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Stanford team creates stable lithium anode

Discussion in 'Battery Discussion' started by Denarius, Jul 31, 2014.

  1. Denarius

    Denarius Active Member

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    Stanford Team Achieves of Battery Design: A Stable Lithium Anode | Engineering


    "Engineers would like to use lithium for the anode, but so far they have been unable to do so. That’s because the lithium ions expand as they gather on the anode during charging.


    All anode materials, including graphite and silicon, expand somewhat during charging, but not like lithium. Researchers say that lithium’s expansion during charging is “virtually infinite” relative to the other materials. Its expansion is also uneven, causing pits and cracks to form in the outer surface, like paint on the exterior of a balloon that is being inflated.


    The resulting fissures on the surface of the anode allow the precious lithium ions to escape, forming hair-like or mossy growths, called dendrites. Dendrites, in turn, short circuit the battery and shorten its life.


    Preventing this buildup is the first challenge of using lithium for the battery’s anode.


    The second engineering challenge involves finding a way to deal with the fact that lithium anodes are highly chemically reactive with the electrolyte. It uses up the electrolyte and reduces battery life.


    An additional problem is that the anode and electrolyte produce heat when they come into contact. Lithium batteries, including those in use today, can overheat to the point of fire, or even explosion. They are, therefore, a serious safety concern. The recent battery fires in Tesla cars and on Boeing’s Dreamliner are prominent examples of the challenges of lithium ion batteries.


    BUILDING THE NANOSPHERES


    To solve these problems the Stanford researchers built a protective layer of interconnected carbon domes on top of their lithium anode. This layer is what the team has called nanospheres.


    The Stanford team’s nanosphere layer resembles a honeycomb: it creates a flexible, uniform and non-reactive film that protects the unstable lithium from the drawbacks that have made it such a challenge. The carbon nanosphere wall is just 20 nanometers thick. It would take about 5,000 layers stacked one atop another to equal the width of single human hair.


    “The ideal protective layer for a lithium metal anode needs to be chemically stable to protect against the chemical reactions with the electrolyte and mechanically strong to withstand the expansion of the lithium during charge,” said Cui, who is a member of the Stanford Institute for Materials and Energy Sciences at SLAC National Accelerator Laboratory.


    The Stanford nanosphere layer is just that. It is made of amorphous carbon, which is chemically stable, yet strong and flexible so as to move freely up and down with the lithium as it expands and contracts during the battery’s normal charge-discharge cycle."
     
  2. Merrill

    Merrill Active Member

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    This stuff is way out of my expertise but looks to be a break through and might bring us less expensive and better car batteries. Can someone who is more familiar with chemistry chime in.
     
  3. Francis Lau

    Francis Lau P-1456

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  4. Merrill

    Merrill Active Member

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    #4 Merrill, Aug 2, 2014
    Last edited by a moderator: Aug 2, 2014
    (mod edit - threads merged)

    Still want to know from someone with the background in this field how far out they are with a real world battery as they describe in the article.
     
  5. daniel Ox9EFD

    daniel Ox9EFD Member

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  6. ItsNotAboutTheMoney

    ItsNotAboutTheMoney Active Member

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    Nano: that's all I need to read.
     
  7. curiousguy

    curiousguy curious member

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    #7 curiousguy, Aug 4, 2014
    Last edited: Aug 4, 2014
    i would like to point out than steven chu, ex-secretary of dept of energy is co-authoring this paper. as i have also had to include "high level management" on previous papers for various reasons, i warn the readers to take the validity of the paper with a pinch of salt whenever politicians (or management) end up as authors. Cui however is considered top tier among battery scientists and he published many high impact papers describing various encapsulation techniques for silicon anodes, sulfur cathodes and now, lithium metal anodes. the validity of his claims still remain to be reproduced in other labs :).

    the paper is very well written in the usual "Cui style". one problem i have as i read it is with the argument that the carbon "domes" are conductive on the inside (and hence foster lithium nucleation during electrodeposition) but insulating on the outside (so no lithium nucleates on top of it). i would like more explanation on this issue since it is magically keeping the whole paper together and details are buried in the supporting info section. the synthesis seems "easy" in the sense of scale up and i would point you to the synthesis of LiFePO4 cathodes which use similar carbon coatings.

    Another problem i see to obtaining thick (commercially useful) lithium anodes is with the carbon dome "detaching" upon housing large masses of lithium. figure 3c shows a cathode which is slightly thicker than 5 micrometers. for reference, commercial Li-ion electrodes are 70-150 micrometers in thickness. Also the TEM figures in 3h do not support the claims without reasonable doubt (as they often are). Some sort of elemental mapping could have been used here to differentiate between Li and C.

    FYI, Cui will be presenting some of his sulfur cathode work at the upcoming American Chemical Society meeting in San Fran. You can ask the man yourself if you wish to participate. (I will also present in the same session)

    Link to paper: http://www.nature.com/nnano/journal/vaop/ncurrent/pdf/nnano.2014.152.pdf i think it is open access, i hope you can read it. i dont know hot to upload the pdf otherwise.
    Link to the ACS meeting schedule: http://www.acs.org/content/acs/en/meetings/fall-2014/program.html
     
  8. Cosmacelf

    Cosmacelf Active Member

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    The stated coulombic efficiency is 99% and the researchers themselves says they have to get to 99.9% efficiency before it'll be useful. That's a big step they still need to take. I think this directly affects real world cycle life. Real world cycles where you charge and discharge very slowly tend to show true cycle life problems for these otherwise promising batteries. So, promising, but a ways to go yet.
     
  9. Merrill

    Merrill Active Member

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    Thanks for the info, I am far from understanding any of this but I think you are saying that all this is yet to be proven.
     
  10. stopcrazypp

    stopcrazypp Well-Known Member

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    Not an expert, nor do I work in this field, but I know enough to know this has is a lot more related to the "lithium metal battery" than to "lithium-ion batteries".
    http://en.wikipedia.org/wiki/Lithium_battery

    The lithium metal battery has higher energy density than typical rechargeable "lithium-ion" batteries, but is so far used only in non-rechargeable batteries, precisely because of the problems pointed out in this paper. The problem means extremely short cycle life, so it's almost unviable as a rechargeable battery. It's also much easier to overheat and catch on fire than lithium-ion. Supposedly this discovery will address both of these problems. But like most things at lab stage, it would be very optimistic to see a commercial cell in even a 5 year time frame.
     

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