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Prevent pouch batteries from swelling during recyling-discharge?
#1
My e-bike harvesting also left me with some pouch batteries, which I do not want to use and are thus candidate for recycling. I order to recycle them safely I want to discharge them to avoid issues on an accidental short-circuit for example.

I currently deep-discharge them by hooking them to a car light, causing them to discharge at 2.5A. How-ever at the final 'stage' of the deep-discharge I find myself with swelling or bulging pouch batteries, without noticeable access heat is generated by the battery.

Example of the pouch battery is shown at the picture on the left is 'orginal', the right is deep-discharged:



So how do I discharge them correctly for safe recycling?
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#2
Set something heavy on them to keep them compressed / keep them flat while your discharging them - maybe a board with a couple of bricks.
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#3
(06-15-2020, 02:52 PM)rickvanderzwet Wrote: My e-bike harvesting also left me with some pouch batteries, which I do not want to use and are thus candidate for recycling.

Why not post them in Marketplace on this sight for someone else to use?
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#4
I agree with Bubba. Post them in the Marketplace. I know there are others in NZ who are on this site.
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#5
(06-15-2020, 09:18 PM)Korishan Wrote: I agree with Bubba. Post them in the Marketplace. I know there are others in NZ who are on this site.

Fair point when I have some more (this was only one battery) and cells are still decent quality (this ones where not) I will do it. How-ever I am based in "The Netherlands" (Europe region), which afaik not many persons  are active in the marketplace.

(06-15-2020, 02:57 PM)OffGridInTheCity Wrote: Set something heavy on them to keep them compressed / keep them flat while your discharging them - maybe a board with a couple of bricks.
Nice tip, thanks I will give it a try.
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#6
Maybe use a smaller load? Eg large 10W resistor 10 Ohms? Take longer though.
A thought - not much energy left if short circuited below say 2.0V at minimum voltage....
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#7
(06-16-2020, 09:37 AM)rickvanderzwet Wrote:
(06-15-2020, 09:18 PM)Korishan Wrote: I agree with Bubba. Post them in the Marketplace. I know there are others in NZ who are on this site.

Fair point when I have some more (this was only one battery) and cells are still decent quality (this ones where not) I will do it. How-ever I am based in "The Netherlands" (Europe region), which afaik not many persons  are active in the marketplace.

Yeah, I meant Netherlands. I was thinking of someone who was in NZ when I typed that. There are several who are in the Netherlands is what I meant Tongue
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

Please come join in general chit-chat and randomness at Discord Chat (channels: general, 3d-printing, linux&coding, 18650, humor, ...)
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#8
OffGridInTheCitySet Wrote:something heavy on them to keep them compressed / keep them flat while your discharging them - maybe a board with a couple of bricks.

Gave it a shot, how-ever no luck. The pressure is great enough to lift the weight:



Did some reading on over-discharging. It seems to be caused by:

Guo, R., Lu, L., Ouyang, M., & Feng, X. (2016). Mechanism of the entire overdischarge process and overdischarge-induced internal short circuit in lithium-ion batteries. Scientific reports, 6, 30248. https://doi.org/10.1038/srep30248 Wrote:Simultaneously, over-deintercalation of lithium at the anode during overdischarge causes decomposition of the solid electrolyte interface (SEI), and the decomposition of SEI generates gases, including carbon dioxide

I have tried to find a source for proper recycling procedures how-ever none found so-far. Only industrial instructions which is about opening and shredding the battery for example. They how-ever explicitly mention the fact that over-discharged cells are harder to recycling: 

Harper, G., Sommerville, R., Kendrick, E. et al. Recycling lithium-ion batteries from electric vehicles. Nature 575, 75–86 (2019). https://doi.org/10.1038/s41586-019-1682-5 Wrote:over-discharging of cells can result in copper dissolution into the electrolyte. The presence of this copper is detrimental for materials reclamation as it may then contaminate all the different materials streams, including the cathode and separator. If the voltage is then increased again or ‘normal’ operation resumed55, this can be dangerous because copper can reprecipitate throughout the cell, increasing the risks of short-circuiting and thermal runaway.
...
In general, this will require the lithium content to be replenished to compensate for losses due to degradation of the material during battery use and because materials may not be recovered from batteries in the fully discharged state with the cathodes fully lithiated
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#9
(06-16-2020, 10:05 AM)Redpacket Wrote: Maybe use a smaller load? Eg large 10W resistor 10 Ohms? Take longer though.

Gave it a try, no luck, still same amount of swelling.

(06-16-2020, 10:05 AM)Redpacket Wrote: A thought - not much energy left if short circuited below say 2.0V at minimum voltage....

It looks like the swelling start to occur at 2.5-3.0V, but I will run some more testing to confirm. My biggest issue is not the lack of energy of the battery, but the fact they potentially gain a lot of space and/or could vent gasses or burst the package. If the gas is not considered harmful (e.g. CO2, H2 or similar) I am fine, how-ever I cannot find out the composition of the gas. Also not sure if bursting the package could generate nasty side effects if air comes in contact with the inner content of the pouch.
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#10
Here is an analysis of the Lithium Ion gas composition. --> https://www.fire.tc.faa.gov/pdf/TC-15-59.pdf

I don't think it talks about any poisons. Does show the flammable components on the gas chromatography.
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