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Question on Lithium battery

  1. May 5, 2009 #1

    Defennder

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    Hi guys,

    A friend of mine working as an EE asked me this question for which she had no answer to. She asked if lithium batteries counts as a thermal battery. I had no idea what "thermal battery" meant, so I found http://en.wikipedia.org/wiki/Molten_salt_battery" [Broken] on Wikipedia but I still couldn't find the answer to that question. Since she is currently ill at present, I'm posing this question on her behalf here. Thanks.

    EDIT: Here's what I understand from the Wikipedia article. It appears that thermal batteries all operate at high temperatures since the electrolyte has to be molten. From http://en.wikipedia.org/wiki/Lithium_battery" [Broken] page it appears that the max operating temperature of a consumer grade lithium battery is 60 degrees Celsius which is way below the required operating temperature of a molten salt cell. Is this understanding correct?

    But could there be other types of Lithium batteries which operate at much higher temperatures using molten salt as electrolyte?
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. May 5, 2009 #2
  4. May 6, 2009 #3
    Thermal batteries contain an electrochemical system that is inert until activated by application of heat. They may be stored on load or open circuit. The cell electrolyte used is a mixture of anhydrous salts which conduct current only when molten. A heat source, which can be ignited either by an electric match or a mechanical primer (percussion cap), is an integral part of a thermal battery. When the battery is ignited, this heat source develops sufficient heat energy to melt the electrolyte and thus permit the battery to deliver a considerable amount of electrical power.
    Activation times are rapid (as low as 0.3-2.5 s). The batteries have an open-circuit voltage of 2.3-3.0 v/cell. Voltage regulation is within 10% of nominal under constant resistive load. The battery operating range covers the interval 1-300 s. There are two principal types of high-temperature thermally activated battery; those based on calcium anodes and those based on lithium anodes. Within each of these types there are many possible configurations available.
    Quite large thermal batteries of lithium type are being produced; one lithium-iron sulphide battery produced by Mine Safety Appliances weighs 3.8 kg, consisting of 30 series cells housed in a container 89mm in diameter by 235 mm long. This battery shows smooth discharges and freedom from electrical disturbance for average current densities varying from 0.3 to 1.86A/cm3. To 80% of the peak voltage, durations range from 3 to 21 min. It is also noteworthy that the cell capacity is very constant at 275A minimum over this range of discharge rates, although there are indications of some reduction at the highest current density. To compare the performance with typical results obtained for the Ca/LiCl-KCI, CaCrO4/Fe system for this capacity of lithium-iron sulphide cell, the current density performance is at least 15 times better than with Ca/CaCrO4, for discharge densities of over 2-3 min, and analysis of the discharge curves also shows that the energy density achieved by the cell (including pyrotechnic) is 113 W h/kg, with 63 W h/kg for the battery. The volumetric energy density of the battery is 113 W h/dm3.
    A further battery design gives a duration of 7min, a short activation time and a low internal resistance for good voltage regulation for a wide range of current drains. It uses two parallel stacks of 75 mm nominal diameter cells, housed in a container 89mm in diameter and 190mm long. The battery weight is 2.9kg. At an average discharge current of 20A (0.23A/cm2 electrode current density), 8min discharge duration is obtained to 80% of the maximum voltage for both conditioning temperatures. The battery internal resistance remains constant for the discharge duration to 80% of mean voltage, with a value of 0.09-0.1 1 ohm. The batteries tested after initial conditioning at +50°C activate in approximately 1.6 s giving 12.8A at 25.5V, and those conditioned at -30°C in approximately 3.0s. The battery design uses anodes with excess coulombic capacity (380 A minimum) and considerable improvement in activation time is possible if these are matched to the rated cathode capacity of 200 A minimum.
    Various other battery designs to meet particular requirements are available from Mine Safety Appliances, who claim that these batteries have a wide range of possible military uses. Designs optimized for maximum energy can achieve energy densities up to 100Wh/kg and power densities of up to 1500Wh/kg.



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  5. May 7, 2009 #4

    Defennder

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    Hi waht, I've already linked that article in my initial post.

    msj, from that text you copied and pasted I understand it's possible for thermal battery to be lithium cells. Maybe I should ask my friend what kind of lithium batteries she's referring to.
     
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