Tech Front: Nanotubes Hold Promise for Extending Battery Life
Researchers at Rice University (Houston) have invented a new way to boost the efficiency of the ubiquitous lithium-ion (li-ion) battery by using ribbons of graphene that start as carbon nanotubes.
Proof-of-concept anodes—the part of the battery that stores lithium ions—built with graphene nanoribbons (GNRs) and tin oxide showed an initial capacity better than the theoretical capacity of tin oxide alone, according to Rice chemist James Tour. After 50 charge-discharge cycles, the test units retained a capacity that was still more than double that of the graphite currently used for li-ion battery anodes.
The research appeared in the June issue of the American Chemical Society journal ACS Nano.
Better batteries are greatly desired by everyone who carries a cell phone or computer or drives an electric car. The Rice team sees the potential for GNRs to contribute to their development. The technology was licensed just last November by AZ Electronic Materials (Branchburg, NJ), a producer of high-quality, high-purity specialty chemicals to the semiconductor and flat-panel display industries. Both Professor Tour and Ralph Dammel, AZ Electronic Materials’ chief technology officer, estimate that commercialization of the technology is about five years out.
Tour and his colleagues developed a method for unzipping nanotubes into GNRs, revealed in a 2009 cover story in Nature. Since then, the researchers have figured out how to make graphene nanoribbons in bulk and are moving toward commercial applications. An area ripe for improvement is the humble battery, and in an increasingly mobile world, battery capacity is becoming a bottleneck that generally limits devices to less than a day’s worth of use.
In the new experiments, the Rice lab mixed graphene nanoribbons and tin oxide particles about 10-nm wide in a slurry with a cellulose gum binder and a bit of water, spread it on a current collector and encased it in a button-style battery. GNRs are a single atom thick and thousands of times longer than they are wide. The GNRs not only separate and support the tin oxide but also help deliver lithium ions to the nanoparticles.
Lab tests showed initial charge capacities of more than 1520-milliamp hours per gram (mAh/g). Over repeated charge-discharge cycles, the material settled into a solid 825 mAh/g. “It took about two months to go through 50 cycles,” said lead author Jian Lin, a postdoctoral researcher at Rice, who believes the material could handle many more without losing significant capacity.
GNRs could also help overcome a prime difficulty with li-ion battery development. Lithium ions tend to expand the material they inhabit, and the material contracts when they’re pulled away. Over time, materials like silicon, which shows extraordinary capacity for lithium, break down and lose their ability to store ions. Other labs at Rice have made breakthroughs that help solve the expansion problem by breaking treated silicon into a powder, achieving great capacity and many cycles.
GNRs take a different approach by giving batteries a degree of flexibility, Tour said. “Graphene nanoribbons make a terrific framework that keeps the tin oxide nanoparticles dispersed and keeps them from fragmenting during cycling,” Tour said. “Since the tin oxide particles are only a few nanometers in size and permitted to remain that way by being dispersed on GNR surfaces, the volume changes in the nanoparticles are not dramatic. GNRs also provide a lightweight, conductive framework, with their high aspect ratios and extreme thinness.”
The researchers pointed out the work is a “starting point for exploring the composites made from GNRs and other transition metal oxides for lithium storage applications.” Lin said the lab plans to build batteries with other metallic nanoparticles to test their cycling and storage capacities.
Co-authors of the paper are Rice graduate students Zhiwei Peng, Changsheng Xiang, Gedeng Ruan and Zheng Yan and Douglas Natelson, a Rice professor of physics and astronomy and of electrical and computer engineering. Tour is the T.T. and W.F. Chao Chair in Chemistry as well as a professor of mechanical engineering and materials science and of computer science at Rice.
Boeing, the Air Force Office of Scientific Research, Sandia National Laboratory and the Office of Naval Research supported the research.
For more information, see www.rice.edu or read the abstract at http://pubs.acs.org/doi/abs/10.1021/nn4016899. ME
Sustainable manufacturing was highlighted in several papers and presentations at the annual NAMRC-MSEC advanced manufacturing conference June 10–14 in Madison, WI. The North American Manufacturing Research Conference of SME and the Manufacturing Science and Engineering Conference of ASME was co-located at the University of Wisconsin-Madison with more than 400 academic, government and industry researchers and manufacturing leaders in attendance.
Sustainability indicators, which have been little employed on the process level, are applied to grinding processes in a NAMRC paper by Barbara Linke from University of California-Davis, Gero Corman and David Dornfeld of UC-Berkeley and Stefan Tönissen from RWTH Aachen (Germany). The study selects simple and relevant sustainability indicators and discusses different means of normalization. The indicators can be displayed as a performance profile individual to each manufacturing process variant. The whole procedure was executed with a grinding process case study. This paper will be published in the Journal of Manufacturing Systems (http://tinyurl.com/NAMRC-Linke).
A conceptual model to assist sustainable manufacturing enterprises through system dynamics is presented in a NAMRC paper by Hao Zhang, Javier Calvo-Amodio and Karl Haapala of Oregon State University (Corvallis, OR). Current methods of balancing economic and financial priorities against environmental and social responsibilities are deficient in aiding proactive engineering management decision making and revealing broader sustainability opportunities. This paper incorporates systems thinking into sustainable manufacturing assessment and develops an understanding of the complex interplay of factors from the operational (micro) scale through the enterprise (macro) scale. The combined approach leads to development of a conceptual model being explored in ongoing research. The paper will appear in the Journal of Manufacturing Systems (http://tinyurl.com/NAMRC-JMS).
A process-based approach for understanding life cycle social impacts in manufacturing is described in a NAMRC paper by Margot Hutchins, Stefanie Robinson and David Dornfeld, all of the University of California-Berkeley. There are substantial challenges to identifying and understanding the social impacts, which occur on various scales in manufacturing, from the level of a unit process to the level of an enterprise. The paper identifies key characteristics of the social impacts that should be considered in addressing sustainability for products and processes. Examples involving a typical manufacturing process—welding—are presented to illustrate the utility of the framework. This paper also will appear in the Journal of Manufacturing Systems (http://tinyurl.com/NAMRC-JMS).
Several MSEC papers focused on sustainable manufacturing metrics and methods. Pil-Ho Lee, Dae Hoon Kim and Sangwon Lee of Sungkyunkwan University (Suwon, Korea) demonstrate that a new hybrid system using electro-hydro-dynamic (EHD) spray lubrication with chilly air reduces milling forces and burrs significantly. An atomization-based cutting fluid (ACF) spray system is proposed as a cooling and lubrication solution for machining hard-to-machine materials (e.g., titanium alloys) in a paper by Alexander Hoyne, Chandra Nath and Shiv Kapoor of the University of Illinois at Urbana-Champaign. On the tool rake face, the ACF spray system forms a thin film from cutting fluid that penetrates into the tool-chip interface to improve tool life.
Also from MSEC, Jatinder Madan, Mahesh Mani and Kevin Lyons of the National Institute of Standards and Technology (NIST; Gaithersburg, MD) present a science-based guideline to characterize energy consumption for a part manufactured using the injection molding process. They discuss selection of process parameters and manufacturing resources, determination of cycle time, theoretical minimum energy computations and estimated energy computations. Because many energy-saving opportunities are wasted by lack of integration between the facility and the production system, Michael Brundage and Cindy Chang of Stony Brook (NY) University and Dongmei Chen and Victor Yu of the University of Texas-Austin propose syncing the energy opportunity window of each machine with peak periods of energy demand of the HVAC system.
Sustainable vehicle manufacturing was covered in two MSEC papers. Chongye Wang, Yong Wang and Lin Li of the University of Illinois-Chicago, Hua Shao of Shanghai Jiao Tong University (China) and Changxu Wu of the State University of New York at Buffalo examine the effects of manufacturing processes on the performance of entire electric vehicle (EV) lithium-ion (li-ion) battery packs while proposing a novel modeling method for analyzing the arrangement of the individual multiple cells for improving EV li-ion battery performance. For a door production line at an automotive body shop, an arrow-based bottleneck analysis method is introduced by Cong Zhao and Jongshan Li of the University of Wisconsin-Madison. Such methods provide a quantitative tool for plant engineers and managers to operate and improve production lines and are also applicable to large-volume manufacturing systems.
In addition to these papers, the panel session Sustainable Manufacturing Approaches: Collectively Are We Stronger?, moderated by Kevin Lyons, group leader, life cycle engineering, NIST, and David Dornfeld, professor and director, Laboratory for Manufacturing and Sustainability, UC-Berkeley, discussed how the collective and consistent practice of sustainability is necessary to achieve beneficial impact, including a common outlook regarding terminologies, methodologies, measurement science and tool development. A roundtable discussion following several individual academic and industry presentations was designed to encourage formation of a special interest group (SIG) for sustainable manufacturing processes to promote standards participation, development and reliable measurement methods, metrics and guidance to evaluate manufacturing process-related sustainability performance.
The NAMRC Founders Lecture, given by Delcie R. Durham, PhD, FSME, PE, of the University of South Florida (Tampa), also addressed sustainable, scalable manufacturing and its evolution over the past 30 years. Durham echoed the presentations by authors and panelists in stating the need for definitions, methods and tools, metrics and standards, industrial implementation and “K-gray” education. ME
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This article was first published in the August 2013 edition of Manufacturing Engineering magazine. Click here for PDF.