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| Author |
Message |
drew
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Aluminum-Air Batteries
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Jul 14 21:17 UTC 1999 |
What is the chemistry of an aluminum-air battery? What electrolyte
is used? How is it physically constructed? How does one get air to
be an "electrode"? And, can it be recharged, like lead-acid cells,
by supplying current when partially or heavily discharged, rather than
by replacing the aluminum core? How quickly can they be charged?
http://members.accessus.net/~voltek/ mentions them briefly but
doesn't seem to have any specifics, except that a byproduct of the
reaction is Al(OH)3.
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| 3 responses total. |
russ
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response 1 of 3:
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Jul 15 00:42 UTC 1999 |
1.) Al + 3 OH- -> Al(OH)3 + 3e-, 2 H2O + O2 + 4e- -> 4OH-
2.) Generally aqueous. More I can't tell you.
3.) Widely varied. There was at least one automotive version
where the aluminum electrode was composed of aluminum filings
on a graphite backing; the metal was carried onto the graphite
by a stream of electrolyte, making it rechargeable almost instantly.
4.) No. Aluminum has a stronger affinity for oxygen than hydrogen
does; you will dissociate water before you can regenerate
aluminum metal. To regenerate metallic Al, you need different
chemistry (and generally a molten salt bath).
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russ
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response 2 of 3:
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Jul 16 01:59 UTC 1999 |
Oh, as for how one gets air to an electrode:
Generally, you have some kind of catalyst-coated conductor, and you
apply air to it. In the case of the automotive battery I read about,
ISTR they used platinum-coated graphite and ran air through or past
the graphite.
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rcurl
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response 3 of 3:
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Jul 21 21:06 UTC 1999 |
I don't know about an aluminum-air battery, but the zinc-air battery
uses a powdered zinc slurry in 30% KOH. The "anode" is the zinc in the
slurry, but a metal 'can' is used to act as the anode terminal. The
cathode terminal is a steel 'can' with a membrane through which oxygen
can diffuse, and the cathode space is a thin (0.5 mm) space filled with
30% KOH solution, and separated from the anode space by another porous
membrane. The byproduct of the reaction is potassium zincate.
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