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Randall A.V.,University of Colorado at Colorado Springs | Perkins R.D.,University of Colorado at Colorado Springs | Zhang X.,Sakti3 | Plett G.L.,University of Colorado at Colorado Springs
Journal of Power Sources | Year: 2012

Battery cell life depends critically on how the cell is used. Therefore, battery chargers and battery management systems must be designed to control cell usage carefully. In order to design optimal battery controls that effect a tradeoff between cell performance (in some sense) and cell life, a model of cell degradation is necessary. This model must be simple and incremental in order to be implemented by an inexpensive microcontroller. This paper takes a first step toward developing such a controls-oriented comprehensive cell degradation model by deriving a reduced-order model of a single mechanism: the growth process of the solid-electrolyte interphase (SEI) layer, along with the resulting resistance rise and capacity loss. This reduced-order model approximates a physics-based PDE model from the literature, is simple and accurate, and may be used in optimal strategies for controlling lithium-ion batteries. © 2012 Elsevier B.V. All rights reserved. All rights reserved. Source


Perkins R.D.,University of Colorado at Colorado Springs | Randall A.V.,University of Colorado at Colorado Springs | Zhang X.,Sakti3 | Plett G.L.,University of Colorado at Colorado Springs
Journal of Power Sources | Year: 2012

Battery cell life depends critically on how the cell is used. Therefore, battery chargers and battery management systems must be designed to control cell usage carefully. In order to design optimal battery controls that effect a tradeoff between cell performance (in some sense) and cell life, a model of cell degradation is necessary. This model must be simple and incremental in order to be implemented by an inexpensive microcontroller. This paper takes a first step toward developing such a controls-oriented comprehensive cell degradation model by deriving a reduced-order model of a single mechanism: lithium deposition on overcharge, along with the resulting resistance rise and capacity loss. This reduced-order model approximates a physics-based PDE model from the literature, is simple and accurate, and may be used in optimal strategies for controlling lithium ion batteries. © 2012 Elsevier B.V. All rights reserved. Source


Liu L.,University of Michigan | Liu L.,University of Kansas | Park J.,University of Michigan | Lin X.,University of Michigan | And 2 more authors.
Journal of Power Sources | Year: 2014

The formation of a SEI layer and its growth cause internal resistance increase and capacity loss, leading to performance degradation of lithium-ion batteries. In order to comprehensively investigate the effects of SEI growth on battery performance, a one-dimensional thermal-electrochemical model was developed. This model is equipped with a growth mechanism of the SEI layer coupled with thermal evolution, based on the diffusional process of the solvent through the SEI layer and the kinetic process at the interface between the solid and liquid phases. The model is able to reveal the effects of diffusivity, reaction kinetics and temperature on SEI layer growth and cell capacity fade. We show that depending on the SEI thickness, the growth can be kinetics-limited or diffusion-limited. With the layer becoming thicker, its growth rate slows down gradually due to increased diffusion resistance. The SEI layer grows faster during charge than discharge due to the difference in the electron flux through the SEI layer and the temperature change during cycling. Temperature rise due to reaction and joule heating accelerates the SEI layer growth, leading to more capacity loss. Our model can provide insights on position-dependent SEI growth rate and be used to guide the strategic monitoring location. © 2014 Elsevier B.V. All rights reserved. Source


News Article
Site: http://www.technologyreview.com/stream/10105/?sort=recent

Earlier this year, Ellen Williams, the director of ARPA-E, the U.S. Department of Energy’s advanced research program for alternative energy, made headlines when she told the Guardian newspaper that "We have reached some holy grails in batteries.” Despite very promising results from the 75-odd energy-storage research projects that ARPA-E funds, however, the grail of compact, low-cost energy storage remains elusive. A number of startups are closer to producing devices that are economical, safe, compact, and energy-dense enough to store energy at a cost of less than $100 a kilowatt-hour. Energy storage at that price would have a galvanic effect, overcoming the problem of powering a 24/7 grid with renewable energy that’s available only when the wind blows or the sun shines, and making electric vehicles lighter and less expensive. But those batteries are not being commercialized at anywhere near the pace needed to hasten the shift from fossil fuels to renewables. Even Tesla CEO Elon Musk, hardly one to underplay the promise of new technology, has been forced to admit that, for now, the electric-car maker is engaged in a gradual slog of enhancements to its existing lithium-ion batteries, not a big leap forward. In fact, many researchers believe energy storage will have to take an entirely new chemistry and new physical form, beyond the lithium-ion batteries that over the last decade have shoved aside competing technologies in consumer electronics, electric vehicles, and grid-scale storage systems. In May the DOE held a symposium entitled “Beyond Lithium-Ion.” The fact that it was the ninth annual edition of the event underscored the technological challenges of making that step. Qichao Hu, the founder of SolidEnergy Systems, has developed a lithium-metal battery (which has a metallic anode, rather than the graphite material used for the anode in traditional lithium-ion batteries) that offers dramatically improved energy density over today’s devices (see “Better Lithium Batteries to Get a Test Flight”). The decade-long process of developing the new system highlighted one of the main hurdles in battery advancement: “In terms of moving from an idea to a product,” says Hu, “it’s hard for batteries, because when you improve one aspect, you compromise other aspects.” Added to this is the fact that energy storage research has a multiplicity problem: there are so many technologies, from foam batteries to flow batteries to exotic chemistries, that no one clear winner is attracting most of the funding and research activity. According to a recent analysis of more than $4 billion in investments in energy storage by Lux Research, startups developing “next-generation” batteries—i.e., beyond lithium-ion—averaged just $40 million in funding over eight years. Tesla’s investment in its Gigafactory, which will produce lithium-ion batteries, will total around $5 billion. That huge investment gap is hard to overcome. “It will cost you $500 million to set up a small manufacturing line and do all the minutiae of research you need to do to make the product,” says Gerd Ceder, a professor of materials science at the University of California, Berkeley, who heads a research group investigating novel battery chemistries. Automakers, he points out, may test new battery systems for years before making a purchase decision. It’s hard to invest $500 million in manufacturing when your company has $5 million in funding a year. Even if new battery makers manage to bring novel technologies to market, they face a dangerous period of ramping up production and finding buyers. Both Leyden Energy and A123 Systems failed after developing promising new systems, as their cash needs climbed and demand failed to meet expectations. Two other startups, Seeo and Sakti3, were acquired before they reached mass production and significant revenues, for prices below what their early-stage investors probably expected. Meanwhile, the Big Three battery producers, Samsung, LG, and Panasonic, are less interested in new chemistries and radical departures in battery technology than they are in gradual improvements to their existing products. And innovative battery startups face one major problem they don’t like to mention: lithium-ion batteries, first developed in the late 1970s, keep getting better.


News Article
Site: http://www.rdmag.com/rss-feeds/all/rss.xml/all

Dyson, the home appliances company, is reportedly entering into the electric car arena. A potentially accidental leak of government documents last week indicated the United Kingdom-based firm was working on an energy-efficient vehicle at its headquarters in Wiltshire, according to The Guardian. Financial support will be given by the country’s government to Dyson as part of a program called the National Infrastructure Delivery Plan, which is a five year initiative aimed at improving different aspects of Britain’s infrastructure through various transportation and communication projects. Details surrounding the vehicle are sparse, but Fortune noted that Dyson’s acquisition of battery startup Sakti3 last year for $90 million could play a crucial role in this venture. According to the documents published by the U.K. government, Dyson will receive a £16m investment to help support research and development into battery technology at the corporate headquarters. Sakti3 is an eight-year old startup specializing in “solid-state” lithium-ion batteries. A key component of this module is that they use solid material for energy storage making them safer and less flammable compared to their counterparts who use a liquid compound. The complex in Wiltshire could be used to manufacture these batteries at a large clip, but Fortune added that Sakti3’s products will probably be used Dyson’s series of cordless vacuums first. Establish your company as a technology leader! For more than 50 years, the R&D 100 Awards have showcased new products of technological significance. You can join this exclusive community!

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