danielfp248
Battery researcher
- Joined
- Sep 7, 2020
- Messages
- 429
Things don't always go as planned when scaling, it'll be interesting to see what you get!
Love reading your posts!
Thanks a lot for your support
Things don't always go as planned when scaling, it'll be interesting to see what you get!
Love reading your posts!
Hi DanielThanks for letting me know Tim! It might be your phone/browser combination that the page is having issues with. Can you access it without problems from a desktop?
Thanks for the info! I'll try to figure out why it isn't working on some phones.Hi Daniel
Works fine on laptop. Still not on phone. Will have to bing read once a week rather than daily on phone.
Hi Daniel
Works fine on laptop. Still not on phone. Will have to bing read once a week rather than daily on phone.
Hi DanielSeems like the issue was a php memory limit problem. I have fixed it so it should work on your phone now!
wondering if are you considering a periodic shorting of the battery in the design.
that could be easily automated, and 've been under the impression it would solve much of the dendrite issues.
want to learn about all this soon (far from being a chemist.. but would love to diy my offgrid battery), so thank you for the awesome research.![]()
Your CFE-1, I assume as a beginner is, carbon felt electrode but what does the -1 signify?It also seems that I have been underestimating compression in my cells by a very large amount when using fiberglass separators. I measured the inner cell height as a function of the distances between the caps of the swagelok cell on the outside and found out that I am actually working with substantially smaller cell gaps than I anticipated, as I am able to compress the device a lot when the cell is closed (fiberglass and carbon felt both compress a lot). This means that I have been working with cells that are actually only around 2.5-3mm tall, which means that I have been measuring and aiming for energy densities in the 40-50Wh/L range, while I previously thought the cells were around 5.8mm tall, as this is what I measured with a caliper when I took apart the devices, but compression makes the devices way shorter.
I put together a cell with double the amount of separator, in an inverted configuration using a GFE-1 cathode pretreated with a 10% TMPhABr solution, using a 4.2M ZnBr2 solution with 1% TW20 which gave me a compressed height of 4.8mm (energy density of 29.81Wh/L). Note that I used a much more concentrated electrolyte because I wanted to try the straight electrolyte from a ZnBr2 synthesis from sodium sulfate and zinc sulfate, the approximate concentration was obtained by measuring the density using a pycnometer. The results are below.
View attachment 29488
View attachment 29489
I stopped cycling the cell here because I wanted to open it to see if any deterioration had happened up until this point - given the higher concentration of ZnBr2 - I saw no evidence of dendrites though. The CE is acceptable at 86.78%, and the EE is the highest within the cells I've measured in inverted configurations at 64.15%.
During the next few days I will put together another cell in this configuration and run it for longer, to see if I can reproduce the above results and see whether these taller cells can produce better results. So far no cell has been stable enough to last more than 100 cycles, we'll see if this one is the charm ?
Your CFE-1, I assume as a beginner is, carbon felt electrode but what does the -1 signify?
Ok thanksIt is GFE-1 (graphite felt electrode), it's just a commercial designation for a specific material https://www.ceramaterials.com/product/gfe-1-pan-graphite-felt/. Note that this is not like an average carbon felt, it has significantly higher conductivity and surface area.
I was thinking maybe Geotextile but would be too thin.Trying to get reproducible compression heights from this non-woven fiberglass separator is quite difficult, the separator in reality breaks down as it is compressed, turning into a sort of pile of mushed up fiberglass, since not all the layers break down in the same way every time, the separator sometimes compresses too much and sometimes too little, the variations are actually quite significant, which makes reproducibility difficult in this sort of setup. I'm trying to find a way to make this compression more reproducible. Maybe if I get a woven fiberglass separator - which would be a sort of compromise between a separator and spacer setup - it would work better? Your opinions are welcome!
Do you know what geotextiles are made of? I am afraid they would not be resistant to bromine.I was thinking maybe Geotextile but would be too thin.