added PVA are shown in Figs.9a and b. There is no significant variation

in dielectric constant with frequency for pure PVA. Where as it increase with

increase in temperature for Mg acid salt added samples. The increase in dielectric

constant and loss at higher temperatures is ascribed to higher charge carrier

density. As the temperature increases, the degree of Mg acid salt dissociation and

re-dissociation of ion aggregates increases which result in increase in number of

free ions or charge carrier density[20].


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Transference number measurement

The ionic transference number of the mobile species in the polymer

electrolyte has been calculated by Wagner's dc polarization method [21], as

described in the "Experimental. This dc polarization measurement has been used

to analyze the mobile species in the electrolyte as either ions or electron. The

polarization current has been monitored as a function of time on the application of

fixed dc potential (1.5 V) across the cell, Cu/electrolyte/Cu. The total ionic

transference number tion, is evaluated using Eq. 1, has been found to be 0.972594

for PVA(0.5)(MgBr2)0.25(PWA)0.25 polymer electrolyte. This shows that the charge

transport in this polymer electrolyte is mainly due to ions.

A typical result of dc and ac measurement for determining tMg+2 for

PVA(0.5) (MgBr2)0.25(PWA)0.25 polymer electrolyte is shown in Fig. 10. The dc

polarization current needs about 3 h to reach the steady state. After dc

polarization, R0 increases from 5 x 103 to 2.5 x 10

4 Ω. The value of tmg2+, is

evaluated using Eq. 2, has been found to be 0.18 at room temperature.

Battery characteristics

Optical micrographs of different compositions of TiO2.x wt. % electrolyte

are shown in Fig. 11(a-e). Irregular shapes of different size are observed in

samples with zero concentration of the electrolyte in the TiO2. Homogenous

dispersion can be observed in samples with high concentration of electrolyte in

the TiO2. No tendency to form agglomerates in the present electrolyte at high

loading level.

b b


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Fig.12. presents XRD patterns of pure TiO2 cathodes and TiO2/graphite,

respectively. As clearly seen, all the diffraction peaks can be indexed to a pure

TiO2 structure phase in accordance with reference[22], except for the strong

peaks at 2Ө=270, corresponding to the diffraction peak of graphite[15].

Fig.13. presents XRD patterns of TiO2.x wt. % electrolyte cathodes. As

clearly seen, the sharp peaks present in the pattern indicate the polycrystalline

nature of the cathodes. The curves show the presence of a crystalline phase with

the characteristic diffraction peaks located at 2θ=25°, 37° and 48°. Such

crystalline nature originates from TiO2 which agrees with reference[22]. Fig. 13

clearly indicates that the addition of electrolyte reduces the intensity of main

peaks followed by broadening the peak area, which is an indication of reduction

in the degree of crystallinity. This reduction in the crystallinity is responsible for

the enhancement in cathode ionic conductivity.

Solid state electrochemical cells were fabricated in the configuration

Mg(anode)/electrolyte/(TiO2)(cathode), and their discharge characteristics at

ambient temperature for a constant load of 100KΩ are shown in Fig. 14. The

typical XRD patterns of pure TiO2 before discharge, after discharge, after charge

and after discharge to the second cycle are shown in Fig. 15. On comparison of

XRD patterns of TiO2 cathodes revealed that, the TiO2 before and after discharge

are in the same phase, except that the peaks are gradually broadened and intensity

decreases after discharge and it return to increase after charge. This can be

attributed to charge in lattice strain due to intercalation and de-intercalation of

magnesium. For magnesium intercalation/deintercalation reaction take place in

the cell, the overall reaction can be written as follow:


20

22 TiOMgxexMgTiO x

The average open circuit voltage during 24 h storage time of the five cells

with configuration Mg/electrolyte/TiO2.xwt % electrolyte is shown in Fig.16.

Low self discharge can be observed. Fig. 17 shows the discharge characteristic of

the Mg/electrolyte/ TiO2.x wt. % electrolyte battery under R=100 kΩ load

resistance, the value of the discharge capacity С was evaluated from the equation:

t

dttVR

C0

)(1

Where C is the discharge capacity, V (t) is the discharge voltage, R is the

applied resistance (100KΩ), and t is discharge time. We integrated the area under

curves of Fig. 17 to estimate the discharge capacities. These values are listed in

table 2. As we see, the cell capacity of the cathode contain 30 wt.% electrolyte ≈

2 mAh is the highest value. This can be attributed to the reduction in the

crystallinity of this medium that have been reported by optical micrographs and x-

ray results, which play an important role in enhancing magnesium

intercalation/deintercalation reaction. Fig. 18 shows the I–V and J–P

characteristics for the Mg/electrolyte/ TiO2.x wt. % electrolyte battery at room

temperature. The I–V curve had a simple linear form which indicates that the

polarization on the electrode was primarily dominated by ohmic contributions.

The internal resistance of the battery was obtained from the gradient of the I–V

curve. The internal resistance, short current and other cell parameters are listed in

table 2. From this table, the internal resistance decreases due to increases the

concentration of the electrolyte in the cathode. This can be explained in terms of


21

change in the ionic conductivity of the cathode due to adding electrolyte as

reported by x-ray results.

5. Conclusion

We have successfully optimized the structure of PVA as the electrolyte for

rechargeable Mg batteries as follow:

1. Ionic conductivity of ≈10-6

S cm-1

was obtained for optimum electrolyte at

room temperature.

2. The polarization experiments of Mg/optimum electrolyte/Mg cells proved

that Mg2+

is mobile in the present polymeric system.

3. A solid-state Mg/electrolyte/TiO2 cell has been assembled and its physical

behavior has studied. The internal resistance of the fabricated cell was

deduced to be ≈600 Ω.

In view of the above advantages, PVA/Mg acid salt polymer electrolyte is a

potential electrolyte material for magnesium batteries.


22

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23

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Nan, Solid State Ionics 179 (2008) 1310.

22. JipengWang, Ying Bai, MuyingWu, Jiang Yin,W.F. Zhang, Journal of

Power Sources 191 (2009) 614–618


24

7. Outcomes

Overall, we have one peer reviewed journal article currently published and

another in preparation.

The researchers developed an innovative and effective protocol to prepare

Mg ion conductor polymer electrolyte with high yield. Further

optimization is in current.

The researchers carried out a comprehensive list of characterizations on

the Mg ion conductor polymer electrolyte as seen in the above sections of

this report.

The researchers fabricated prototype magnesium battery. Further

optimization is in current.

The researchers recommend future work that will focus on doped with

multifunctional materials (non-ionic plastic polymer) and therefore higher

conductivity.


25

8. Planning for the next reporting period:

Study the impact of multifunctional materials like succinonitrile on

thermal stability, structure, groups, phase transitions, free volumes and

morphology of PVA(1-x) (MgBr2)x/2(PWA)x/2 membrane.

Coating the magnesium metal with optimum electrolyte using spin coating

technique.

Conduct synthesis of cathodes of non-magnesium compounds (e.g. MnO2,

CoO2, MoS2, FeS2 ).

Fabricate magnesium cells utilizing optimized membranes (manipulated

with succinonitrile) and optimized electrode formulations.

Conduct charge/discharge spectroscopic analysis of nominated magnesium

cells.

Conduct EDAX and X-ray spectroscopic analysis of electrodes before and

after discharge. Establish overall reaction.


26

9. The PI evaluation of the progress of the project:

Project started at 20/10/2010 for two years. One year until now. Through

this we made a comprehensive survey of work in digital libraries in order to

determine the starting point. This is followed by preparation of a series of

electrolyte in order to allow magnesium ion to pass through. Topography of the

samples were studied and the crystal structure and analysis of electrical

impedance and dielectric parameters. This is followed by fabrication magnesium/

electrolyte /titanium cells. The preliminary results showed that the way in which

walking is the way of a promising, with some improvement in the electrical

conductivity of the electrolytes. On this basis, the team members will study

influence of succinonitril material to improve the electrical properties of

electrolytes in order to reduce the internal resistance of the battery and we will

study the batteries with different cathodes, such as CoO2, CuSO4, MoS2,……….

In the end, the principal investigator see that the results obtained, as well as the

expected results in the near future are very promising and will come back by

benefit to our community.


27

10. International Cooperation

Communications with experts will lead to good planning. Therefore, PI have

made short term visit to Wollongong University, Australia for scientific

cooperation in magnesium battery as follow:


28

11. Conferences The PI plans to share in an international conference as follow:


29

The PI shared in the following conference by an article as follow:

THE EGYPTIAN

MATERIALS RESEARCH SOCIETY

33 Abd El–Khalek Tharwat, Cairo, Egypt

Tel. & Fax: 23925997

E-mail: contact@ egmrs.org

Web site: http://www.egmrs.org

____________________________________________

Eg-MRS 2010

THE XXIX INTERNATIONAL CONFERENCE

ON

SSoolliidd SSttaattee SScciieennccee aanndd

MMaatteerriiaallss PPhhyyssiiccss

&

WORKSHOP

ON

PPhhoottoonniicc CCrryyssttaallss aanndd GGrraapphheennee

Sharm El-Shiekh, Egypt03 - 06 October 2011

______________________

Dear Dr. Eslam Sheha

It is a pleasure to inform you that your paper entitled:

"Ionic conductivity and dielectric properties of (PVA)0.5(MgBr2)0.25(PWA)0.25

solid polymer electrolyte’’

By: Eslam Sheha

Has been accepted for oral presentation in the 29th

conference (Eg-MRS 2011).

Please, confirm your attendance by payment the registration fees (1200 L.E)

Kind regards.

Conference Chairman

Mohamed El Oker Prof. Dr. Mohamed El Oker.

EEEggg---MMMRRRSSS


30

12. Actual or Expected Problems Encountered and Resolutions

Description of problems encountered:

1. The internal resistance of the fabricated Mg/Solid acid battery is

still high.

2. Delay of importing Battery Tester

Description of actions taken to resolve the problems:

3. Investigate the effect of non-ionic plastic polymer on the ionic

transport of PVA(1-x) (MgBr2)x/2(PWA)x/2 membrane.

4. We postponed studying capacity against cycle number for the next

report.


31

13. Implementing team(s):

Name Title Contact Post

Eslam Mohamed Sheha Ph.D +20107414705

PI: The PI has the overall

responsibility of the project and the

documents. The responsibility

specifically includes planning,

supervising, keeping everyone going

and call the group together.

Shimaa Ibrahim Abo

Elazm

M.Sc (S) +20194392928

Researcher "B": Membrane

development and ion transference

analyst

Rania Gamal Abd -

Elghar M.Sc (s) +20170268845

Researcher "B": Impedance

analyst

Blal Ahmed M.Sc (s) +20109560056 Researcher "B": SEM analyst

Tarek Salh M.Sc (s) +20194434174 Researcher "B": X-ray analyst

Mona Mohamed Abd-

Elmgid M.Sc (s) +20111081718 Researcher "B": Battery analyst

Mabrouk Kamel El-

Mansy Professor +20121097778 Fulltime counselor

Zaiping Guo Professor +(626)3952958 Battery counselor


32

14. Brief monetary report:

Item Allocated

budget

Actual

Expenditures Comments

Salaries 96000 96000

Equipment - 10000 (Indirect cost)

Chemicals &

Consumables 10000 9000

Local Travel

International Travel 35000 30000

Other costs (including

indirect costs) 28000 28000

Total Expenditure 169000 163000


33

Table 1. Activation energy and conduction index (n) a against Mg acid salt

concentration for PVA(1-x) (MgBr2)x/2(PWA)x/2 films.

n E2 (eV) E1 (eV) C

0.98 0.36

0.78

0

0.82

0.03

0.64

0.05

0.69

0.37

0.88

0.1

0.68

0.36

0.87

0.15

0.22

0.02

0.71

0.2

0.2

-0.42456

0.54

0.25

14. Appendices


34

Concentration Internal

Resistance

(K.Ohm)

Cell Capacity

(mAh)

maximum

power

density(Pmax)

( mW/cm2)

short

current

density

(mA/cm2)

0 2.2509

1.25

0.137

0.0859

10% 2.0535

1.65

0.189

0.1018

20% 0.6643

1.54

0.161

0.0946

30% 0.603

2.04

0.0889

0.0699

40% 0.9185

1.92

0.172

0.0972

Table2. Cell parameters against different concentration of electrolyte in the cathode (TiO2).


35

Fig.1a. the components of the Sewgelock cell

Stainless steel

Collector

Stainless steel

collector

Electrolyte

+

-

Mg TiO2

1.51 mm mm

0.6 mm 1.38 mm

Fig.1b Prototype magnesium cell


36

X 2200 10um WD 16 X 2200 10um WD 16

Fig.2. The SEM micrograph for the surface of PVA(1-x)(MgBr2)x/2(PWA)x/2 acid salt membrane with

a. x=0, b. x=0.2

a b


37

0 10 20 30 40 50 60 70

2 dergree

Inte

ns

ity

(a

.u)

PVA

x=0.2

x=0.4

Fig.3. X-ray diffraction pattern for PVA(1-x)(MgBr2)x/2(PWA)x/2 films with, x=0,0.2,0.4 .


38

1.00E-10

1.00E-08

1.00E-06

1.00E-04

0 0.05 0.1 0.15 0.2 0.25 0.3

c (wt.%)

b (

s.c

m-1

)

Fig.4. Cole Cole plots for PVA(1-x)(MgBr2)x/2 PWA(x/2) films

Fig.5. The ionic conductivity of PVA with various concentrations of Mg acid salt.

0.0E+00

5.0E+06

1.0E+07

1.5E+07

0.0E+00 5.0E+06 1.0E+07 1.5E+07

z' (ohm)

z''

(oh

m)

x=0.2

x=0.3

Rb

Cb


39

Fig 5

-22

-20

-18

-16

-14

-12

-10

-8

5 6 7 8 9 10 11 12 13 14

ln() (Hz)

ln(

) (s

.cm

-1)

x=0

x=0.1

x=0.2

x=0.3

x=0.4

x=0.5

Fig.6 Arrhenius plot for PVA(1-x)(MgBr2)x/2PWA(x/2) acid salt membrane

Fig.7 Variation of conductivity with frequency for PVA(1-x)(MgBr2)x/2(PWA)x/2 acid salt membrane

-21

-19

-17

-15

-13

-11

-9

-7

2.2 2.4 2.6 2.8 3 3.2 3.4

1000/T (K-1

)

ln(

) (s

.cm

-1)

x=0

x=0.1

x=0.2

x=0.3

x=0.4

x=0.5


40

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.0E+02 1.0E+03 1.0E+04 1.0E+05 1.0E+06

(Hz)

'

x=0

x=0.1

x=0.1

x=0.3

x=0.4

x=0.5

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.E+02 1.E+03 1.E+04 1.E+05 1.E+06

(Hz)

''

x=0

x=0.1

x=0.2x=0.3

x=0.4

x=0.5

Fig.8 Variation of a. ' and b.'' with frequency at 303 K for (PVA)(1- x) (MgBr2)x/2(PWA)x/2 acid salt

membrane


41

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

290 310 330 350 370 390 410 430

T (K)

'

x=0

x=0.1

x=0.2

x=0.3

x=0.4

x=0.5

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

290 310 330 350 370 390 410 430

T(K)

''

x=0

x=0.1

x=0.2

x=0.3

x=0.4

x=0.5

Fig.9 Variation of a. ' and b.'' with temperature at frequency 1 kHz for ( PVA)(1-x)

(MgBr2)x/2(PWA)x/2 acid salt membrane


42

Fig.10 Variation of polarization current as a function of time for PVA(0.5) (MgBr2)0.25(PWA)0.25

acid salt membrane.

0

50

100

150

200

250

-10 10 30 50 70 90 110 130

Time (minutes)

cu

ren

t (

A)

0.E+00

1.E+04

2.E+04

3.E+04

0.E+00 1.E+04 2.E+04 3.E+04

z' (ohm)

z''

(oh

m)

Befor after


43

a b

c

e

Fig.11. The Optical micrographs (X50)of:

(a) zero electrolyte; (b) 10% electrolyte; (c)

20% electrolyte; (d) 30% electrolyte; (e)

40% electrolyte in the cathode.

d

50 X


44

0 10 20 30 40 50 60 70

2 (degree)

Inte

nsity (

a.u

)

TiO2-G

TiO2

Fig12. XRD patterns of pure TiO2 and TiO2 /Graphite.


45

0 10 20 30 40 50 60 70

2(degree)

Inte

nsity (

a.u

)

10%

20%

30%

40%

Fig13. XRD patterns of TiO2.xwt.%electrolyte , x=10,20,30 and40.


46

Fig.

14. Discharge curves, voltage against time

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

-1 19 39 59 79 99

T (hours)

V (

volt)

Cycle 1

Cycle 2


47

0 10 20 30 40 50 60 702 (degree)

Inte

nsity (

a.u

)

Base

Discharge1

Charge

Discharge2

Fig15. XRD patterns of the pure cathode before discharge, after first discharge, after first

charge and after second discharge.


48

0

0.4

0.8

1.2

1.6

2

0 5 10 15 20 25 30

Time (h)

Voltage (

V)

Base

Fig16. Open-circuit voltage during 24 h of storage.


49

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0 50 100 150 200 250 300

T (h)

V (

vo

lt)

x=Zero

x=10%

x=20%

x=30%

x=40%

Fig.17. Discharge curves of Mg/electrolyte/TiO2 for different concentration (x) of the

electrolyte in the cathode where x=0, 10%, 20%, 30%, 40% at constant load resistance.


50

Fig18. The plot of I-V and J-P curves for the battery

with different concentration of the electrolyte in the

cathode where a (zero), b (10%), c (20%),

d (30%), e (40%).

0

0.05

0.1

0.15

0.2

0.25

0 0.03 0.06 0.09Current density (mA cm-2)

Pow

er

density

(m

W c

m-2

)0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 0.03 0.06 0.09 0.12

Current (mA)

Volta

ge (

V)

a

0

0.05

0.1

0.15

0.2

0.25

0 0.02 0.04 0.06 0.08 0.1Current density (mA cm-2)

Pow

er

density

(m

W c

m-2

)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14

Current (mA)V

olta

ge (

V)

b

0

0.05

0.1

0.15

0.2

0.25


Pow

er

density

(m

W c

m-2

)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 0.03 0.06 0.09 0.12

Current (mA)

Volta

ge (

V)

c 0

0.05

0.1

0.15

0.2

0.25

0 0.02 0.04 0.06 0.08Current density (mA cm-2)

Pow

er

density

(m

W c

m-2

)

0

0.2

0.4

0.6

0.8

1

1.2

0 0.02 0.04 0.06 0.08 0.1

Current (mA)

Volta

ge (

V)

d

0

0.05

0.1

0.15

0.2

0.25


Pow

er

density

(m

W c

m-2

)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 0.03 0.06 0.09 0.12

Current (mA)

Volta

ge (

V)

e


51


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