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Perfect battery

  1. May 17, 2006 #1
    What materials for positive pole, negative pole and what acid when put together create a perfect battery?
    (I'm not talking about everyday purpose for a batery (so never-mind how bio-hazardous a material is), but a theoretical (greatest voltage, greatest current possible, yet stable enough (so it's chemical reaction doesn't cause immediate explosion (a perfect battery - what else to say))))
     
  2. jcsd
  3. May 17, 2006 #2

    chroot

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    There is no such thing as a "perfect battery." There are, in fact, dozens of different trade-offs, and many people have spent many decades trying to make batteries better. Currently, lithium-ion batteries are generally considered the "best battery" on the market.

    I hardly see how a biohazardous battery that presents an enormous explosion hazard could possibly be considered "perfect," but maybe that's just me.

    http://en.wikipedia.org/wiki/Lithium_ion

    - Warren
     
  4. May 18, 2006 #3
    Well, confining within the laws of science, it cannot be perfect. But, you can try to find the greatest voltage possible out of a stable battery. As chroot said, lithium-ion batteries are the best, but you may be able to go higher than that.
     
  5. May 18, 2006 #4
    Interesting.
    (I was just thinking - different acids used in a battery surrely give different results in electric current, and different elements (metals) have different electric potential properties - I thought - maybe there are some better pairs of metals but they are not used because they are... well... really too nasty; is this the case? (that was a main question))
     
  6. May 18, 2006 #5

    mrjeffy321

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    If you look at a table of standard reduction potentials,
    http://www.csudh.edu/oliver/chemdata/data-e.htm
    You can see that if you use element which are on the extremes (good oxidizers / good reducers), then you will have a much higher output voltage from a batter than metals which are closer together.

    For example, a common, homemade, battery involves using Copper and Zinc metal. Looking at the above table, we can see that (ideally) would could get a voltage of 1.1 volts.
    If, instead, we used Flourine and Magnesium as the electrodes in the cell, we could get a potential of 8.61 volts. On that table, Lithium metal is not shown, however, it has an even lower standard reduction potential than Mg.
    However, when you start getting into reaction like those between Lithium and Flourine, they start getting explosive (think of Na + Cl, except even more violent).
     
  7. May 19, 2006 #6
    I've found some other table that shows Lithium:
    http://www.uwsp.edu/chemistry/tzamis/stdreductionpots.gif
    Are there shown ALL the elements that can make-up a battery?
    What voltage could you get from Li-F combination?
    Surely there must be a way to make even the most energetic battery stable so it doesn't react violently, so it could have a practical use...
     
  8. May 19, 2006 #7

    mrjeffy321

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    The formula to find the electric potential (voltage) from a galvanic cell is,

    E_Standard_cell = E_standard_oxidation - E_standard_reduction

    Oxidation takes place at the anode, Reduction takes place at the cathode.

    The standard electric potential of a cell equals the standard reduction potential of the substance being recuced minus the reductio potenial of the substance being oxidized.

    When the cell is not at standard conditions (which is in most cases), the cell potential is,
    E_cell = E_standard_cell - (RT/n*F)*ln([reduction] / [Oxidation])
    where R is the gas rate constant, T is the temperature, n is the number of moles of electrons in the reaction, F is the Faraday constant, [reduction] and [Oxidation] are the molar concentrations of the ions of the substance being reduced and oxidized.
    This is known as the Nernst Equation.
     
  9. May 20, 2006 #8
    Nice.

    (and some more letters to fullfill the "10 letters for posting" quota)
     
  10. May 20, 2006 #9

    mrjeffy321

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    Let me correct myself,

    Although I said it correctly on words, the formula I gave you is reversed.

    The standard electrode potenial of a cell should be,
    E_Standard_cell = E_standard_reduction - E_standard_oxidation

    The reduction potential of the cathode minus the reduction potential of the anode.
     
  11. May 29, 2006 #10
    Thanks.

    (and some more letters to fill-in the 10 letters or more per post quota)
    :smile:
     
  12. May 29, 2006 #11

    Gokul43201

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    The way to do that is to forcibly slow down the reaction/transport rate, and hence reduce the current. In terms of electronics, this means that your battery comes with a large internal resistance - hardly making it ideal.
     
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