# So I tried making my own LiFePO4s...



## Greenflight (Sep 13, 2007)

So I was testing a dynamometer rig one night in October of last year and my 8-year-old pack of Interstate floodies finally had a cell reversal and spewed battery acid all over the shop. I was less than thrilled, but nevertheless set to work trying to track down replacements, and promptly became utterly disenchanted with the state of the battery industry these days.

I got curious about manufacturing processes and raw materials, like LiFePO4... turns out you can just buy the stuff, who knew.

A year later I have a controlled atmosphere nitrogen glove box, a chamber vacuum sealer, a vacuum oven, vacuum mixing equipment, a slot die film coating machine, an ultrasonic metal welder... and one cell that sort of works. Actually, worked... the electrolyte all leaked out eventually. 

Performance was god awful, too. Don't even ask, all I know is that it took a charge off of my power supply and stored it for a while. Hey, this was a proof-of-concept project.

Anyway, long story short, there are a *lot* of rough edges around what I ended up with, but I was able to replicate all of the manufacturing processes needed to make a lithium battery in a garage in Indiana. Mostly in the winter. It was a moderately expensive effort but not hundreds-of-millions-of-tax-dollars expensive. More like self-employed-guy's-savings-account expensive... this was really as grassroots as it gets.

I jumped through a bunch of hoops to do this on the cheap... the glovebox and welder are both surplus units I bought on eBay and refurbished. The film coater would have probably been a six-figure item to buy, so I had no choice but to hack it together in-house. The vacuum sealer is an odd combination of a plexi dome from eBay, miscellaneous hardware, and parts from about four flattening irons.

For the time being the project is on the back burner, eventually I'd like to go for another round and see if I can make something more quantifiable but that's pretty up in the air.

I kept all of this under wraps because while I was doing it I had some delusion of somehow making money off of it. Now that that's worn off I figured I might as well show off a bit.

I went into this thinking of lithium batteries as some kind of magical object made by wizards on the moon... turns out it's really much more analogous to making a sandwich. So I guess the point here is that there's no such thing as magic!

Cheers!

Andrew


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## nimblemotors (Oct 1, 2010)

That is very impressive. May I suggest that you figure out how to make Zinc-Air cells? There was another person who made some, but no details. 
They should be very inexpensive, yet hold 4x more energy than lithium per lb,
just very low power, like 10ah but only 1 amp for 10 hours i.e. c/10,


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## Duncan (Dec 8, 2008)

Thanks for that!
Excellent job!


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## david85 (Nov 12, 2007)

Good to see you're still around Greenflight! Its been a while.


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## aeroscott (Jan 5, 2008)

any ideas what the weakness is. Other then you need to be from China to make lithiums. LOL Great work , thanks!
I wonder if other chemistries would be more successful.


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## piotrsko (Dec 9, 2007)

From what I observed: garages are notoriously not level 3 clean room. How were you making the plates? The big folks do this micro holes thing, sort of like sintered bronze ( really surface sensitive in a garage) and have access to odd chemical combinations for electrolyte.

Additives to the plates, or lithium?

Dang fine experiment however. The schools and big boys didn't get to manufacture right off the starting block. I say keep it up and we should see an independent manufacturer next couple of years.


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## aeroscott (Jan 5, 2008)

Lots of surplus stuff in silicon valley . filters , blowers etc.


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## Greenflight (Sep 13, 2007)

piotrsko said:


> From what I observed: garages are notoriously not level 3 clean room. How were you making the plates? The big folks do this micro holes thing, sort of like sintered bronze ( really surface sensitive in a garage) and have access to odd chemical combinations for electrolyte.
> 
> Additives to the plates, or lithium?
> 
> Dang fine experiment however. The schools and big boys didn't get to manufacture right off the starting block. I say keep it up and we should see an independent manufacturer next couple of years.


Thanks!

I started out with plain old copper and aluminum foil for the electrodes. PVDF+graphite in NMP for the copper, PVDF+graphite+LiFePO4 for the aluminum. If/when I do this again I'll toss in some acetylene black. Process went like this:

1) Dry PVDF/graphite/LiFePO4 powders in vacuum oven for a few hours.
2) Mix with NMP solvent using an electric mixer, and alternate between mixing and degassing to keep things dry - this gives you a nice slurry.
3) Wipe down electrode with NMP on a rag if it's been sitting out, or if it's straight off the roll just leave it.
4) Use either a really crude doctor blade or the film coater to deposit the slurry onto the electrode.
5) Use infrared heaters to cook off the NMP.
6) Profit.

It really doesn't take a level 3 clean room to get "pretty decent" results. The only part that's really, really moisture sensitive is the electrolyte filling/vacuum sealing, and that's what the glove box is for. The electrolyte is LiPF6, which is really pretty commonly used in production cells and is quite sensitive to degradation if exposed to moisture. The rest of it is pretty shirtsleeve if you keep stuff under vacuum when you're not using it, etc.

Andrew


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## aeroscott (Jan 5, 2008)

sounds very doable , I had no idea.


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## bwjunkie (Jul 31, 2013)

That's awesome man, thanks for trying and keeping up the dream, i've drempt this a few times, and it's really nice to know there is someone trying.

Regarding moisture, is there any chance a dry climate geography would help? Hah that is the only thing constructive I could think of.

you rule
josh


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## weber (Apr 22, 2009)

Andrew,

I was so blown away by your post -- not just what you did, but the way you wrote about it, that I laughed out loud and said to my wife, "That's engineering poetry". She responded on cue, "How can you have engineering poetry". So I read it out loud to her. She laughed too, at your last paragraph. I actually had trouble reading that. I got a bit choked up. 

The fact is, engineers like you are the _real_ magicians.

Awesome work, man.


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## piotrsko (Dec 9, 2007)

Hey the clean room wasn't a critique of your process, your reply indicates that you seriously considered the garage implications which wasn't obvious in the first post. 

Have you done testing with your system to see how far off capacity your size is against a comparable commercial product? I'll bet you aren't that far off, maybe 10%.

Sorry, the manufacturing engineer that I used to be just went "ding: extreme INTERESTING"

BTW the secret to being a rocket scientist is anal retentive, not genius.


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## Greenflight (Sep 13, 2007)

weber said:


> Andrew,
> 
> I was so blown away by your post -- not just what you did, but the way you wrote about it, that I laughed out loud and said to my wife, "That's engineering poetry". She responded on cue, "How can you have engineering poetry". So I read it out loud to her. She laughed too, at your last paragraph. I actually had trouble reading that. I got a bit choked up.
> 
> ...


Thanks weber! So glad to hear you enjoyed the story. I'll admit that this was a pretty surreal project and there were a few times when I couldn't believe things were actually working.

Andrew


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## Greenflight (Sep 13, 2007)

piotrsko said:


> Hey the clean room wasn't a critique of your process, your reply indicates that you seriously considered the garage implications which wasn't obvious in the first post.
> 
> Have you done testing with your system to see how far off capacity your size is against a comparable commercial product? I'll bet you aren't that far off, maybe 10%.
> 
> ...


No worries - there are tons of things to critique about the process. 

My gut feeling was that I could probably hit 80-90% of a commercial product, but I never validated that. The big thing that I think is hard to match is internal resistance, which is tied pretty heavily to both surface control and active material formulations. I used significantly more binder than I probably needed (about 10%) since my variability was through the roof, for instance. 

I'm guessing energy density is much easier to hit since it's tied pretty directly to mass fraction of active material.

The first proto had enough functional issues that it wasn't really practical to test it. If I run another batch at some point there will be a lot more numbers!

Andrew


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## miko81 (Apr 2, 2012)

Hi Greenflight

Very nice. I was also looking for making sample battery but it cost few thousand $ to buy just material (I couldnt buy small quantities of copper foil...). How are results, did you mesured capacity??

Wish you all the best in future.
Respect!!


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## aeroscott (Jan 5, 2008)

what is the cleaning procedure for the foils ?


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## bwjunkie (Jul 31, 2013)

Money is still a possibility to continue your research. Maybe put up a Kickstarter that only delivers pictures for the first milestone, I know I would donate to the cause, and I bet a few others would to.

Josh


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## piotrsko (Dec 9, 2007)

What a concept: open source diy batteries. It boggles the mind.


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## Greenflight (Sep 13, 2007)

miko - I didn't come up with anything stable enough to pull numbers off of. Materials are definitely not too cheap, but my copper/aluminum foil cost roughly $600. I got most of my raw materials from these guys: http://www.mtixtl.com/

aeroscott - Just a wipedown with NMP if I felt it was necessary.

Josh - I appreciate that. Unfortunately money was only one gating factor - I've actually still got enough supplies to do another run or two. I ended up moving across the country a couple of months ago so everything got stuffed into a storage unit for the time being.

Andrew


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## JRP3 (Mar 7, 2008)

That's taking DIY to a new level.


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## tomofreno (Mar 3, 2009)

I don't know if you did it or not, but if not, prior to doing more runs it would be good to identify the leading journals in this field then spend months at a university library that has a strong materials science group (so they have all the journals) doing literature searches, copying and studying articles to bring yourself up to speed on the state of the art, learning pitfalls and proper technique to improve the chances of success.

A lithium supplier told me early efforts by some of the Chinese manufacturers were plagued by impurities in powders resulting in wide variability in cell performance with high infant mortality. I expect that to be successful requires at least a year or so of review/study, the right (maybe expensive) equipment, and meticulous attention to detail/good note taking. Maybe you will get lucky, but as they say, serendipity favors the prepared mind. If you decide not to continue, well, at least you had fun trying and learned a bit.


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## PhantomPholly (Aug 20, 2008)

Awesome story. Just proves again that so many things out there are within our own capability if we are willing to take the time to research and practice!


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## david85 (Nov 12, 2007)

I have to admit, I had written off the idea of making any kind of lithium polymer batteries on a small scale. I'm quite happy to eat my words in light of this.


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## liveforphysics (Jan 16, 2014)

Greenflight- My hat's off to you! Wow! Amazing DIY project!

Thank you for sharing!


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