DEVELOPMENT OF ALUMINUM AIR SEAWATER BATTERY

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DEVELOPMENT OF ALUMINUM AIR SEAWATER BATTERY

BY

MAZIATI AKMAL MOHD HATTA

A dissertation submitted in fulfilment of the requirement for the degree of Master of Science (Materials Engineering)

Kuliyyah of Engineering

International Islamic University Malaysia

JUNE 2014

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ii

ABSTRACT

The feasibility of aluminium-air seawater battery as potential power source for marine applications is investigated. The cell, measuring 20 mm x 30 mm, comprises of an aluminium anode and laminated sheet of E4 air electrode. Two cell designs are studied i.e. the enclosed and open configurations. The electrolyte used is sodium chloride (0.5 M and 4 M) and seawater. Sodium chloride (NaCl) electrolyte of 0.5 M is used as a substitute for seawater while that of 4 M possesses the highest electrolyte conductivity. The open configuration design mitigates the electrolyte and heat management issues, and hence enhances the cell discharge performance markedly.

The open configuration cell, however, prevents the serial cell arrangement. As such, the cell design needs to be optimized in order to increase its performance. It is discovered that, the key design element is the air electrode. Merely by adopting multipolar air electrode design, the energy output of Al-air seawater cell is extended from 173 mWh to 779 mWh (rated at 1 mA), a significant improvement factor of 4.5.

Generally, as the rating current is doubled, the energy output will be halved. Besides, other design aspects that could be implemented to improve the discharge performance are using parallel stacks arrangement and scaling up the cell size. The parallel twin- stack cell extended the discharge duration from 11 days to 26 days, also rated at 1 mA.

On the other hand, the fourfold increment of the electrodes’ size from 20 mm x 30 mm to 40 mm x 60 mm would double the energy output. The electrochemical reactions of Al-air seawater cell are established from the physical characterizations of X-ray diffraction and cyclic voltammetry. Taking into account the parasitic corrosion of aluminium electrode in seawater, the anodic efficiency of the Al-air cell is estimated around 79 %.

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iii

صخللما

نم ةيئاولها موينلملاا ةيراطب مادختسا نم يودلجا لوح ثحبلا تم ردصمك رحبلا ءام

يف ةقاطلل لمتمح تاصاوغلا تاقيبطت

. هيللخا , اهسايق و تريميلم 02

تريميليم 02

,

ءاوه نم ةددضنم هحيفص نم نوكم بطقو موينلملاا نم ةعونصم دونا ىلع ىوتتح . E4

م ناميمصت ةسارد تتم حوتفلماو قلغلما بيكترلا لثم ايلالخا ن

. تيلوتركللإا

مويدوصلا ديرولك وه مدختسلما (

0.5 M and 4 M

رحبلا ءامو )

. يمدوصلا ديرولك

ءابرهكلاب لحنلما

(NaCl)

نم

0.5 M

لوللمحا امنيب رحبلا ءالم ليدبك همادختسا تم

نم ةيئابرهك ةيلصوم ىلعا كلتما 4M

. ا ففخ حوتفلما ميمصتلا ةيلمعو تيلوتركللإ

ةرارلحا ةرادا ,

ظوحلم لكشب ايلالخا غيرفت ءادا زيزعت تم انه نمو .

حوتفلما نيوكتلا

ةيلخلل , كلذ عمو ,

لسلستلما ايلالخا بيترت عنم .

وحنلا اذه ىلع ,

جاتيح ةيللخا ميمصت

ةئافكلا ةدايز لجا نم ينستح لىا .

بطقلا وه يسيئرلا ميمصتلا رصنع نا فشتكا مقل

اولها يئ . ةيبطقلا ددعتم يئاوه بطق ميمصت دامتعا درجبم ,

ةيلخ نم ةجرالخا ةقاطلا

نم تدادزا ةيئاولها موينلملاا لىا هعاسلا في تاو يليم 370

تاو يليم 777

هعاسلل (.

لدعبم يربما يلم 1

) , لىا لصي يربك ينستح لماعم . 5.4

هماع ةروصب ,

نا امك

فعاضتي رايتلا لدعم ,

صقنت ةجرالخا ةقاطلا فصنلل

. كلذ لىا ةفاضا ,

تاهاتجا

يزاوتلما بيتترلا مادختسا يه غيرفتلا ءادا ريوطت لجا نم اهقيبطت نكيم يرخا ميمصت ةيللخا مجح ةدايز و تاعومجملل .

ةيلمع تددم ايلالخا نم ينتيزاوتم ينتعوممج

نم غيرفتلا لىا موي 11

موي 02

, لدعبم اضيا يربما يليم 3

. يرخا ةيحان نم ,

ةفعاضم

نم بطقلا مجح تريميليم 02

X

لىا تريميليم 02

52 تريميليم

X

ابمر تريميليم 22

ةجرالخا ةقاطلا ةيمك فعاضي .

رنكللاا تلاعافتلا نكيم ةيئاولها موينللاا ةيللخ يئايميكو

سكا ةعشا راسكنلا ةيئايزيفلا صئاصلخا نم اهيلا لوصولا

x-ray

و

cyclic

voltammetry

. ابتعلااب ذخلااب رحبلا ةايم في موينلملاا بطق لكات ةيلمع ر

,

لياوبح تردق ةيئاولها موينلملاا ةيللخ ةيدونلاا ةئافكلا

79 .%

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APPROVAL PAGE

I certify that I have supervised and read this study and that in my opinion; it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a thesis for the degree of Master of Science (Materials Engineering).

………

Raihan Othman

Supervisor

………

Mohd Hanafi Ani Co-Supervisor

I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a thesis for the degree of Master of Science (Materials Engineering).

………

Souad A. Mohamed Internal Examiner

………

Shoichiro Ikeda External Examiner

This thesis was submitted to the Department of Materials and Manufacturing Engineering and is accepted as a fulfilment of the requirement for the degree of Master of Science (Materials Engineering).

………

Mohammad Yeakub Ali

Head, Department of Materials and Manufacturing Engineering This thesis was submitted to the Kulliyyah of Engineering and is accepted as a fulfilment of the requirement for the degree of Master of Science (Materials Engineering).

……….

Md. Noor Salleh

Dean, Kulliyyah of Engineering

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DECLARATION

I hereby declare that this thesis is the result of my own investigations, except where otherwise stated. I also declare that it has not been previously or concurrently submitted as a whole for any other degrees at IIUM or other institutions.

Maziati Akmal bte Mohd Hatta

Signature……….. Date………...

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INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA

DECLARATION OF COPYRIGHT AND AFFIRMATION OF FAIR USE OF UNPUBLISHED RESEARCH

DEVELOPMENT OF ALUMINIUM AIR SEAWATER BATTERY

I hereby affirm that The International Islamic University Malaysia (IIUM) holds all rights in the copyright of this Work and henceforth any reproduction or use in any forms or by means whatsoever is prohibited without the written consent of IIUM. No part of this unpublished research may be produced, stored in a retrieval system, or transmitted, in any form or by means, electronic, mechanical, photocopying, recording or otherwise without prior written permission of the copyright holder.

Affirmed by Maziati Akmal bt Mohd Hatta

……… ………

Signature Date

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ACKNOWLEDGEMENTS

In the name of Allah, the Most Gracious and the Most Merciful. First and foremost, all praises to Allah for the strengths and His blessing in completing this thesis.

First of all, I would like to express my gratitude and deepest thanks to my supervisor, Dr. Raihan Othman, who guided me through my master. Dr Raihan prompted me into developing bold arguments and helped me improve my stream of thought. His talent to teach, patience, experience and scientific excellence make him an irreplaceable person to work with.

I would also like to thank my Co supervisor Dr Mohd. Hanafi Ani for the valuable advice and succinct comments that he provided me when needed, for which I am indebted.

One of the most important factors influencing your mood during the master work is probably the people that you work with in the lab. They can “make your day”

just by smiling to you and being kind. Therefore, I would also like to express my thanks to the PhD and master students in the Energy Laboratory; Bro Shahrul, Sis Noraini, Sis Norliza, Sis Sharifah, Sis Aimi, and Sis Hanisah. My research would not have been possible without their helps. Not to forget, my acknowledgement also goes to all lab technicians who have guided me to do the experiments and allowed me to use the equipments.

Special thanks to the Department of Materials Engineering which has provided the support and equipment needed to complete my thesis. I would also like to thank the Ministry of Higher Education (MOHE) and International Islamic University Malaysia (IIUM) for the financial support throughout my studies.

Finally, I would like to thank my husband and my family. They were always there supporting and encouraging me with their best wishes. They were cheering me up and stood by me through the good times and bad. Thanks to them for being supportive and listening to me all these years.

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LIST OF TABLES

Table No. Page No.

1.1 Comparisons of metal air batteries

2.1 Characteristics of Al-air system as compared to conventional aluminium batteries

2.2 Considerable efforts have been made to develop high performance aluminium anode

4.1 Bulk resistance for NaCl prepared with different concentration and seawater at room temperature

4.2 Conductivity of seawater and various concentrations of NaCl electrolyte measured at room temperature using different technique

4.3 Corrosion data calculated from Tafel polarization for aluminium in 0.5 M and 4 M NaCl

2 7

14 36

39

66

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LIST OF FIGURES

Figure No. Page No.

1.1 Flow chart of research methodology 5

2.1 Essential components of the aluminium air battery and 10 the species involved.

2.2 Potentiodynamic polarization of aluminium in neutral solution 12 2.3 Schematic diagram of air cathode and species involved at air 17

electrode.

2.4 Exploded view of battery stack 19

2.5 Bipolar and monopolar battery configurations 20 2.6 Development status of aluminium air batteries 22 3.1 The engineering drawing design of battery holder layout 23 3.2 Schematic diagram of Aluminium-air battery component 26

developed in laboratory.

3.3 Open configuration of Al-air seawater battery 27

3.4 Design of the impedance cell 29

3.5 The electrochemistry test equipment 30

3.6 Schematic diagram of Tafel equipment in our laboratory 31

4.1 Impedance plots for various concentrations of NaCl and seawater 35 4.2 Conductivity versus various concentrations of NaCl and seawater.

Data were obtained from EIS measurement 37

4.3 Conductivity of NaCl solution of various molarities as

determined from conductivity meter 38

4.4 Open circuit voltage profiles of Al-air cell employing different

electrolytes 40

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4.5 Discharge capacity of Al-air cells using NaCl electrolytes 41 and seawater

4.6 Discharge capacity of Al-air cells using close and open

configurations rated at 1mA 43

4.7 Al-air seawater cell performance was extended markedly to

almost compatible with Al-air cell using 4 M NaCl 43 4.8 Discharge profiles of Al-air seawater battery rated at different

load 45

4.9 Total energy output of battery rated 0.5, 1, and 2 mA 45 4.10 The polarization and power density profiles of the open

configuration Al-air cell 47

4.11 Power density plot for Al air seawater battery obtained

from polarization and discharge method 48

4.12 Power output plot for typical AA alkaline battery 49 4.13 The discharge performance of Al-air seawater cell with a single

and parallel cell configuration 51

4.14 The influence of electrode size on the cell discharge performance 52 4.15 Discharge profiles of various cathode configurations rated at

1 mA 54

4.16 The cell design for bipolar, tripolar and multipolar air electrode 54 4.17 The energy density enhancement as multiple air electrodes

was adopted 55

4.18 The discharge profiles of the cell using multiple anodes 55 4.19 Camera images of the discharge product during discharging

process 56

4.20 SEM images showing the Al(OH)3 gelatinous microstructure 57 on Al plate with different magnification (a) 3,500x (b) 7,000.

4.21 X-ray diffractograms indicating new structure formation after

Al-air battery after being discharged in the seawater 57

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4.22 Cyclic voltammogram of aluminium electrode at a scan rate

10 mV/s 58

4.23 Voltammograms of aluminum electrode in NaCl at different

scan rates 59

4.24 CV profiles of the air electrode in 0.5 M NaCl at scan rates of 10

and 30 mV/s 61

4.25 The bar chart distribution for m and R² values across the

entire polarization curve of aluminium in 0.5 M NaCl 64 4.26 The corresponding interval of linearity on the anodic and

cathodic polarization curves 65

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LIST OF ABBREVIATIONS

Ag/AgCl Al

ASTM

°C CV EDX EIS E_eq

Epp

e.m.f FeCN Hg H2O2 Icrit

M_w

mA mAh

mpy

mW

mV/s OCV

PTFE SEM SHE

V XRD

θ Ƞ

Silver/Silver chloride electrode

Aluminium American Society for Testing and Materials Degree Celsius

Cyclic voltamettry

Energy Dispersive X-Ray

Electrochemical Impedance Spectroscopy Equilibrium potential

Pasivation potential Electromotive Force Iron cyanide

Mercury

Hydrogen peroxide Critical current density

Molecular Weight of Water Vapour

miliampere

miliamperehour mil per year miliWatt

miliVolt per second

Open Circuit Voltage (no current applied) Polytetrafluoroethylene

Scanning Electron Microscope Standard Hydrogen Electrode Operating Voltage (applied load) X-ray diffraction

Theta

Anode consumption efficiency

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CHAPTER ONE INTRODUCTION

1.1 OVERVIEW

In the recent years, a significant worldwide attention has been paid to the development of new types and novel generations of electrochemical power sources.The interest is mainly driven by the quest for environmental friendly and efficient renewable power sources. One of the emerging fields of research in response to this is the research and development of metal-air batteries.

Metal-air batteries are also known as metal fuel cells as one of their reactants is ambient oxygen. By substituting hydrogen gas with electroactive metal and coupled with ambient air, metal-air batteries offer several advantages over their fuel cells counterpart. The most obvious being the elimination of compressed hydrogen storage cylinder. Furthermore, the use of ambient oxygen which does not require storage permits the whole battery compartment to be utilized by the electroactive metal.

These advantages contribute towards a lightweight, high energy density power source. Table 1.1 lists metal anodes that have been considered for metal-air system (Li and Bjerrum, 2002; Linden and Reddy, 2001).

Among metal-air batteries, Al-air system is most unique - it is the only metal- air system that is capable to operate in saline electrolyte such as the seawater. Other than the inherently safe, non-corrosive saline electrolyte, aluminium as the anode material for the system is abundant, low cost and non-toxic. The Al-air seawater battery is thus a non-polluting, green energy source with high energy density. In addition, Al-air battery is a mechanically rechargeable battery which only requires the

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replacement of discharged anodes after each cycle (Egan et al., 2013). Another important advantage of aluminium-air seawater battery is its infinite shelf-life in the inactive dry state with facile activation by addition of the seawater (Souza and Vielstich, 2003).

Though aluminium-air battery using alkaline electrolyte demonstrates much superior performance as compared to the system using seawater or saline electrolyte, aluminium-air seawater battery is still the preferred portable energy source for niche marine applications such as to power remote navigation buoys and deep sea exploration devices.

Table 1.1

Comparisons of anodes for metal-air batteries Metal anode Capacity

(Ah/g)

Theoretical Voltage

(V)

Theoretical Energy Density

(kWh/kg)

Li 3.86 3.4 13.0

Ca 1.34 3.4 4.6

Mg 2.20 3.1 6.8

Al 2.98 2.7 8.1

Zn 0.82 1.6 1.3

Fe 0.96 1.3 1.2

Another seawater battery system investigated for long duration undersea application is magnesium-air seawater activated batteries. The magnesium-air system has a voltage of 2.20 V and is expected to be capable of more than 500 Wh/kg when conﬁgured for large scale unmanned undersea vehicles. However, magnesium anodes exhibit the irreversible polarization and high-self discharge rates which show no major advantages over the aluminum-air battery (Blurton and Sammels, 1979).

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1.2 PROBLEM STATEMENT AND ITS SIGNIFICANCE

One of the leading issues in aluminium-air seawater electrochemical system is electrolyte management as a result of hydroxide gel formation or hydrargillite crystallization (Milusheva et al., 2011). Water is consumed during cell discharge since hydrargillite binds water. Consequently as the cell becomes water starved, anodic passivation accelerates causing premature cell failure. In one embodiment, the aluminium-air seawater cell is constructed using an open configuration. In this design, both anode and cathode are held in a casing that is open to the surrounding seawater.

The flow of seawater over the electrodes would naturally remove the benign reaction product into the sea. Details on the electrochemical performance of this type of Al-air seawater cell are scarce in the literature. Hence, the current work is accentuated towards the development of high energy density aluminium-air seawater cell using open configuration.

1.3 RESEARCH OBJECTIVES

This work intended to develop Al-air seawater cell for marine applications. Hence, the research has been focussed to achieve the following objectives:

i. To design, fabricate and characterize Al-air seawater system employing open cell configuration

ii. To compare the performance characteristics of Al-air cell using the enclosed and open configurations

iii. To optimize the design of Al-air seawater cell employing the open configuration.

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4 1.4 RESEARCH METHODOLOGY

The components of this research work include:

i. Cell and components design

The cell holder was prepared from acrylic boards using CNC machining. The Al plate was mechanically polished by using different grades of alumina suspension to remove native oxide layer before use.

A commercial air electrode supplied by Magna Value Sdn Bhd was used as the cathode. The cathode comprised of laminated fibrous carbon layer supported by a nickel mesh.

ii. Characterization of aluminium-air battery

The fabricated Al-air cell was characterized according to its open circuit potential, continuous discharge capacity test at current drain of 1 mA, polarization profile and the subsequent power density plot. A NEWARE Potentiostat/Galvanostat instrumentation was utilized to perform the measurements. All measurements were carried out at ambient temperature of 25ºC.

iii. Physical/Electrochemical characterizations

X-ray Diffractometer (XRD) was used to identify the reaction product of Al-air seawater battery and supported by the Scanning Electron Microscope (SEM) observation. Cyclic voltammetry was performed to ascertain the reaction mechanisms of the cell. In order to analyse the corrosion rate of Al anode in seawater, Tafel extrapolation analysis was utilized.

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Figure 1.1: Flow chart of research methodology

Electrochemical Characterization

Data verification and analysis END YES 1. Open Circuit Voltage

2. Discharge

3. Polarization Measurement 4. Tafel Extrapolation 5. Cyclic Voltamettry

Physical Characterization

1. XRD

2. SEM

YES

NO

NO START

Development of Aluminum-air seawater battery

List parameters to be considered

Materials selection design layout and process

Preparation of battery prototype

Review: Journals, articles, books

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6 1.5 SCOPE OF RESEARCH

This work was initiated with comparative performance analysis of the Al-air seawater cell employing enclosed cell design and open cell design. The seawater electrolyte was simulated using NaCl salt. Once an open cell design is employed, the serial cell stacks arrangement is no longer possible. As a result, the cell discharge capability and performance can only be improved based on design considerations such as the electrode size, parallel cell configuration or bipolar cell design. Hence the main focus of the present research was to evaluate the various cell design aspects as mentioned.

Finally, physical characterizations such as SEM and X-ray diffraction measurements, electrochemical methods of cyclic voltammetry, and resistance polarization were performed to ascertain the aluminium-air cell reaction mechanisms in seawater.

1.6 THESIS ORGANIZATION

The present thesis is organized into five chapters. Chapter one provides an overview of the current work. Chapter two gives the historical background on the development of Al-air cell followed by literature review on its electrochemical properties. Chapter three highlights the details of experimental procedures and characterization techniques which include the fabrication of aluminium-air cell, electrochemical and physical characterization. Chapter four discusses the results and findings obtained. Finally, Chapter five summarizes the findings of this research, followed by recommendations for further work on this subject matter.

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CHAPTER TWO LITERATURE REVIEW

2.1 INTRODUCTION

Aluminium is abundant and inexpensive, has a large specific capacity of 2.98 Ahg^-1 and a vigorous reducing power (Eº =-2.33 V vs SHE) (Li and Niels, 2002). Coupled with air depolarizing electrode, aluminium-air battery possesses the highest energy density than other conventional aluminium electrochemical systems. Table 2.1 compares the properties of conventional aluminium batteries with aluminium-air system.

Table 2.1

Characteristics of Al-air system as compared to conventional aluminium batteries

Batteries system

Open circuit Voltage (V) Capacity (Ah/kg)

Theoretical Energy Density (Wh/kg)

References

Theoretical Measured

Al-AgO 2.7 2.0 378 1020 Karpinski et al.

(2000)

Al-H2O2 2.3 1.8 408 940 Hasvold et

al.(1999)

Al-FeCN 2.8 2.2 81 230 Licht and

Marsh (1992)

Al-S 1.8 1.4 595 1090 Licht and

Peramunage (1993) Al-air

(alkaline)

2.7 2.0 2985 8140 Kaisheva

(2005) Al-air

(saline)

1.23 1.0 1084 8036 Morris et al.

(2002) and Kaisheva (2005)

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The actual operating voltage of aluminium-air battery is significantly lower than the expected potential of 2.7 V because aluminium is normally covered by a native oxide film. This passive oxide layer increases the internal resistance of the electrode and causes a delay in reaching a steady state voltage (Doche et al., 1997). The oxide film can be removed by dissolution in concentrated alkali solution or by amalgamation (Li and Bjerrum, 2002).

When immersed in seawater, Al-air battery generates potential of about 1 V (Wilcock and Caufman, 1997). The system relies on the corrosion of the reactive metal anode and the reduction of dissolved oxygen at an inert cathode. The flow of seawater over the cathode improves battery performances because it thins the boundary layer for oxygen. Moreover, batteries based on the use of oxygen dissolved in seawater have an additional advantage. A cathode, which is open to the ocean, is spaced around an anode so that the reaction product can fall out into the ocean (Opitz, 1968; Han and Liang, 2006). As for the metal anode, the utilization of seawater as electrolyte lead to high power density since electrodes is not housed in an enclosure that could affect the anodic efficiency.

Despic et al. (1976) were the first who explored Al-air batteries with seawater electrolyte. The reaction product is generally a hydroxide, rather than an oxide and during the discharge operation, water is consumed as summarized in the following equation (Drazic et al, 1983):

 

2 2 3

3 3

Al O H O Al OH

4 2

   (Eq. 2.1)

In an enclosed design of aluminium-air seawater battery, electrolyte management is required. The reaction product has a transient high solubility in the electrolyte and tends to become gel-like when it first precipitates (Linden, 1995). In one approach the electrolyte was stirred in a reciprocating manner, which minimized

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gel formation and produced a finely divided product which was dispersed in the electrolyte (Fitzpatrick and Strong, 1989). Concerning aluminium hydroxide as reaction product, it should be remarked that Al (OH₃) is benign and not harmful to environment (Vargel, 2004).

2.2 ALUMINIUM-AIR BATTERY CHEMISTRY

The aluminum-air cell consists of an aluminum anode, placed in a seawater or alkaline electrolyte, which reacts with oxygen from the air or other source. Electricity is produced as the aluminum oxidizes. Physically, a typical cell consists of aluminum plates and a gas diffusion cathode coupled by an electrolyte, as shown in Figure 2.1. It may be noted that only aluminium and water are the main reactants used up during discharge. Hence, recharging of the battery is very simple. It requires adding water and also replacing the aluminium anode when it is already consumed.

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Figure 2.1: Essential components of the aluminium-air battery and the species involved

During the electrochemical reaction, anodic Al oxidizes to Al³⁺ (McCafferty, 2003), while at the cathode, oxygen, water and the electrons that flow through the external circuit from the aluminium react to produce hydroxide ions. The hydroxide ions then react with the aluminium ions to form aluminium hydroxide. The following equations summarize the chemistry that is involved in the aluminium air seawater battery.

Anode : 2Al  6H O 2Al OH2 