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Thanks for your support! How are you planning to build the battery? What geometry, cathode/anode materials, electrolyte characteristics, etc? Are you going to cover the ABS in a carbon material to prevent its reaction with Bromine? Let me know :)

Thanks for the suggestions :) There is no other thing I can think of that can cause shorts on charge/discharge besides dendrites, they also respond as you would expect from them (form faster at higher current densities and larger over-potentials for example). I will follow both of your pieces...

With all my recent work in flow batteries in the Zn-I system, I decided to take a new look into Zn-I batteries. In particular a few new papers on back-plating of Zn exist, which is an interesting geometry solution to the problem of dendrite formation. I had never tried it before because I lacked...

The issue with hydrogen evolution is two fold, not only does this cause the potential release of an explosive gas, but it also increases the pH of the battery. As the pH goes up, iron oxides and hydroxides can start to precipitate. This is why Fe flow batteries that rely on Fe plating need to...

A lot of shorting was happening, preventing me from doing any substantial testing. It seems that using the Whatman 42 filter paper as separator was making things even worse. The fact that the paper turns completely black - as in the picture I showed in this thread - demonstrates that it is in...

Many things can suppress hydrogen evolution reactions, basically you need additives that will make the reduction of protonated water more kinetically unfavorable. That is, to increase the activation energy of the hydrogen evolution reaction at the electrode. There is a very ample corpus of...

After cycling this battery 75 times, we start to see some important deterioration in the energy efficiency and stored charge. Voltaic efficiency has dropped quite substantially as well. Charging cycles are now taking the battery past the 2.1V mark, where there is expected to be substantial...

There is a very good reason why these chemicals are used. Common soluble silicon precursors, like potassium silicate, will lead to charge neutral silica gel, which will not have any cation or anion selectivity. This is why TEOS and MPTES are critical to the setup. I have potassium silicate...

I don't have an oven though :)

I just built my first cell changing my Swagelok cell stainless steel electrodes covered with conductive HDPE to graphite electrodes. The results are pretty awesome. This eliminated all shoulders in the charge/discharge curves (they were side reactions from the stainless steel!) and the internal...

This is a new experiment, using a GFE-1 cathode treated with 10% TMPhABr, 16 fiberglass separator layers, electrolyte is 3M ZnBr2 + 20% PEG-200. Charging to 20 mAh at 10mA, discharging to 0.5V. So far, 4 cycles without dendrites shorting the battery ? Energy density at this point is ~38.77...

Bear in mind elemental chlorine and fluorine are gases, very poisonous and corrosive gases, so it is really hard to keep them properly contained in a battery system. For chlorine or fluorine you will have to go with flow battery designs - to properly store these gases - this is not easy, safe...

You can buy small quantities to experiment with (both Mn-EDTA and Fe-EDDHA) from borms (https://www.borms.eu/)

After 20 cycles, the battery is still going strong. Energy efficiency has decreased slightly, but Coulombic efficiency remains above 92%. No sign of dendrites yet :) I will continue cycling, see how long it takes for the battery to fail!

35 cycles now, still going...

Thanks! I have read these patents. Their batteries are very different though - they form elemental Bromine - and they therefore have very particular configurations, materials and very bad self-discharge problems (due to the migration of Br2 through the cell). Zinc dendrites for them are not so...

I've been talking to a few people about their desire to build DIY setups using these cells and the fact that doing any large scale processing of solutions to create ZnBr2 solutions is probably not going to be an option. With this in mind it does seem that testing an electrolyte that requires as...

First results of PEG-200 plus Tween 20. Seems promising ? (although since I have now posted here, dendrites are probably going to short the battery in a few cycles ;) ) https://chemisting.com/2020/11/13/zinc-bromine-batteries-peg-200-plus-tween-20-to-eliminate-dendrites-first-public-results-ever/

These are the results for the cell with ZnCl2 15m + KI 7.5m in distilled water, MGL280 cathode, Zn anode, W42 separator. Charged to 1.3V, discharged to 0.5V at 5mA. The cell died after 9 cycles due to what seems to be a dendrite related short.

I successfully made my ZnI2 solution today. Here is how I did it: Make sure you read everything first, also make sure you only do this in a very well ventilated place, have a respirator and adequate safety equipment at hand. As a precaution I also kept 1L of a 100g/L solution of sodium...

https://chemisting.com/2022/12/08/measuring-and-improving-the-performance-of-pva-cellulose-cation-exchange-membranes/

I ran another test on the same architecture at 0.5 mA but this time charging to 1000 uAh. I was able to get a Coulombic efficiency of 88.2% with an energy efficiency of 74%. This gives me a lot of hope for the upcoming graphite electrode plus carbon paper tests I'll be carrying out next week!

https://chemisting.com/2022/12/15/nafion-equivalent-permselectivity-values-using-a-diy-pva-cellulose-cation-exchange-membrane/

Bear in mind that an "organic" RBF is not a battery that contains an organic molecule but a battery where the redox chemistry happens in the orbitals of an organic molecule. Meaning the organic molecule is actively involved in the redox process. In the case of an Mn-EDTA/Fe-EDDHA battery, the...

I do it as a hobby, I have no plans or goals to ever make any of this commercial. It is just to learn and share with anyone interested.

Increasing the ZnCl2 increases the electrical resistance a lot, without preventing the shorting that happens. The battery made with 22m ZnCl2 died after a few cycles. Increasing ZnCl2 to 30m gave even worse results as virtually all cell capacity is lost due to the huge increase in resistance (as...

These are the results for a cell with ZnCl2 15m + KI 5m in vinegar, CCP cathode, Zn anode, W42 separator. Charged to 1.3V, discharged to 0.5V at 5mA. I ran the battery for 39 cycles, when decay became too pronounced. Also, got the carbon papers today! So I will be doing a test with an MGL280...

Thanks for your welcome message! I hope the community can provide some feedback, comments and suggestions about my experiments! About the red coloring, I certainly didn't add anything red! Might just be some light effects from the copper electrodes I have been using.

Wrote a post about the current problem with TBABr and the three main experimental ideas I want to try to increase its solubility in concentrated ZnBr2 solutions (https://chemisting.com/2020/09/17/zinc-bromine-batteries-how-can-we-increase-the-solubility-of-tbabr/)

https://chemisting.com/2022/12/17/first-tests-of-a-fe-eddhamn-edta-system-towards-a-fe-mn-flow-battery-at-neutral-ph/

This cell failed on the first cycle due to dendrites :unsure: Lower KI does lead to a ton of polarization, my guess is due to Iodine depletion at the battery's cathode.

See this paper for a comprehensive comparison between Lithium Ion, Sodium Ion and flow batteries https://www.sciencedirect.com/science/article/pii/S0378775323008029

Thanks for posting and reading my content! It is very difficult to create these batteries in a durable manner. There are mainly 2 issues faced by batteries that use O2. The first is that they require effective transport of oxygen containing species, which only happens under very basic...

I'm going to be moving out of the US within the next two weeks, so I will sadly be unable to perform any experiments till February :) However I will be happy to answer anyone's questions about Zn-Br batteries or any of my previous research.

I have been battling a lot of stability problems in the devices. As you can see in the tests in #93 and #89, whenever I have tried to go to capacities >20Wh/L using graphite electrodes in the Swagelok cell, I have had decreasing capacity values when charging to constant potential. These...

So I've learned that, while Titanium is "resistant" to bromine, under the oxidative potential in a Zn-Br cell it is attacked quite strongly by Br and pitted pretty aggressively. This electrode was certified as Ti-6Al-4V 0.5. See the electrode after it was put into a Zn-Br cell and run for a few...

Same to you!! Thanks for all the interesting discussions!!

Result of a single cycle on the "proof of concept" 1cm2 device. Charged to 25mAh. There was an abrupt loss of voltage at around 20mAh, so probably something unexpected happened. I will get this device out of the solution and take a look at how it evolved through this high SOC cycle. However no...

I also just published a post about non-aqueous solvents in Zn-Br batteries and my future experiments with propylene carbonate to explore this route (https://chemisting.com/2020/11/14/zinc-bromine-batteries-what-about-non-aqueous-solvents/).

The first battery I am trying to replicate comes from this research paper (https://onlinelibrary.wiley.com/doi/full/10.1002/sstr.202100119). The authors use a 1M ZnSO4 and 1M MnSO4 solution with 0.2M acetic acid. Using a carbon cloth cathode and a Zn anode. They however charge at constant...

Changing the anode doesn't seem to prevent the above from happening (using 1% Tween20 + 1% PEG200 + 3M ZnBr2). Either with a GFE-1 anode or with a Zinc anode, the results are pretty similar. No dendrites but a consistent deterioration of the charging and discharge voltages. See the results below...

Thanks for helping clarify! Note that it is not just energy density but energy efficiency that is critical. I want a battery where I can get out at least 60%+ of the energy I put in.

Thanks for your reply! I discuss that paper extensively on my blog. Note that their capacity, energy density and specific power numbers are incredibly misleading, since they are calculated without considering the mass of the electrolyte or total mass of the cathode (for the capacity) or the...

Curves started to heavily deteriorate around the 24th cycle, but not due to dendrites. Opening up the battery when charged to 15mAh revealed no dendrites present at all. It seems the PEG-200 + Tween 20 combination is effective at suppressing dendrites in this configuration while retaining...

I just got the sample kit of carbon cloth electrodes I will be testing within my cells. It contains the following carbon cloth choices, all from AvCarb (https://www.fuelcellearth.com/fuel-cell-products/carbon-cloth-variety-kit/): CCP – Carbon Cloth Plain 15 mil thick CC4P – Carbon Cloth Plain...

After 5 cycles dendrites started to become a problem. You can see this in this charge cycle as the voltage drops as dendrites start to generate shorts in the battery. It seems the higher ZnBr2 concentration has reduced the solubility of TMPhABr to the point were dendrite formation is happening...

In the case of this battery crossover would lead to permanent loss of capacity. It doesn't poison the catholyte/anolyte though, you will just lose some capacity as a function of time. However, the fully intermixed electrolyte is still functional, so you can never lose more than 50% of the...

It seems to work fine for me. Let me know if you are still seeing a problem.

Flow batteries are definitely better suited to 1. Flow batteries can have high CE and EE values (>95% and >90%) but those are much more costly to achieve. Currently such installations are at around 300 USD per 100 kWh, the lower EE ones using microporous membranes and none vanadium chemistries...

Nothing forbids you thermodynamically from charging an electrochemical system with heat and then discharging it by putting it in cold temperature and reversing the directionality of the reaction. This requires a reaction that has a positive enthalpy change and a positive entropy change such...