Electrochemical Engineering Across Scales E-Book

• Herausgeber: Wiley-VCH
• Kategorie: Wissenschaft und neue Technologien
• Serie: Advances in Electrochemical Sciences and Engineering
• Sprache: Englisch

Seitenzahl: 642

Veröffentlichungsjahr: 2015

Beschreibung

In Volume XV in the series "Advances in Electrochemical Science and Engineering" various leading experts from the field of electrochemical engineering share their insights into how different experimental and computational methods are used in transferring molecular-scale discoveries into processes and products. Throughout, the focus is on the engineering problem and method of solution, rather than on the specific application, such that scientists from different backgrounds will benefit from the flow of ideas between the various subdisciplines.

A must-read for anyone developing engineering tools for the next-generation design and control of electrochemical process technologies, including chemical, mechanical and electrical engineers, as well as chemists, physicists, biochemists and materials scientists.

Leseprobe

Table of Contents

Cover

Advances in Electrochemical Science and Engineering

Title Page

Copyright

Series Preface

Preface

List of Contributors

Chapter 1: The Role of Electrochemical Engineering in Our Energy Future

References

Chapter 2: The Path from Invention to Product for the Magnetic Thin Film Head

2.1 Introduction

2.2 The State of the Art in the 1960s

2.3 Finding the Right Path to Production

2.4 Key Inventions for Thin Film Head Production

2.5 Concluding Thoughts

Acknowledgments

References

Chapter 3: Electrochemical Surface Processes and Opportunities for Material Synthesis

3.1 Introduction

3.2 Underpotential Deposition (UPD)

3.3 Metal Deposition via Surface-Limited Redox Replacement of Underpotentially Deposited Metal Layer

3.4 Underpotential Codeposition (UPCD)

Acknowledgments

References

Chapter 4: Mathematical Modeling of Self-Organized Porous Anodic Oxide Films

4.1 Introduction

4.2 Phenomenology of Porous Anodic Oxide Formation

4.3 Mechanisms for Porous Anodic Oxide Formation

4.4 Elements of Porous Anodic Oxide Models

4.5 Modeling Results

4.6 Summary and Outlook

References

Chapter 5: Engineering of Self-Organizing Electrochemistry: Porous Alumina and Titania Nanotubes

5.1 Introduction

5.2 Formation and Growth of TiO

2

and Al

2

O

3

Nanotubes/Pores

5.3 Improved Ordering via Nanopatterning

5.4 Crystallinity and Composition

5.5 Applications

5.6 Conclusions

References

Chapter 6: Diffusion-Induced Stress within Core–Shell Structures and Implications for Robust Electrode Design and Materials Selection

6.1 Introduction

6.2

Ab initio

Simulations: Informing Continuum Models

6.3 Governing Equations for the Continuum Model

6.4 Results and Discussion

6.5 Summary and Conclusions

References

Chapter 7: Cost-Based Discovery for Engineering Solutions

7.1 Introduction

7.2 The Liquid Metal Battery as a Grid Storage Solution

7.3 Historical Odyssey

7.4 Project Description

7.5 Conclusion

References

Chapter 8: Multiscale Study of Electrochemical Energy Systems

8.1 Introduction

8.2 Architectures of Energy Systems

8.3 The Big Picture

8.4 Storage Components

8.5 Conversion Components, DEFC

8.6 Materials and Molecular Processes

8.7 Conclusions – Folding It Back

Acknowledgments

References

Index

End User License Agreement

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Guide

Cover

Table of Contents

Preface

Begin Reading

List of Illustrations

Figure 1.1

Figure 1.2

Figure 2.1

Figure 2.2

Figure 2.3

Figure 2.4

Figure 2.5

Figure 2.6

Figure 2.7

Figure 2.8

Figure 2.9

Figure 2.10

Figure 2.11

Figure 2.12

Figure 2.13

Figure 2.14

Figure 2.15

Figure 2.16

Figure 2.17

Figure 2.18

Figure 2.19

Figure 2.20

Figure 2.21

Figure 2.22

Figure 2.23

Figure 2.24

Figure 2.25

Figure 2.26

Figure 3.1

Figure 3.2

Figure 3.3

Figure 3.4

Figure 3.5

Figure 3.6

Figure 3.7

Figure 3.8

Figure 3.9

Figure 3.10

Figure 3.11

Figure 3.12

Figure 3.13

Figure 3.14

Figure 3.15

Figure 3.16

Figure 3.17

Figure 3.18

Figure 3.19

Figure 3.20

Figure 3.21

Figure 3.22

Figure 3.23

Figure 3.24

Figure 3.25

Figure 4.1

Figure 4.2

Figure 4.3

Figure 4.4

Figure 4.5

Figure 4.6

Figure 4.7

Figure 4.8

Figure 4.9

Figure 4.10

Figure 4.11

Figure 4.12

Figure 4.13

Figure 4.14

Figure 4.15

Figure 4.16

Figure 4.17

Figure 5.1

Figure 5.2

Figure 5.3

Figure 5.4

Figure 5.5

Figure 5.6

Figure 5.7

Figure 5.8

Figure 5.9

Figure 5.10

Figure 5.11

Figure 5.12

Figure 5.13

Figure 5.14

Figure 5.15

Figure 6.1

Figure 6.2

Figure 6.3

Figure 6.4

Figure 6.5

Figure 6.6

Figure 6.7

Figure 6.8

Figure 6.9

Figure 6.10

Figure 6.11

Figure 7.1

Figure 7.2

Figure 7.3

Figure 7.4

Figure 7.5

Figure 7.6

Figure 7.7

Figure 7.8

Figure 7.9

Figure 7.10

Figure 7.11

Figure 7.12

Figure 7.13

Figure 7.14

Figure 8.1

Figure 8.2

Figure 8.3

Figure 8.4

Figure 8.5

Figure 8.6

Figure 8.7

Figure 8.8

Figure 8.9

Figure 8.10

Figure 8.11

Figure 8.12

Figure 8.13

Figure 8.14

Figure 8.15

Figure 8.16

Figure 8.17

Figure 8.18

Figure 8.19

Figure 8.20

Figure 8.21

Figure 8.22

Figure 8.23

Figure 8.24

Figure 8.25

Figure 8.26

Figure 8.27

Figure 8.28

Figure 8.29

Figure 8.30

List of Tables

Table 2.1

Table 5.1

Table 5.2

Table 6.1

Table 6.2

Table 6.3

Table 7.1

Table 7.2

Table 7.3

Table 7.4

Table 7.5

Table 7.6

Table 7.7

Table 8.1

Table 8.2

Advances in Electrochemical Science and Engineering

Advisory Board

Philippe Allongue, Ecole Polytechnique, Palaiseau, France

A. Robert Hillman, University of Leicester, Leicester, UK

Tetsuya Osaka, Waseda University, Tokyo, Japan

Laurence Peter, University of Bath, Bath, UK

Lubomyr T. Romankiw, IBM Watson Research Center, Yorktown Heights, USA

Shi-Gang Sun, Xiamen University, Xiamen, China

Esther Takeuchi, SUNY Stony Brook, Stony Brook; and Brookhaven National

Laboratory, Brookhaven, USA

Mark W. Verbrugge, General Motors Research and Development, Warren,

MI, USA

Edited by

Richard C. Alkire, Philip N. Bartlett and Jacek Lipkowski

Advances in Electrochemical Science and Engineering

Volume 15

Electrochemical Engineering Across Scales: from Molecules to Processes

Editors

Richard C. Alkire

Department of Chemical and

Biomolecular Engineering

University of Illinois

Urbana, IL 61801

United States

Philip N. Bartlett

Department of Chemistry

University of Southampton

Southampton SO17 1BJ

United Kingdom

Jacek Lipkowski

Department of Chemistry

University of Guelph

N1G 2W1 Guelph, Ontario

Canada

All books published by Wiley-VCH are carefully produced. Nevertheless, authors, editors, and publisher do not warrant the information contained in these books, including this book, to be free of errors. Readers are advised to keep in mind that statements, data, illustrations, procedural details or other items may inadvertently be inaccurate.

Library of Congress Card No.: applied for

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The Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data are available on the Internet at <http://dnb.d-nb.de>.

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Print ISBN: 9783527333455

ePDF ISBN: 9783527692149

ePub ISBN: 9783527692125

Mobi ISBN: 9783527692132

oBook ISBN: 9783527690633

Series Preface

With this volume, we are pleased to welcome Professor Philip N. Bartlett as coeditor. Professor Bartlett matriculated at the University of Oxford and at Imperial College, University of London, and held academic posts at the University of Warwick and University of Bath prior to moving in 1992 to the University of Southampton where he is currently Professor of Electrochemistry. His research interests focus on the templated electrodeposition of nanostructured materials and on bioelectrochemistry. His contributions have been recognized in numerous ways that include selection as Fellow of the Royal Society, and Fellow of the Royal Society of Chemistry, and major awards from the Royal Society of Chemistry, the International Society of Electrochemistry, and The Electrochemical Society, among others.

The purpose of the series is to provide high quality advanced reviews of topics of both fundamental and practical importance for the experienced reader.

Preface

Fifty years ago, in a short article in this series on the topic of electrochemical engineering,1 Carl Wagner wrote:

… molecular engineering may be important in the future development of industrial electrochemical processes.

Today, that time has come. Electrochemical engineering is undergoing a renaissance owing to development of a new generation of methods for bridging between molecular-scale discoveries, concepts, theory, experimental data, and their application to products and processes based on electrochemical operations.

This volume describes electrochemical systems for which new experimental and computational approaches are used to facilitate movement between scientific fundamentals and technological applications. These applications range from capturing the future value from “bottom-up” discoveries to quantifying small-scale failure modes for “top-down” investigations, and to making strategic decisions on very large scale electrochemical energy technologies. These new approaches are flexible, and can be used as a template to guide work on additional applications beyond those for which they were originally developed. Taken together, these approaches provide wholly new capabilities for producing well-engineered electrochemical products and processes, while insuring quality at the molecular scale. The continued development and reduction to routine generic use of these modern engineering methods will provide essential tools for the design and control of next-generation electrochemical process technologies.

Hegedus describes the intersection of energy technology, economics, and societal issues that point to the increasingly critical role of electrochemical technologies in our energy future. An example of advanced battery technology is presented to highlight the role of electrochemical engineering in addressing critical problems at the nano- and molecular scales, and their relation to the design of well-engineered electric vehicle propulsion systems.

Romankiw and Krongelb describe the creation of the magnetic thin film head from initial concept to manufactured product. This iconic application represents one of the most significant advances of electrodeposition science and engineering in the last half century. They point out that inventions that bring about a major advance in the state of the art invariably require ancillary advances to achieve a viable manufacturing process. The key point is the need to treat the process invention, the materials science, and the design of the device as an integrated interdisciplinary effort from the inception of the concept to its emergence as a product.

Brankovic and Zangari describe manipulation of metal surface atoms to achieve controlled, uniform structures by means of underpotential codeposition as well as surface-limited redox replacement of underpotentially deposited metal layers. Quantitative relationships are described for the stoichiometric, energetic, and kinetic phenomena that accompany the nucleation and growth of these unique structures. The chapter provides the fundamental results needed for the development of functional materials, with examples in areas of catalysis, photovoltaics, and magnetic systems.

Hebert emphasizes the view that porous anodic oxide formation should be considered as a process involving pattern formation far from equilibrium. As such, the scaling relations and critical parameter ranges associated with anodizing can be understood by using mathematical approaches that have been used with success for pattern formation in other systems in which large-area patterns are formed at high rates.

Schmuki and Lee describe the discovery, characterization, and milestone innovations associated with the practical use of self-organized porous Al2O3 and TiO2 nanotubes formed by electrochemical processes. The principles and mechanisms for formation of both these materials have similarities, even though a wide variety of chemical and physical properties can be obtained. This chapter may be seen as the “applied” side to the chapter by Hebert.

Verbrugge, Qi, Baker, and Cheng address the life of lithium-ion batteries and its relation to small-scale phenomena associated with deformation of active materials along with solvent decomposition. Numerical ab initio calculations are described that, even in the absence of detailed structural knowledge, can inform continuum mathematical models in making decisions on robust electrode design and materials selection.

Sadoway and Spatocco describe the methodology of “cost-based discovery” to address the challenge of developing new technology for massively large-scale applications through the example of grid-level energy storage for intermittent renewable energy sources. By this methodology, the earliest stages of research include cost as a determining factor in the choice of materials and process chemistry, for example, by using earth-abundant elements and simple manufacturing techniques. By this view, parts of the periodic table are axiomatically off limits on grounds of scalability.

El-Sayed, Knoll, and Stimming examine multiscale components in discussing options associated with renewable energy generation and storage options associated with an urban city block. Behavior at multiple scales is incorporated for the electrochemical systems as well as for the materials and molecular processes involved. The approach combines scientific “bottom-up” with engineering “top-down” approaches mediated by the capabilities of computer science and engineering.

This volume will be of interest to chemical, mechanical, electrical, and computational engineers, as well as chemists, physicists, biochemists, and surface and materials scientists. The opportunities for impact in this field are far greater than what the current researchers trained in electrochemical engineering can accomplish. By providing up-to-date reviews with extensive coverage of background topics, this volume should be of interest to students and professionals entering the field, as well as for experienced researchers seeking to expand their scope and mastery.

Richard C. Alkire

Urbana, Illinois, USA, July, 2014

1

 Carl Wagner, “

The Scope of Electrochemical Engineering

,” Advances in Electrochemistry and Electrochemical Engineering, ed. C. W. Tobias, Vol. 2, page 2 (1962).

List of Contributors

Daniel R. Baker

General Motors Research and Development

Chemical and Materials Systems Laboratory

30500 Mound Road

Warren

MI 48090-0955

USA

Stanko R. Brankovic

University of Houston

Departments of Electrical and Computer Engineering

and Chemical and Biomolecular Engineering

N308 Eng. Bldg. 1

Houston

TX 77204-4005

USA

Yang-Tse Cheng

University of Kentucky

Department of Chemical and Materials Engineering

177 FPAT

Lexington

KY 40506-0046

USA

Hany El-Sayed

Technical University Munich

Department of Physics

James-Franck-Street 1

85747 Garching

Germany

Alois Knoll

Technical University Munich

Institute of Robotics and Embedded Systems

Department of Informatics

Boltzmannstrasse 3

85748 Garching

Germany

and

TUM CREATE

Center for Electromobility

1 CREATE Way

CREATE Tower

138602

Singapore

Sol Krongelb

Emeritus, IBM T.J. Watson Research Center

9 Greenlawn Road

Katonah

NY 10536

USA

Kurt R. Hebert

Iowa State University

Department of Chemical and Biological Engineering

2114 Sweeney Hall

Ames, IA 50011

USA

L. Louis Hegedus

RTI International

3040 East Cornwallis Road

P.O. Box 12194

Research Triangle Park

NC 27709-2194

USA

and

1104 Beech Road

Bryn Mawr

PA 19010

USA

Chong-Yong Lee

University of Erlangen-Nuremberg

Department of Materials Science

Institute for Surface Science and Corrosion (LKO)

Martenstrasse 7

91058 Erlangen

Germany

Yue Qi

General Motors Research and Development

Chemical and Materials Systems Laboratory

30500 Mound Road

Warren, MI 48090-0955

USA

and

Michigan State University

Department of Chemical Engineering and Materials Science

428 S. Shaw Lane

Room: 3509,

East Lansing

MI 48824

USA

Lubomyr T. Romankiw

IBM T.J. Watson Research Center

1101 Kitchawan Road

Yorktown Heights

NY 10598

USA

Patrik Schmuki

University of Erlangen-Nuremberg

Department of Materials Science

Institute for Surface Science and Corrosion (LKO)

Martenstrasse 7

91058 Erlangen

Germany

and

King Abdulaziz University

Department of Chemistry

Faculty of Science

Jeddah 21569

P.O. Box 80203

Saudi Arabia

Donald R. Sadoway

Massachusetts Institute of Technology

Department of Materials Science and Engineering

77 Massachusetts Avenue

Cambridge

MA 02139-4307

USA

Brian L. Spatocco

Massachusetts Institute of Technology

Department of Materials Science and Engineering

77 Massachusetts Avenue

Cambridge

MA 02139-4307

USA

Ulrich Stimming

Technical University Munich

Department of Physics

James-Franck-Street 1

85747 Garching

Germany

and

TUM CREATE

Center for Electromobility

1 CREATE Way

CREATE Tower,

138602

Singapore

and

Technische Universität MÜnchen

Institute for Advanced Study (IAS)

Lichtenbergstr. 2a

85748 Garching

Germany

and

Newcastle University

School of Chemistry, Faculty of Science, Agriculture and Engineering

Bedson Building Newcastle upon Tyne

NE1 7RU

UK

Mark W. Verbrugge

General Motors Research and Development

Chemical and Materials Systems Laboratory

30500 Mound Road

Warren

MI 48090-0955

USA

Giovanni Zangari

University of Virginia

Department of Materials Science and Engineering

395 McCormick Road

Charlottesville

VA 22904

USA

1The Role of Electrochemical Engineering in Our Energy Future

L. Louis Hegedus

Richard Smalley, Nobel Prize-winning chemist (1996) and co-discoverer of buckminsterfullerene (C60), presented a seminar at Columbia University in New York on 23 September 2003. The title of his talk was “Our Energy Challenge” [1]. He ranked the top 10 challenges facing mankind for the coming 50 years and made a compelling argument for energy being the number one challenge, and that it will also dominate the remaining nine challenges (water, food, environment, poverty, terrorism and war, disease, education, democracy, and population). Eleven years into his 50-year prediction, his analysis is holding strong.

The US National Research Council has produced a series of reports about America's energy future, culminating in the 2009 report America's Energy Future: Technology and Transformation [2].These reports outline a desirable energy future that is clean, sustainable, and secure, and relies on domestically supplied low-carbon or carbon-free primary energy resources, combined with efficient fuel conversion and end-use technologies. All this may, to a considerable extent, hinge upon technologies to generate, store, distribute, and utilize electricity.

Energy technologies, however, represent only the necessary, but not sufficient, conditions for achieving the above. Sufficient conditions include economics (reasonably well recognized and understood) and a whole host of issues in the societal dimensions, including energy policies, politics, public education and public attitudes, energy security, foreign policy, and even defense. These come together with issues of the environment, ecology, and even climate. The resulting “energy conundrum,” the dimensions of which are inseparable and interactive, has only recently started receiving analytical attention [3].

In spite of the complexity of the energy conundrum, the dominant primary energy resources have been evolving in a remarkably orderly pattern as depicted by the logistic analysis of Gruebler and Nakicenovic [4]. In Figure 1.1, F is the estimated fractional saturation level of a given primary energy resource in a given year, and 1 − F represents the remaining potential. Plots of for the United States over the years 1800–2000 revealed logistic substitution waves of the primary energy sources, from wood to coal to oil to natural gas to uranium. Although not yet significant in 2000, it is reasonable to expect that renewable energy, such as wind and solar, will eventually start making the next logistic wave.

Figure 1.1 Historic logistic wave patterns of the primary energy sources in the United States. (Redrawn from Figure 15 of [2].) F is penetration as a fraction of saturation.

The current energy infrastructure in the United States is best visualized by the energy flow charts of the Lawrence Livermore National Laboratory [5]. Figure 1.2 shows that in 2011 (the latest year for which data were available) the United States used about 97.3 quads (10E15 British thermal units) of energy from our primary energy resources – solar (0.158), nuclear (8.26), hydro (3.17), wind (1.17), geothermal (0.226), natural gas (24.9), coal (19.7), biomass (4.41), and petroleum (35.3). Altogether, 39.2 quads were used for generating 12.6 quads of electricity. One remarkable feature of our energy infrastructure is that almost none of this electricity was used for transportation (0.26%), and another remarkable feature is that almost none of the natural gas was used for transportation either (inspection reveals that the 3% shown in Figure 1.2 corresponds mostly to the amount of natural gas used to power the compressors of the natural gas pipelines, classified as “transportation”).

Figure 1.2 Estimated US energy use in 2011. About 40% of the primary energy sources were used for the generation of electricity [3].

Before the historic 18 June 2010 news release of the Potential Gas Committee [6], announcing a 39% one-step upgrade (largely by reclassifying the economic viability of extracting shale gas via horizontal drilling and hydraulic fracturing), the natural gas resources of the United States were viewed as rather limited. Electricity, generated primarily from coal, natural gas, and nuclear resources, was viewed by some as being limited as well: coal due to its environmental, ecological, and climate-change implications; natural gas due to its perceived limited domestic supply, high price, and large price fluctuations; and nuclear resources due to a combination of public safety concerns and the somewhat related high capital costs. The newly perceived natural gas plenty (about 100 years supply at current rates of consumption), and the expectation of low natural gas prices for decades, prompted many existing and planned power plants to shift to natural gas. It has also prompted a re-evaluation of how natural gas and electricity could be used for powering light-duty vehicles instead of oil.

In a 2013 report of the National Research Council [7], projecting technologies suitable for replacing 80% of oil and reducing 80% of CO2 emissions from the light-duty vehicle fleet by 2050, it was concluded that there will likely be enough natural gas to help electrify light-duty vehicle transportation. (Other ways of using natural gas for vehicle propulsion include converting it into liquid synthetic fuels such as gasoline, diesel, and methanol; compressed natural gas, liquefied natural gas, or natural gas-derived hydrogen for fuel cells.) Fuel cell vehicles are approaching volume production standards but are still too expensive, and of course they rely on the development of a hydrogen fueling infrastructure.

So what are the leading-edge technical issues within the domain of electrochemical engineering? A recent review of the history, accomplishments, and future potential of the field [8] focuses on electrochemical processes and electrochemical processing. While it does mention fuel cells, it leaves batteries unmentioned.

A broader view of the field was represented by a 2007 assessment of US electrochemical engineering research competencies as part of the international benchmarking of US chemical engineering competencies [9]. The study makes observation of the fact that electrochemical engineering has drifted out of the core of the chemical engineering curriculum, with the exception of a handful of leading universities. Among the most notable developments in the field over the previous 10 years were the advances in rechargeable Li ion batteries with liquid, gel, or polymer electrolytes and advances in fuel cells with proton-conducting membranes. For the future, the report projects “increased relevance of the field again, due in part to the world's repeated energy crises.” Six years after that prediction, we agree.

Electrochemical engineering, similarly to many other engineering disciplines, has been advancing from the scales of macro to micro, nano, and molecular. This increasing overlap in scale with the molecular sciences has become a major stimulus to both, and the catalyst for much recent progress. Let us examine this thought through the example of advanced battery technology for electric vehicles.

The electrification of light-duty vehicles via the electric grid has the appeal of relatively affordable infrastructure additions. However, it requires batteries that are safe and affordable, provide high energy density (weight, volume, vehicle range, and cost are all affected), provide high power density (performance), have a long cycle life, rely on the domestic supply of key raw materials that would preferably be recyclable but in any case environmentally acceptable, and, last but by far not least, can be recharged quickly to alleviate the customer's range anxiety. Electric vehicles have a number of strong appeals that include the cost of only a few cents of electricity per mile, no tailpipe emissions, greatly simplified vehicle systems (independently controllable electric motors on each wheel, no exhaust system, flexible battery packaging), and startling acceleration due to the fact that an electric motor has its full rated torque at 0 rpm vs. an internal combustion engine that has a narrow revolutions-per-minute band in its torque curve.

We are witnessing the rapid penetration of Li ion battery technologies, originally developed for portable electronics, into battery-electric hybrids, plug-in hybrids (such as the Volt) and battery-electric vehicles (such as the Nissan Leaf and the Tesla Model S). Essentially, all the battery price and performance issues listed before have remained active at various levels; thus, intensive research and development work is continuing on Li ion battery technology. In its wake, batteries are being developed with Li metal anodes and solid-state electrolytes (for a combination of high energy density, safety, and high cycle life), with potential game changers on the horizon that might include consumable (rather than rechargeable) Mg or Al anodes with air cathodes (metal–air “fuel cells”), with very large energy density, simple construction, safe aqueous electrolytes, and instant refueling capability; and the rechargeable Li–air battery that has a theoretical volumetric energy density approaching that of gasoline and that appears to be a potentially achievable “holy grail.” The specific energy (weight-specific energy density) of gasoline is about 13 kWh kg−1, of which about 1.7 kWh is available at the wheels after the thermodynamic and frictional losses have been allowed for. In comparison, the specific energy of today's rechargeable Li ion batteries is about 150 Wh kg−1 at the cell level, or about 105 Wh kg−1 at the battery pack level. A 200-kg Li ion battery pack yields a driving range of about 70 miles [10].

In a critical review of the Li–air battery [10], it was estimated by cell-level calculations that the Li–air battery could have a practical specific energy of about 1000 Wh kg−1 (6.7 times that of today's Li ion battery) “if several fundamental challenges can be overcome.” This would increase the range of the electric car to or beyond the range of today's gasoline-powered vehicles.

So what are the fundamental challenges in making the Li–air battery suitable for propelling the electric car, and how can electrochemical engineers contribute to the solutions? As we will see, the problems cover a dynamic range of close to 10E10, from a meter (size of the battery pack) all the way to Angstroms, the molecular scale. We will also see that most (but not all) of the technical challenges appear to reside at the nano- and molecular scales.

There are four types of rechargeable Li–air batteries under development, based on their electrolytes: aprotic, aqueous, solid-state, and aprotic–aqueous hybrid. All have Li metal as their preferred anode (negative electrode), and the preferred cathode (positive electrode) is catalyst-impregnated porous carbon.

The Li anode requires a protection layer that has to conduct Li ions, is thin, hole-free, chemically stable, flexible to accommodate volume and shape change, and has a high elastic modulus to suppress dendrite formation.

The cathode (air electrode) presents particular challenges for aprotic systems: besides being electronically conductive, it has to have a high surface area, which requires small pore diameters; good diffusive properties, which require large pore diameters; and a high pore volume to accommodate the insoluble discharge reaction by-product Li peroxide without pore plugging, which impedes the diffusion of O2 to the electrode's surfaces. Complex multimodal pore structures have been investigated to find an optimum.

Membranes are being developed for aprotic batteries to prevent H2O from air to enter the cathode of the aprotic battery. The aqueous battery system, in turn, needs membrane technology that selectively transfers OH− ions.

Aqueous batteries require a reservoir for the discharge product LiOH·H2O due to its relatively low saturation concentration in the aqueous electrolyte.

Catalysts are being developed to help both the reduction of O2 (discharge reaction) levels and the evolution of O2 (charge reaction) in the cathode system. These would enhance the rate of discharge (specific power) and the rate of charge, respectively.

Both the aprotic and the aqueous electrolytes need to have high Li ion conductivity, temperature stability, and low viscosity. They also have to be reversible (non-reactive) during the charge–discharge cycles. According to Christensen et al. [10], a sufficiently reversible aprotic electrolyte has yet to be found.

As we can see from the above, the technical challenges cover a wide range of scales from battery systems through battery packs, battery cells, battery components, micro- and nanoscale component and materials structures, all the way to chemical compositions and molecular entities. Solving these problems requires working simultaneously along two dimensions: one of these is the collaboration between specialists, and the other one is the engagement of engineers whose interests, training, and experience cover the exceptional dynamic range demanded by modern technologies, as exemplified here by the Li–air battery, leading us to the theme of this volume.

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2The Path from Invention to Product for the Magnetic Thin Film Head

Lubomyr T. Romankiw and Sol Krongelb

2.1 Introduction

Innovations in science and technology over the last several decades have changed the way we conduct our business and personal lives. Technological inventions and advances, however, can have such immense impact only if the ideas of visionaries in the laboratory are transformed into useful products on a manufacturing line. The traditional approach to achieving a manufactured product has been to have a development group refine the newly invented idea into a functional device with marketable features. The development engineers subsequently hand over the design to manufacturing engineers to implement a manufacturing-worthy process. This approach may work, more or less, with inventions that can be built with existing process technology. However, an invention that brings about a major advance in the state of the art often requires a number of ancillary inventions to achieve a viable manufacturing process. Process inventions and the supporting process and materials science become so intertwined with the design of the device that all three – process, underlying science, and design – must be treated together in an interdisciplinary effort from the inception of the structure to its emergence as a product. Indeed, the interdisciplinary approach can be advantageous even if no new technology is involved.

The importance and practice of such an interdisciplinary program is best understood by following the evolution of a specific invention from initial concept to manufactured product. IBM's creation of the magnetic thin film head, which brought about a quantum jump in magnetic data storage and simultaneously transformed electrochemical technology from a shop art to a precision manufacturing process, provides an appropriate example. Every invention is, by its very definition, unique, and so it is not possible to define the details of a single path that will lead any invention into production. The authors hope that this chapter will help the reader understand the principles that made the thin film head program so successful in advancing information storage on disk and tape, and to adapt those elements appropriate to his or her work to similarly advance today's technology to new heights.

2.2 The State of the Art in the 1960s

To appreciate how the magnetic thin film head evolved from a concept into a product, one needs a few background details on the state of the art in digital computers and in device fabrication process technology in the 1960s – the period during which the thin film head was conceived and its fabrication process was developed. Maissel and Glang's [1] Handbook of Thin Film Technology, published in 1970 provides a detailed discussion on the practice and the underlying science of the various thin film fabrication processes used in the electronics industry at that time. The discussion in this section deals only with those aspects of technology relevant to the thin film head. The time line of manufacturing technology evolution in Figure 2.1, simplified to focus on these aspects, will help the reader follow the discussion and appreciate how the interplay among fabrication processes that were developed for seemingly different applications brought the thin film head into mass production.

Figure 2.1 A time line of advances in technologies pertinent to the invention of the thin film head. Note that a combination of inventions from the areas of plating, patterning, and materials science were needed to manufacture the thin film head.

Figure 2.1 highlights the evolution of process technology for fabricating the three major elements of the computer and for electroplating technology:

The processor, which rapidly carries out the logical and computational operations specified by the programs.

The working memory, which the processor uses in performing these operations.

The high-density, fast-access data storage that holds the programs and data. (The thin film head is a critical component of disk and tape storage systems.)

Electroplating technology, in the fourth row, initially had little relevance to computer fabrication. At the end of the 1950s, where this time line starts, plating was seen as a shop art that lacked the precision and control necessary to build any part of the computer other than the circuit boards. In the next decade, however, plating would become the key technology that enabled mass production of the thin film head. Of course, the processor, memory, and storage elements had to be interconnected for the computer to function. As the speed of the computer increased, interconnections became a significant factor in computer performance and took on the form of transmission lines with precisely fabricated structures. While the details of interconnection technology are beyond the scope of this chapter, it may be noted that during the 1990s, electroplating also assumed a key role in the fabrication of critical interconnections [2, 3].

The time axis in Figure 2.1 starts with the left column, which reflects the state of the art in the relevant manufacturing technologies at the end of the 1950s and the objectives for further advances in each of these areas. The next three columns respectively highlight the 1960s, when the major advances that defined the future paths for each of the technologies were made; the 1970s, when the thin film head became a manufacturable product; and the 1980s and beyond, when technology based on the work of the previous two decades continued to evolve into today's production processes.

2.2.1 The Processor

The invention of the integrated circuit in the late 1950s [4, 5] set the stage for an intensive effort to develop LSI (large-scale integration) processes in the 1960s. This technology formed semiconductors on a silicon substrate and interconnected them by thin metal patterns on the flat surface to create functional circuit chips. The essential steps in LSI fabrication included a combination of oxidation processes to form SiO2 on the silicon surface, photolithographic and chemical etching steps to provide openings in the SiO2, and diffusion or ion implantation to produce appropriately doped n and p regions for the semiconductor devices. The aluminum (and subsequently aluminum–copper) that was evaporated or sputtered over the surface and photolithographically patterned by wet chemical etching formed the metal elements of the semiconductor devices and the interconnections among them.

LSI enabled the computer industry to meet the objectives for the next-generation processors by mass producing chips with large arrays of interconnected circuits, thus eliminating much of the more expensive manual assembly of individual components. This technology also increased the speed of data processing and transmission within the machines by shrinking the size and increasing the density of the circuits on the chip. A vast majority of people working in advanced electronic fabrication were involved in some aspect of LSI processing, giving rise to rapid advances in this technology. LSI continued to evolve and remains the underlying technology for today's semiconductor devices.

2.2.2 Memory

The engineers working to advance memory technology were also looking for improved performance and lower cost. State-of-the-art magnetic core memories of the late 1950s were expensive to build because they required several thin wires to be threaded through an array of tiny toroidal cores in specific patterns. Two alternative technologies to replace core memories – magnetic thin film memory and solid-state memory – were pursued concurrently.

The solid-state memory approach used large arrays of memory cells, each cell being an integrated transistor circuit that could store one bit of data. By 1968, the advances in semiconductor memories and the fact that these memories could easily be combined with the transistor circuitry on the processor chip led IBM to curtail most magnetic memory work [6]. (Some bubble memory work, in which the plating process described in this chapter was used to build magnetic bubble devices, did continue through the 1970s.) LSI processes were effectively used to fabricate semiconductor memory, and, as the yellow time lines in Figure 2.1 indicate, this technology continues to build both the memory and the processor for today's computers.

Magnetic film memory and an advanced version, the much denser coupled film memory, were serious contenders to semiconductor memory. The magnetic film approach was to deposit films of copper and permalloy (a magnetic alloy of Ni and Fe with appropriate magnetic properties for memory devices) by evaporation, sputtering, or electroplating and to pattern the respective layers by deposition through a mask or by etching with a photoresist mask to produce the various magnetic film memory configurations [7]. Thin magnetic films promised faster switching than ferrites, and building thin film structures was less expensive than assembling core arrays. Using electroplating instead of evaporation would make the thin film structures even less costly to produce, and one of the authors (L.T.R.) was pursuing the electrochemical approach. However, electrodeposition as it was understood and practiced at that time was hard-pressed to reproducibly produce the required magnetic properties. It was the inventions of a new plating tool and of new fabrication processes that enabled IBM to use electroplating in magnetic film memory production (see Sections 2.2.4 and 2.4.2).

Magnetic film memory was only used by IBM on two System/360 Model 95 computers that were built under special contract for NASA in 1968. With an access time of 67 ns [6, 8], this memory provided a level of performance that was not achieved by semiconductor memory until several years later. However, the most important impact of IBM's magnetic memory program on computers came when the electrochemical fabrication processes that had been invented to build film memory structures became a key enabler of a new technology to manufacture the thin film head for data storage.

2.2.3 Data Storage

High performance data storage systems entered a new era in 1956 with the announcement of the RAMAC 305, the first IBM system to offer a disk drive storage system (Figure 2.2). This system used fifty 24 in. diameter magnetic disks, each with sets of moving arms containing inductive read/write heads. Data were recorded on both sides of the 50 disks at a density of 2 kb in.−2 to create a system with a total capacity of 5 MB. Each head consisted of a coil that was hand-wound around a magnetic core and was mounted so that the pole tips were flying in close proximity to the spinning disks. In the write mode, current pulses through the coil encoded data by creating appropriately magnetized spots in concentric, circular tracks in the magnetic coating on the disk's surface. In the read mode, the system used the voltage induced in the coil as the magnetized spots moved past the pole tips to sense the data.

Figure 2.2 The RAMAC 305, announced in 1957, was IBM's first system to use magnetic disk storage technology. It used 50 disks, each 24 in. in diameter with a storage density of 2000 bits/in.2 to provide a total machine capacity of 5 MB. The cabinet visible beyond the operator housed the memory of the RAMAC system with its stack of 50 disks.

An important measure of performance for a data storage system was the areal density of data on the disk. A higher areal density, in addition to giving the system greater storage capacity on a smaller diameter disk, also meant faster access to data as well as a reduction in the cost per bit of information stored. The size and configuration of the pole tips at the head/disk interface were key factors in determining the size of the magnetized spots and thus, the areal density. By 1965, engineers had decreased the dimensions of the hand-wound heads and made other improvements in technology to achieve an areal data storage density of 300 kb in.−2. There was, however, a limit to how small mechanically wound heads could be made; at best, the existing fabrication technology might be pushed to gain only one or two more orders of magnitude in areal density. There would still be the need for a mass production process to eliminate the significant cost of winding each head individually. An advanced disk storage device of that era along with a close-up photo of a ferrite head with a wound coil is shown in Figure 2.3 [9].

Figure 2.3 The hand-wound ferrite read/write head remained in use through much of the 1980s until disk drive manufacturers could learn and implement the new thin film head fabrication technology. The figure shows the popular 5.25 in. Seagate ST-251 disk drive of that era along with a greatly enlarged view of the ferrite head mounted at the tip of the actuator arm.

Various proposals for miniature structures to replace the wire-wound heads had been made over the years since the introduction of the RAMAC system, the most promising of which was the thin film head shown schematically in Figure 2.4. The first patent for a thin film head was filed by Gregg in 1961 and issued in 1967 [10]. Other patents and publications that appeared throughout the 1960s and 1970s presented alternate designs and/or theoretical analyses for thin film heads, but there was no viable process that could manufacture the proposed devices in a structure that met the advanced needs of the next generation disk drive system.

Figure 2.4 Schematic drawings of thin film head structures discussed in this chapter. (a) A single-turn horizontal head, (b) a single-turn vertical head, and (c) a multi-turn vertical head.

As computer manufacturers tried to come up with a suitable manufacturing process, the task fell to their experienced device fabrication engineers. Since the vast majority of people working in advanced electronic fabrication were involved in some aspect of LSI processing, it is not surprising that these engineers sought to adapt the technology of the silicon world to thin film head fabrication. As they envisioned the fabrication of the head, permalloy, an alloy of nickel and iron with appropriate magnetic properties, would be evaporated or sputtered as a blanket film and patterned by photolithographic and etching processes to form the magnetic yokes of the head; the copper windings in the head would be created by similar deposition and etching steps; and sputtered SiO2 would be deposited and patterned by etching to provide insulation. Arrays of heads would be mass produced on a single substrate that would later be diced into individual devices for mounting in the disk drive unit. From the late 1960s through 1979, virtually all computer manufacturers had programs to adapt LSI type processes to the manufacture of a thin film head.

2.2.4 Electroplating Technology

By the 1960s, electroplating had been in use for many decades to deposit a variety of metals for jewelry, decorative coatings, corrosion protection, and wear resistance. However, no attempts to tailor magnetic or most other physical properties in electroplated metallic deposits had been reported. With few exceptions, the processes were carried out by artisans using proprietary solutions and process steps with little understanding of the underlying science. Plating was generally regarded as a shop art and, while being accepted for the fabrication of printed circuit boards, had never been regarded useful in the production of electronic devices with precisely tailored material properties. In particular, those who tried to electroplate magnetic alloys found it difficult to consistently obtain the required magnetic parameters, especially in the configurations required for memory and other devices.

Electroplating did have cost advantages and, with the invention of the through-mask plating process described later in this chapter, offered the greatest precision in fabricating microstructures out of plateable materials. As one of the authors (L.T.R.) was attempting to use plating to fabricate magnetic film memories, he encountered the variable results and instability of the magnetic properties of plated permalloy that others had found in doing similar work. He, however, was able to develop sufficient understanding of the plating process and of the plated permalloy, which led to the inventions of a new plating tool, the appropriate plating solutions, and the deposition and annealing parameters that ensured reproducible, stabilized, and precisely controlled magnetic properties in the deposited films [11]. The advances in electroplating that came out of these studies were crucial to the invention of the thin film head and are summarized in Section 2.4.2.

2.3 Finding the Right Path to Production

2.3.1 First Demonstrations of a Thin Film Head

The first demonstration of a batch-fabricated thin film write head came not from a program to advance recording head technology but rather, out of the magnetic film memory work that was described in Section 2.2.2. One of the structures built during this program, the coupled film memory [12], is shown in Figure 2.5. As is pointed out in the caption, the lower line is essentially a copper conductor passing through a closed magnetic yoke. By putting a gap in the yoke, a one-turn magnetic recording head can be obtained. To meet the requirements of a high-density storage system, however, the gap would have to be very narrow – less than 2 µm.

Figure 2.5 Coupled film memory structure. Although designed for use as a magnetic film memory, the part of the structure comprised of the copper conductor C1 with permalloy layers P1 and P2 wrapped around it could just as well function as a one-turn magnetic head if there were a gap in the permalloy surrounding the copper.

One of the fruits of IBM's film memory program was the invention of through-mask plating, a new fabrication process that did not use the conventional subtractive approach of chemically etching a blanket film of permalloy or copper through a photoresist mask to form the required patterns. Instead, through-mask plating put an inverse mask with openings for the pattern elements on a conductive seed layer, and the required structure was created by the additive process of electroplating through the openings in the resist. Used in combination with the advances in electroplating that also came out of the magnetic film work, through-mask plating had the capability of producing well-defined, thick, 3-D permalloy patterns with precisely controlled magnetic properties. The first batch-fabricated thin film heads, each a single-turn, horizontal structure such as shown in Figure 2.6, were produced using the through-mask-plating approach [13]. The gap was created by including a 2 µm wide band of electron beam resist [14] in the mask for plating the upper layer of permalloy.

Figure 2.6 Perspective view showing the dimensions and structure of the first thin film recording head fabricated with a 2 µm gap.

The structure described in the previous paragraph had not been designed to fly over a spinning disk. However, the static test results reported in the cited reference [13] supported the conclusion of theoretical analyses that “microminiaturized heads fabricated from thin films are expected to give satisfactory performance.” In particular, (i) “the dimensions of the written bits corresponded very closely to the dimensions of the gap” and (ii) no lag in switching was seen with equipment having a time resolution of better than 5 ns.

The next step was to build a thin film head that could be flown over a spinning disk to test the read and write performance in a real data storage system. This head was similar to the initial demonstration structures except that the new devices were designed as vertical instead of horizontal heads. (Figure 2.4 shows the head configurations that are relevant to the discussion in this chapter.) The difference was in the location of the gap and in how it was created. In the horizontal head, the top layer of permalloy interfaced with the disk, and the gap was the break in this layer created by the e-beam resist. In the vertical head, the gap was determined by the thickness of a nonmagnetic layer that was introduced between the upper and lower permalloy layers at one end of the structure where these layers were patterned as pole tips. When the wafer was diced into individual heads, the sandwich of the permalloy pole tips and the nonmagnetic copper separator was exposed at the edge of each head. In use, the head was mounted perpendicular to the disk so that the exposed edge interfaced with the disk's magnetic surface, hence the designation “vertical head.” The vertical head was seen as the preferable configuration for a product because after dicing the substrate became the slider, which could be aerodynamically designed to fly in very close proximity to the disk without ever touching or resting on the disk. Furthermore, since thin film deposition processes were capable of excellent thickness control, the deposition of a nonmagnetic spacer could produce submicron gap widths with tight tolerances and without the need for electron beam lithography. Functional tests found that the head could both read and write data on a magnetic disk, but the read back signal for a single-turn head was too small for a practical storage system. It was clear that a thin film head for a functional data storage product would have to be a multi-turn device as shown schematically in Figure 2.4c.

2.3.2 Interdisciplinary Design of a Functional Head

The fabrication of the first thin film write head by technology invented during the film memory program was triggered by the recognition that part of the coupled film memory structure was basically the same as the structure of a single-turn, horizontal inductive head. Furthermore, it was discovered that the plate-through-mask technology could be extended to produce the thick, high aspect ratio structures required for the head. One of the authors of this chapter (L.T.R.), who had invented the through-mask plating technology and had done much of the research that made the electroplating of permalloy a reproducible process, was then using this technology to build the thin film head. As he became familiar with the head structure, it became apparent that LSI processes would be hard pressed to build the thick, 3-D structures required for the thin film head and that through-mask plating was a more appropriate approach for head fabrication.

When Dave Thompson, an engineer who had expertise in magnetics, joined IBM in 1969, he joined Romankiw's program to design functional heads to be built in Yorktown using electroplating processes. Romankiw and Thompson combined their respective expertise in fabrication and in magnetics to design a multi-turn head that would meet the functional requirements of the next-generation data storage system and, although challenging, could be produced with the proposed fabrication paradigm. These challenges and the reasons they had to be resolved to make a viable head included the following:

Creating a five-turn coil with 2 µm high by 3 µm wide copper conductors spaced 3 µm apart.

(The turns of the coil had to be as close to the gap as possible since leakage between the upper and lower legs of the yoke reduced the efficiency of the turns as their distance from the gap increased. For a yoke with 10 μm separation between the legs, this requirement dictated that all the turns had to be within 100 μm from the gap. The through-mask plating process could form the coils, but, as noted in Section 2.4.3.3, removing the seed layer from the narrow spaces between turns required special attention.)

Patterning 2 µm thick, magnetically oriented permalloy with tight composition control and with perfectly smooth edges.

(Irregularities at the edges could pin the magnetic domains, increase H

c

, and create unpredictable domain patterns. Meeting the requirements for permalloy in the head was not possible with through-mask plating and required the invention of the plating frame as discussed in Section 2.4.3.2.)

Providing insulation between the coil and the permalloy that had a near-planar surface for the deposition of the upper permalloy film.

(Insulation was necessary in the multi-turn head to prevent current shunting between the turns by the permalloy. The upper yoke had to be deposited on a near-planar surface because any significant surface topography could impede magnetic switching.)

Producing 2–3 µm thick resist patterns with near vertical walls for through-mask plating.

(The only commercially available high-resolution resist was designed for semiconductor processing, where only 0.5 μm thick resist was required.)

Addressing these and other fabrication issues while building the five-turn vertical head was an essential step in learning how to carry out each of the process steps in the specific context of the thin film head and in integrating these operations into a viable manufacturing process. Several additional inventions that were crucial to the successful manufacture of the head were made during this phase of the work and are discussed in Section 2.4. A cross-section photograph of one of the first five-turn heads is shown in Figure 2.7. Details of other prototype heads that were fabricated during this program are shown in Figure 2.8.

Figure 2.7 Cross section of one of the first five-turn heads that were completed in Yorktown. The first turn of the coil separated the legs at the right end of the head and defined the thickness of the nonmagnetic gap that will be exposed when the end of the head is lapped back to the plane A–A perpendicular to the photo.

Figure 2.8 SEM (scanning electron microscope) photos taken during the fabrication of prototype versions of product heads. (a) Photoresist plate-through pattern for a 16 turn coil. (b) Plated coil after removal of resist and seed layer. The turns were of the order of 3 µm wide with 2 µm spaces where the coil passed through the magnetic yoke to minimize the distance between the gap and the back closure of yoke. Dashed outline shows the area of the yoke. (c) Cross-section drawing of an eight-turn head. Cutting and lapping the structure in the plane A–A perpendicular to the plane of the drawing exposed the gap that interfaced with the disk. (d) SEM photo of a cross section of the eight-turn head.

It is worth noting that the interdisciplinary design approach, wherein the fabricator of the head was actively involved in its design, resulted in a structure that was so well matched to the capabilities of the fabrication process that it took less than 2 months from the start of fabrication to the completion of a working head. Furthermore, the tools and processes that were ultimately used in production were basically the same as those created during the thin film memory program even though the permalloy and copper patterns in the heads were nearly an order of magnitude thicker than in the memory structures.

2.3.3 Early Tie-in to Manufacturing

A crucial factor in bringing the new fabrication approach to the manufacturing floor was the establishment of close ties with IBM's General Products Division (GPD) laboratory in San Jose, the division that had the responsibility for developing and manufacturing IBM's next generation of data storage systems. The Watson researchers realized that if their work was to become an IBM manufacturing process, it was GPD that would have to accept and implement the technology. Romankiw and Thompson therefore fostered a relationship with their colleagues in San Jose by keeping them informed on a weekly basis of every step in Yorktown's progress in head fabrication. GPD was aggressively pursuing the LSI approach and, initially, showed little interest in an alternative process. However, in the absence of any completed heads of their own, GPD was willing to evaluate structures such as the single-turn vertical head that had been built in Yorktown.