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Battery Innovation Multiplies Li-ion Energy Density Several Times

Discussion in 'Battery Discussion' started by Electric700, Feb 27, 2015.

  1. Electric700

    Electric700 Member

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  2. dirkhh

    dirkhh Middle-aged Member

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    To quote Elon:

    (source: Tesla CEO Elon Musk On Breakthrough Battery)
     
  3. techmaven

    techmaven Active Member

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    Silicon anode technology is something Panasonic announced, but as far as I know, hasn't shipped. Anything to help solidify the technology and get it shipping is great.
     
  4. igotzzoom

    igotzzoom Member

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    Very promising. I think there's more interest and research into batteries now than there has been for a long time, if ever. I think the OE's realize that until they can deliver consistent 150-200-mile EV ranges at an affordable price, electrics aren't really going to take off.
     
  5. ScepticMatt

    ScepticMatt Member

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    #5 ScepticMatt, Feb 27, 2015
    Last edited: Feb 27, 2015
    Panasonic has been working on Silicon anodes for 4 Ah 1860 cells since before 2009, and they should be out already if they weren't delayed.

    edit:
    Panasonic Develops High-Capacity Lithium-Ion Battery Cells That Can Power Laptops and Electric Vehicles | Headquarters News | Panasonic Global

     
  6. Robert.Boston

    Robert.Boston Model S VIN P01536

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    In some fairness, the author of the paper didn't suggest that Tesla Motors should work with them. But they do, at least, have a functional cell. Wrong format (disk, not cylinder), but it's a lot better than a PowerPoint deck.
     
  7. Electric700

    Electric700 Member

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    Great points. Once they change the format to something EV makers (e.g. Tesla) can use, they could start final testing in areas like safety, functionality, and reliability. Afterward they should be able to begin commercial trials.
     
  8. chickensevil

    chickensevil Active Member

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    Yeah but the reason Tesla uses Cylinder is because it is the best that they can get more than anything (note: that is best by their requirements... And people have different requirements) so if they received a radically new format but it was actually what they were looking for I'm sure changes could be made.
     
  9. Cosmacelf

    Cosmacelf Active Member

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    Silicon anodes are one of the holy grails of lithium ion battery cell research since they can, in theory, hold 10x the charge (by weight) of a traditional carbon anode. The issue has always been that silicon by itself swells to 3x volume when charged, which destroys (literally) the battery after not very many charge cycles.

    AFAIK, no one to date has produced a viable silicon anode battery.

    Now, unmentioned in the article are specifics like power to weight and power to volume of the cell. With all those nano fibers and structure, it is possible this cell is just a moderate improvement over what we have now.
     
  10. Cosmacelf

    Cosmacelf Active Member

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    The devil is in the details. I read the paper the news reports are based on (http://www.nature.com/srep/2015/150206/srep08246/pdf/srep08246.pdf). On page five, there is a chart:

    Capture.JPG

    It shows that to get 2-3 times the specific capacity of a graphite anode (372 mAhg-1), they had to charge/discharge at a C/10 rate. At a C/5 rate, the capacity got close to the graphite anode. Tesla's cells charge/discharge at around a maximum of 1C to 1.5C rate (when Supercharging or accelerating at high speed). They didn't test all the way up to a 1C rate, but the chart doesn't look promising.

    Bottom line, as formulated, this cell is useless for EVs.
     
  11. hobbes

    hobbes Active Member

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    Good research. Too often people (including myself) are too lazy to do the "paperwork" and jump to a conclusion... And also good they published their results for everyone to read.

     
  12. Electric700

    Electric700 Member

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    Thank you, I didn't see that report (at http://www.nature.com/srep/2015/1502.../srep08246.pdf). Perhaps in a future iteration they will be able to charge at 1.5 C while also maintaining the high overall energy storage capacity and longer life.
     
  13. DrGuest

    DrGuest Member

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    I just read this today.

    "The newest direction Tesla is headed toward is silicon—not the Valley, but the material that is changing the way batteries are made. Tesla’s new 90 kilowatt-hour battery pack—an upgrade announced Friday that increases pack energy by 5% and adds about 15 miles of range to its vehicles—might look the same. But the inclusion of silicon is an advance for lithium-ion technology.
    During a call with reporters last week, CEO Elon Musk said the company had improved the battery by shifting the cell chemistry for the pack to partially use silicon in the anode.
    “This is just sort of a baby step in the direction of using silicon in the anode,” Musk said during the call. “We’re still primarily using synthetic graphite, but over time we’ll be increasing silicon in the anode.”
    For the unfamiliar, this might sound like minor tinkering. It’s actually an important and challenging step for Tesla (and other battery manufacturers) that could lead to a better, cheaper battery."

    http://www.readability.com/m?url=http://fortune.com/2015/07/22/this-is-teslas-plan-for-a-cheaper-car/?xid=yahoo_fortune
     
  14. deonb

    deonb Active Member

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    Not quite.

    If I can choose between a battery that's e.g.

    * 90 kWh @ 1.5C

    vs. a split battery that should weigh the same:

    * 80 kWh @ 1.5 C
    * 30 kWh @ C/10


    I would prefer the latter.

    This gives you 90 miles of emergency low performance range in reserve (in exchange for 30 miles high performance range). Sure, it will be at very very low performance, but it will still be helpful to get you to a charger in a pinch.
     
  15. WarpedOne

    WarpedOne Supreme Premier

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    Trivia - average power draw in C of 85D is:

    280miles @65mph with 80kWh usable is 4.3 hours of driving and 18kW of average power draw.
    18kW for 85kWh means 0,21 C average load

    A hybrid pack would have to at least match this average C rating to be useful in a civil car i.e. offer same average capabilities.
    What mixture of 1.5C and 0.1C cells would result in average 0,21C capability?
    x*1.5 + (1-x)*0.1=0.21
    x= 7.85%
    A least 8% kWh must be in those 1.5C cells.

    If one tenth capacity is of 1.5C cells and nine tenth out of 0.1C cells, the pack will be able to discharge at 0,24C average (20kW in 85kWh pack).
    If 1kWh of 1.5C cells weighs the same as 3kWh of 0.1cells, a hybrid pack weighing the same as 90kWh battery would have 10kWh + 3*80kWh = 250kWh capacity and 60kW average discharge rate.

    Or go with half the weight: 10kWh + 3*40kWh = 125kWh at 400 pounds less total weight and
    Or go with a more reasonable option: 30kWh + 3*50kWh = 180kWh with 43 kW average power capability.

    I cannot say such a hybrid pack would not make sense if 0.1C cells at 1/3 the weight were real.

    BUT:
    Cells in tesla's pack are under much higher maximum loads: 480kW out of 85kWh pack is 5.6C load.
    In a lower cost car with maximum power draw of 240kW, half of the pack could be those 0.1C cells, the other half being current 5.6C capable cells and the car would still on average perform the same, except the range at same weight would double.

    BUT x 2:
    hybrid pack need not include 5.6C cell and 0.1C cells. The cells themselves WILL be hybridized. They will have high capacity and a bit lower C rate.
     
  16. deonb

    deonb Active Member

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    True. And it would need to meet some minimal peak as well. You can't go up a hill "on average". At some point the power will be too low to move the car.

    This doesn't mean 0.1 C (with 30kWh cells, this is 3kW) isn't useful for other things.

    You can run the air conditioner, some part of the heating coils & vampire drain on those cells. With the ~3 hours of driving range we have, that can add 9 kWh which you don't have to drain out of the main pack.

    And if you do get stuck, maybe you can't move the car, but it's still a useful backup - pull over, and click: "Charge main pack from emergency", and it can charge up... sure at 3kWh, but at least that still means after a couple of hours you can at least move the car 5 to 10 miles. Might just be enough to get you off the highway and to a charger or at least a 110V outlet.

    The other thing it can do is to augment a 110V slow charge and give you an extra 3 kWh. Which can turn an overnight 20 miles added to 50 miles added instead.

    All useful things.
     
  17. WarpedOne

    WarpedOne Supreme Premier

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    That's why it is a hybrid - there is some capacity that is capable of high power discharge and is being charged at 0.1C while not in use from the other low-power side of the pack. Remember MS85 is only capable of ~70kW of constant discharge, above this it overheats and limits power draw. 70kW is about 0.85 C constant discharge.

    A 1:3 mix of current 5.6C and 0.1C high density cells would be capable of 130kW max discharge and have 2,5 times the range at same weight.
    A 1:1 mix would be capable of 240kW max discharge and have 2 times the range.
    A 3:1 mix would have 360kW max power and have 50% higher range.

    But still... 90kWh pack is a hybrid, just not at pack level but at the chemistry level. Future pack will have higher capacity at same weight and same power.
    Using same chemistry, power would rise with capacity, but also would weight.

    Being a hybrid at the chemistry level this means it autobalances - highpower side discharges faster than lowerpower side and is then charged internaly from the lowerpower side. Sides being conceptual not physical things.
     
  18. brucet999

    brucet999 Active Member

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    For the benefit of non-engineers, what does a 1C rate mean? Is C/10 one tenth the rate of 1C?
     
  19. ItsNotAboutTheMoney

    ItsNotAboutTheMoney Active Member

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    C means fully charging or discharging in 1 hour.
     
  20. bwa

    bwa Member

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    There seems to be a lot of room for further developments in this area from the skimming I'm doing of all your secondhand reporting.

    But I'm posting a sort of humorous mental image: a new battery that expands downward toward the road as it charges and shrinks back upward as it discharges. When it's fully charged, the car would be closer to the road and act more like a lowered car. (Or, the suspension could raise the rest of the car to compensate.) All the battery parts would have to have their various moving parts and flex parts designed in. Not so solid-state any more.
     

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