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Thread: Batteries and electrolytes

  1. #1 Batteries and electrolytes 
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    Some batteries, for example sodium-sulfur use solid (ceramic) electrolyte. There were some reports that glasses or polymers could be used as an electrolytes. But how exactly does it work? Shouldn't anode material dissolve in electrolyte during discharge and shouldn't cathode material dissolve during charging? Does sodium dissolve in ceramic? Or sodium sulfide?


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    Ion conductivity.
    Fast ion conductor - Wikipedia, the free encyclopedia


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  4. #3  
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    Probably you didn't understand my question. I've thought that electrolyte should be not only conductive, but also have ability do dissolve anode and cathode material within itself.
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  5. #4  
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    Quote Originally Posted by Stanley514 View Post
    Probably you didn't understand my question. I've thought that electrolyte should be not only conductive, but also have ability do dissolve anode and cathode material within itself.
    OH. Right you are!
    No it is not really a requirement that the anodes or cathodes dissolve into the electrolyte, but I do see where you are coming from now. Lead-acid and carbon-zinc batteries do that.

    So what happens if the chemicals you use for the anode and cathode are liquids or gases and the reactions are on the surface of a solid electrolyte instead of on the surface of a solid cathode?
    Last edited by dan hunter; July 30th, 2014 at 02:47 PM.
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    So what happens if the chemicals you use for the anode and cathode are liquids or gases and the reactions are on the surface of a solid electrolyte instead of on the surface of a solid cathode?
    I didn't know that Sodium sulfide which forms on cathode of sodium-sulfur battery always stays liquid. Its melting point (anhydrous) is 1176 C. Also there are attempts to create sodium-sulfur batteries as well as Lithium-air batteries (with solid electrolyte) which work at room temperature. Lithium at room temperature suppose to be solid?

    AbstractSolid-state lithium–air cells using lithium anode, a polymer electrolyte, Li1+x+yAlx(Ti, Ge)2−xSiyP3−yO12 inorganic solid electrolyte, and an air electrode composed of carbon nanotubes and an inorganic solid electrolyte are constructed and their electrochemical properties investigated. The cells show a reversible capacity of about 400 mA h g−1 during the first few cycles. The rate performance and impedance measurements are also examined. The large cell resistance, which mainly comes from the interfacial resistance between Li and the polymer electrolyte, limits the rate performance. The results indicate that such all-solid-state lithium–air batteries without polymer electrolytes have good potential for development.
    Electrochemical Performance of Solid-State Lithium–Air Batteries Using Carbon Nanotube Catalyst in the Air Electrode - Kitaura - 2012 - Advanced Energy Materials - Wiley Online Library

    They mention high resistance, but still it works...
    I thought that in order to make ions of some substances to be conducted through an electrolyte you have to broke atomic bonds of this substance. Even liquids suppose to have some atomic bonds, though weaker than solids.
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  7. #6  
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    Quote Originally Posted by Stanley514 View Post
    I thought that in order to make ions of some substances to be conducted through an electrolyte you have to broke atomic bonds of this substance. Even liquids suppose to have some atomic bonds, though weaker than solids.
    Ion migration is simply a function of field strength vs bond strength.
    Ions migrate in solid state semiconductors leading to degradation and failure.
    This is the reason for MTBF ratings.
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    Ion migration is simply a function of field strength vs bond strength.
    In order to obtain free ions you need to break crystalline structure of a metal or ceramics.
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  9. #8  
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    Quote Originally Posted by Stanley514 View Post
    In order to obtain free ions you need to break crystalline structure of a metal or ceramics.
    Where do you get that from?

    Anyway, here is something related to your statement. Note that the material is still a solid even when it is conductive to ions.
    Ionic conductivity (solid state) - Wikipedia, the free encyclopedia

    also:
    http://www.nuigalway.ie/chemistry/do...ecture5lfj.pdf
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  10. #9  
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    Where do you get that from?

    Anyway, here is something related to your statement. Note that the material is still a solid even when it is conductive to ions.
    Ionic conductivity (solid state) - Wikipedia, the free encyclopedia

    also:
    http://www.nuigalway.ie/chemistry/do...ecture5lfj.pdf
    Solid ion conductors conduct ions, but you still need to have relatively free (or solved) ions outside of such conductor in order to conduct them through. Its like metals conduct electrons but you still need to have relatively free electrons outside of metal conductor to conduct them through.
    Why, do you think in this case hydrogen fuel cells require platinum catalyst? If you can conduct hydrogen protons through a proton conductor without any obstacles, why to bother with platinum?
    Last edited by Stanley514; September 24th, 2014 at 01:40 PM.
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  11. #10  
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    This is a very timely thread. I have been trying to educate myself on solid electrolyte batteries so we can better evaluate some new li-ion chemistries.
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