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First curve is done, the battery behaved very well on first charge/discharge. CE =85.86% EE = 68.22% ?. Total charge recovered was 21.13 mAh, energy density is at ~45Wh/L. For battery configuration see #122

I just published a new blog post showing the first results I have using a PC/TBABr electrolyte on the cathode to sequester Bromine. They are not very good, but you won't find them anywhere else ...

For hardware, I use a DYI built potetionstat/galvanostat. As described in my blog (https://chemisting.com/2020/08/30/building-a-diy-opensource-usb-potentiostat-galvanostat-part-three/). About software, I use the python software provided in the potentiostat's paper to operate the hardware and...

Thanks! I am a chemist, so very aware of PPE :)

I recently got a visit from a friend and was able to have her bring me my potentiostat :). She couldn't bring me my battery materials though, so I won't be performing experiments in this direction yet. However, I have obtained all the materials necessary to build a home cyclic voltammetry setup...

Zinc ions are indeed attracted to negative charges, however in solution things are "neutralized" at a very small scale. A Zinc ion will not just be like an isolated point charge in solution, it's charge will be neutralized by a solvation sphere made by water molecules with their oxygen atoms...

Thanks for reading the thread. Here are my answers: Depends on what I want to test. Tests with lower current take longer, but are much more susceptible to Coulombic losses caused by diffusion, however, they lead to less side reactions (as potentials are lower). By comparing high and low current...

The battery lasted 95 cycles before failing due to dendrites:

After six cycles the battery cell is already at a Coulombic efficiency of 85% with an energy efficiency of 70%. Let's see how it evolves as more cycles are done! I'm super excited, my hypothesis seems to have worked :eek:

Current test cell (described in #122), still alive and well after 18 cycles (CE=87.69%, EE=68.17%):

15,000 catholye + 15,000 anolyte at 35Ah/L would give you 525kAh which at a mean discharge voltage of 1.23V would give you 645 kWh, this is 0.645MWh, so very massive system. At 1mL per cm2 of electrode area you would also need to have 1500 m2 of electrode area, which at a standard 25cmx25cm per...

Since this is Australia, importing to the EU would increase the price by 30% at least. They would need to drop the price further to compete with LiFePO4 server batteries. It is very cool though.

Still going strong after 39 cycles. Charging to 15mAh and discharging to 0.5V at 15mA. Current energy density still above 20 Wh/L.

Thanks for sharing! :) In my experimental research 1% Tween 20 was enough to largely prevent dendrites at a current density of 10mA/cm2. It is a pretty cheap additive, so you might want to give it a try in your setup when you start your research. I hope you will be able to post charge/discharge...

I've been thinking a lot recently about whether it is better to use a non-woven fiberglass separator setup or a PTFE o-ring setup. With the issue of zinc dendrites largely solved by a 1% Tween 20 addition and the use of 1.5M ZnBr2 instead of 3M, it seems that separators might be the better...

Here is a blog post I just published discussing why the inverted architecture is likely necessary to get these batteries to work long term. https://chemisting.com/2020/11/25/zinc-bromine-batteries-why-an-inverted-configuration-is-likely-more-practical/

To some extent, but not entirely. It eliminates the self-discharge issue in the sense that you can move the bromine away to store it somewhere - so the self-discharge across long periods of time is eliminated - but when the battery is charged/discharged you can still have bromine diffusion...

So, going to higher capacity/current density, zinc dendrites become a huge problem again, really fast. After 5-10 cycles the separators are fully pierced and the battery is effectively killed by dendrites. :( This a classic problem when trying to increase the charge speed of Zinc containing...

Sorry, I don't have any unpopulated PCBs. However, if you're building a DIY potentiostat, I would recommend building the upgraded version they published in 2020, instead of the one I built (https://www.sciencedirect.com/science/article/pii/S2468067220300729). This one has much higher max current...

Thanks a lot for your support :) I sadly don't have the equipment to properly characterize a battery of this size yet! I will probably post the instructions on my blog after the stability and characteristics of this setup are confirmed so that others can try building the petri dish version. I...

I got a little bit more (10 cycles) before failure due to dendrites. Talking about this with a friend in battery research, it seems that the dendrites can become more of a problem as the electrolyte becomes more depleted and migration becomes harder for Zinc ions. This is part of the reason...

I agree, Robert does a great job sharing and getting people excited about chemistry. I support his channel and admire his work in this sense. However, his Zn-Br battery designs are just not practical or efficient designs. Those foam batteries have huge energy efficiency losses and the jar...

I have made the new cell with filtered electrolyte and have also decided to introduce a waiting time of 5 minutes after adding the electrolyte - before closing the Swagelok cell - to ensure the electrolyte is able to properly soak through the entire device. These are the results of this cell so...

Thanks a lot for your support! Messages like this mean a lot to me. Very happy to share :)

2% PEG 200 + 2% Tween 20 + 3M ZnBr2 results are coming :)

Volume is 0.089mL, counting both electrodes and separators.

This is not an issue, the chemistry will not be able to support >50mA/cm2 anyway.

You cant use it this way. The FeEDDHA chelate dissociates under strongly acidic conditions. You end up with Fe3+ and H4EDDHA in solution.

I ordered everything from China and it was sent through DHL, I believe you should be able to get everything to France without much trouble if this mail couriers are working fine.

The first experiment charged/discharged the batteries at 1mA, these last experiments did so at 5 mA. The higher current means that a higher voltage is needed to charge the battery - due to its high internal resistance - which means more side reactions are likely to happen, so more energy is...

Thanks! I don't know what the bump was about. However, I can speculate a bit. In other cells 45 cycles was around the point where Zinc dendrites started to become a serious problem - which was evident after opening the batteries up - in this case it's likely that dendrites also started to build...

@curiouscarbon @svetz Thanks for your support guys, really appreciate it! ?

These are some efficiency measurements as a function of the number of cycles for a cell with CC4 that was initially prepared with 100uL of ZnBr 0.5M + TBABr 0.2M electrolyte with 50uL of TBABr 1M added on top of the cathode after assembly. The cell was charged to 500 uAh at 1mA and discharged to...

For LiFePO4 the cost per kWh is still above 130 USD. It is definitely still too early to be talking about anything at large scale, but flow batteries - even at these lower energy efficiencies - can often make better sense than Lithium batteries. The 75% EE is only my first practical result, I'm...

In my research of Zinc-Bromine battery literature I also discovered that Robert Murray Smith filed an application for a patent for an improved electrolyte for a Zinc-Bromine battery where the sequestering agent is made of - the most British thing ever - black tea...

Thanks for your support :) I specifically want to avoid any processes that make the batteries more complicated, I want to get a battery that works and lasts for a long time without the need for things like periodic shorting. The use of Tween 20 greatly reduced dendrite formation, so those...

An update on some things I have learned so far: If you place GFE-1 material - as is - in a flask with elemental iodine at 55C for 10min (what the paper says they did), there is virtually no uptake of Iodine by the material. The GFE-1 cathodes are theoretically very high surface area, so...

I just published a blog post about the above issues 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...

I just published a blog post about the results at higher capacities, the Zn dendrite issue and some tests I will be carrying out to try to address it (https://chemisting.com/2020/10/06/zinc-bromine-batteries-problems-at-higher-capacities-with-tmphabr/)

For a chemist, metallic chelates are very familiar, they have very reversible electrochemistry and - Fe and Mn ones - can be bought for affordable prices. They are also very well studied. Things like Lignosulfonates are much less studied, so I would have never considered something like this for...

A picture of the first test cell I made for these tests, now evaluating the CC6 carbon cathode. Note this cell goes into the Swagelok cell for testing.

Here are some new results using propylene carbonate. I was now able to get a cathode saturated with an organic phase to behave quite efficiently. The fact that lower currents give better CE/EE values points to self-discharge being significantly slower, although this won't be confirmed until I...

After 4 cycles we are at CE=79%, EE=58%. Last cycle shown below.

I have also 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...

I've received my PEG-200 and have prepared a solution as follows: Added 0.720g of ZnBr2 to a 10mL volumetric flask Added 1mL of water and dissolved the ZnBr2 Added 2mL of PEG-200 Completed to volume with 1M TBABr solution The solution was sadly still very cloudy - TBABr precipitated upon...

My objective is not to create something that can rival a product that took millions of dollars, dozens of people and a decade for a company to develop - that would be very naïve. My objective is to provide a solution that could be viable to explore and use for people who want to DIY some...

After 100 cycles the CE and EE remained stable. Final values were CE=89.79%, EE=73.68%. I am now going to try another 100 cycles at a higher current density (these were done at 2mA, I am now going to try see how it changes at 5mA).

Also note that this is not the actual BMS but an architecture to develop one. It will still take a lot of effort for someone to take FoxBMS and create an actual BMS to use with a particular flow battery application. Currently there is no project in FoxBMS that actually tackles the flow battery...

Also, you can get a 1.0M TBABr + 1.0M ZnBr2 solution if you use 50% Isopropyl alcohol / 50% water mixture. Sadly the TBABr3 is soluble in this mixture as well, so the battery strongly self-discharges :( This is evident in the terrible drop in Coulombic and energy efficiencies at lower charging...

Creating cathodes by soaking CC4 cloth in a 50% TMPhABr solution and then allowing them to dry before putting them into the battery seems to work significantly better than solid TMPhABr layers outside the cathode. These are the results so far charging to 3000 uAh and discharging to 0.5V at 2mA...