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Portables Power Hardware

Nanowires Boost Laptop Battery Life to 20 Hours 238

brianmed writes to tell us that Stanford researchers have created a new use for silicon nanowires that promise to reinvent lithium-ion batteries. "The new version, developed through research led by Yi Cui, assistant professor of materials science and engineering, produces 10 times the amount of electricity of existing lithium-ion, known as Li-ion, batteries. A laptop that now runs on battery for two hours could operate for 20 hours, a boon to ocean-hopping business travelers. [...] The lithium is stored in a forest of tiny silicon nanowires, each with a diameter one-thousandth the thickness of a sheet of paper. The nanowires inflate four times their normal size as they soak up lithium. But, unlike other silicon shapes, they do not fracture."
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Nanowires Boost Laptop Battery Life to 20 Hours

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  • by TopSpin ( 753 ) * on Wednesday December 19, 2007 @01:39PM (#21753482) Journal
    A short but more technical story found here [].

  • Re:Promising (Score:5, Informative)

    by TheRaven64 ( 641858 ) on Wednesday December 19, 2007 @01:51PM (#21753658) Journal
    It's not exactly a memory effect, but LiIon batteries do degrade over time. Unlike NiCd cells, their life is best preserved by keeping them about around 50% charge. You get a lot of people complaining that their batteries wear out quickly because they still think the things they learned about NiCd cells apply, so they fully discharge and recharge their LiIon cells, which is the absolute worst case for them.
  • Wrong. (Score:4, Informative)

    by TheMeuge ( 645043 ) on Wednesday December 19, 2007 @01:52PM (#21753666)

    obviously, you're unaware of the natural leakage of rechargeable batteries. even in the "off" position, most rechargeable batteries will discharge in a matter of weeks on the upper end.

    That's highly incorrect. Lithium ion batteries have a self-discharge rate of about 5% per month. However, while the battery is connected to a power supply, some energy is always consumed, just like the way desktop PSUs consume power when the computer is off, but when the PSU cutoff switch is not switched off. That's why laptops will not stay charged for months when unused. Take the battery OUT of the laptop, and you will be able to power it on a year after you turn it off.

    Low-self-discharge (LSD) NiMH cells (such as Sanyo Eneloop) have discharge rates that are even lower... up to as little as 20% per year.
  • Re:Promising (Score:3, Informative)

    by ChronoReverse ( 858838 ) on Wednesday December 19, 2007 @02:01PM (#21753818)
    That's not memory, that's battery aging. Li-Ion batteries, instead of having memory, simply age and lost capacity over time. If your battery is warm and at anything significantly above or below ~60%, then it loses capacity at a much higher rate.
  • Re:patent (Score:5, Informative)

    by Dahamma ( 304068 ) on Wednesday December 19, 2007 @02:06PM (#21753882)
    Universities have patent licensing programs for this, and often support their facultry or students in founding companies based on their research.

    I'm sure Stanford has made a killing by licensing to or investing in companies. Here's a list of their startup investments - not necessarily patent related, but I'm sure many were founded by Stanford professors or alumni with patents licensed back from the university... []

    They probably made over a billion on Google alone...
  • by Animats ( 122034 ) on Wednesday December 19, 2007 @02:09PM (#21753902) Homepage

    Because of the Bayh-Dole Act [], which commercialized federally-funded research.

  • by Anonymous Coward on Wednesday December 19, 2007 @02:09PM (#21753912)

    With clever engineering it should be possible to make a laptop exclusively used in low power mode solar powered if it's normally left out when not in use.

    You mean like this one? []
  • Re:Promising (Score:3, Informative)

    by Rei ( 128717 ) on Wednesday December 19, 2007 @02:35PM (#21754270) Homepage
    If I could spend 2 grand and break even in a year,

    Wow, you have no familiarity with the concept of long-term investments do you? No, solar isn't an economical investment in most places. But if you expect your investments to return your expenditures in one year, I'd hate to see what your retirement plan looks like.

    For anyone interested in seeing how the economics of solar power works out where they live, check out this handy-dandy photovoltaics economics calculator [].
  • by Hal_Porter ( 817932 ) on Wednesday December 19, 2007 @02:41PM (#21754344)

    How does the power density of these compare to gasoline?
    Lousy []

    Material Volumetric(Wh/l)Gravimetric (Wh/kg)

    Fission of U-235 4.7 x 1012 2.5 x1010
    Boron 38,278 16361
    JP10 (dicyclopentadiene)10,975 11,694
    Diesel 10,942 13,762
    Gasoline 9,700 12,200
    Black Coal solid =>CO2 9444 6667
    LNG 7,216 12,100
    Propane (liquid) 7,500 - 6,600 13,900
    Black Coal Bulk =>CO2 6278 6667
    Ethanol 6,100 7,850
    Methanol 4,600 6,400
    Liquid H2 2,600 39,000
    Secondary LiOn Polymer 300 130 - 1200
    Secondary Lithium-Ion 300 110
    Nickel Metal Hydride 100 Wh/l 60Wh/kg
    Lead Acid Battery 40 25
    Propane (Gas - 1 bar) 28.1 13,900
    Compressed Air 17 34
    Ice to water 9.3 9.3

    If this new battery is 10x as efficient it is still 3x worse than gasoline.
  • Re:Promising (Score:3, Informative)

    by TooMuchToDo ( 882796 ) on Wednesday December 19, 2007 @02:51PM (#21754452)
    Li-Ion batteries degrade over time no matter what, no matter how charged you keep them. Their shelf life begins when they're manufactured and starts to degrade every calendar month.
  • Re:Recharge Cycles (Score:3, Informative)

    by Androclese ( 627848 ) on Wednesday December 19, 2007 @02:57PM (#21754546)
    From an article listed below this post, it talks about only having done 10 cycles so far. Borrowed Link [] So there is still work to do, but the science is promising.
  • Re:patent (Score:3, Informative)

    by xebra ( 140155 ) on Wednesday December 19, 2007 @02:59PM (#21754558)
    Obviously you never read any of your employment contracts :). I have a relative with a number of patents for steps used to refine petroleum. Obviously he's not a billionaire just because the technologies in his patents are used during the processing of a quarter billion gallons of oil each day!

    "The Employee hereby assigns and transfers to the Company without further consideration his entire right, title and interest in and to all Inventions developed while in the employ of the Company."

    Sign on the dotted line or you're not hired! The article mentions the professor may start a company to exploit his discovery. To do so, he will have to license the technology from Stanford, even though the patent is in his name!
  • by Hal_Porter ( 817932 ) on Wednesday December 19, 2007 @03:42PM (#21755094)
    Antimatter would be e=2mc^2. E.g. 1 kilo of antimatter would combine with 1 kilo of air (or some other matter)

    Dividing by 3600J gives 5 * 10^13 Wh/kilogram*+(c%5E2)%2F++3%2C600&btnG=Search []
  • by Rei ( 128717 ) on Wednesday December 19, 2007 @04:01PM (#21755382) Homepage
    . If you use your figure of 900MJ, and charging is 90% efficient

    There's your problem right there. Li-ion batteries have a charge efficiency of around 99.9% []; you're two orders of magnitude off. Even if you go off by an order of magnitude and say 99% efficient, assuming a specific heat of 1J/g*C, with 7.2MJ/kg, that's only a 72 degree rise in temperature over 5 minutes or so (240W of heat), which a cooling system could easily manage (your computer case fan probably dissipates more heat than that). With the actual 99.9% efficiency, it's a 7.2 degree rise in temperature and 24W of heat, respectively.

    The other issue is that we (US) have nowhere near the generation capacity to handle a nation full of electric cars.

    Another widespread false concern. The fact is that the US has significant surplus generation capacity at night, more than enough to begin the transition (it's not like everyone collectively throws out their vehicles and switches at once). Furthermore, it's much *cheaper* to build new electricity production infrastructure than it is to produce gasoline production infrastructure. And, for gasoline-powered cars, you have to keep producing new gasoline-production infrastructure even when gasoline demand remains constant since oil fields run dry. You're just replacing one type of infrastructure demand with another -- one that's easier to meet to boot.
  • Re:On that note... (Score:3, Informative)

    by Agripa ( 139780 ) on Wednesday December 19, 2007 @11:45PM (#21760752)
    There are a number of lithium based chemistries which can be used to provide 1.5 volts in either primary or secondary applications. Energizer primary 1.5 volt lithium cells use lithium iron disulfide. They have a little more then twice the energy density of alkaline in high current applications and no advantage at low currents.

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