My adventures building a DIY Mn/Fe flow battery

[danielfp248]

Glad you like it I already emailed them regarding sample, so lets see how that turns out and ofc I will make sure you get some. I am going to look over the book I linked to just to see what I can pick up in terms of info.

Maybe there is a way to make the ceramic silicon with nicer chemicals...

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 solution and several mineral acids, plus fiberglass membranes. To do a simple test I prepared a silica gel fiberglass embedded membrane by dipping it in potassium silicate and then in 10% phosphoric acid, then drying it at 50C. I repeated the coating process 3 times to ensure the fiberglass was completely saturated with silica gel. I then measured the permselectivity of this membrane, which was <5%, as expected. To introduce the charged groups that give a membrane anion or cation specificity, you absolutely need more reactive silicon species that are adequately functionalized.

So they definitely make it look much more trivial than it is. You need the proper precursors - that provide the proper functionality - and then careful proportions to get the proper nanostructure. This is what the patents do show.

If you get some do send some my way, definitely a very interesting approach to test if you can get your hands on a membrane.

 

[Patrik L]

See, you do know ... I knew it All I need to know. I am sure that with the right equipment, these membranes can be made, but that is a completely different scenario.

They are open for business, so lets hope they are interested in a nobody

 

[Patrik L]

We might have another material to consider, but will keep this entry a bit shorter

Durable, High Performance Cation Exchange​

​

Premion - Hydrocarbon polymer membrane - (sulfo-phenylated polyphenylene).

Pemion™ is a breakthrough proton exchange membrane (and cation exchange) and polymer product (PEM & CEM) in advanced development at Ionomr.

Pemion represents a fundamental shift in the approach to proton exchange technology through its migration from Perfluorinated Sulfonic Acid (PFSA) chemistry to environmentally-benign hydrocarbon materials while maintaining maximum durability. These hydrocarbon materials also provide considerably higher performance, lower gas crossover and eliminate environmental concerns associated with End-of-Life (EOL) disposal of fluorinated compounds.

The resulting gains in performance and reductions in gas crossover provide a revolutionary impact on hydrogen fuel cell cost through reduction in precious metal usage, longer lifetimes through reduced degradation and higher efficiency by operating at higher temperature with less fuel crossover. Other applications impacted by this technology are advanced battery technologies including electrodes, coatings and solid electrolytes.

Unlike their PFSA counterparts, Ionomr’s hydrocarbon products have substantially reduced toxicity and environmental impact during both manufacturing and disposal. Additionally, Pemion boasts one of the highest room temperature conductivities available, while maintaining its mechanical stability (Adamski et al., Angew. Chem. Int. Ed. 2017, 56, 1 – 5) for an improved total efficiency and longer system life.

***​

It looks to be using Methanol and/or Isopropanol as solvents via one of the review papers. It indicates to outperform NAFION.

Sources:

1. 

   Pemion™ - Proton-Exchange Materials - Ionomr Innovations Inc.

   Pemion™, a breakthrough hydrocarbon Proton Exchange Membrane (PEM) – provides considerably higher performance, durability and lower gas crossover while eliminating environmental concerns of Fluorine.

   ionomr.com

2. The Solutions Center - Resources - Ionomr Innovations Inc.

   Find out more about Ionomr's tech in specific applications. View peer-reviewed papers, Material Safety Data Sheets and Safety instructions.

   ionomr.com
3. https://freidok.uni-freiburg.de/fedora/objects/freidok:219063/datastreams/FILE1/content
4. https://pubs.rsc.org/en/content/articlepdf/2021/ma/d1ma00511a

 

[danielfp248]

We might have another material to consider, but will keep this entry a bit shorter

Durable, High Performance Cation Exchange​

View attachment 129732
​

Premion - Hydrocarbon polymer membrane - (sulfo-phenylated polyphenylene).

Pemion™ is a breakthrough proton exchange membrane (and cation exchange) and polymer product (PEM & CEM) in advanced development at Ionomr.

Pemion represents a fundamental shift in the approach to proton exchange technology through its migration from Perfluorinated Sulfonic Acid (PFSA) chemistry to environmentally-benign hydrocarbon materials while maintaining maximum durability. These hydrocarbon materials also provide considerably higher performance, lower gas crossover and eliminate environmental concerns associated with End-of-Life (EOL) disposal of fluorinated compounds.

The resulting gains in performance and reductions in gas crossover provide a revolutionary impact on hydrogen fuel cell cost through reduction in precious metal usage, longer lifetimes through reduced degradation and higher efficiency by operating at higher temperature with less fuel crossover. Other applications impacted by this technology are advanced battery technologies including electrodes, coatings and solid electrolytes.

Unlike their PFSA counterparts, Ionomr’s hydrocarbon products have substantially reduced toxicity and environmental impact during both manufacturing and disposal. Additionally, Pemion boasts one of the highest room temperature conductivities available, while maintaining its mechanical stability (Adamski et al., Angew. Chem. Int. Ed. 2017, 56, 1 – 5) for an improved total efficiency and longer system life.

***​

It looks to be using Methanol and/or Isopropanol as solvents via one of the review papers. It indicates to outperform NAFION.

Sources:

1. 

   Pemion™ - Proton-Exchange Materials - Ionomr Innovations Inc.

   Pemion™, a breakthrough hydrocarbon Proton Exchange Membrane (PEM) – provides considerably higher performance, durability and lower gas crossover while eliminating environmental concerns of Fluorine.

   ionomr.com

2. The Solutions Center - Resources - Ionomr Innovations Inc.

   Find out more about Ionomr's tech in specific applications. View peer-reviewed papers, Material Safety Data Sheets and Safety instructions.

   ionomr.com
3. https://freidok.uni-freiburg.de/fedora/objects/freidok:219063/datastreams/FILE1/content
4. https://pubs.rsc.org/en/content/articlepdf/2021/ma/d1ma00511a

I mean, there are currently several published alternatives that work better than Nafion and that are purportedly "cheaper". The question is, can I buy them easily off any place like alibaba or ebay? If the answer is you can't, then they might as well not exist in the short term.

You will often find, as with several commercially available SPEEK membranes, that the cost ends up being much higher than Nafion, just due to the scale (Nafion is produced in multiton quantities per year, unlike most other membranes).

I often find it's often more productive to ask the question "what can I really buy right now at the lowest cost?" than "what is theoretically available out there?". The second question usually leads to a lot of promises that really do not materialize into things you could use right now in DIY.

 

[Patrik L]

Sure, the "what can I really buy right now at the lowest cost?" is among the most productive question in terms of right now and it is paramount I will say for the total cost.

I did a speculative cost calculation using CMI-7000 and a target of 24kW potential (as in what I can constantly discharge) based upon 20mA/cm^2 and ended up at over 8000€ and some 40m^2 of membrane... I'd like for that to change... LOL. So I started looking at alternatives.

My other worry is longevity and while the Ceramic Silica-gel looks interesting, waiting for a reply is tedious and its Sunday, so I killed some time. And that is not how one perform scientific experimentations, its one at a time, collect data, and then decide the next step. I also like to have backup plans and side-ideas that can be beneficial, so here we are. But honestly, I want to see this battery succeed and so doing via affordable and approachable methods. That's all.

 

[Patrik L]

Its when I read this that I get worried regrading longevity of PFSA.

"In all, this first cellulose-based membrane separator for AORFB (all organic redox flow battery) system largely outperformed commercial Nafion 115 membrane in terms of device functional stability, as evidenced by 63% versus 5% capacity retention after 90 cycles. Visibly, the cellulose membrane does not change its aspect after cycling, while Nafion takes on a strong orange color, which indicates that the latter membrane is not impermeable for the dye."

OBS: The sulfonation was performed by sodium metabisulfite - (It is used as a disinfectant, antioxidant, and preservative agent)

Sulfonated Cellulose Membranes Improve the Stability of Aqueous Organic Redox Flow Batteries.

https://onlinelibrary.wiley.com/doi/full/10.1002/aesr.202200016

I wonder if this paper could help your cellulose membrane. Microfluidization is part of their process. I don't know, maybe I am overthinking the use of PFSA as a problem, but its not uncommon to read that its longevity or cyclability can sometimes be short.

 

[Patrik L]

I mean, there are currently several published alternatives that work better than Nafion and that are purportedly "cheaper".

If you don't mind, would you care to share some inside towards what those are, just so that I can widen my resources.

 

[danielfp248]

This 2021 review of membranes provides a good summary: https://www.mdpi.com/2077-0375/11/3/214. Note that the cost section is very hypothetical - assuming membranes got produced in a larger scale - in reality you cannot buy most of these membranes right now at a price point lower than Nafion. The CMI-7000 membrane is one of the few you can, although it does not outperform Nafion, it's just cheaper.

 

[danielfp248]

Its when I read this that I get worried regrading longevity of PFSA.

"In all, this first cellulose-based membrane separator for AORFB (all organic redox flow battery) system largely outperformed commercial Nafion 115 membrane in terms of device functional stability, as evidenced by 63% versus 5% capacity retention after 90 cycles. Visibly, the cellulose membrane does not change its aspect after cycling, while Nafion takes on a strong orange color, which indicates that the latter membrane is not impermeable for the dye."

OBS: The sulfonation was performed by sodium metabisulfite - (It is used as a disinfectant, antioxidant, and preservative agent)

Sulfonated Cellulose Membranes Improve the Stability of Aqueous Organic Redox Flow Batteries.

https://onlinelibrary.wiley.com/doi/full/10.1002/aesr.202200016

I wonder if this paper could help your cellulose membrane. Microfluidization is part of their process. I don't know, maybe I am overthinking the use of PFSA as a problem, but its not uncommon to read that its longevity or cyclability can sometimes be short.

This wouldn't work for me, my membrane is not simply cellulose, it is a cellulose support (filter paper) with most of the membrane bulk weight actually being PVA. This process involves oxidizing the cellulose first - with periodate, which I don't want to use - to create aldehyde groups that you can then sulfonate with bisulfate but this same process does not work with PVA. Periodate will just break the PVA apart.

To create a pure cellulose membrane you also need to create nano-cellulose fibers and then create the membrane out of those, something I'm not interested in doing at this point.

 

[Patrik L]

Thanks for the link, will dive in.

Indeed, they make nano-cellulose and one need proper equipment for that, something neither of us have. But I do find it interesting non the less. I was also checking Fumapem FS-930, but it got higher resistance compared to CMI-7000. So if nothing changes, CMI-7000 and possibly the Membrion silica membrane is our best option for the time being.

 

[Patrik L]

I just noticed something regarding current density.

Fumasep FS-930: 150-400mA/cm^2
CXM-200 (CMI-7000): <50mA/cm^2

 

[danielfp248]

I just noticed something regarding current density.

Fumasep FS-930: 150-400mA/cm^2
CXM-200 (CMI-7000): <50mA/cm^2

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

 

[Patrik L]

Got it. I find myself spending hours scouring the internet for THE membrane and I will not give up until my non scientific brain can't lift any more rocks. This is fine, I think I am learning ...

 

[Patrik L]

Besides Sulphuric Acid, what other approach to sulfonating are there ?

 

[danielfp248]

Besides Sulphuric Acid, what other approach to sulfonating are there ?

Depends on what you're sulfonating, different organic groups can be sulfonated by different reagents. Most sulfonating agents are far worse than sulfuric acid, reagents like chlorosulfonic acid. Although very reactive organic groups, like aldehydes, can be sulfonated with mild reagents like bisulfates.

 

[Patrik L]

Since I am not a chemist it can be challenging to know exactly where to look for information etc. But I like the silicon dioxide angle, so what if one takes a simpler rout and don't use sulfination but start with potassium silicate or sodium silicate and incorporate ionic salts and produce something similar to agar salt bridge and finally use glass fibre as a scaffold. Silicone polymer with cation permselectivity .... come on man ... LOL

And this, a bit above my paygrade, but could contain useful information: Polymers for Battery Applications—Active Materials, Membranes, and Binders.

News: Membrion replied to my initial email and wanted more info, which I gave them yesterday and are now waiting for a response. I also contacted Saltworks to possibly obtain samples of their IonFlux membrane(s) which looks equally interesting. This is like fishing and using multiple hooks and baits.

 

[danielfp248]

Since I am not a chemist it can be challenging to know exactly where to look for information etc. But I like the silicon dioxide angle, so what if one takes a simpler rout and don't use sulfination but start with potassium silicate or sodium silicate and incorporate ionic salts and produce something similar to agar salt bridge and finally use glass fibre as a scaffold. Silicone polymer with cation permselectivity .... come on man ... LOL

And this, a bit above my paygrade, but could contain useful information: Polymers for Battery Applications—Active Materials, Membranes, and Binders.

News: Membrion replied to my initial email and wanted more info, which I gave them yesterday and are now waiting for a response. I also contacted Saltworks to possibly obtain samples of their IonFlux membrane(s) which looks equally interesting. This is like fishing and using multiple hooks and baits.

Sorry, that approach won't work. Salt bridges are not going to be stable in an exchange membrane for this type of application. Neither do they have the properties required (permselectivity, conductivity, etc). The "silicon dioxide" angle you saw, works precisely because of the silicon precursors used, as I mentioned, that is precisely WHY it works. Silicon dioxide is not why it works, it's because the precursors create a silicon dioxide that has the proper chemical functionalization.

A cation exchange membrane absolutely requires a negatively charged group that is covalently anchored to an insoluble structure.

 

[Patrik L]

Slowly realizing that .. and I also realized that no matter which SPEEK approach I look at, Sulfuric acid is involved and the journey sort of stop there. Getting hold of Sulfuric acid as a private consumer (EU) is no longer possible, not even in the form of dilute 37% battery acid and I am not about to manufacture it from Sulphur and hydrogen peroxide in my garage. So unless some other sulfination approach pops up, that approach to DIY ends here.

It is perhaps not the end of the world, but I would have enjoyed producing my own membranes as an alternative - always have more than one approach. Atm and besides your CMI-7000, I am on hold for further Membrion communication, Saltworks and Fumatech is another approach I am waiting on.

So now the waiting starts ... LOL

 

[Patrik L]

Saltworks replied and its a dead end.

Thank you for reaching out and your interest in Saltworks. We appreciate the opportunity to work on this project with you, but unfortunately must decline, as we do not sell individual ion exchange membranes. We exclusively integrate them into our full-scale, turnkey systems (FlexEDR series) for industrial wastewater desalination applications. Should you see projects that require industrial wastewater desalination, brine minimization/zero liquid discharge, and/or lithium refining, please do reach out to us and we’d be happy to assist.

We wish you all the best with this project!

Kind regards

Sheida Arfania, M.A.Sc.
Business Development Associate
Saltworks Technologies Inc.

 

[Patrik L]

Hmm, in an article First published: 09 June 2022 they claim: Herein, we report an all-iron redox flow battery containing Fe/Fe(II) and Fe(III)/Fe(II) redox couples separated by a self-made anion exchange membrane. We also examined the impact of adding Zn(II) ions on the electrochemical performance of the Fe/Fe(II) redox couple. The coulombic efficiency, voltage efficiency and energy efficiency of the cell with 0.03 m ZnCl2 was found to be greater (90 %, 70.96 % and 63.86 %) than those of the cell without ZnCl2 (80 %, 62.06 % and 49.64 %). The results reveal that the addition of small amounts of Zn(II) ions to the Fe/Fe(II) electrode suppresses the hydrogen evolution reaction and increase the cell performance.

Wouldn't the reaction between Zn(II) and H2 produce Zink Hydride ... (ZnH2)