New ion exchange membrane recipe using water softener resin and PVC cement
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Hello, I recently open sourced a novel ion exchange membrane recipe using a high speed grinder on water softener resin and mixing with PVC cement. They can be produced for less than $1 a square yard with properties similar to other name brand ion exchange membranes. You can find more details on the following GitHub https://github.com/Rowow1/Open-sourced-off-the-shelf-ion-exchange-membrane
The patent in the GitHub describes more details, but I also made the following video where I released the files patent as a CCL1.0 license. I have lots of other ideas I would love to assist this community in but I hope this can demonstrate the significance change in scope of redox flow batteries.
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Thanks for sharing. What is the exact chemistry of the resin you are using? Typically resins used in water softening applications will degrade significantly with the highly concentrated oxidants present in flow battery catholytes. Did you find a fluorinated resin used in water softening that would be low cost?
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We use the following cation exchange resins: https://www.amazon.com/dp/B079P7QCJF
So far they last a very long time without issue. We have them operating for months in very harsh mining conditions with Ph0 and oxidizing redox potentials over 1.5v. I have measured a ORP level of 1000mv but thats the maximum my meter can go. The chemicals being made by our continuous mining unit produces a theoretical level of 1.65v. Would love to be able to buy a proper ORP meter and test it for sure.Regardless our cells run for almost a year without issue, and with really dirty mining solution waste. We havent really experienced any sort of degradation such as fouling etc so we dont know the limits of these membranes, only that they already perform very great. Would love to test on various resins and so forth.
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This is a polystyrene crosslinked sulfonated resin. It is not going to resist the conditions of flow batteries due to the reactions the aromatic units will go through, which will decompose the resin with time. Bear in mind the problem is NOT solely about the oxidation potential itself, but about the concentration of oxidative species. Potential will control whether some reactions happen or not, but the speed of these reactions will be determined by concentration. A +1.5V potential might be survivable in the long term at mM concentrations but at M concentrations the story can be very different. Sulfonated polystyrenes are not chemically suitable for the application.
Viable low cost alternatives for flow batteries must have more structurally sound backbones, like for example sulfonated poly(ether ether ketone) (SPEEK) membranes (even these won't survive all chemistries). Since the ion exchange membrane is not an easy to remove component and it has to survive for +10 years of very harsh conditions we have therefore decided to use microporous membranes instead. Of course, for demonstration or short term applications, I am sure a polystyrene membrane would be ok with some chemistries.
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This is a polystyrene crosslinked sulfonated resin. It is not going to resist the conditions of flow batteries due to the reactions the aromatic units will go through, which will decompose the resin with time. Bear in mind the problem is NOT solely about the oxidation potential itself, but about the concentration of oxidative species. Potential will control whether some reactions happen or not, but the speed of these reactions will be determined by concentration. A +1.5V potential might be survivable in the long term at mM concentrations but at M concentrations the story can be very different. Sulfonated polystyrenes are not chemically suitable for the application.
Viable low cost alternatives for flow batteries must have more structurally sound backbones, like for example sulfonated poly(ether ether ketone) (SPEEK) membranes (even these won't survive all chemistries). Since the ion exchange membrane is not an easy to remove component and it has to survive for +10 years of very harsh conditions we have therefore decided to use microporous membranes instead. Of course, for demonstration or short term applications, I am sure a polystyrene membrane would be ok with some chemistries.
@danielfp248 we use solutions ranging from 10-20% hydrochloric acid. There are many polystyrene crosslinked sulfonated resin membranes used in flow cells. I don't understand the immediate resistance.
I recommend trying first before making assumptions. At the end of the day try different resins if it's a concern for you. The potential of these membranes and their low cost/manafacturing method have significant impacts. Is there a better community to discuss this research as I may have entered the wrong place
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@danielfp248 we use solutions ranging from 10-20% hydrochloric acid. There are many polystyrene crosslinked sulfonated resin membranes used in flow cells. I don't understand the immediate resistance.
I recommend trying first before making assumptions. At the end of the day try different resins if it's a concern for you. The potential of these membranes and their low cost/manafacturing method have significant impacts. Is there a better community to discuss this research as I may have entered the wrong place
@rowow I don't know what to tell you. While sulfonated crosslinked polysterene membranes can work great for many flow cell applications (they absolutely have no problem with strongly acidic environments), they will have problems with many flow battery chemistries due to the chemical properties of these membranes and the highly concentrated oxidative environments the membranes are subjected to. You can look at the research on membrane degradation if you want to learn more about this.
These resins have existed for a long time, they have been tested, their problems are well known. You are welcome to try them in flow batteries and share your results here.
As I mentioned the concerns about cost, dendrite formation in deposition chemistries and chemical degradation are mainly why we decided to go with microporous instead of ion exchange membranes. Even if ion exchange membranes were very low cost, for an open source flow battery we believe microporous membranes actually offer better robustness.
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First off, @rowow , thanks for making your membrane approach open-source! Out of curiosity, is the patent application alongside it meant to prevent patent trolls from taking advantage of it?
@danielfp248 has looked into membranes quite a bit and I agree that the only way to know for sure about a membrane's chemical compatibility is to test it with the proposed electrolyte during operation, where it will be exposed to, to take our standard zinc-iodide cell as an example, zinc dendrites (which can puncture an IEM) and high concentrations of triiodide, which can be pretty aggressive and "weird", in the sense that it has attacks and goes through many polymers that are otherwise resistant to similar classes of chemicals.
So far we've used paper and Daramic (polyethlyene + silica microporous separators used in lead-acid cells) because our chemistries are meant to be symmetric (and can tolerate mixing) and they are generally quite chemically resistant and handle dendrites better than an IEM. We're not against IEM use by any means, but so far we haven't spent much time on them because of the previously mentioned problems, and it's not our main focus/skill set. We've had our hands full with electrolyte development and cell/system design, so we've essentially opted to keep the membrane "can of worms" (from our perspective) closed---that said, it would be really interesting to test your membrane approach in the dev kit with say, Zn-I, to see how it compares to Daramic---I just don't think we have the time right now to fabricate the membranes ourselves.
It seems you probably have most of the resources already to test your membranes with ZnI? The other thing that would be quite different in terms of membrane requirements for a battery vs. a refining process would be conductivity, I'm not sure if you've done measurements in terms of Ohm*cm² but this would be a harder target to reach for RFB applications.
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First off, @rowow , thanks for making your membrane approach open-source! Out of curiosity, is the patent application alongside it meant to prevent patent trolls from taking advantage of it?
@danielfp248 has looked into membranes quite a bit and I agree that the only way to know for sure about a membrane's chemical compatibility is to test it with the proposed electrolyte during operation, where it will be exposed to, to take our standard zinc-iodide cell as an example, zinc dendrites (which can puncture an IEM) and high concentrations of triiodide, which can be pretty aggressive and "weird", in the sense that it has attacks and goes through many polymers that are otherwise resistant to similar classes of chemicals.
So far we've used paper and Daramic (polyethlyene + silica microporous separators used in lead-acid cells) because our chemistries are meant to be symmetric (and can tolerate mixing) and they are generally quite chemically resistant and handle dendrites better than an IEM. We're not against IEM use by any means, but so far we haven't spent much time on them because of the previously mentioned problems, and it's not our main focus/skill set. We've had our hands full with electrolyte development and cell/system design, so we've essentially opted to keep the membrane "can of worms" (from our perspective) closed---that said, it would be really interesting to test your membrane approach in the dev kit with say, Zn-I, to see how it compares to Daramic---I just don't think we have the time right now to fabricate the membranes ourselves.
It seems you probably have most of the resources already to test your membranes with ZnI? The other thing that would be quite different in terms of membrane requirements for a battery vs. a refining process would be conductivity, I'm not sure if you've done measurements in terms of Ohm*cm² but this would be a harder target to reach for RFB applications.
@kirk said in New ion exchange membrane recipe using water softener resin and PVC cement:
First off, @rowow , thanks for making your membrane approach open-source! Out of curiosity, is the patent application alongside it meant to prevent patent trolls from taking advantage of it?
YES!!! protecting against patent trolls was exactly the point. I didnt want to deal with being in court the next 15 years prohibited from using my own technology arguing whether or not its open sourced. The certain japanese gaming company patenting a certain game mechanic recently is a great example how terrible the patent situation is...
@danielfp248 has looked into membranes quite a bit and I agree that the only way to know for sure about a membrane's chemical compatibility is to test it with the proposed electrolyte during operation, where it will be exposed to, to take our standard zinc-iodide cell as an example, zinc dendrites (which can puncture an IEM) and high concentrations of triiodide, which can be pretty aggressive and "weird", in the sense that it has attacks and goes through many polymers that are otherwise resistant to similar classes of chemicals.
I personally favor ferric chloride so I dont have any experience with zinc iodide. But I hope this membrane will allow the community to also see other membrane ideas in general. A user on my discord server sent the following research paper which discussed using a carbon slurry as a carrier for the metal to plate off. Really interesting study I wonder what you think, very much worth replicating also and may solve the dendrite/plating issue.
https://link.springer.com/article/10.1557/s43581-022-00046-8It seems you probably have most of the resources already to test your membranes with ZnI? The other thing that would be quite different in terms of membrane requirements for a battery vs. a refining process would be conductivity, I'm not sure if you've done measurements in terms of Ohm*cm² but this would be a harder target to reach for RFB applications.
I dont have any zinc iodine. I can see about fitting it into a test cell to demonstrate but honestly that would be a month out. I am trying to launch a website store right now alongside many other video ideas first to publish. I havent properly measured its conductivity, definetly varies based off solution. I just know that theres a very low voltage drop when electrolyzing across the membrane vs directly in solution at the same distance. Additionally I get 100-200ma/sqcm depending on the fabrication method. When using the proposed ball milling and spray method you can get paper thin sheets. Currently with my mining setup, the electrodes are the limitation not the membranes.
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I found a research paper about sulfonating PEEK resin: https://www.mdpi.com/2076-3417/14/10/3980
Even when processing the resin DIY, the photo paper remains a lot cheaper! It’s definitely convenient that the chemistries in use can tolerate some mixing.
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@kirk said in New ion exchange membrane recipe using water softener resin and PVC cement:
First off, @rowow , thanks for making your membrane approach open-source! Out of curiosity, is the patent application alongside it meant to prevent patent trolls from taking advantage of it?
YES!!! protecting against patent trolls was exactly the point. I didnt want to deal with being in court the next 15 years prohibited from using my own technology arguing whether or not its open sourced. The certain japanese gaming company patenting a certain game mechanic recently is a great example how terrible the patent situation is...
@danielfp248 has looked into membranes quite a bit and I agree that the only way to know for sure about a membrane's chemical compatibility is to test it with the proposed electrolyte during operation, where it will be exposed to, to take our standard zinc-iodide cell as an example, zinc dendrites (which can puncture an IEM) and high concentrations of triiodide, which can be pretty aggressive and "weird", in the sense that it has attacks and goes through many polymers that are otherwise resistant to similar classes of chemicals.
I personally favor ferric chloride so I dont have any experience with zinc iodide. But I hope this membrane will allow the community to also see other membrane ideas in general. A user on my discord server sent the following research paper which discussed using a carbon slurry as a carrier for the metal to plate off. Really interesting study I wonder what you think, very much worth replicating also and may solve the dendrite/plating issue.
https://link.springer.com/article/10.1557/s43581-022-00046-8It seems you probably have most of the resources already to test your membranes with ZnI? The other thing that would be quite different in terms of membrane requirements for a battery vs. a refining process would be conductivity, I'm not sure if you've done measurements in terms of Ohm*cm² but this would be a harder target to reach for RFB applications.
I dont have any zinc iodine. I can see about fitting it into a test cell to demonstrate but honestly that would be a month out. I am trying to launch a website store right now alongside many other video ideas first to publish. I havent properly measured its conductivity, definetly varies based off solution. I just know that theres a very low voltage drop when electrolyzing across the membrane vs directly in solution at the same distance. Additionally I get 100-200ma/sqcm depending on the fabrication method. When using the proposed ball milling and spray method you can get paper thin sheets. Currently with my mining setup, the electrodes are the limitation not the membranes.
We don't have the equipment or time to prepare these membranes but if you send us samples of 100-400um thick membranes we can test them out.
