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My adventures building a Zinc-Bromine battery
#41
I have started experiments using a separator-less setup, since I wasn't able to surmount the issue of Zinc dendrite formation in a fiberglass separator configuration. You can read more here https://chemisting.com/2020/10/24/z...ng-a-configuration-without-a-solid-separator/
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#42
I needed to change my PVC spacer for Teflon o-rings in order to prevent reactivity with the generated bromine. I just published an update on my blog with some recap about current experimental results and what I am testing right now. https://chemisting.com/2020/10/31/z...eflon-o-ring-separators-capacity-and-peg-200/
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#43
I've been thinking about starting an Instagram account to share pictures and stories about the fabrication of these devices and my experiments. Do you guys think this would be interesting for you? Let me know Smile
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#44
(11-02-2020, 09:14 PM)danielfp248 Wrote: I've been thinking about starting an Instagram account to share pictures and stories about the fabrication of these devices and my experiments. Do you guys think this would be interesting for you? Let me know Smile

Yes, I'd definitely enjoy it. Although, I'm surprised even more people are not glued to this post.
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#45
Thanks a lot for your support guys Big Grin 

I will probably start an Instagram account to share some additional visual with you guys pretty soon. 

I just published a blog post about some issues I was having with cell stability when building spacer based cells (that have no separator) and how they were majorly fixed by going back to a metallic Zn anode. However, the question of dendrites is still there and higher PEG-200 concentrations or NaCl/NaBr additives are ineffective at preventing them at higher ZnBr2 concentrations. https://chemisting.com/2020/11/08/zinc-b...d-failure/
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#46
I dont have Instagram or simulair nor even you-tube ect.
I would like it here on this forum....
Sorry for saying and i hesitated a real long time...realy long time to say this:
Start your experiments fresh with out any filer or what so ever, and make your cells higher, this would be the best bet...
So the zinc dendrites can have the space to form and the bromine can have the space to accumulate below.
The trick i think that would work is a conjunction between height and diameter, incl the surface of the electrodes.
Incl the simplicity of the chemicals.
You are adding a problem/barrier and solve it with a other problem...
When i had my 10cm/4inch high cell in 6cm/2.1 inch in dia all problems would seem to dispersal...
Remember i am also like you still learning..oke... in my primitive conditions.
I hate to write a negative comment, cous i can not think of one! in any of your work..So no negative things from here!

But please consider to rule out the fillers and just let it flow and with that flow take the losses for granted.
In my option the fillers are a dead track...no matter what fillers or fill in...
Again I did not meant to be rude...i greatly appreciate your work and afford.....A LOT!!!

The zinc dendrites is something you can not work around it, work with them, give them space, give the bromine space as well....

Sorry i had to get this of my chest, i really did not mean this negative, bud the track you are on, I think it is a dead one, forget fillers...
My one cent, sorry...
Btw i found a lost testing cell i build....after 5 months, it still holds 1.852v, but i dont remember if i charged it to the full?
Things that i consider as important: height and diameter of the cells and no fillers...
The chemistry can be updated/enhanced for faster charging and discharging, but that is it...it has its limits.
Oke we/you level the path...now try to buy in big volumes....that would be the next problem....not every country allows 1000kg of znbr2 to someones home(my country does allow btw).
I really hope you dont get this negative, those are just my thoughts and what i have learned with experimentation.

Soon i will have some time to experiment, i will keep you updated....Thanks in advance and keep going, i am following this with a lot of interested,

With best regards, Igor.
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#47
(11-11-2020, 06:44 PM)100kwh-hunter Wrote: I dont have Instagram or simulair nor even you-tube ect.
I would like it here on this forum....
Sorry for saying and i hesitated a real long time...realy long time to say this:
Start your experiments fresh with out any filer or what so ever, and make your cells higher, this would be the best bet...
So the zinc dendrites can have the space to form and the bromine can have the space to accumulate below.
The trick i think that would work is a conjunction between height and diameter, incl the surface of the electrodes.
Incl the simplicity of the chemicals.
You are adding a problem/barrier and solve it with a other problem...
When i had my 10cm/4inch high cell in 6cm/2.1 inch in dia all problems would seem to dispersal...
Remember i am also like you still learning..oke... in my primitive conditions.
I hate to write a negative comment, cous i can not think of one! in any of your work..So no negative things from here!

But please consider to rule out the fillers and just let it flow and with that flow take the losses for granted.
In my option the fillers are a dead track...no matter what fillers or fill in...
Again I did not meant to be rude...i greatly appreciate your work and afford.....A LOT!!!

The zinc dendrites is something you can not work around it, work with them, give them space, give the bromine space as well....

Sorry i had to get this of my chest, i really did not mean this negative, bud the track you are on, I think it is a dead one, forget fillers...
My one cent, sorry...
Btw i found a lost testing cell i build....after 5 months, it still holds 1.852v, but i dont remember if i charged it to the full?
Things that i consider as important: height and diameter of the cells and no fillers...
The chemistry can be updated/enhanced for faster charging and discharging, but that is it...it has its limits.
Oke we/you level the path...now try to buy in big volumes....that would be the next problem....not every country allows 1000kg of znbr2 to someones home(my country does allow btw).
I really hope you dont get this negative, those are just my thoughts and what i have learned with experimentation.

Soon i will have some time to experiment, i will keep you updated....Thanks in advance and keep going, i am following this with a lot of interested,

With best regards, Igor.

Thanks for your post Igor  Smile I tried doing taller cells, the main issue with building taller cells with more space between the electrodes is the huge loss in energy efficiency that comes with it. The potential required to charge the cells increases dramatically due to this, going from a 3mm spacing to a 6mm spacing, there is already an almost 20% drop in the energy efficiency of the devices because of added resistance from the solution. Because of the conductivity limits of ZnBr2 solutions, high energy efficiency cells only appear possible with very short electrode distances (<3mm), this is corroborated by the commercial ZnBr2 products, which also use very short electrode distances. 

I am curious about your setup though. How high was your energy efficiency? How many Wh could you get out for each Wh you could put in? With a cell with the geometry you describe, I would expect you to have energy efficiencies below 10-20%, meaning you would need to put in 10 Wh to extract 1-2Wh.  Was this the case? What were the voltages you needed to charge your cells? Let me know!
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#48
I thought I read somewhere that there flow cells that solved or at least delayed the dendrite problem and that is what they are doing on the larger scale commercial cells.
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#49
(11-12-2020, 01:13 AM)Bubba Wrote: I thought I read somewhere that there flow cells that solved or at least delayed the dendrite problem and that is what they are doing on the larger scale commercial cells.

Flow batteries do not eliminate the dendrite issue, they often need periodic short circuiting through a shunt to make sure all dendrites are gone and prevent their long term buildup. They do account for them, minimize them and try to operate with them in mind though, this is indeed viable to a point at a large scale. However this is part of the reason why Zn-Br flow batteries have a low market share, as these dendrite issues create longer down time and increase operational costs. Besides this point, I personally want to explore static Zn-Br batteries, not flow batteries  Big Grin

I also recently posted my first results using Tween 20 + PEG-200 using fiberglass separators Big Grinhttps://chemisting.com/2020/11/13/zinc-b...ults-ever/
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