Reliability and aging mechanisms of all solid state thin film lithium ion microbatteries

RELIABILITY AND AGING MECHANISMS
OF ALL-SOLID-STATE THIN FILM LITHIUM ION
MICROBATTERIES







ZHU JING







NATIONAL UNIVERSITY OF SINGAPORE
2012
RELIABILITY AND AGING MECHANISMS
OF ALL-SOLID-STATE THIN FILM LITHIUM ION
MICROBATTERIES





ZHU JING
(B. Eng., Sichuan University

M. Eng., Sichuan University)




A THESIS SUBMITTED
FOR THE DEGREE OF DOCTOR OF PHILOSOPHY
DEPARTMENT OF MECHANICAL ENGINEERING
NATIONAL UNIVERSITY OF SINGAPORE
2012
Declaration
i
DECLARATION

I hereby declare that the thesis is my original work and it has been written by
me in its entirety. I have duly acknowledged all the sources of information which have
been used in the thesis.
This thesis has also not been submitted for any degree in any university
previously.









_________________________
ZHU JING

20 July 2012

List of Publications
ii
LIST OF PUBLICATIONS

The research described herein was conducted under the supervision of Prof. Lu
Li and Associate Prof. Zeng Kaiyang from the Material Science Division, Department
of Mechanical Engineering, National University of Singapore (NUS). The majority
portions of this dissertation have been published to international journals, or presented
at various international conferences.

Journal papers:
1. J. Zhu, K. B Yeap, K. Y. Zeng, L. Lu, Nanomechanical characterization of
sputtered RuO
2
thin film on silicon substrate for solid state electronic devices, Thin
Solid Films, 519 (2011) 1914-1922.

2. J. Zhu, K. Y. Zeng, L. Lu, Cycling effect on morphological and interfacial
properties of RuO
2
anode film in thin film lithium ion microbatteries, Metallurgical
and Materials Transactions A, in press, DOI: 10.1007/S11661-011-0847-0., (2011)
1-9.

3. J. Zhu, K. Y. Zeng, L. Lu, Cycling effects on interfacial reliability of TiO
2
anode
film in thin film lithium ion microbatteries, Journal of Solid State Electrochemistry,

16 (2012) 1877-1881.

4. J. Zhu, J. K. Feng, K. Y. Zeng, L. Lu, In-situ study of topography, phase and volume
changes of TiO
2
anode in all-solid-state thin film Li-ion battery by biased scanning
probe microscopy, Journal of Power Source, 197 (2012) 224-230.

5. J. Zhu, K. Y. Zeng, L. Lu, Cycling effect on morphological and interfacial
properties of LiMn
2
O
4
cathode film in thin film lithium ion microbatteries,
Electrochemica Acta, 68 (2012) 52-59.
List of Publications
iii
6. J. Zhu, K. Y. Zeng, L. Lu, In-situ nanoscale mapping of surface potential in
all-solid-state thin film Li-ion battery using Kelvin probe force microscopy, Journal
of Applied Physics, 111(2012) 063723.

7. J. Zhu, K. Y. Zeng, L. Lu, Nanoscale mapping of Li-ion diffusion on cathode and
anode surface in all-solid-state Li-ion battery by Electrochemical Strain Microscopy,
to be submitted.

8. X. Song, K. B. Yeap, J. Zhu, J. Belnoue, M. Sebastiani, E. Bemporad, K. Y. Zeng,
A. M. Korsunsky, Residual stress measurement in thin films using the
semi-destructive ring-core drilling method using Focused Ion Beam, Procedia
Engineering, 10 (2011) 2190-2195.

9. X. Song, K. B. Yeap, J. Zhu, J. Belnoue, M. Sebastiani, E. Bemporad, K. Y. Zeng,
A. M. Korsunsky, Residual stress measurement in thin films at sub-micron scale
using Focused Ion Beam milling and imaging, Thin Solid Films, 520 (2012)
2073-2076.
*Collaboration with Department of Engineering Science, University of Oxford, UK

Conference Presentations (Oral)
1. J. Zhu, K. Zeng and L. Lu, “Determine the interfacial properties of sputtered RuO
2

thin film on Si substrate by nanoindentation techniques”, International Conference
on Materials for Advanced Technologies (ICMAT 2009), Jun. 28 – Jul. 2, 2009,
Singapore (presented by J. Zhu)

2. L. Lu, H. Xia, J. Zhu, K. Y. Zeng, J. K. Feng, “Microbatteries – Processing and
Properties”, 7
th
Shanghai – Hong Kong Forum on Mechanics and Its Application,
Mar. 13, 2010, Hong Kong (distinguished plenary talk by L. Lu).

3. J. Zhu, K. Zeng and L. Lu, “Effects of electrical cycling on interfacial properties
of RuO
2
anode film in lithium ion microbatteries”, The 5
th
International
Conference on Technology Advances of Thin Films & Surface Coatings (Thin
Films 2010), Jul. 11 – 14, 2010, Harbin, China (presented by K. Zeng).

List of Publications

iv
4. J. Zhu, K.Y. Zeng, and L. Lu, “Mechanical responses to electrochemical cycling of
anode film in lithium ion microbatteries”, The 3
rd
International Forum on Systems
and Mechatronics (IFSM 2010), Sep.7 – 9, 2010, Singapore (presented by J. Zhu).

5. J. Zhu, K.Y. Zeng, and L. Lu, “Cycling effects on surface morphology and
interfacial reliability of RuO
2
anode in thin film lithium ion batteries”, E-MRS 2011
Spring Meeting & E-MRS/MRS Bilateral Conference on Energy, May 9 – 13, 2011,
Nice, France (presented by J. Zhu).

6. J. Zhu, K.Y. Zeng, and L. Lu, “Cycling effects on interfacial reliability of LiMn
2
O
4
cathode film in thin film lithium ion batteries”, International Conference on
Materials for Advanced Technologies (ICMAT 2011), Jun. 26 – Jul. 1, 2011,
Singapore (presented by J. Zhu)

7. J. Zhu, K.Y. Zeng, and L. Lu, “In-situ study on cyclic changes of topography, phase
and volume of TiO
2
anode in all-solid-state thin film Li-ion battery by biased
scanning probe microscopy”, MRS 2012 Spring Meeting, Apr. 9 – 13, California,
USA (presented by J. Zhu).

8. J. Zhu, K.Y. Zeng, and L. Lu, “Effects of electrical cycling on morphology,

nanomechanical and interfacial reliability of electrode materials in thin film lithium
ion microbatteries”, The 6
th
International Conference on Technology Advances of
Thin Films & Surface Coatings (Thin Films 2012), Jul. 14 – 17, 2012, Singapore
(invited talk by K. Y. Zeng).

Conference Presentations (Poster)
1. J. Zhu, K. Zeng and L. Lu, “Cycling effect on morphological, nanomechanical and
interfacial properties of RuO
2
anode film in thin film lithium ion battery”, MRS-S
Trilateral Conference on Advances in Nanoscience-Energy, Water & Healthcare
(MRS-S 2010), Aug. 9 – 11, 2010, Singapore.

2. J. Zhu, K. Zeng and L. Lu, “In-situ study on topography, phase and volume changes
of TiO
2
anode in all-solid-state thin film Li-ion battery by biased scanning probe
microscopy”, International Conference of Young Researchers on Advanced
Materials (ICYRAM 2012), Jul. 1 – 6, 2012, Singapore.

Acknowledgements
v
ACKNOWLEDGEMENTS

First of all, I would like to express my sincere gratitude to my supervisors, Prof.
Lu Li and Associate Prof. Zeng Kaiyang, for their guidance, supervision,
encouragement and invaluable advice throughout my Ph.D. study. Their scientific
attitude, knowledge and research skills have provided a solid foundation for this study.

It is a great honor for me to carry out Ph.D. study under their supervisions.
In addition, I would like to express my appreciation to Institute of Material
Research and Engineering (IMRE) for its experimental support. I especially thank Mr.
Wang Weide for his help on magnetron sputtering experiments and Mrs. Shen Lu for her
assistance on nanoindentation experiments. Most sincere thanks also to the staff in
Department of Mechanical Engineering (NUS),
Mr. Thomas Tan, Mr. Ng Hong Wei, Mr.
and Abdul Khalim Bin Abdul, for their supports and assistance.
Also, many thanks are conveyed to my seniors and colleagues, Dr. Xia Hui, Dr.
Wang Shijie, Dr. Wang Hailong, Dr. Yan Feng, Dr. Wong Mengfei, Dr. Chen Lei, Mr. Xiao
Pengfei, Mr. Ye Shukai, Mr. Song Bohang, Mr. Lin Chunfu and Miss. Li Tao, for their
helps and friendship. I especially thank Dr. Yeap Kongboon and Dr. Feng Jinkui for their
advices and guidance at the beginning of my Ph.D. study.
Finally, I deeply appreciate my family, especially my husband, Zhu Jianhua.
Without their understanding, support, encouragement and earnest love, I would not able
to complete my Ph.D. study so smoothly.
Table of Contents
vi
TABLE OF CONTENTS

DECLARATION i
LIST OF PUBLICATIONS ii
ACKNOWLEDGEMENTS v
TABLE OF CONTENTS vi
SUMMARY xii
LIST OF TABLES xiv
LIST OF FIGURES xv
LIST OF SYMBOLS xxi

Chapter 1. Introduction 1

1.1 Overview of Lithium Ion Batteries 2
1.1.1 Principles of Operation 2
1.1.2 Current Status and Challenges 3
1.2 Research Objective and Significance 4
1.3 Thesis Outline 7
Chapter 2. Literature Review 8
2.1 Materials for Electrode 8
2.1.1 Anode Materials 9
2.1.2 Cathode Materials 13
2.2 All-Solid-State Thin Film Lithium Ion Microbatteries 17
Table of Contents
vii
2.3 Aging Studies for Lithium Ion Batteries 20
2.4 Methods to Determine the Interfacial Adhesion of Thin Film/Substrate
Structure 24
2.4.1 Mechanical Bending Tests 24
2.4.2 Indentation Tests 25
2.5 Scanning Probe Microscopy 31
Chapter 3. Materials and Experimental Methodology 36
3.1. Material Preparation 37
3.1.1 Target Fabrication 37
3.1.2 Film Deposition 37
3.2 Electrochemical Characterization 38
3.2.1 Battery Assembly 38
3.2.2 Galvanostatic Cycling 39
3.3 Microstructural Characterization 39
3.3.1 X-ray Diffraction 39
3.3.2 Energy Dispersive X-ray Spectroscopy 40
3.4 Morphology Characterization 40
3.4.1 Surface Profilometer 40

3.4.2 Field Emission Scanning Electron Microscope 41
3.4.3 Atomic Force Microscope 41
3.5 Mechanical Characterization 42
Table of Contents
viii
3.5.1 Elastic Modulus and Hardness 42
3.5.2 Interfacial Toughness Characterization 43
3.5.3 Crack Profile Characterization 45
3.6 In-situ Scanning Probe Microscopy Study 46
3.6.1 Biased Atomic Force Microscopy 46
3.6.2 Kelvin Probe Force Microscopy 46
3.6.3 Electrochemical Strain Microscopy 48
Chapter 4. Extension and Verification of Experimental and Analysis Method for
Interfacial Toughness of Hard Film/Soft Substrate 51
4.1 Thin Film Characterization 52
4.2 Comparative Analysis of Different Indentation Tests 54
4.2.1 Load-Displacement Curves 54
4.2.2 Indentation Induced Delamination 56
4.3 Interfacial Adhesion Mechanics 64
4.4 Interfacial Toughness Determination 69
4.4.1 Elastic Modulus and Hardness 69
4.4.2 Interfacial Toughness 70
4.5 Summary 73
Chapter 5. Interfacial Reliability and Aging Mechanism of Thin Film Anode 75
5.1 Cycling Effect on Reliability of Rutile RuO
2
Anode 76
5.1.1 Structural and Electrochemical Characterization 76
Table of Contents
ix

5.1.2 Surface Morphology 80
5.1.3 Nanomechanical Degradation 85
5.1.4 Interfacial Reliability 87
5.2 Cycling Effect on Reliability of Anatase TiO
2
Anode 91
5.2.1 Structural and Electrochemical Characterization 92
5.2.2 Surface Morphology 94
5.2.3 Nanomechanical Degradation 97
5.2.4 Interfacial Reliability 98
5.3 Summary 101
Chapter 6. Interfacial Reliability and Aging Mechanism of Thin Film Cathode
103
6.1 Cycling Effect on Reliability of Spinel LiMn
2
O
4
Cathode 103
6.1.1 Structural and Electrochemical Characterization 104
6.1.2 Surface Morphology 106
6.1.3 Nanomechanical Degradation 110
6.1.4 Interfacial Reliability 115
6.2 Cycling Effect on Reliability of Layered LiNi
1/3
Co
1/3
Mn
1/3
O
2

Cathode 118
6.2.1 Structural and Electrochemical Characterization 118
6.2.2 Surface Morphology 121
6.2.3 Nanomechanical Degradation 123
6.2.4 Interfacial Reliability 125
Table of Contents
x
6.3 Summary 127
Chapter 7. Effects of Charge/Discharge Rate and Depth of Discharge (DOD) on
Interfacial Reliability 129
7.1 Effects of Charge/Discharge Rate on Reliability 129
7.1.1 Electrochemical Characterization 129
7.1.2 Surface Morphology 130
7.1.3 Nanomechanical Degradation 132
7.1.4 Interfacial Reliability 134
7.2 Effects of Depth of Discharge (DOD) on Reliability 135
7.2.1 Electrochemical Characterization 135
7.2.2 Surface Morphology 136
7.2.3 Nanomechanical Degradation 139
7.2.4 Interfacial Reliability 141
7.3 Summary 142
Chapter 8. In-situ Electrochemical Study on All-Solid-State Thin Film Lithium
Ion Batteries by Scanning Probe Microscopy 144
8.1 Electrochemical Characterization of All-Solid-State Thin Film Lithium
Ion Batteries 145
8.2 In-Situ Experimental Setup 146
8.3 Biased Atomic Force Microscopy 148
8.4 Kelvin Probe Force Microscopy 162
Table of Contents
xi

8.5 Electrochemical Strain Microscopy 172
8.6 Summary 178
Chapter 9. Conclusions and Recommendations 181
9.1. General Conclusions 181
9.2. Recommendations for Future Works 185
References 187
Appendix 208


Summary
xii
SUMMARY

Lithium ion batteries are the most dominant power sources for portable and
mobile applications due to their high energy density, long cycle life and no memory
effect. Recently, all-solid-state thin film lithium ion batteries have attracted considerable
attentions due to their promising applications in precise electronic devices, such as
semiconductor chips, implanted medical devices, and micro-electromechanical systems
(MEMS), etc. All the above applications require longer battery life and higher energy
density; thus, it is very necessary to investigate the complex aging mechanisms of thin
film lithium ion batteries. Despite numerous studies on aging issues, a comprehensive
understanding of mechanical failure as well as the degradation of interfacial reliability
is still not available. For small-scale all-solid-state thin film lithium ion microbatteries,
the interfacial reliability of electrode is very crucial to maintain both structural
integrity and electrochemical cycling performance. Therefore, the main objective of
this thesis is to correlate the degradation of interfacial reliability with the capacity
fading, and to analyze the related aging mechanisms of lithium ion batteries.
The correlation study can be divided into three parts. In the first part, various
thin film electrodes with different structures, such as rutile RuO
2

, anatase TiO
2
, spinel
LiMn
2
O
4
and layered LiNi
1/3
Co
1/3
Mn
1/3
O
2
, have been prepared using magnetron
sputtering technique. Additionally, a novel all-solid-state thin film lithium ion
microbattery (TiO
2
/LiPON/LiNi
1/3
Co
1/3
Mn
1/3
O
2
) has been fabricated successfully
Summary
xiii

though multilayer deposition. In the second part, a practical nanoindentation
experiment and analysis method is established to quantitatively measure the interfacial
reliability of thin film electrode, based on the theoretical analysis of adhesion
mechanics. To validate the feasibility and reliability of this method, three indenter tips
(90° wedge, 120° wedge and conical) are used for the self-assessment. Through these
comparative analyses between different indentations, a comprehensive understanding
of interfacial delamination process of thin film electrode is obtained. In the third part,
combining newly-developed nanoindentation method and other instrumental techniques,
the correlation between capacity fading and the changes in interfacial adhesion,
mechanical behavior as well as surface morphology has been established for different
thin film anodes and cathodes, respectively. In addition, the effects of charge/discharge
rate and depth of discharge (DOD) on the degradation of interfacial reliability have been
also investigated. Overall, the results of correlation studies provide new perspectives
into aging studies of lithium ion batteries from mechanical aspect.
The last part of this thesis covers explorative studies on local aging mechanisms
of all-solid-state thin film lithium ion microbatteries, using a combination of various
Scanning Probe Microscopy (SPM) techniques, i.e. Biased Atomic Force Microscopy
(biased-AFM), Kelvin Probe Force Microscopy (KPFM), and Electrochemical Strain
Microscopy (ESM). As a result, the combination of SPM techniques is an innovative
and powerful tool to characterize the local electrochemical phenomena of lithium ion
batteries, paving promising pathways for exploring aging mechanisms at nanoscale.
List of Tables
xiv
LIST OF TABLES

Table 2.1
Overview of SPM-based technologies for battery characterization.


Table 3.1

Deposition parameters for magnetron sputtering.


Table 3.2
Specifications for different indenter tips.


Table 4.1
Average values of interfacial toughness and the key calculation
parameters for the RuO
2
/Si system using 90° wedge, 120°
wedge and
conical indentations.


Table 5.1
Average values of interfacial toughness and the key calculation
parameters for RuO
2
thin film anode on Ti substrate at different stages of
cycling.


Table 5.2
Average values of interfacial toughness and the key calculation
parameters for TiO
2
thin film anode on Ti substrate at different stages of
cycling.

Table 6.1
Average values of interfacial toughness and the key calculation
parameters for LiMn
2
O
4
thin film cathode on Ti substrate
at different
stages of cycling.


Table 6.2
Average values of interfacial toughness and the key calculation
parameters for LiNi
1/3
Co
1/3
Mn
1/3
O
4
thin film cathode on Ti substrate at
different stages of cycling.


Table 7.1
Average values of interfacial toughness and the key calculation
parameters for LiMn

2
O
4
thin film cathode on Ti substrate after 50 cycles
with different current densities.


Table 7.2
Average values of interfacial toughness and the key calculation
parameters for LiMn
2
O
4
thin film cathode on Ti substrate
at different
depth of discharge (DOD).


List of Figures
xv
LIST OF FIGURES

Fig. 1.1
(a) Schematic of basic operation principle of lithium ion battery; (b)
Comparison of energy densities of different rechargeable batteries.


Fig. 2.1
Rutile and anatase crystal structures of TiO
2

.


Fig. 2.2

Two dimensional layered (LiMO
2
) and three dimensional spinel (LiM
2
O
4
)
crystal structures.


Fig. 2.3
Olivine crystal structure of LiFePO
4
showing Li in 1D channels.


Fig. 2.4
Schematic drawings illustrating (a) the shape and components; and (b) the
cross-sectional layout of all-solid-state thin film lithium ion batteries.


Fig. 2.5
Schematics of (a) sandwich specimen; and (b) four-point-bending test.

Fig. 2.6
Schematic diagram of microwedge indentation experimental setup (a)
plan view and (b) cross-sectional view images (no buckling condition).


Fig. 2.7
Schematic diagram of events in Microwedge Indentation Test (MWIT) (a)
no buckling; (b) double-buckling; and (c) single-buckling.


Fig. 3.1
Overview of the experimental methods in this project.


Fig. 3.2
Schematic of wedge indentation configuration and interfacial
delamination.


Fig. 3.3
The schematic diagram of (a) dc-writing operation in biased-AFM and (b)
KPFM measurements.


Fig. 3.4
Schematic of operation principle of ESM method on a battery material.


Fig. 4.1
(a) XRD patterns and (b) FESEM surface image of the as-deposited RuO

2

film on Si substrate; the arrows indicate the reflections from RuO
2
phases.


Fig. 4.2

Indentation load-displacement (P-h) curves on RuO
2
films using (a) a
standard Berkovich indenter; (b) a conical indenter; (c) a wedge indenter
of 90°; and (d) a wedge indenter of 120°.

List of Figures
xvi


Fig. 4.3
FIB cross-sectional views of 90° wedge indentation on RuO
2
film: (a)
initiation of interface crack; and (b)-(d) propagation of interface crack.


Fig. 4.4
FESEM plan views of 90° wedge indentation on RuO
2
film: (a)

indentation impression; (b) corner cracks; (c) delamination crack shape;
and (d) spall-off event.


Fig. 4.5
FIB cross-sectional view of 90° wedge indentation at high load of 40 mN.


Fig. 4.6
FIB cross-sectional views of 120° wedge indentation on RuO
2

film: (a)
initiation of interface crack; (b) propagation of interface crack; and (c)
spall-off event.


Fig. 4.7
FESEM plan views of 120° wedge indentation on RuO
2
film: (a)
indentation impression; (b) delamination crack shape; and (c) spall-off
event.


Fig. 4.8
FIB cross-sectional views of conical indentation on RuO
2
film: (a) no
interface crack; (b)-(c) initiation and propagation of interface crack.

Fig. 4.9
FESEM plan views of conical indentation on RuO
2
film: (a) central film
crack and delamination crack shape; (b)-(c) initiation and propagation of
radial cracks.


Fig. 4.10
P/S
2
-h curve from the nanoindentation with the CSM option on RuO
2
film
with the penetration depth of ~200 nm.


Fig. 5.1
(a) The first cycle discharge/charge curves and; (b) cycling performance
of RuO
2
thin film anode up to 100 cycles.


Fig. 5.2
XRD patterns of RuO
2
thin film anode: (a) as-deposited; and (b) after one

discharge/charge cycle. The dots represent
the reflections from Ti
substrate and the arrows indicate the reflections from RuO
2
phase.


Fig. 5.3
Ex-situ FESEM images of RuO
2
thin film anodes taken at (a)
as-deposited; (b) 10th cycles; (c) 50th cycle; and (d) 100th cycles.


Fig. 5.4
Ex-situ AFM surface topography (2D and 3D images) of RuO
2
thin film
anodes taken at (a) as-deposited; (b) 10th cycles; (c) 50th cycle; and (d)
100th cycles


List of Figures
xvii
Fig. 5.5
Surface roughness measured by AFM of RuO
2
thin film anode at different
stages of cycling.

Fig. 5.6

Calculated elastic modulus and nano-hardness of RuO
2
thin film anodes at
different stages of cycling.


Fig. 5.7
Indentation load-displacement curves of (a) as-deposited; (b) 10 cycled;
(c) 50 cycled; and (d) 100 cycled RuO
2
thin film anodes.


Fig. 5.8
(a) FESEM plan view and (b) FIB cross-sectional view images of
indentation induced interfacial crack pattern in RuO
2
thin film anode.


Fig. 5.9
XRD patterns of as-deposited TiO
2
thin film.


Fig. 5.10

(a) The first cycle discharge/charge curves and; (b) cycling performance
of TiO
2
thin film anode up to 100 cycles.


Fig. 5.11
Ex-situ AFM surface topography (2D and 3D images) of TiO
2
thin film
anodes taken at (a) as-deposited; (b) 10th cycles; (c) 50th cycle; and (d)
100th cycles.


Fig. 5.12
(a) Surface roughness measured by AFM; and (b) Calculated elastic
modulus and nano-hardness of TiO
2
thin film anodes at different stages of
cycling.


Fig. 5.13
Indentation load-displacement curves of (a) as-deposited; (b) 10 cycled;
(c) 50 cycled; and (d) 100 cycled TiO
2
thin film anodes.


Fig. 5.14

(a) FESEM plan view and (b) FIB cross-sectional view images of
indentation induced interfacial crack pattern in TiO
2
thin film anode.


Fig. 6.1
XRD patterns of LiMn
2
O
4
powder and as-deposited LiMn
2
O
4
thin film
prepared by magnetron sputtering.


Fig. 6.2
(a) The first cycle charge/discharge curves; and (b) cycling performance
of LiMn
2
O
4
thin film cathode up to 100 cycles.


Fig. 6.3
Ex-situ FESEM images of LiMn

2
O
4
thin film cathodes taken at (a)
as-
deposited; (b) 10th cycles; (c) 50th cycle; (d) 100th cycles; and
enlargement view of (e) as-deposited film and (f) 100th cycled film.


Fig. 6.4
Ex-situ AFM 3D topography images of LiMn
2
O
4
thin film cathodes taken
List of Figures
xviii
at (a) as-deposited; (b) 10th cycles; (c) 50th cycle; and (d) 100th cycles.


Fig. 6.5
Surface roughness measured by AFM of LiMn
2
O
4
thin film cathodes at
different stages of cycling.


Fig. 6.6

Elastic modulus and hardness of LiMn
2
O
4
thin film cathodes at different
stages of cycling.


Fig. 6.7
Indentation load-displacement curves of LiMn
2
O
4
thin film cathodes at (a)
as-deposited; (b) 10 cycles; (c) 50 cycles; and (d) 100 cycles.


Fig. 6.8
(a) FESEM plan view and (b) FIB cross-sectional view images of
indentation induced interfacial crack pattern at LiMn
2
O
4
/Ti substrate
interface.


Fig. 6.9
XRD patterns of LiNi
1/3

Co
1/3
Mn
1/3
O
2
commercial powder and
as-deposited LiNi
1/3
Co
1/3
Mn
1/3
O
2
thin film prepared by RF magnetron
sputtering.


Fig. 6.10
(a) The first cycle charge/discharge curves; and (b) cycling performance
of LiNi
1/3
Co
1/3
Mn
1/3
O
2
thin film cathode up to 100 cycles.

Fig. 6.11
Ex-situ FESEM images of LiNi
1/3
Co
1/3
Mn
1/3
O
2
thin film cathodes taken at
(a) as-deposited; (b) 10th cycles; (c) 50th cycle; (d) 100th cycles.


Fig. 6.12
Ex-situ AFM 3D topography images of LiNi
1/3
Co
1/3
Mn
1/3
O
2
thin film
cathodes taken at (a) as-deposited; (b) 10th cycles; (c) 50th cycle; and (d)
100th cycles.


Fig. 6.13

Surface roughness measured by AFM of LiNi
1/3
Co
1/3
Mn
1/3
O
2
thin film
cathodes at different stages of cycling.


Fig. 6.14
Elastic modulus and hardness of LiNi
1/3
Co
1/3
Mn
1/3
O
2
thin film cathodes at
different stages of cycling.


Fig. 6.15
Indentation load-displacement curves of LiNi
1/3
Co
1/3

Mn
1/3
O
2
thin film
cathodes at (a) as-deposited; (b) 10 cycles; (c) 50 cycles
; and (d) 100
cycles.


Fig. 7.1
(a) The first cycle discharge curves; and (b) cycling performance of
LiMn
2
O
4
thin film cathode up to 50 cycles with different charge/discharge
current densities.
List of Figures
xix


Fig. 7.2
Ex-situ FESEM images of LiMn
2
O
4
thin film cathodes taken after 50
cycles with different current densities: (a) 5 μAcm
-2

; (b) 10 μAcm
-2
; (c) 50
μAcm
-2
; (d) 100 μAcm
-2
.


Fig. 7.3
(a) Surface roughness measured by AFM; and (b) elastic modulus and
hardness of LiMn
2
O
4
thin film cathodes after 50 cycles with different
current densities.


Fig. 7.4
Indentation load-displacement curves of LiMn
2
O
4
thin film cathodes after
50 cycles with different current densities: (a) 5 μAcm
-2
; (b) 10 μAcm
-2

; (c)
50 μAcm
-2
; (d) 100 μAcm
-2
.


Fig. 7.5
The first cycle discharge curve of LiMn
2
O
4
thin film cathode.


Fig. 7.6
Ex-situ FESEM images of LiMn
2
O
4
thin film cathodes taken at different
DOD: (a) 0%; (b) 25%; (c) 50%; (d) 75%; (e) 100%.


Fig. 7.7
(a) Surface roughness measured by AFM; and (b) elastic modulus and
hardness of LiMn
2
O

4
thin film cathodes at different DOD.


Fig. 7.8
Indentation load-displacement curves of LiMn
2
O
4
thin film cathodes at
different DOD: (a) 0%; (b) 25%; (c) 50%; (d) 75%; (e) 100%.


Fig. 8.1
(a) The first cycle Galvanostatic charge/discharge curves; and (b) cycling
performance of TiO
2
/LiPON/LiNi
1/3
Co
1/3
Mn
1/3
O
2
full cell over 100
cycles.


Fig. 8.2

(a) Schematic of in-situ SPM measurement on active battery area (1
×
1
μm
2
), which is the overlapping portion of anode/electrolyte/cathode
(indicated by white frame); (b) FIB cross-
sectional image of thin film
battery; (c) cyclic electrical field applied to the battery to probe Li-ion
diffusion vs. SPM scan number.


Fig. 8.3
In-situ AFM scanning images (1×1 μm
2
) of thin film anode within the
microbattery polarized to cyclic potential.
From left to right column:
height images, amplitude images and phase images. (a) scan 1; (b) scan 2;
(c) scan 4; (d) scan 6; and (e) scan 8.


Fig. 8.4
In-situ 3D topography images of Fig. 8.3 (at the same location): (a) scan
1; (b) scan 2; (c) scan 4; and (d) scan 6.


List of Figures
xx
Fig. 8.5

(a)
Distribution histogram of phase angles during the first cycle; (b)
analysis of in-situ phase images: evolution of main phase angle and new
phase intensity vs. SPM scan number.


Fig. 8.6
(a) Magnification of “nano-spots” in amplitude image, and (b) phase
image; (c) corresponding line section of amplitude and phase images at
the same location.


Fig. 8.7
(a) SPM images (3×3 μm
2
) and line sections of thin film anode in the
selected thin film Li-ion microbattery at the same location, polarized to
cyclic potential; (b) analysis of in-situ SPM
experimental results:
percentage changes in surface roughness (RMS), length,
height, and
volume vs. SPM scan number.


Fig. 8.8
Distribution histograms of surface potential for (a) TiO
2
anode in full
battery; and (b) single layer TiO
2

film during the first positive/negative
polarization cycle;


Fig. 8.9
(a) Schematic of electronic band structure of TiO
2
semiconductor; (b)
Schematic energy band diagrams for single layer TiO
2
; and (c) TiO
2
thin
film anode within the battery. (E
v
: vacuum level; E
f
: Fermi energy level;
Φ
sample
: work function of sample and Φ
tip
: work function of tip)


Fig. 8.10
(a) Potential shift
vs.
SPM scan number for both TiO

2

anode film and
single layer TiO
2
film; (b) Surface potential loops of TiO
2

anode film
obtained under the reversible electrical field.


Fig. 8.11
(a) Topographic image (1×1 μm
2
) of TiO
2
anode film after the positive
polarization (+3 V); (b) Corresponding surface potential mapping; (c)
Line section images in (a) and (b); (d), (e), (f) are topographic, surface
potential, and line section images of TiO
2

anode film after the negative
polarization (-3 V), respectively.


Fig. 8.12
(a) Surface topography of the LiNi
1/3

Co
1/3
Mn
1/3
O
2

cathode surface; (b)
band- excitation ESM amplitude on resonance
frequency; (c) contact
resonance frequency image; and (d) phase image on resonance frequency.


Fig. 8.13
(a) Surface topography of the TiO
2
anode surface within the battery; (b)
band-excitation
ESM amplitude; (c) resonance frequency image; and (d)
phase image on resonance frequency.


List of Symbols
xxi
LIST OF SYMBOLS

A
c

Interface crack area

a
Short crack length of an elliptical shaped delamination or crack radius of a
circular shaped delamination


b
Long crack length of an elliptical shaped delamination or width of thin
film line for Microwedge Indentation Test


d
Plastic depth into the thin film line for Microwedge Indentation Test

E
f

Elastic modulus of the thin film or Fermi energy level


E
f
’
Effective elastic modulus of the thin film


E
v

Vacuum level


G Strain energy release rate


H
Hardness


h
Indentation depth/displacement


h
p

Plastic indentation depth


l
Length of the wedge indenter tip


P
Indentation load


P
critical

Critical indentation load for interfacial delamination


P
max

Maximum indentation load


r
Crack radius of a circular shaped delamination


S
Contact stiffness


t Thickness of the thin film

List of Symbols
xxii


V
0

Plastic indentation volume

V
c

Interfacial crack volume


V
CPD

Electrostatic contact potential difference


V
AC

AC voltage


V
DC

DC voltage


V
SP

Surface potential

Y Dimensionless constant to determine the critical buckling stress


ΔZ
Tip-sample separation distance


2ϕ
Inclusion angle of the indenter tip


Φ
tip

Work function of the conductive tip

Φ
sample

Work function of the sample


σ
0

Indentation induced stress


σ
c

Critical buckling stress


σ
c
a

Critical buckling stress for wedge indentation


σ
c
b

Critical buckling stress for conical indentation


Ψ
Phase angle to determine the mode mixity


ω
Dimensionless scalar function


v
Poisson’s ratio

Γ
i

Interfacial toughness


θ

Bragg angle in X-ray diffraction


Chapter 1
1
Chapter 1. Introduction

Lithium ion batteries have been widely used as power sources for portable and
mobile applications such as digital cameras, mobile phones and laptop computers, due
to their advantages of high energy density, long cycle life and little memory effect
[1-3]. Lithium ion batteries can be fabricated into different configurations because of
their design flexibility, such as cylindrical, coin, prismatic and thin film batteries.
Among of these, all-solid-state thin film lithium ion batteries have been developed in
more recent years due to the reduction in scale and power requirement of
micro-electronic devices. These microbatteries can be directly integrated into precise
electronic devices, including smart cards, implanted medical instruments, memory
chips in integrated circuits (IC) and micro-electromechanical systems (MEMS) [4-7].
All these applications require both long battery lifetime and high energy density. Thus,
it is very essential to understand the aging mechanisms of lithium ion batteries [8-10].
However, the investigation of aging mechanism is very challenging since capacity
fading originates from various interacting processes occurring at the same time [11].
This chapter is organized as follows. Section 1.1 provides a brief overview of

lithium ion batteries. The research objective and significance are presented in Section
1.2. This is followed by a thesis outline presented in Section 1.3.