Li-ion battery recycling at home

Technical discussion on converting internal combustion to electric
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jonescg
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Li-ion battery recycling at home

Post by jonescg »

For lack of a better place to put this thread, I figures starting here might be a good place.
Ultrasonic bath.jpg
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https://www.bjultrasonic.com/shop/power ... aner-130l/
A friend bought an ultrasonic cleaning bath from China for about $3000 landed. Not knowing what to expect, and given it looked identical to every other ultrasonic bath on offer, it seemed like a worthwhile gamble. It arrived in a wooden crate with not much regard for the product, but it should be fairly robust. We filled it up with water and plugged it in. Turned it on at the wall and it promptly tripped the RCBO.

OK, time to open it up. Oh. My. Dog.
Chinese quanlity.jpg
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I think I counted two cable ties in the whole mess. Nothing tied down or secured, and the heatsink which was supposed to soak heat from the FETs was suspended by two badly aligned long M3 screws. A bit more troubleshooting revealed that the output of the board with the three red capacitors was shorted! Disconnecting it revealed the short was at the transformer, which seems to have been wired up incorrectly. We re-wired it, tried it again, and is seemed to be OK. Reassembled, turned it over, filled it up, turned it on... tripped the RCBO.

Clearly there was a short somewhere. We repeated the process until it turned on and the LED display on the front lit up saying mostly garbage... It's OK, as long as it works right? Pressed the On button... Bang. Tripped again.

SO I conclude this is a dangerous, badly made piece of junk which has no place near humans. However, there's no reason it can't be made to work with a new ultrasonic generator.

All the transducers are fixed to the stainless steel basin which is otherwise acceptably made. However the black wire on all paralleled transducers is common with the chassis. I wonder if this was the problem all along? I attached the 32 paralleled transducers to a 24 V, 50 Hz AC supply and the unit softly hummed. So they seem to be working.

Would it seem reasonable to attach the paralleled transducer to a new 40 kHz, isolated generator and amplifier? Could I just get one as a spare from a reputable supplier?

If it costs $500 to make it useful, a $3500 ultrasonic bath is a good deal. It's a waste of metal otherwise.
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Re: Ultrasonic cleaning bath project...

Post by lobster »

Ultrasonic Generators & Spare part assemblies, all below $420

https://www.bjultrasonic.com/category/u ... price-desc

Cheers, Steve
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Re: Ultrasonic cleaning bath project...

Post by jonescg »

I think that's the same place the bath was bought from. And if the generator is the same, it too might blow up on switch-on.
I guess I'd like to know that the transducers aren't stuffed, and if not, then maybe a more reputable supplier can fit the bill?
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Re: Ultrasonic cleaning bath project...

Post by lobster »

Chris,

as an ex Elec/Nav/Com/Radio Tech I would suggest some simple elimination checking could find an easy fix.

Can you measure the AC supply side to determine is it tripping on earth leakage or over current, the bath may have a marginal earth leakage or your RCBO breaker may be feeding another device on the same circuit also with a low leakage current?

Can you disconnect various components, transformers, contactors or modules to enable some parts to be powered up?

Multi-meter resistance to earth and diode checks and close visual inspection of components for burning or rupture can find a surprising number of electronic circuit faults without much effort.

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Re: Ultrasonic cleaning bath project...

Post by jonescg »

Yeah I did a stack of that snooping, but the tell-tale was the spark once I pressed the On button. It seems strange to me that the two transformers are wired up in series, but maybe that's just part of the circuit. I'm wondering if the neutral-earth arrangements in Australia are not conducive to how this thing is wired up? The breaker is good - only one thing on it being a 15 A GPO. I haven't spotted any failed FETs, but it's more likely a chassis thing. I'm also surprised that the output of the generator which leads to the transducers is grounded to chassis - but of an oversight?
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Re: Ultrasonic cleaning bath project...

Post by jonescg »

Anyway, I abandoned the existing ultrasonic generator and ended up buying a new generator which could be wired up externally to the bath.

So far so good, although it seems a bit underpowered. Draws about 6 amps max from the mains, so barely 1100 W.
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Backyard Li-ion battery recycling

Post by jonescg »

Continuing my backyard chemistry efforts...

So over the years, I have built lots of things with Li-ion battery cells, and while some are still in use, many have been put out to pasture. And by put out to pasture, I mean discharged and safely stored in a bin in my shed. Two Voltron battery packs and a few Prelude pouch cell modules are in there waiting to be recycled, while I have a wide selection of variously stuffed hobby LiPo pouch packs in need of recycling.

Knowing full well that recycling was an iffy proposition in Australia, I've been researching how to recycle them myself to ensure the materials are put to good use. I spent a lot of time pouring through the scientific literature and found a few different methods with various levels of success. They all seem to work on paper, but might require exotic materials or equipment I don't have at my disposal. So Chris Dodd of CD Dodd scrap metals and I decided to work on the first few steps in the recycling process.

I had painstakingly separated all of the Li-ion pouch cells by cutting them open and separating the cathode from the anode and separator, so most of my experimental work has been on dealing with the cathodes alone. But a more streamlined system would be a bit simpler - shred the whole lot and then start the separations. This will probably be the way to go, particularly since you can mix the shredded cells in water and the plastics float to the top while the metals and active material sinks:
float sep plastic.jpg
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The cathodes are mostly Li-CoO2, which is standard faire for RC LiPo. Most research indicates that the cathode is 30% aluminium and up to 50% cobalt, with the rest being carbon and binders.
J Electrochem Soc 164_1_A6184 2017.JPG
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Several papers suggest dissolving the binders in N-methyl pyrrolidone, so I ordered a drum and started playing around. Well, this is a mighty solvent which will dissolve any polymer other than polyethylene, but it was no match for the PVDF binder and cathode materials. So I needed another approach. Ultrasonic removal made sense, so we ordered a 130 litre machine (as discussed above). I've probably overloaded it but I'm also trying to keep the liquid volumes to a minimum. So far plenty of black stuff has been removed, but there's heaps left on there, so the digestion is an ongoing process. I've also added some acid to the bath in an effort to get the cathode layers to let go of the active material, but I'm reluctant to get the pH too low as the aluminium will start to react and dissolve.
When the solution is completely dissolved in acid, you get a burgundy red solution which is everything metallic in acidic solution:
acid digested cathode solution.jpg
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Dissolved Al3+ is not too big a deal, but it's a pest to remove from the mixture. At very low pH, it exists as the free ion, but as the pH is increased towards neutral, you get some weird intermediate species including Al(OH)2- and eventually at pH 6.5, solid Al(OH)3 as a fluffy precipitate. This will settle, leaving (hopefully) everything else in solution. Cobalt ions (Co2+) will react with hydroxide ions to form a brilliant blue CoOH2 precipitate, but it soon turns to a brownish precipitate that looks like... well...
NaOH precipitate of acid digest.jpg
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The thing is, this happens at about the same pH as the formation of Aluminium salts. If it's too alkaline, all the cobalt crashes out and the aluminium goes back into solution. So there might be a two step process here to get rid of the cobalt first before removing the aluminium. I tried bicarbonate instead, which looks a little more promising. Al3+ will react with bicarbonate to form Al)OH)3 with the release of CO2. Trouble is, cobalt also forms an insoluble carbonate which is pink in colour, but I have a feeling most of that is still in solution since the pH is probably around neutral, and there's still a pink solution on top of the pinkish-grey precipitate:
Bicarbonate precipitate of acid digest.jpg
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I need to get a pH meter as litmus paper is too flakey. Will update on the progress over the coming weeks.
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Re: Ultrasonic cleaning bath project...

Post by Rusdy »

I reckon CSIRO should hire you and fund the research! Surely this is a lucrative future market?
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Re: Ultrasonic cleaning bath project...

Post by 4Springs »

No labels on jars. :shock: Grits teeth...
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Li-ion battery recycling at home

Post by jonescg »

4Springs wrote: Mon, 23 Aug 2021, 19:15 No labels on jars. :shock: Grits teeth...
Hey, I just got myself a pH meter. No more taste testing for alkalinity!

Also: topical webinar:
https://youtu.be/oZ6oFQstRiY
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Re: Ultrasonic cleaning bath project...

Post by 4Springs »

jonescg wrote: Mon, 23 Aug 2021, 20:05 Hey, I just got myself a pH meter. No more taste testing for alkalinity!
Oh, I don't know why you'd bother. You'd naturally get an idea of pH when you mouth pipette wouldn't you?
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Re: Ultrasonic cleaning bath project...

Post by brunohill »

I used to work with an old Scottish bloke that could smell a sulphric acid solution and tell you the w/w % strength to 0.1 decimal place. We gave up doing titrations to prove him wrong because we couldn't.
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Li-ion battery recycling at home

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Finally stumped up to buy some decent glassware for this activity. Not cheap, but definitely the right tools for the job.

I took the dried, poo-coloured metal hydroxide precipitate and resuspended in 2 M H₂SO₄. After much fizzing and frothing, I filtered the mixture and boiled the filtrate down to about half volume. As it cooled, short, red needle-like crystals of cobalt sulphate formed which were filtered in a Buchner funnel. The filtrate of this will go into the next lot.
Filtered H2SO4 post neutralisation.jpg
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CoSO4 crystals.jpg
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This mass of CoSO₄ was from a handful of cathode foils - maybe 60 or 70 g. I think future efforts will start with acid digestion because the alkaline route creates a lot of aluminium salts which are hard to work around.

[ Edited Coulomb: SO4 → SO₄, H2 → H₂. Left the file names alone. ]
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Li-ion battery recycling at home

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Today I decided to carefully recycle one single LiPo pouch cell. The cell weight was 130 g.

I opened it up and separated it into cathode, anode, separator and foil pouch.

Outer pouch - 6 g
Separator - 10 g
Anodes - 51 g
Cathodes 61 g

The difference was probably electrolyte which evaporated quickly.

Next I cut the cathode up into flakes about 2 cm x 4 cm, and put them in the stainless bowl. I would have used a beaker if I had one big enough.

I prepared about 400 ml of 3 M H2SO4 which was poured over the cathode flakes. This almost immediately released the active material from the aluminium foil, but it also generated a bit of hydrogen gas as it was slowly dissolving. After the initial chaos died down, I started to fish out the aluminium foil and wash it in DI water. It took a while, but I figured if I didn't need to have all that soluble aluminium in the mix, I might as well put it out. I'm trying to work out how much of what is present in a cell so you can sort of judge the reagents.
Acid digest of LiCo cathode.jpg
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Once the foil was out, I added H2O2 at the recommended 6% v/v final concentration. This made the mixture effervesce and hopefully extract yet more cobalt than the sulfuric acid was already. Peroxide is expensive and a bit of a pest to work with, especially when in solution with acids.
20210927_115640.jpg
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Once this died down, I filtered the solution, getting rid of the PVDF and carbon.
Filtering PVDF and carbon.jpg
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Next step was to neutralise the acid and precipitate the cobalt hydroxide once the pH exceeds 7. I wanted to take it all the way to 12 to make sure any aluminium remained in solution as Aluminate, and not as solid Al(OH)3 which is a pest.
About to add NaOH.jpg
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This immediately released oxygen from the remaining peroxide, causing plenty of bubbles. Everything was still in solution right up to pH 5, but the red soon turned to sludgy green-brown as the pH tipped into the alkaline.


Neutralised.jpg
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Now, this sludge is made of super fine particles, the likes of which will immediately block even the most generous of filters. So a trick is to add some more water and boil the solution to agglomerate the particles into larger particles which might get caught by a Whatman grade 1 filter. It's a bit hairy boiling it in a glass 5 l beaker, as the whole lot wants to bump whenever a small pocket of sludge is superheated. Bumping is kind of the point though; that's what forces them together. After boiling for about 30 min, I turned the heat off and let it cool down. I'll try and filter it tomorrow. Or at least decant it.
boiling to agglomerate ppt.jpg
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The volumes involved are pretty crazy. I need to filter a bit over 1.5 litres of solution for just one cell worth of pure cathode! I can probably add the NaOH directly to minimise the volumes, but you need to decant the mixture anyway. I can't see that boiling would make sense at scale. Perhaps a dewatering centrifuge might work? I need to keep the filtrate as this will contain any lithium ions which can be precipitated using NaCO3.
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Re: Li-ion battery recycling at home

Post by jonescg »

[ Edited Coulomb: SO4 → SO₄, H2 → H₂. Left the file names alone. ]
[/quote]

How did you do that?! I must know...
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Re: Li-ion battery recycling at home

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jonescg wrote: Thu, 30 Sep 2021, 20:31How did you do that?! I must know...
Ah! I saw your NaCO₃, and assumed that you usually have a way of composing UTF8 characters like the so-called "subscript 3", and you somehow forgot with the earlier post, or were using an unfamiliar computer or whatever. But now I see that you actually laboriously used [ size ] .. [ /size ] tags. Rather more work, and harder to check your work while editing.

I use a nifty free Windows program called WinCompose, discovered by my nifty colleague Weber. It allows me to easily type things like 240 VAC; the space between the '0' and the 'V' is a narrow no-break space, perfect for separating units from numbers, expressing numbers like 2 000 000 in a region-independent manner, and so on. Being "no-break", the browser never separates the unit from the value.

WinCompose has all the Greek characters of course, like α, β... useful for 470 μF, 2πr, and the like. Degree sign: 25°C (though I'm naughty and don't use a narrow space between the number and the degree symbol, even though it's just one extra keystroke). I also use superscripts (50 mm² cable), subscripts (LiFePO₄ chemistry), and more (≈10 times a day, certainly ≥ 2, and usually ≠ 0). Accented characters (Gödel, touché). If I don't know a sequence, I can pop up a list and search it. Highly recommended. It's also customisable; Weber has customised many things for us. The neat thing about the characters is generates is that they are a standard, and most fonts have them all, so they work across devices, etc.

To generate the small 3, I type right-alt-_-3. It's memorable, because underscore is the ultimate subscripted character, in a sense. It's quite easy to get used to the commonly used ones. Even for someone like me, with a very poor memory.

Indispensable for every home battery recycler :D For emoticons, however, I just use windows-.

Sadly, there is a forum that forbids Unicode characters (I think it's My Nissan Leaf), and I often forget, and it sometimes takes me minutes to weed out all the special characters that I've generated. I've asked them to turn off that prohibition, to no avail.
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Re: Li-ion battery recycling at home

Post by Nagaman »

Does anyone keep up with the electrochemist Dr Euan McTurk and his Plug-life Television series on YouTube ?
His current work is on lithium air battery technology.
https://iopscience.iop.org/article/10.1 ... 04jes/meta
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Re: Li-ion battery recycling in industry

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ABC article on the two large Lithium battery recyclers in Australia, one of which is taking the recalled LG Chem (now LG Energy Solutions) batteries.

https://www.abc.net.au/news/2021-10-25/ ... /100564234
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Re: Li-ion battery recycling at home

Post by jonescg »

Yeah the hierarchy is basically - repair, re-purpose, and finally recycle. It looks like Envirostream is just exporting shredded cells to Korea?
Not a huge investment to make valuable materials right here in Australia.
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Re: Li-ion battery recycling at home

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Thought I should let you know how this single cell teardown went.

The cobalt hydroxide (and oxides) were so fine they would block up the filter paper, so short of a centrifuge I don't have much choice. So I decanted the Na₂SO₄-rich solution and left the hydroxide sludge behind. Then I did several 1.5 litre washes with rain water - stirring it up and letting it settle for a few days before draining again. Then this weekend I decanted the (mostly) water and resuspended the black sludge in dilute H₂SO₄. After several hours the solution had turned red again indicating hydrated CoSO₄·7H₂O, however there was still lots of black stuff left over. Assuming I'd not added enough H₂SO₄, I continued to add enough concentrated acid until it all dissolved, but to be fair, I've not been stirring it like I should have. I filtered most of the CoSO₄ solution and started to boil it down on the hotplate.
CoSO4 monohydrate.jpg
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CoSO₄·7H₂O (left) and CoSO₄·H₂O (right). Sulfuric acid does a great job of keeping the cobalt sulfate dehydrated (and therefore beetroot coloured).


Before too long the solution was bumping pretty badly, meaning the solids were abundant. Great! Lots of CoSO₄ (monohydrate). So I set it up to filter through a Buchner funnel and filter paper, except the filter paper more or less dissolved in what is now very concentrated H₂SO₄! I clearly added way too much sulfuric acid.

Anyway, decanting is about the only way forward from here. I can't neutralize the acid without adding new cations to the mix, so I will perhaps try washing with acetone.

[ Edited Coulomb: fixed subscripts, dots. ]
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Re: Li-ion battery recycling at home

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Thanks for fixing my formulas Coulomb :) Only one more to go; I decanted most of the sulfuric acid liquor and resuspended the CoSO4.H2O crystals in acetone. This filtered through a paper filter just fine, and was washed a second time in acetone doesn't appreciably dissolve the CoSO4, but it does dissolve the H2SO4 really well. So I'll let that acid/acetone mixture evaporate a bit and pour it back into the next batch for recycling. I don't want to have too much acetone in the acid as it will eventually react to form Aldol adducts.
Filtered and washed CoSO4 monohydrate.jpg
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Once this dries I'll weigh it and see how the yields stack up. I might then try to recrystallize it as the heptahydrate just so its a more consistent product.
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Re: Li-ion battery recycling at home

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I have seen this before somewhere.
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Re: Li-ion battery recycling at home

Post by Bukes »

Should be able to make a centrifuge relatively easily, given your experience with rapidly spinning electric stuff!

What outputs are you hoping to get to with the process? Eg pure cobalt / lithium or some other end stage?
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Re: Li-ion battery recycling at home

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I think a settling tank with multiple flushes/decanting will work okay. The centrifuge needs to be so big, or continuous. My goal is to prevent the ~100 kg of spent batteries from heading to landfill, and extract the roughly 10 kg of cobalt sulfate for other researchers to use in their battery manufacturing.
Mostly just proving how damn easy it is to recycle Li-Ion battery cells.
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Re: Li-ion battery recycling at home

Post by Bukes »

Do you have the path of reactions generally worked out, or are you xperimenting and working it out? Happy to help with research and ideas.
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