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Robert would have us believe everyone could be building 100 kWh batteries in their kitchens using 19th century technology. Sadly there are good reasons why those technologies never received massive adoption. I've always been critical of the lack of quantitative rigor and data in his videos...

Lead acid is at 80-90 Wh/L. This is at currently less than 1/4th of that. We will need to see if we can reach those types of capacities! The cost relative to lead acid should be substantially less if we do get there.

First 5 cycles to 4mAh, for the battery built in #51: As you can see, up until now we have great cycling stability, with increasing capacity for the first 5 cycles and increasing CE and EE values. This behavior matches the results that we got when charging to only 1mAh. Maximum energy...

First success with fabrication of a DIY cation exchange membranes using a process to phosphorylate and crosslink PVA and cellulose: https://chemisting.com/2022/11/27/a-diy-cation-exchange-membrane-with-pva-and-cellulose/

Highest energy efficiency results yet. EE=76% CE=83% (second cycle, charge/discharge 5mA). Using the GFE-1 cathode, pre-treated by soaking in 10% TMPhABr and then drying in air.

You can make it with phosphoric acid as well, I just ran out and had only 14% H2SO4 at hand.

Bear in mind that the pH of a 15m ZnCl2 solution is really low (pH < 2), given the pKa of acetic acid is 4.75, it provides no protons under these conditions. Given that ZnCl2 is several orders of magnitude more acidic (very strong Lewis acid), the acidity of acetic acid is not relevant. It does...

This is an experiment using a symmetric cell with Spectracarb 2050A-0850 as both anode and cathode, using 2 layers of W42 filter paper as separator and a 5m KI + 15m ZnCl2 electrolyte. Cell was charged to 1.6V at 5mA/cm2 and discharged to 0.5V. Cell ran for 76 cycles, although some dendrite...

Exp 29 put the anode on top, dendrites formed just as fast. I don't think this has anything to do with "dendrites fighting gravity" - the force of gravity is known to have very weak effects on dendrite formation - but just that the cathode carbon cloth doesn't let electrolyte flow past it very...

@metaros Unscrupulous people who want free scientific papers will often download telegram, add the scihub bot (@scihubot) and send it the DOI website address of any paper they want to download so that the bot sends it back for free. This is something you should absolutely never do.

These are the results for a cell with ZnCl2 15m + KI 5m in distilled water, MGL280 cathode, Zn anode, W42 separator. Charged to 1.3V, discharged to 0.5V at 5mA. Curves are cleaner than for a carbon cloth, EE is higher and CE is similar. There is an evident decay in capacity after 27 cycles.

Yes, these ones are the higher cycle numbers. I have no idea how sensitive to temperature the precipitate is (TPABr3). From a review of the literature it seems stable - melts at 71C without decomposing - but I don't know how its solubility in water changes as a function of temperature (could be...

These are all the charge/discharge plots for the last described battery up until now with the CE and EE information, in case you guys want a better look into the evolution of the charge/discharge curves as a function of time.

These should not self-discharge in the traditional sense, since your storage is put into tanks and the amount that is left within the stack is negligible. The expected self-discharge would be due to reactions of atmospheric oxygen with reduced Fe-EDDHA.

There are many problems with gravity batteries that use weights, in the context of towers it has never worked so far due to basically problems with keeping weights stable in the wind. The only viable trials up until now are using mine shafts, at least to the best of my knowledge. Water has...

The influence of CO2 should be minimal, since at neutral pH it is not taken up in a major way by solutions and no significant amount of carbonates are formed. Oxygen will react right away with reduced Fe-EDDHA, so any you don't keep out will just discharge your battery. You have to keep it out...

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 :)

I invite you to follow my new thread on Zn-MnO4 batteries https://diysolarforum.com/threads/my-adventures-building-a-zn-mno4-battery.32150/ This doesn't mean I won't continue doing Zn-I experiments at some point.

No problem, very happy to have you here. I'm not posting that much right now (busy with work!) but keep posting!

It is GFE-1 (graphite felt electrode), it's just a commercial designation for a specific material https://www.ceramaterials.com/product/gfe-1-pan-graphite-felt/. Note that this is not like an average carbon felt, it has significantly higher conductivity and surface area.

So I decided to take apart this battery after 11 cycles. Here's the final result: Final curve has a CE=86.41% and an EE=68.74%. The reason why I took it apart is because there started to be some deterioration of the cell. The coulombic efficiency wasn't sufficiently high and the cycles were...

After all the adventures trying to build the Mn-Fe flow battery, I have now shifted to a Zn-I flow battery. Since I now have a full setup to actually test flow batteries, I have arrived at this chemistry after testing several other alternatives. You can see some of my experimental results on my...

I had the idea to use PTFE o-rings as spacers, I ordered some with the exact outer diameter I needed (0.5") from McMaster-Carr. These are 1.77mm thick, so I can stack them to get any spacing size I require while keeping the setup very reproducible. I will build cells with these after I get them...

I'm glad you enjoy reading about my experiments! About physical barriers, there are two main issues with them. One, physical barriers are physical barriers to everything, including ions, so they greatly increase the electrical resistance of batteries. A battery with a 2mm oasis foam layer has a...

Thanks, I saw it! I will be using Nafion to measure some reference values. However my objective is to create some PVA based membranes to use instead of Nafion. Since my particular use case (Fe/Mn flow batteries at pH 7) doesn't require so much chemical stability, I can probably get away with a...

Battery from #203, still going strong at 50 cycles. Deterioration has been really small, energy efficiency has dropped but now stabilized and Coulombic efficiency has remained in the 87-90% range. Stored charge has also remained pretty consistent.

Haha, I have tried only purple. About the grafoil. Both are part of the electrode. Although the grafoil is just the exposed current collector. The felt is needed as you need the surface area for the iodine to deposit on. The capacity of the cathode will be limited if the surface area is not...

You cannot do felt on both sides as felt is not really good for depositing zinc. The Zn starts forming dendrites over the surface of the felt which actually can go all the way around with time since the felt is taller. With a flat metal electrode as anode the Zn deposits are actually much better...

I repeated the entire process of building the pouch cell and tried charging it. The overpotential is now massive, even at a current of 0.4mA/cm2 the starting charging potential is already above 1.6V, at the same current density as the proof of concept cell the potential is 2.3V ? . In...

The Sn approach I mentioned does something like this, when the dendrite reaches the Sn layer, it is no longer thermodynamically favorable for the dendrite to grow. Dendrites grow mainly because there is a gradient of Zn ion concentration going from the electrode to the bulk of the solution. As...

It is an interesting idea, to make the iodine electrode electrochemically in WiS and then swap it. I'll leave it as a possibility for a future test.

The first separator-less battery has now done 10 cycles. The battery still lives but some signs of Zinc dendrites touching the cathode have started to show up - sudden downspikes in the charging potential in cycle 9 for example - however the battery has so far been able to recover from these...

I am very happy with the voltage, that is more than I thought I could get for an all-soluble water chemistry with chemicals already available in bulk at neutral pH. Sulfonated membranes are very well established. You cannot DIY them easily though, because the synthesis involve sulfonating...

More information about the DIY flow battery on my blog : https://chemisting.com/2024/03/15/an-open-source-diy-flow-battery/

I have also taken the data from this paper (https://pubs.acs.org/doi/10.1021/je00044a025) to create a way to calculate the molal concentration of a MnCl2 solution from its density. I will use this to accurately estimate the molality - moles of substance per kg of solvent - of my final MnCl2...

I just wrote a post about the charge/discharge potential degradation. https://chemisting.com/2020/11/20/zinc-bromine-batteries-increases-in-resistance-in-tw20peg-200-containing-solutions/ I am also currently running an experiment using a Titanium electrode with a GFE-1 cathode and a graphite...

First cycle with a GFE-1 cathode pretreated with 10% TMPhABr and a 3M ZnBr2 + 20% PEG-200 electrolyte saturated with home NaCl. Charging to 15mAh at 5 mA, discharging to 0.5V. CE = 94.37%. EE=74.60% Energy density is 31 Wh/L. So far very good Coulombic and energy efficiency values, let's see...

Today I published a post about the Swagelok cell I use for small scale battery testing and why cells like these are very important for reproducible small scale battery research. https://chemisting.com/2020/12/25/zinc-bromine-batteries-about-my-swagelok-cell-for-small-scale-battery-testing/

Just published a post about some thoughts in building an actual practical battery (https://chemisting.com/2020/09/13/zinc-bromine-batteries-initial-thoughts-about-a-practical-battery/). Still very far away - I need to understand TBAB cells, other carbon cathode choices, different ZnBr2...

Thanks for the reply David! :) What's the conductivity and surface area of the felt you're using? The GFE-1 graphitic felt I am using has very high conductivity, so I haven't had to use any additional conditioning to improve its characteristics but I'm interested on the properties/cost of...

Yes, ZnBr2 batteries can get to really high energy densities. They must have solved both the zinc plating and Br crossover issues if they got to this point. So far however sales seem to be limited to trials in Australia.

Note a recent paper looked into Mn|Fe for a RFB in a concentrated H2SO4+HCl mix. Without any chelating agents modifying the redox potentials, the potential is only around 0.6V. Another issues is that since all the species are cations (Fe2+, Fe3+, Mn2+, Mn3+), several of them effectively cross...

Sure, you can control dendrites this way and make your energy efficiency drop to 10% due to the omhic losses that happen. Whenever you hear people talking about solutions having the energy efficiency and coulomb efficiency data measured with their ideas is fundamental. Although Robert loves to...

For small scale charge/discharge experiments I will also have basically constant circulation of electrolyte, but for scaling that up you will need a BMS for a flow battery. This is an interesting side project if anyone who knows about this wants to take a go. There are currently no open source...

Thanks for your message and kind words! :) I really appreciate your support. I would certainly want to try a ceramic separator sometime, if just to see how it does in terms of dendrites and internal resistance, but sadly ceramics require more equipment than I have or can procure in the small...

I have received my PTFE spacers (0.5 outside diameter o-rings, 1.17mm thick). This is the first cell constructed using them, this cell uses 3 PTFE separators, GFE-1 cathode treated with 10% TMPhABr and a 3M ZnBr2, 1% PEG-200 solution (I ran out of ZnBr2 3M 20% PEG-200 solution, I am waiting for...

I started having some weird stability issues with devices in the separator-less setup ☹️ Trying to figure out what's going on. Here is a pretty plot showing what I'm experiencing:

So my new experiments are using a solution that is 1M ZnSO4 and 0.1M ZnI2. This gives a theoretical capacity of 13.4 mAh in terms of Iodine, which is the limiting factor. However, there is a big difference with the batteries in the literature. These batteries start their life in a charged...

Sadly it didn't even last 4 cycles ☹️ If anything it seems the NaCl made things substantially worse.

Thanks for your support :) I will start testing self-discharge as soon as I find some solution to the Zinc dendrite problem!