Flow Battery Research Collective

@kirk hah, nice to hear. I was already thinking that this was unnecessarily tight.

@danielfp248 Good trick, now I only need a syringe.

@kirk @sepi I think Bert's models are free to download off his site, but if you wanted to read the paper, I'm happy to email them to you or you can reach out to him for a copy.

@muntasirms Thanks for sharing. This is all very interesting. I have made several experiments with Zn/Fe fully symmetric cells (since Zn plates preferably over Fe), using glycine as a chelating agent to make sure Fe stays soluble at mildly acidic pH on the catholyte side. It hasn't really worked very well, I see big increases in ohmic resistance as a function of time, but I don't see any iron oxides forming on the cathode or on the membrane. I don't see full dissolution of the plated metal though, so I bet it has something to do with the oxidation of that metallic deposit (since probably some Fe+Zn alloy is depositing anyway). I have never tried WISE electrolytes in flow batteries, and had actually never read the Fe+MgCl2 paper you mentioned. I just ordered MgCl2 and CaCl2, so I'll give that a try as soon as I have those salts! If we can get 1M FeCl2 work with MgCl2, then that would be amazing as a demonstration for the kit at both small and large scales.

@kirk In general this is exactly the way how all of us should act here (and in all other open source projects). But it is always better to have something like this in advance and it does not harm. I highly welcome to have a written code of conduct. Thanks Kirk, for taking care.

@kirk Yes, that is the pump. I should add a disclaimer that I still consider it early tests but if anyone wants to try some of these builds alongside me, I'm happy to share notes! Although it works, the sizing of the cavity for the tubing isn't quite ideal. The tube tends to twist. So I have a bit of refinement on either tubing choice or modifying the build files. Or trying other existing setups out there. Thanks for the other notes! I continue, just slowly.

@danielfp248 thanks so much for your answers. I have more :). Is there a potential between bulk solutions while the battery is operating or while its resting? I guess you can imagine the whole battery as an equivalent classical electrical circuit (with electrons as charge carriers) with current sources at the electrode-electrolyte junctions and resistors for the electrolytes and separator. Does that make sense? This would also mean that the electrolytes would be at equal potential when no current flows.

On it, thanks @sepi !

@Vorg @Vorg said in Designing the large-format cell: I'm 99% sure this is not possible, but maybe tossing it out there would give someone an idea for another direction to look. This problem of a shunt current makes my envision some sort of FET like object with a passage between source and drain to allow fluid to flow through it while a "gate voltage" pinches off current flow through it. There are A LOT of different approaches out there for dealing with shunt currents---right now the approach I'm taking is "we'll cross that bridge when we come to it"---and the "long manifold" approach that balances the overall sum of [pressure drop] + [shunt current losses] seems like a promising passive approach, ie. not requiring moving parts or actively driven auxiliary electrodes. It is the most common approach I've seen commercial entities take, but that's not to say it's the best. Like you describe, an "ionic diode" of sorts would be ideal! There are approaches where people have passed "protective" currents through the manifold to cancel out the shunt currents, but it is an active control method if I understand correctly. [image: 1753447479974-f2e8b9c0-6aeb-4d7a-9fd9-a939d49d5bde-image.png] [image: 1753447486945-5e839262-0e6e-45c8-ae69-f08f721ca900-image.png] The shunt current protective currents were then passed through the protective electrodes inserted at the first and last channel/manifold node point connections. The shuntage currents through the channels were reduced/eliminated. The effects with the passage of protective current for a charge mode are shown in Figure 5. Similar data at other conditions are given in Zahn, Grimes, and Bellows, 1980. Source: White, R.E. (1984). Electrochemical Cell Design, Springer US, Boston, MA Chapter: SHUNT CURRENT CONTROL METHODS IN ELECTROCHEMICAL SYSTEMS - APPLICATIONS Patrick G. Grimes and Richard J. Bellows Advanced Energy Systems Laboratory Exxon Research & Engineering Company Linden, New Jersey 07036