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A battery made with a GFE-1 cathode pretreated with 10% TBABr (soaked and then air-dried as I do with TMPhABr) cannot even be charged to 15mAh due to its very high resistance. The very low solubility of the TBABr in the electrolyte causes the coating to be extremely inactive and basically an...

Doesn't seem like it. It seems to be an issue with electrolyte leaking or cathode/graphite contact. It'll take me some time to figure out and fix.

The problem with TPAB is that its solubility in ZnBr2 solutions is really low, so in practice you cannot get more than a 0.5M solution of TBAP+ZnBr2 which seriously limits your capacity. TEABr's perbromide is a liquid, so it will not be an effective way to sequester the Br unless you're able to...

I don't add any current collector to the carbon, see my Swagelok cell configuration here https://chemisting.com/2020/12/25/zinc-bromine-batteries-about-my-swagelok-cell-for-small-scale-battery-testing/

Thanks for posting! Doing deep discharge cycles works to some extent but it doesn't really solve the problem fully.

I stopped the battery after 138 cycles, when it started showing accelerated capacity loss. I also fixed a small error in my EE calculation, so the average EE is actually around 78%, not 80%.

Most expensive part is the shipping, if you are able to buy say, 10, it would be way cheaper.

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...

It seems I was too greedy and I got failure due to dendrites after only 2 cycles.

I left the current at 5mA, so it's now taking longer per cycle.

I appreciate the support! Feel free to ask any questions you might have :)

Can you measure charge/discharge curves with it? These are the most fundamental measurements in battery science.

Both bromine and iodine will react with ABS, so you sadly cannot use that without any treatment. They will also react quite fast with this plastic. If you want a cheap material for battery construction I would go with glass, which is stable against both bromine and iodine. This is why Zn-Br...

I'm doing an additional experiment with the remaining saturated NaCl electrolyte, added some PEG to bring the total PEG-200 concentration to close to 30-35%. Just one last experiment before I get NaBr and ZnSO4 so that I can do those experiments instead.

Wherever you have the ability to pump large volumes of water and store them, this is definitely the best solution.

Amidoxime membranes are not any more easily accessible to diy synthesis compared with sulfonated membranes. Another membrane technology that is great but you can neither make nor buy. So really not useful in this context. To keep the conversation here focused I would like to keep it constrained...

This thread is not about flow-batteries though! It's about static zinc-bromine systems.

Yea, exactly that one. They calculate their capacity values with only 3mg of cathode material - which is the activated carbon they add to a whole other bunch of things that make up the cathode - for the specific capacity and energy values they use those 3mg plus the mass of ZnBr2+TPABr, ignoring...

It doesn't work in an acidic environment. Acid hydrolyses cellulose, so the membrane falls apart in a strongly acidic environment. Bear in mind that the carboxylic groups in this membrane also get protonated in acidic environments, so it loses its cation selectivity. This membrane only works in...

This is part of the reason why, in practice, zinc-bromine flow batteries ended up being really complicated, hard to maintain and offer low specific energy and power values. A static system would get rid of most of these problems, provided the self-discharge issues can be solved effectively.

It's amazing how everytime I post about something, the next cycle I start seeing issues ☹️ This time zinc dendrites killed the battery just one cycle after:

That would be the plan. It will take me a while to save the money for all the things I need (3D printer, membranes, electrodes, pumps, etc), so it will probably be 6-12 months before I can even do some tests.

Sadly it was an epic fail ? Some of the nail polish peeled off and huge dendrites grew at the interface between the current collector and the PE. I likely need to do much more diligent cleaning of surfaces before applying the coatings.

I have published a blog post showing what happened when I tried to push the energy density of the batteries above 40 Wh/L. I was able to achieve it, if only for a single cycle! Zinc dendrites got all the way to the cathode so I am trying an experiment with a different anode to figure this out...

I published a post about the cause of the increase in internal resistance and how I think I have solved the issues: https://chemisting.com/2020/11/22/zinc-bromine-batteries-why-internal-resistance-was-increasing/ :)

So I have some good news and some bad news. On the good side, I confirmed the commercial Fe-EDDHA standard potential at pH 7 to be around -564mV Vs Ag/AgCl. I also confirmed the reaction to be reversible, as expected. Given the redox potential for Mn-EDTA +660mV, a battery using both reactions...

Thanks for sharing! First impressions after reviewing this literature. This would be a nice to buy if they made it available, but sadly I don't think it would lend itself easily to DIY, as-is, at least not for me. This requires the use of TEOS and MPTES, both not easy to get or "nice to handle"...

Actually I hadn't seen that! Thanks for the link :)

I have done some first tests using the following architecture: Basically strips of copper tape are first placed on a square of PE sheet, then a copper tape disc (sanded to a clean surface) and grafoil strip are placed on the anode and cathode sides respectively. A carbon felt is then glued to...

Thanks for the info! I'll try to figure out why it isn't working on some phones.

Trying to prepare a solution of known ZnBr2 concentration from NaBr and ZnSO4 doesn't seem to be an easy task. The amounts required of both are pretty large and the very large amounts of sodium sulfate formed greatly increases the difficulty of extracting all the solution while maximizing the...

Today I published a post showing what happens when you create a battery with the same configuration and electrolyte as the one in #203 but without any sequestering agent in the cathode. As you can see, the differences are quite significant with the CE and EE values dropping quite dramatically...

No, the surface area of the copper anode is indeed much smaller than the surface area of the felt, by a factor of perhaps a thousand or more. The felt is a very porous conductive solid, while the copper is a simple flat surface. The difference is that the zinc can deposit over zinc while iodine...

I measured the capacitance of the cells using cells without ZnBr2. Their capacity due to capacitance is just around 1uAh, which is reasonable given the electrode separation and dielectric constant of the solution.The charge extracted here is more than 30x that, so it is due to a chemical...

I ran one single cycle but it had some issues, gave CE>100 and discharge capacity > 4mAh, even though I had charged it to 4mAh. The battery probably had some charge remaining from the previous short cycles that ran to 1mAh. I shorted the battery for 5 min to completely discharge it and started...

Best results for CC4 Coulombic efficiency = 69.96% Energy efficiency = 43.43% Current = 1mA Charged to 500 uAh Zinc anode (0.2 mm) Fiber glass separator (8 layers) Electrolyte (0.5M ZnBr2 + 0.2M TBABr) 0.5 inch diameter Measured in a Swagelok cell with graphite electrodes

Note thay those diffusion coefficients are extremely low. From the same paper: "Within duration of 10 years a crossover of only 0.35 mol% of the initial Fe-racEDDHA concentration can be extrapolated for a hypothetical cell " Most papers will report crossover values, they have to be analyzed to...

I am now running the exact same setup described in #200 in order to confirm stability at higher cycle numbers. Battery holding really well so far after 14 cycles. Energy density is 26 Wh/L. This is confirming that the elimination of Fe impurities increases both voltaic and energy efficiencies...

I think this would make the most economic sense for off loading peak renewable production for same-day use, so for short term grid regulation operations.

These are the CC4 electrode results at 10mA. The fact that the Coulombic efficiency and Energy efficiency are better at higher current is a direct indication that there are some serious self-discharge problems with this cell. This is because both processes charge/discharge the same amount of...

Next experiment has had a couple of modifications. First, I have added 1% PEG-200 to the electrolyte to reduce Zinc dendrite growth. Second, I have changed the battery structure to go back to 8 continuous layers of fiberglass, followed by a 50mg layer of TMPhABr, right next to the cathode...

Thanks for your comments David! It's always great to find someone working on the same thing ? Your development history is also very interesting. Could you share some charge/discharge curves with us? I would be very interested to look at the types of efficiencies and capacities you have been...

An important advantage of flow batteries over normal batteries in general is that all parts of a flow battery are serviceable and repairable, batteries always need to be scraped and disposed of when their life cycle is over. A flow battery might only require the replacement of specific parts but...

So it seems that using PC as a cathode electrolyte will not work. See my latest post: https://chemisting.com/2020/12/06/zinc-bromine-batteries-why-propylene-carbonate-will-not-work-as-a-cathode-electrolyte/

In the meantime - while I get the chemicals for the next round of experiments - I created a battery using carbon felt as the cathode, where the electrolyte was prepared by dissolving 0.720g of ZnBr2 in 1mL of water, then taking that to 10 mL in a volumetric flask using a 1M TBABr solution. As...

Thanks for following my progress and reading my blog :) The gel batteries by gel-ion are certainly interesting. You can read more about their approach by reading the patent for their technology: https://patents.google.com/patent/EP3103156A1/en The approach certainly makes sense, being that...

This cell short circuited after only 3 cycles, on opening there seemed to be a lot of salt precipitation. The cetrimonium chloride seems to cause a loss of solubility of the Zinc salts, at least at this concentration. If I try cetrimonium chloride again, it will likely be only at 500ppm. I will...

https://chemisting.com/2022/11/20/the-best-low-cost-fe-mn-flow-battery-some-perspectives-about-solubility-and-chelates/

There was a dendrite failure after 83 cycles. The results looked really good up until that point:

A cell with a 3 PTFE o-ring spacer configuration and the 1% PEG-200 + 1% Tween 20 + 3M ZnBr2 electrolyte has gone through 20 cycles now with practically the same behavior as the fiberglass separator cell. Charging to 15mAh at 15mA, discharging to 0.5V. The energy density is also around 28-30...