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What makes Li Ion age ?

What determines the lifetime (decrease in capacity) of a Li Ion accumulator ?

To my current investigation this is determined by the charge / discharge cycles.

So the function for "age" should be:

age = ac current amplitude * time

This would mean when the accumulator is used where the dc current is zero, but the ac current amplitude is high (rectagular 1C pp for example, frequency >1Hz), the user can not determine "charging" or "discharging", but the accumulator should age quite quickly (300 effective charge cycles in 25 days ). Obviously the Li Ion should not be fully charged in this example, so I assume it stays at .5C charge.

Is this assumption correct ? Does it depend on ac current frequency ? Is there a model to determine the "age" of a Li Ion accumulator ? Is there some further information concerning this ?

Raymund Hofmann

Reply to
Raymund Hofmann
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On Sat, 11 Jun 2005 16:24:19 +0200, "Raymund Hofmann" wroth:

It could be easily tested.

That could be part of the test also. My guess is that high frequency AC currents could be passed through the cell's intrinsic capacitance without having any direct effect on its internal chemistry.

As far as I can determine, the age or lifespan is determined from tests.

I have seen detailed information concerning the chemistry involved with charging and discharging LiIon cells but not any good explanation for aging such as I have seen for NiCad and lead acid cells.

Jim

Reply to
James Meyer

On Sat, 11 Jun 2005 07:24:19 -0700, Raymund Hofmann wrote (in article ):

Cross-posting to sci.chem.electrochem.battery

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Please, no "Go Google this" replies. I wouldn\'t 
ask a question here if I hadn\'t done that already. 

DaveC
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Reply to
DaveC

Not so much usage. More the oxidation of the cells that increase internal resistance. To minimize the effect keep the cell's cool and not full (40% ideal).

So if you own a laptop and mostly use it on mains power, then I guess you could put you battery pack in the fridge when not used. Lift span may double.

More details at:

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Reply to
Joop

Aging of Li-ion depends much more on voltage and temperature where they are stored, and storage time than on actual cycling.

For your exapmle, when storing at 50% charged state (which is very nice voltage by itself) and cycling at 1Hz with 1C pulses, battery would has no additional aging compared to just storage without pulses, if (!) it would not be self-heating (e.g. under assumption of active cooling). However, it will be substantialy self-heating under 1C pulses, so temperature increase up to 40-50C will be main reason why battery will accelerate its aging during this period. Good paper on different aging mechanisms in Li-ion is:

Soo Seok Choi, Hong S. Lim, Journal of Power Sources 111 (2002) 130?136

Regards, Evgenij

Reply to
Evgenij Barsukov

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