Reply to polymer battery questions from yahoo
Hello all,
I posted on yahoo to 'MKT_entropy' about the battery chemistry. He took apart my post as follows. Let's have at it, and see what jives or not. I have some feedback of my own, but have to hold off for now.
Happy hunting, all!
Rich
PS Paul, where are you? Have you any take on this?
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polymer battery issues
by: MKT_entropy (40s/M/North East)
9014 of 9015
I'll post what I know, quoting the original message for clarity.
Of course, I don't know everything...
[... The bi-cell sandwich has a cathode w/ electrolyte containing lithium ions, which are shuttled between the two
anodes that 'sandwich' the cathode. ...]
The sandwitch can be made either way, anodes or cathodes outside.
[...It appears this electrolyte is gel-like, but I'm not sure...]
This is true fro all so-called polymer Li or Li-ion batteries of any practical significance. The differences are in the
material used to prepare the Jell-O and in how it is prepared.
[... They showed them 'injecting' it into the cathode with syringe-like devices...]
Which means that it is the cathode that had to be outside.
[... I'd also read that the Bellcore patent used some microscopic honeycomb-like structure to contain the gel, but
again this could be wrong...]
I guess any swollen polymer can be described that way, especially if it is phase-separated on a microscopic scale
(tens or hundreds of angstroms)
[... The anode materials, and how well they accept and release the lithium ions, are a key component. The lithium
ions are shuttled back and forth between the two anodes,
not the two anodes, but between an anode and a cathode, or, less ambiguously, between the positive (Mn, Co,
Ni, V oxide) and negative (Li, Li-Al, coke, graphite,...) electrode.
[...hence the name 'rocking chair battery'
(there's an old link to an article describing this; anyone have it handy?). Two materials which apparently work well
are cobalt and manganese. Valence uses manganese dioxide. Lev mentioned that the cobalt implementation
'contains twice the lithium it needs,' while their manganese formulation only has exactly the amount of lithium it
needs...]
Right. But pulling more Li from LiCoO2 (lithium cobaltate) than about 50-60 % of the available stuff results in the
permanent damage to the material (doesn't cycle well) and may lead to plating of Li on the negative electrode,
since there is not enough carbon there to intercalate it completely within the carbon structure.
to be contd...
M_e
Posted: Feb 9 1999 7:03PM EST as a reply to: Msg 9002 by rkwolf
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M_e, part 2
by: MKT_entropy (40s/M/North East)
9015 of 9015
[... Valence does have a public patent using vanadium in the anode, and possibly other patents are pending...]
Cathode. As have tens of other organizations over the past 20 years. Jusdt check the USPTO patent database.
[... The head of R&D, Joe Lundquist, spoke first, and he said their research is focusing on needs for higher energy
density. He said the customers were satisfied with their improvements in the area of the number of recharge cycles.
To attain higher energy density, he said they would be working to develop new cathodes.
This tells me it might involve moving away from the Bellcore patent...]
If I understand the issue correctly (you can read all these patents, and I did), the Bellcore technology is not limited
to Mn spinel; it deals with a way to put a working cell together independent of the particular composition.
[... Regarding Valence patent protection in the manganese polymer arena, Lev indicated that the Japanese were
likely sticking with cobalt so as to 'work around' the Valence patents. Also, their safety regulations are not as strict
as in the US, so they can sell the product there more easily...]
This is false, totally false. Often just the reverse (where Li hexafluoroarsenate based electrolytes were forbidden
first?)
[... ULBI has some form of manganese, but their process didn't work right when scaled up to their production
machinery (they were relying on outside vendors for the laminate, like valence had been doing initially, he said)...]
Might be true; I don't know.
[... The only other potential competitor using manganese would be Moli Energy, he thought. Everyone else was
using cobalt oxide.
And yes, Lev made clear that the problem was in using the cobalt formulation for the bigger batteries. The reason
was that they require more stringent temperature regulation. They can be dangerous when they are overheated or
overcharged (he said they had no overcharging problem with their cells, making the charging
circuitry simpler), something about the lithium plating onto the anode, and how it can explode. He mentioned that
he knew the problems well, because in their joint venture with Alliant, they also make cobalt-based batteries for
the government (which has less stringent safety requirements)....]
All true by my reckoning.
[... Conversely, Lev stated that they tested their manganese batteries at three temperature ranges: 25 degC, 45
degC, and 60 degC. He said that 45 deg the battery may lose up to 3-5% and at 60 deg up to 7-8% of its storage
capacity. He said customers were very pleased with this, as it was comparable to what the liquid electrolyte
batteries get, but without the safety problems...]
Sounds very reasonable to me.
Hope it helps,
M_e
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