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NMC chemistry issues

Discussion in 'Battery Discussion' started by 30seconds, Jul 17, 2014.

  1. 30seconds

    30seconds Active Member

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    Interesting article on the NMC chemistry not being durable enough for auto use. I wasn't aware that so many companies were waiting for this. Besides explaining VW/Audi's hyperbolic press releases it may have been (if true) the reason why so many other companies have been reluctant to think about more available chemistries - they thought a breakthrough was just around the corner.

    Can the world Quartz
     
  2. flashflood

    flashflood Member

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    Musk was smart to bet against miracle batteries. There have been reports of breakthroughs "just around the corner" for at least the last 30 years. Most recently, silicon electrodes were going to solve everything, and a few years before that it was carbon nanotubes. It sucks to bet against human ingenuity, but certain problems -- high-capacity batteries, nuclear fusion, cost-effective solar, a universal cure for cancer -- seem to offer up false hope over and over again. Progress has been made on all of these, but painfully slowly. The smart bet is that batteries will continue to improve, gradually, and that the miracle battery is not coming -- ever.
     
  3. ggies07

    ggies07 Active Member

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    #3 ggies07, Jul 17, 2014
    Last edited by a moderator: Mar 13, 2016
    So here is that video of Prof. Jeff Dahn talking about how/why Li-ion Batteries die that would correspond to this news. Somewhere in the video he talks about partnering with some auto makers and doing some testing. It obliviously didn't pan out, but I would love another discussion from him as to why. From the article he seems to have such a positive attitude and I dig that. Anyway, just goes to show that Tesla the company deserves all its praise(and value).

    For a refresher:
     
  4. yobigd20

    yobigd20 Well-Known Member

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    i don't remember if its that video above or another video where the guy is an expert at this (I think he may have worked for or with Tesla at some point?) and said that the battery chemistry, configuration, thermal and battery management system that Tesla has used in the Model S is really sophisticated and ingenious and that these battery packs will easily last at least 20 years. I don't know how that's "not durable enough" for auto use. for comparison's sake, my camaro lasted 7 years before everything started breaking , blown transmission, etc. my murano lasted 7 years before a rod knock destroyed the engine. and my land rover lasted a couple months before it was lemoned due to design defects. even if the battery pack lasts 10 years that'll be far longer than any ICE car held up that I've owned haha.
     
  5. trils0n

    trils0n 2013 P85

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    Tesla doesnt use the NMC batteries this article talks about. Tesla's batteries are plenty durable.
     
  6. flashflood

    flashflood Member

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    Indeed. As Prof. Dahn explains, it isn't actually charge/discharge cycles that age Li-ion batteries: it's simply the total time spent at high voltage and/or high temperature, both of which increase the rate of unwanted, irreversible reactions between lithium ions and the organic electrolyte. So Tesla actively cools the batteries, and recommends not charging to full capacity. (In Li-ion battery chemistry, voltage is roughly linear with state of charge. This is not true of all chemistries: NiMH, for example, has an almost flat voltage vs. SOC curve, which is why cheap battery testers that only measure voltage (without load) don't work on rechargeable AAs.) If you want to preserve your battery, best thing you can do is keep it cool and don't charge it above 70% (which keeps individual cells under 4V) unless you actually need to.

    Not mentioned in Prof. Dahn's video is that Li-ion batteries also suffer irreversible damage due to dendrite formation when discharged much below 3V. I don't know what cell voltage Tesla defines as zero rated miles, but it's best not to push that end of the spectrum either. I try not to venture outside the 20-80% range, which is over 100 miles -- which is plenty for an ordinary commute plus a few random errands.

    All that said, I wonder how much the lifetime beyond ten years matters. If there's a P150 upgrade available before then, I'm in -- along with (I suspect) many of us.
     
  7. ggies07

    ggies07 Active Member

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    I understood that, but I also thought it was partly the discharge/charge......The slide he gives for CE=chargeout/chargein and he says if you can get that to 1.000000, then you cells would last forever. So he made it seem as though discharge/charge has something to do with it.
     
  8. flashflood

    flashflood Member

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    That's what battery makers assumed for a long time. They observed that capacity declines with each charge cycle, so they inferred that it was the charge cycle itself that caused wear. What Prof. Dahn discovered is that the reason CE declines is not the act of cycling, but rather the simple fact that as part of the full charge process, you're making the cell spend a certain amount of time (toward the end of the charge) at high voltage. It is (mainly) at high voltage that lithium ions react irreversibly with the electrolyte.
     
  9. ggies07

    ggies07 Active Member

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    ah-ha! Thanks for the clarification.
     
  10. stopcrazypp

    stopcrazypp Well-Known Member

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    #10 stopcrazypp, Jul 17, 2014
    Last edited: Jul 17, 2014
    Nissan has been working on NMC since before the Leaf launched (2009). It's planned to be ready in 2015 (and will likely be used in their Infiniti EV and the next-gen Leaf due to be out soon):
    http://www.greencarcongress.com/2009/11/nissan-nmc-20091129.html

    LG was already working on an NMC / manganese-spinel blend for the Volt in 2011. The 2013 Volt (released in 2012) likely incorporated this chemistry for a slight capacity bump.
    http://www.popsci.com/cars/article/2011-01/gm%E2%80%99s-new-battery-chemistry-it%E2%80%99s-already-chevy-volt

    However, what your article is talking about is mainly about *high voltage* NMC (nominal voltage at 4.7V), while the previous examples are all standard voltage (nominal voltage at 3.6-3.7V).

    The closest example is Envia (which GM famously invested in and then it went into trouble with some lawsuits):
    http://www.hybridcars.com/envia-li-ion-battery-yields-world-record-energy-density-41768/

    The 3.6-3.7V NMC (which is pretty much ready for commercial use already) will be able to roughly match the Model S's density, but the high voltage 4.7V version will beat it by roughly 60%. Plus it'll probably be cheaper and be more thermally stable. So a lot of automakers are banking on this chemistry as sort of the "holy grail".

    Elon, on the other hand, hedged his bets by designing the pack to handle even the least thermally stable cells (the old lithium cobalt cells in the Roadster) which allows him the flexibility in picking the most energy dense cells without regard to thermal stability. He also insists on long range/large capacity packs so that even cells with marginal cycle life and C-rate can be used without worry (while other automakers have to stress out about picking cells with 1000-2000+ cycle life and also with high C-rate). It's actually a very smart strategy that exposes him to less risk in case some of these "holy grail" chemistries never pan out.
     
  11. daniel Ox9EFD

    daniel Ox9EFD Member

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    I stumbled across this article about funding for Li-ion research projects from the DOE:
    US DoE Funds 6 Lithium-Ion Battery Research Projects Targeted At 200 Wh/kg
    in "Five other projects also using promising, but problematic in the implementation" there is one from 3M, now I know Prof. Jeff Dahn is working with 3M, and it says its an advanced NMC battery solution, could this be the same kind of battery solution as the one mentioned in the article? Anyway, his would mean the DOE did not give up on NMC as a chemistry, which might be inferred from the article.
    Also they are aiming for 200 Wh/kg which seems confusing since Tesla already has an energy density of 240 Wh/kg, so perhaps there is a big difference on cost per Wh? Otherwise the article doesn't make sense.
     
  12. evme

    evme Member

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  13. Jeff N

    Jeff N Active Member

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    As far as I can tell and as the PopSci article says, the NMC blended battery chemistry was already used in 2011 Volts but GM has since tweaked the chemistry and/or construction of the cells to increase the pack capacity from 16.0 kWh in 2011 to 16.5 kWh in 2013 and 17.1 kWh in 2015. They also changed the usable state of charge from 65% in 2011 to 69% in 2014.
     
  14. omgwtfbyobbq

    omgwtfbyobbq Member

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    I think many major manufacturers took notice. Well, except for Nissan. ;)

    Toyota for example religiously cycles the ~3.7V/20ah (Panasonic?) NMC cells in the PIP between 25% and 85% of overall capacity and has air drawn in from cabin (and maybe from the outside) any time the batteries are being charged or discharged to prevent heat at high SOCs. Regen power is also limited based on SOC (30kW at low SOC versus 10kW at high SOC), presumably to perserve battery life.

    http://energy.gov/sites/prod/files/2014/03/f13/vss110_rask_2013_o.pdf
     

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