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Bob Blick <bobblick@ftml.net> writes:
> http://www.nature.com/nmat/journal/vaop/ncurrent/full/nmat3623.html
>
> Only excerpt and first few diagrams available without subscription, but
> there's enough to see what they are getting at. I think it's only for
> LiFePO4 batteries (3.2V) as opposed to the 4.2V ones in cellphones and
> computers.

That looked interesting! I used my magic powers as a student at a
university to get hold of a full-text copy and thought you might be
interested in some of the details.

 - They look at LiFePO4 and Li4Ti5O12.

   They say that the reason for using these rather than Li(Ni, Co, Al)O2
   (my god, this is horrible to type) or others is that the first two
   are "safe and inexpensive". It looks like they're interested in
   automotive applications (where memory effects would be pretty
   important, I suppose)

 - They claim that you can see a memory effect in a single C/2
   discharge-charge with LiFePO4

   Playing around with Engauge digitizer, I reckon the bump you can see
   is about 4mV (from about 3.47V to 3.474V). However, they say that
   even this small memory effect can significantly throw off a state of
   charge calculation be relevant due to the flatness of LiFePO4's
   discharge curve.

 - A constant-current discharge down to 2.4V didn't erase the memory
   effect, but a subsequent full charge did.

 - The effect is more pronounced with higher discharge rates

 - They don't see any effect with the titanium-based one.

 - The final three pages of text are a model of the two chemical
   reactions that they believe explains the result (and I didn't read
   them carefully)


Thanks for the pointer: I learned something this evening!


Rupert

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