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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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  • Promising (Score:3, Interesting)

    by jimbo3123 ( 320148 ) on Wednesday December 19, 2007 @01:22PM (#21753222) Homepage
    The article makes this sound very promising.

    It may very well be the leap that keeps battery technology ahead of ultra-capacitors for the foreseeable future.
  • Re:Promising (Score:4, Interesting)

    by explosivejared ( 1186049 ) <hagan@jared.gmail@com> on Wednesday December 19, 2007 @01:31PM (#21753356)
    I'll say it sounds promising. A major hindrance to using alternative energy (eg solar), which is what most want to move to, to produce electricity is storing the power. The sun and wind, among other things, can't exactly be controlled manually to produce power on a whim. Inefficient storing is a major drawback. Any advance that improves storage capacity (for any platform) by an order of magnitude is promising to say the least. The article barely touched on how important this could be.
  • by GospelHead821 ( 466923 ) on Wednesday December 19, 2007 @01:33PM (#21753376)
    It's sort of funny that you should say that. I work for a company that manufactures some battery-powered instruments. We actually have to ship the batteries separately from the instruments because they classify as a more hazardous material than the rest of the shipment.
  • by Stormcrow309 ( 590240 ) on Wednesday December 19, 2007 @01:56PM (#21753734) Journal

    Actually with some thought, a human can count to over 2 million on their hands. Ever considered about rotating your hand by 180 degrees as part of your numbering system? It is commonly done in american sign language to count to 100 on one hand. Using three positions per hand, you can count to over 1.2 times 10 to the 27th power. Of course, trying to remember hand positions in such a system would likely be difficult.

  • by BoRegardless ( 721219 ) on Wednesday December 19, 2007 @01:57PM (#21753738)
    As a guess based on my experience, the actual implementation of a design, with prototyping, testing for failure modes, integral monitoring, sensors and such, I will bet that another 1-2 dozen patents will be filed and $10s of millions will be spent getting or trying to get the "pre-production" version over a 3-5 year time frame. If they leverage by working with an existing battery manufacturer, maybe they get it to 2-3 years.

    Given that the initial results suggest an energy density increase of an order of magnitude, I suspect VCs are already crawling into Palo Alto & up to Standford.

    What happens between the "experiment" where a 10/1 advantage is produced, to the final produceable & safe product, it is not uncommon to see 10/1 advantages slip to 5/1.

    Other notes in this thread have joked at 10 times the explosive power, which battery manufacturers have worked out in existing batteries, but this one will offer BIGGER challenges. I wouldn't know how to calculate the "explosive power" of the end design if safeties failed, but this will be critical.

    Any serious damage which might cause a catastrophic short would cause some companies to NOT accept these batteries, like airlines for instance. My pure guess is that physical damage, in say an automobile accident, or similar "mashing", will make the design of safety features be what takes the most time and effort.
  • by Total_Wimp ( 564548 ) on Wednesday December 19, 2007 @02:48PM (#21754426)
    I doubt you'll have to worry about this for awhile. While everyone is looking at this as longer battery life, the more probable initial use will be to make smaller, lighter batteries with the same, or just a little more, power as you're currently used to.

    This is going to be expensive in the beginning. Companies will be looking for a way to leverage the new tech without the battery becoming more expensive than all the other parts combined. But they might still have an advantage without breaking the bank too badly if they can offer smaller notebooks.

    But what about your cell phone? Surely they'll want to give you 20 hours of talk time? Same thing here. Size is a really big deal in handheld devices. You can bet Apple will have more interest in making iphones 1/8 of an inch thinner than giving you a product you could use for a week straight without recharging. Of course, cost is likely to be a factor here as well.

    Then there's you folks. If the cost were exactly the same, and you had to choose between long life and better portability, how would you choose? Laptop makers very often offer extended life batteries that happen to be kind of bulky. Sometimes they offer batteries that aren't bulky, but they take up your optical drive. I've seen a couple of people use these, but only a couple. Same thing with cell phones. Most cell phones let you swap batteries to your heart's content, but most people just don't buy spare batteries, and even fewer buy the bulky extended life batteries.

    As much as they bitch about battery life, I think the truth is that what most people have is kind of ok with them most of the time. Sure, you might need better life, and I'm sure you'll be able to get it, much like you can get it now, but I think laptop manufacturers are going to tend to serve the masses for most of their products.

    "But wait!" you say, "the whole idea is that you can have more power plus a smaller size." Well, not really. When this tech becomes available, the comparison won't be with lithium whatever batteries. The comparison will be with devices that have the new tech, but less of it. All of a sudden a battery the size of your current laptop battery will look like a huge, heavy beasts compared to the new ones. You'll gladly have only 5 hours of battery life instead of carrying around something so _heavy_(how did you ever manage it?).
  • by Rei ( 128717 ) on Wednesday December 19, 2007 @02:54PM (#21754488) Homepage
    Well, let's go with 200 Wh/kg for conventional li-ion batteries. Thios would be 2000 Wh/kg, i.e., 7.2 MJ/kg. Gasoline has an energy density of about 45 MJ/kg.

    Of course, you're comparing the energy density of the stored electricity, not of the chemical energy of the battery as a whole, which isn't really fair.

    Anyways, let's look at vehicle range. The gasoline has 6.25 times the energy density, but only burns at 25-30% efficiency in the engine. The charge/discharge of lithium-ion batteries is almost lossless. The motor would be 85-90% efficient. Looks like, kilogram per kilogram, gasoline gets twice the range. On the other hand, there are other practical considerations -- namely, the fact that electric motors are much smaller and lighter than an internal combustion engine. I wouldn't be surprised if you could shave a hundred, hundred fifty kilograms off the engine/motor mass by switching from ICE to electric. If you filled this remaining space with batteries, that'd be ~900MJ, the equivalent of 20 gallons of gasoline, extra for the electric vehicle. Factor in a 12 gallon gas tank that's being replaced by electric (that's what my Saturn has, so that's the number I'm using), that's the equivalent of 26 gallons of range for the electric and 12 gallons of range for the gasoline vehicle. The electric goes over twice as far. But it gets even better, as you'll only get your optimum 25-30% gasoline efficiency at the optimal RPM; they perform poorly at low speeds, for example. Electrics perform well over a wide range. Then you need to factor in that the electric has all of the benefits of hybrid vehicles already there -- regenerative braking, no waste at stop lights, and so forth. All in all, I'd expect around three times more range with an electric using batteries like these than you get in a gasoline vehicle. And to top it all off, given that they're using nanowires, the surface are will be incredible, so the charge time should be very fast -- just a few minutes.

    If this is legit, and if there aren't any degradation or safety problems that sneak up on them, when it comes out, gasoline vehicles can be expected to go "extinct" quite quickly. Who *wouldn't* want to be able to drive a thousand, perhaps even two thousand miles on a single charge, at a price of 1-2 cents per mile?
  • by _Quinn ( 44979 ) on Wednesday December 19, 2007 @03:43PM (#21755100)
    The big win is that we can more readily regulate emissions from stationary power plants (of higher efficiency that an IC engine), and weight is not a concern for the scrubbers and filters. Further along in the future, changing the problem from synthesizing gasoline to generating electricity more cleanly is an even bigger win.
  • by Hal_Porter ( 817932 ) on Wednesday December 19, 2007 @03:52PM (#21755260)
    Hmm, fair point.

    I got 20% efficiency for 4 stroke gasoline engines [wikipedia.org], vs 85% for brushless DC electric motors. [wikipedia.org]

    Actually there's an article here that quotes the density of the new battery as 3000Wh/kg. [sciencedirect.com]. 12200 as an energy density for old Lithium Ion batteries is completely bogus by the way.

    12,200*0.2 = 2440
    3000*0.85 = 2550

    Not as good as you said since the battery still has 4x worse energy density but you're right that engine efficiency makes up for it.
  • by Rei ( 128717 ) on Wednesday December 19, 2007 @04:45PM (#21756060) Homepage
    Indeed. The standard is that cars in homes either charge "slowly" (a relative term) or purchase a "home charger" that is itself charged slowly but discharges quickly into the vehicle. Such a home charger can also provide backup power to the house and even do load balancing for the grid (which would probably get you a discount on your electric bill). "Gas" stations that end up as charging stations won't have this problem, as they'll almost certainly just get fatter wires installed.
  • Re:On that note... (Score:3, Interesting)

    by jayteedee ( 211241 ) on Wednesday December 19, 2007 @05:50PM (#21757080)
    The cell voltages for NiCd, NiMh, and Alkaline are APPROXIMATELY 1.2, 1.2, 1.5 volts respectively. The cell voltage for Li is about 3 volts, so AAA, AA, C, and D's are out of the question without a DC/DC converter or voltage regulator on the battery to limit the voltage to about 1.6 volts or less. They could make a 9V battery, but they are going the way of the Dodo. Even C's and D's are dying. Some of the newer rechargeable C and D cells are actually AA battery inside a C or D casing (check out the capacities some time at your local favorite store, and check the weight of the package). They still do make full C and D rechargeable cells, but they are not as readily available in box stores.

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