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
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
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Print ISBN: 9783527333455
ePDF ISBN: 9783527692149
ePub ISBN: 9783527692125
Mobi ISBN: 9783527692132
oBook ISBN: 9783527690633
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.
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
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
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.