A Stable Lithium Anode – the “Holy Grail” of Battery Design

Dean Sigler Electric Powerplants, Sustainable Aviation Leave a Comment

A Stanford University team of researchers, including Nobel Prize winner and former U. S. Secretary of Energy Steven Chu and Yi Cui, long familiar to CAFE Blog readers, are using carbon nanospheres to coat lithium electrodes and help them resist expansion problems that formerly fractured them, and to keep elements in the battery’s reactive electrolytes from dissolving them. This approach has enabled the team to craft a pure lithium anode, with all the promise of high energy density that such an electrode holds.   It’s also stable, a boon to longevity for these cells. As reported in the news release By Andrew Myers for the Stanford Engineering School, “’Of all the materials that one might use in an anode, lithium has the greatest potential. Some call it the Holy Grail,’ said Cui, a professor of Material Science and Engineering and leader of the research team. ‘It is very lightweight and it has the highest energy density. You get more power per …

Solar Cells a Few Atoms Thick

Dean Sigler Electric Powerplants, Sustainable Aviation Leave a Comment

Researchers at the Vienna University of Technology have come up with a way to create one-atom thick, flexible, semi-transparent solar cells.  Instead of the graphene often touted as a means toward such an end, however, the scientists have turned to atom-thick layers of tungsten diselenide for their wonder material. Experiments show that ultrathin layers of tungsten and selenium may have properties that would make them applicable even to electric aircraft use – if they can capture a significant amount of energy – or at least as much as thin-film silicon cells can. Graphene has been a popular favorite since its Russian “discoverers” were awarded the Nobel Prize in physics in 2010.  One of the strongest materials, graphene can manage stresses and strains better than most and has “great opto-electronic properties.”  Its atomic-scale thinness allows it to transform optical signals into electronic pulses extremely quickly. Despite these outstanding characteristics, “The electronic states are not very practical for creating photovoltaics,” according to …

Dr. Cui’s Pomegranate-inspired Battery Bears Fruit

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Dr. Yi Cui seems to get inspiration from food.  A few years ago, his research team came up with a “yolk-shell structure” that helped contain the high amount of lithium that silicon anodes were able to absorb.  That battery design promised much, and an embellishment of that design seems to hold even greater promise. His newest effort, working at Stanford University with the Department of Energy’s SLAC National Accelerator Laboratory, features an electrode “designed like a pomegranate – with silicon nanoparticles clustered like seed in a tough carbon rind.”  This approach, according to its inventors, overcomes several remaining obstacles to the use of silicon in a new generation of lithium-ion batteries. Yi said the battery’s efficiency and longevity are promising.   “Experiments showed our pomegranate-inspired anode operates at 97 percent capacity even after 1,000 cycles of charging and discharging, which puts it well within the desired range for commercial operation.” Cui’s team has been working on preventing anode breakup for the …

That’s No Yolk!

Dean Sigler Electric Powerplants, GFC, Sustainable Aviation Leave a Comment

Dr. Cui is at it again!  In a seemingly endless stream of announcements, his work with silicon anodes keeps promising improvements in battery capacity and longevity.  The Stanford professor and his team, Stanford’s National Accelerator Laboratory (Formerly the Stanford Linear Accelerator Center), and the Environmental Molecular Sciences Laboratory (EMSL) at Pacific Northwest National Laboratory all published papers on their latest joint accomplishment. Conceptual drawing of silicon filling carbon shell, TEM photo of actual expansion, and life cycle analysis for yolk-shell batteries Expansion and contraction of anodes and cathodes during charging and discharging of batteries causes flexing and eventual breakdown of a battery’s internal components.  Cui and other researchers have tried various strategies to mitigate or eliminate this flexing, but the latest tactic seems to promise longer battery life and greater power and energy. Calling it a “yolk-shell structure,” researchers seal commercially available single silicon nanoparticles in “conformal, thin, self-supporting carbon shells, with rationally-designed void space between the particles and the …

Imperfect Carbon as Good as Pricy Platinum

Dean Sigler Electric Powerplants, Sustainable Aviation Leave a Comment

The expense of platinum catalysts has been an impediment to the development of fuel cells and metal-air batteries.  Scientists at Stanford University may have found an inexpensive, higher-performance alternative in “unzipped” carbon nanotubes that show an imperfect face to the world. Findings published in the May 27 online version of the journal Nature Nanotechnology quote chemistry professor Hongjie Dai, co-author of the paper.  “Platinum is very expensive and thus impractical for large-scale commercialization. Developing a low-cost alternative has been a major research goal for several decades.” With platinum ranging from almost $800 to over $2,200 an ounce, carbon nanotubes, with their conductivity and inexpensive production costs provide a desirable combination of performance and price. Nanotubes are rolled-up sheets of graphene, a one-atom thick layer of pure carbon – 10,000 times narrower than a human hair. Dai’s team nested two or three nanotubes, each smaller than the next layer outward, an amazing feat considering the submicroscopic size of the tubes.   To …

Combining the Best of Batteries and Supercapacitors

Dean Sigler Electric Powerplants, Sustainable Aviation 1 Comment

The CAFE Blog has been tracking developments in batteries and supercapacitors for nearly the last two years, and the annual Electric Aircraft Symposia have attracted speakers on a wide range of innovations in these areas.  Gizmag reminded us this week how much all of this may soon affect the ability of energy storage and power devices to change our world. Their report highlighted work on an energy storage system that combines the energy capacity of batteries with the power density and quick recharging capabilities of capacitors being done at Rice University, and linked that to research at the University of Illinois by Dr. Paul Braun on creating faster charging batteries with higher energy densities than currently possible.  Gizmag then did a callback to something covered earlier by CAFE, the use of structural panels in electric vehicles as energy storage devices. Both researchers pointed to the big disappointment in electrical devices – batteries.  They are either short-lived in their application or take …

A Thousand-Fold Point of Light

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Shortly after reading of MIT’s 100-fold breakthrough in light-gathering capabilities for solar cells, we saw the news about a one-thousand-fold increase claimed by Rice University researchers.  Professor of physics and astronomy Doug Natelson announced the findings of his research group, which includes his graduate student Dan Ward, and colleagues in Germany and Spain. In his blog, Natelson stated, “My student (with theorist collaborators) had a paper published online in Nature Nanotechnology yesterday, and this gives me an excuse to talk about using metal nanostructures as optical antennas. The short version: using metal electrodes separated by a sub-nanometer gap as a kind of antenna, we have been able to get local enhancement of the electromagnetic intensity by roughly a factor of a million (!), and we have been able to determine that enhancement experimentally via tunneling measurements.” In a brief discussion with this reporter, Natelson deflated any ideas that this technology would be powering up solar cells in the near future.  …