Unocic publications: http://web.ornl.gov/sci/physical_sciences_directorate/mst/Microscopy/unocic_r_pubs.shtml
On Fri, Mar 14, 2014 at 6:30 AM, brucedp5 <[email protected]> wrote: > > > http://www.eenews.net/stories/1059995867 > New technique lets scientists examine the quirks of lithium-ion batteries > in > real time > Umair Irfan March 11, 2014 > > With some custom-built hardware and an electron microscope, researchers at > Oak Ridge National Laboratory recently invented a way to watch how > lithium-ion batteries work in real time at nanometer scales. > > A nanometer is one-billionth of a meter, a measure that scientists use to > quantify unseeably tiny things, such as the width of a molecule. The > technique helps scientists understand how batteries age and eventually > fail, > paving the way toward new cell designs that last longer and hold more > energy. The researchers outlined their methods last month in the journal > Chemical Communications. > > Raymond Unocic, a co-author and a research and development staff scientist > at Oak Ridge, explained that the team was investigating a structure known > as > a solid electrolyte interphase (SEI). It forms on a battery's electrodes as > the electrolyte breaks down during the charge and discharge cycle. > > As an SEI forms, it sops up some of the lithium ions in the cell, leading > to > a permanent capacity loss. It also hinders the remaining lithium ions as > they shuttle back and forth between the electrodes, degrading the > performance of the cell. "This is the first time people were able to > understand how this interphase forms," Unocic said. > > Researchers have linked SEI to dendrite formation, as well. Dendrites are > tiny, growing branches of lithium metal that build up on electrodes as a > cell ages. If the branches get long enough, they can pierce the membrane > separating the anode and the cathode, shorting the cell and causing > catastrophic failure. > > These problems are becoming more pressing as lithium-ion cells move beyond > the small packs powering laptops and phones -- a market they have mastered > -- toward the hefty and expensive batteries that will drive electric cars > and trucks for up to a decade. > > Previous studies had a hard time replicating a real lithium cell because > the > liquid electrolyte would evaporate in the vacuum inside the transmission > electron microscope specimen chamber. In this study, researchers designed a > cell with gold electrodes that used a liquid electrolyte built into a > bespoke microscope specimen holder. > > "The most significant thing we have is the ability to image electrodes in a > liquid cell, but at the same time, we're able to couple that with > quantitative electrochemical measurements," Unocic said. > Moment-by-moment view of aging process > > The researchers charged and discharged the cell and carefully watched what > happened, sweeping across a range of voltages. They found that an SEI > started forming early in the cell's operating life as polymer layers. "We > see it right away," said Robert Sacci, a postdoctoral associate in the > Materials Science and Technology Division at Oak Ridge and a co-author. "It > happens really close to where we start depositing the lithium." > > The researchers also saw what they interpreted as the seeds of lithium > dendrite formation within the SEI. "If we push this hard enough and we did > not care about breaking the microscope, we could probably grow lithium > dendrites," Sacci said. > > After substantial testing, automakers are confident lithium-ion batteries > will last a long time. Researchers found that the aging process in the > cells > starts almost right away, with measurable changes in performance over time. > With the new microscopy system, scientists can watch the breakdown > carefully > as it happens rather than simply conducting autopsies on decrepit > batteries, > using the observations to build better battery chemistries for the future. > > "SEI is a critical component in all the advanced batteries," said Kang Xu, > a > chemist at the U.S. Army Research Laboratory who was not involved in this > study. "With this technique, we can directly observe the growth of SEI and > we can study its growth mechanistically." > > However, visualizing how a battery works in real time is only one of the > tools needed to understand a vexing problem. "Solid electrolyte interphases > are very complex, and one needs a combination of different techniques to > get > a comprehensive picture of what is actually going on at the > electrolyte/electrode surfaces," Xu said. > > The Oak Ridge researchers said they want to start investigating other > battery materials, like carbon nanofibers and silicon. They are especially > interested in lithium metal, which has a very high energy density compared > to conventional graphite electrodes but has a troubling tendency to grow > dendrites. By figuring out how these structures form, scientists can come > up > with ways to slow them down or stop them altogether. > > The ultimate goal, however, is to make battery energy storage more > practical, whether in cars or on the grid, and figuring out how an SEI > forms > is a crucial step in that direction. > 'Center stage' of research > > "It's at center stage for a good reason," said Kevin Gering, technical lead > for battery energy storage at the Idaho National Laboratory, who was not > involved in this study. "The SEI is really the gatekeeper for battery > performance and lithium-ion chemistries." > > Automakers including General Motors Co. and Tesla Motors Inc. can't just > offer batteries -- often the single most expensive component in a hybrid or > an electric car -- with good sticker performance out of the gate; they have > to guarantee that same performance years from now, whether in Phoenix or > Minneapolis. > > And how long a battery lasts is often different from how well it holds a > charge. Nissan's all-electric Leaf, for instance, has an eight-year > warranty > against defects on its battery but only a five-year warranty against > capacity loss below nine bars as shown on the car's capacity gauge. > > "If you're talking about [battery] longevity in vehicles, the biggest issue > right now is thermal management," Gering said. "In general, higher > temperatures accelerate chemical kinetic reactions." This includes SEI > formation, though the cold introduces its own challenges. > > "Dendrites tend to be more of an issue at lower temperatures when you > charge > too aggressively," he added. > > Oak Ridge's Sacci said the team is working on making a more realistic cell > that they can observe at the nanometer level. "We're getting closer and > closer to simulating an entire cell on a much smaller length scale," he > explained. > > Eventually, researchers expect their new visualization system will lead to > payoffs like greater energy densities and lower costs. "We can look at > site-specific phenomenon in these small cells, but we're trying to chip > away > at these real-world problems," Unocic concluded. > [(c) 2014 E&E Publishing] > > > > http://bestmag.co.uk/event/2014-battery-congress > 2014 Battery Congress > Event Date: Wednesday, 11 June, 2014 to Thursday, 12 June, 2014 > A forum for, engineers, managers, scientists, academic researchers, and > industry executives to discuss advances in battery technology and > applications and management systems. There will be a conference and > exposition dedicated to the integration of new battery technologies in > vehicular and other energy system applications. Topics will include EVs and > plug-in hybrids, lithium-ion battery systems, safety and modeling, > nickel-metal hydride batteries, thermal management, global and national > programmes. > More information http://batterycongress.org > Event Venue: Troy, Michigan, US ... > > > > > http://www.dailycal.org/2014/03/11/berkeley-lab-researchers-designing-bionic-leaf/ > Berkeley lab researchers designing a bionic leaf > March 11, 2014 ... At the Joint Center for Artificial Photosynthesis, > scientists and graduate students from different universities are trying to > design a new kind of solar cell powered by artificial photosynthesis. Such > an approach would address the two key problems in solar energy: energy > storage and the production of a potential carbon-neutral transport fuel ... > > > > > For all EVLN posts use: > > http://electric-vehicle-discussion-list.413529.n4.nabble.com/template/NamlServlet.jtp?macro=search_page&node=413529&query=evln&sort=date > > Here are today's archive-only EV posts: > > EVLN: Feds Block LA's Purchase Of BYD e-Buses > EVLN: Bangalore.in 's first electric bus draws cheers > EVLN: OSU students build a world's top-racing electric-motorcycle > EVLN: EV Connect OCPP allows EVSE a 'Switchable Network Guarantee' > EVLN: EURO 10k 1seater & fold-up EVs are coming > EVLN: 4states rolling out the red carpet for $B gigafactory bid > + > EVLN: Audi announced will produce 400mi range R8 E-tron > > > {brucedp.150m.com} > > > > -- > View this message in context: > http://electric-vehicle-discussion-list.413529.n4.nabble.com/EVLN-Scientists-examine-li-ion-battery-quirks-in-real-time-tp4668428.html > Sent from the Electric Vehicle Discussion List mailing list archive at > Nabble.com. > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > For EV drag racing discussion, please use NEDRA ( > http://groups.yahoo.com/group/NEDRA) > > -- Put this question to yourself: should I use everyone else to attain happiness, or should I help others gain happiness? *Dalai Lama * Tell me what it is you plan to do With your one wild and precious life? Mary Oliver, "The summer day." To invent, you need a good imagination and a pile of junk. Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html> A public-opinion poll is no substitute for thought. *Warren Buffet* Michael E. Ross (919) 550-2430 Land (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone (919) 631-1451 Cell (919) 513-0418 Desk [email protected] <[email protected]> -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140314/3abcb39b/attachment.htm> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
