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My adventures building a Zinc-Bromine battery
#11
See my latest post on ZnBr2+TBABr and why it is probably not the best sequestering agent to use, as its solubility in the presence of ZnBr2 is very limited. https://chemisting.com/2020/09/15/zinc-b...ing-agent/
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#12
I am about to give up on the TBABr as a sequestering agent. The solubility limit is just too low (about 0.2M TBABr + 0.2M ZnBr2). Although TBABr is very highly soluble on its own, its just not soluble at all in the presence of concentrated ZnBr2 solutions. Since for a practical battery to rival Li-Ion we are bound to need ZnBr2 in the order of 2M, it is not going to be practical to have TBABr as a sequestering agent. Although there are some potential solutions to at least partially alleviate the problem - additives like PEG200 or chelating agents for the Zn like EDTA - this is all going to complicate the chemistry and make it harder to reach any commercial or larger scale DIY development.

I will try using PEG200 to see how much TBABr I can get into solution with ZnBr2, but after that I will pursue other sequestering agents instead. I will be using TPABr - what the recent Chinese paper on Zn-Br batteries used - and TMPhABr, both which I ordered from Alibaba. I'll keep you posted on what I get!
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#13
I have done some experiments using TBABr suspensions, trying to create batteries with some solid TBABr within the battery structure to see what happens. Here are some of the results (https://chemisting.com/2020/09/19/zinc-b...-in-there/). Although these are interesting, I don't think I will be dedicating a lot more time to TBABr, as its issues seem to outweight its potential advantages. That said, I'll continue cycling the above mentioned cell for a few more days, see how the Coulombic and Energy efficiencies behave after a larger number of cycles.

A Colombic efficiency of around +90% with an energy efficiency close to 60% is not a terrible result, but given that we know that much higher results are possible with an adequate sequestering agent (CE > 98% with EE > 80%), I see no reason why we should limit ourselves to TBABr.
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#14
This latest cell finally died - shorted by zinc dendrite formation - the next test using PEG200 should also help eliminate this dendrite problem.
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#15
I must say this....
You are quick with testing, big thumb up from me.
Good update at your site also.
Keep it going please, i am still following with intressed.

Best Igor
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#16
I wrote a post about my Zn-Br batteries and where they are realistically going to get once they are improved (https://chemisting.com/2020/09/25/zinc-b...-required/)
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