My adventures building a Zinc-Bromine battery

svetz said:

Thanks! I actually meant test results, something similar to #203

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Not at this moment in time. I don't really have the equipment. At the moment I'm mostly interested in getting out what I put in and keeping it there for as long as possible (as many times as I can). Need to invest in some better equipment but costs are too high to buy.

Hi
I have attached a Charge/Discharge curve of one of my test cells. This was done using a ZKE electronic load. The curves do not show the charge current, which was set at a CC of 14mA on my PSU. The charge time was only 5 minutes and the discharge 2 minutes. I chose a resistance that would discharge the cell over 2 minutes. I realise that these times need to be extended to fully charge and discharge the cell to get realistic results. There does not appear to be any decay in the cell for 50 cycles. I recently did a 200 cycle test without decay but my software crashed when I tried to save the results. Up to date the cell does not appear to lose any capacity over a 24 hour period although I do intend to increase this to 7 days to see the results.

That's pretty impressive, but why no dendrites?

svetz said:

That's pretty impressive, but why no dendrites?

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My electrolyte has the usual additives to suppress dendrites and my separator is something I developed a few years ago to suppress dendrites and self discharge. At the moment it could be because of the depth of charge. I need to do further testing with a deeper charge cycle to see if dendrites develop. They are definitely reduced at the moment but further testing is required to see if and when the cell fails. Hopefully it won't but I have got used to failure in this game. Self discharge was always my biggest problems so I decided to solve that first. If I couldn't stop that then dendrites were irrelevant.

Identernet said:

...Self discharge was always my biggest problems so I decided to solve that first....

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Some self-discharge isn't that big a deal. For example, in an off-grid scenario, the minimum setup is that the batteries are consumed overnight (e.g., <14 hours); so a loss of a few percent per day isn't as big of a deal as it would be for long-term battery storage. Even for designs with a 3-day reserve, that's only 72 hours. Let's say it's a 10% loss over three days, then the trick is to have the costs such that adding 10% more batteries is economically viable.

My original zinc bromide batteries were discharging at an alarming rate ie 75% in 12 hours, but they are much better now. I agree with your statement regarding an acceptable amount of self discharge with it's regard to cost. My cell costs are very low, so should be ok. I intend to do some more tests based on a 0.5C charge/discharge rates to full charge and see how they go as dendrites may now be my only problem.

Identernet said:

Hi
I have attached a Charge/Discharge curve of one of my test cells. This was done using a ZKE electronic load. The curves do not show the charge current, which was set at a CC of 14mA on my PSU. The charge time was only 5 minutes and the discharge 2 minutes. I chose a resistance that would discharge the cell over 2 minutes. I realise that these times need to be extended to fully charge and discharge the cell to get realistic results. There does not appear to be any decay in the cell for 50 cycles. I recently did a 200 cycle test without decay but my software crashed when I tried to save the results. Up to date the cell does not appear to lose any capacity over a 24 hour period although I do intend to increase this to 7 days to see the results.

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Thanks for sharing!

Having charge/discharge curves that plot voltage as a function of the injected/extracted charge is vital, because this allow us to determine a wide variety of important data (coulombic efficiency, energy efficiency, capacity, etc). This is the most fundamental measurement in battery characterization for this reason. You can build Zn-Br batteries with very low self-discharge and relatively high coulombic efficiency at the expense of absolutely dismal energy efficiency values. Such a battery wouldn't be useful in practice.

For this reason, most conversations about dendrites, self-discharge, hydrogen evolution, etc, are not meaningful, if we don't know the capacity, energy and coulombic efficiency values of the battery, which are it's most important characteristics.

Given the charts you posted, do you have enough information to calculate the CE, EE and capacity of your battery? This would help us understand the properties of the battery you're testing.

Hi Daniel
I agree with you regarding what you say, unfortunately the only equipment I have is my Chinese electronic load, my PSU and timer relays. I am really interested in the potentiostat you built from the paper at the start of you post. As soonas I saw the flush components I knew I was flogging a dead horse trying to make it myself, having tried flush soldering before. I have soldered a lot of conventional boards but wouldn't attempt that. I was going to contact the chinese company who manufactured yours. Would you recommend that and would I be able to use your contact with them as a reference. I have just done a charge/discharge and calculated my coulombic efficiency (CE) at around 80%.
I,m not sure how the specific capacity would be calculated for this type of battery. Would the zinc be included, the electrolyte or the active material (carbon) only. If it was the carbon only then it would be off the scale.

Identernet said:

Hi Daniel
I agree with you regarding what you say, unfortunately the only equipment I have is my Chinese electronic load, my PSU and timer relays. I am really interested in the potentiostat you built from the paper at the start of you post. As soonas I saw the flush components I knew I was flogging a dead horse trying to make it myself, having tried flush soldering before. I have soldered a lot of conventional boards but wouldn't attempt that. I was going to contact the chinese company who manufactured yours. Would you recommend that and would I be able to use your contact with them as a reference. I have just done a charge/discharge and calculated my coulombic efficiency (CE) at around 80%.
I,m not sure how the specific capacity would be calculated for this type of battery. Would the zinc be included, the electrolyte or the active material (carbon) only. If it was the carbon only then it would be off the scale.

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PCBway did a great job when I had them assemble the PCB, so it should be fine. I don't know if you can give somebody as reference - since they are a very big company - but feel free to use it if you can. All the files you need for the job are freely available with the paper describing the potentiostat/galvanostat.

About the CE, it tends to be really high for these batteries, above 80% values are fairly common. Most interesting would be the energy efficiency, since this is the weak spot of these batteries and setups that have low self-discharge tend to have very low values (often lower than 20%).

About the capacity, since these batteries are most interesting for static applications, the volumetric capacity in Wh/L of battery is most interesting. The denominator should include the volume of all the battery materials, cathode, anode and electrolyte/separator. If you want to calculate the capacity using weight, in Wh/kg then you need to include all active materials as well.

Hi
Thanks for that.
Sorry, what I meant was to reference the board they did for you, that way it would probably make it easier for them, if you see what I mean. Could I ask roughly how much they charged if that''s ok?

Identernet said:

Hi
Thanks for that.
Sorry, what I meant was to reference the board they did for you, that way it would probably make it easier for them, if you see what I mean. Could I ask roughly how much they charged if that''s ok?

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It was around 160 USD including shipping via DHL. However, components might be more expensive now. Here is the information for my order in case any of it is useful for you :

These are the files. They might charge you to create a component placement file, sadly I don't have that one.

Thanks for that. I really appreciate it and hope it helps others.

Identernet said:

Thanks for that. I really appreciate it and hope it helps others.

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Also note that the max current for this is 25mA so it is meant to characterize small devices.

Identernet said:

My original zinc bromide batteries were discharging at an alarming rate ie 75% in 12 hours, but they are much better now. I agree with your statement regarding an acceptable amount of self discharge with it's regard to cost. My cell costs are very low, so should be ok. I intend to do some more tests based on a 0.5C charge/discharge rates to full charge and see how they go as dendrites may now be my only problem.

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Hello how did you reduce self discharge for your battery?

Hi Juptron
I've been working on these batteries on and off for about 4 years, so I don't really want to disclose my methods. I trust you will understand this. I can tell you that you will need some form of sequestration as Daniel discusses, otherwise you have no chance. I found that my separator played a large part also, both in stopping dendrites and self discharge. The cell also need to be sealed well as bromine vapours and electrolyte leakage results in massive self discharge also.
I would gladly make my methods open source but I don't want Universities/companies getting any of my research. Universities like to charge people to access papers which have ultimately been paid by the taxpayer, hence my dislike of their methods. Obviously I can't afford patent protection. Patents are in place to protect the already rich Universities/Companies.

Identernet said:

Hi Juptron
I've been working on these batteries on and off for about 4 years, so I don't really want to disclose my methods. I trust you will understand this. I can tell you that you will need some form of sequestration as Daniel discusses, otherwise you have no chance. I found that my separator played a large part also, both in stopping dendrites and self discharge. The cell also need to be sealed well as bromine vapours and electrolyte leakage results in massive self discharge also.
I would gladly make my methods open source but I don't want Universities/companies getting any of my research. Universities like to charge people to access papers which have ultimately been paid by the taxpayer, hence my dislike of their methods. Obviously I can't afford patent protection. Patents are in place to protect the already rich Universities/Companies.

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Ok thanks for sharing, good success to you and everyone on this..

I think it's pretty awesome the work you've done. My only concern is that because of the bromide / bromine it would be best left to industrial batteries where professional waste services can be employed.

In the hands of a consumer, you know where 90% goes - straight to the landfill.

I know other inventors like Charles Renard (1847-1905) gave up on bromine and stuck to chlorine-zinc in the end, but that was after the early flow batteries for blimps stuff.

I gotta' re-read the thread slowly, because it sure is fascinating. Nice job and thanks for sharing.

So guys, I moved countries earlier this year and hadn't had the time to start my home-research into Zn-Br batteries again. However, I have now reached a stable situation and will start researching Zn batteries again. I will start another thread as I will start research into some additional Zn chemistries, since some problems of the Zn-Br chemistry seem to make them hopelessly impractical for long-term DYI batteries.

These are the problems that I believe make static Zn-Br batteries an impractical choice and why I won't research them any further:

1. Sequestration of the Br2 requires the use of sequestering agents. Most of these have low solubility values in concentrated ZnBr2 solutions (>0.5M). High capacity batteries require high concentrations of ZnBr2, which means a highly soluble sequestering agent with a very low solubility perbromide would be required.
2. The low solubility perbromides effectively sequester bromide as insoluble perbromides, but then they inevitably reduce the conductivity of the cathode on deposition. If large amounts are deposited, then the reduction of the perbromides becomes difficult due to this. This inherently limits capacity.
3. There is hydrogen generation at the anode. This leads to a basification of the battery that eventually pacifies the anode, as Zn oxides and hydroxides deposit on the anode. This kills the battery and would require refurbishing.
4. Using an inverted geometry (Zn anode at the bottom and carbon cathode at the top) effectively fixes the hydrogen evolution issue, but at the expense of making the issue of self discharge worse (as elemental bromine and solid perbromide can fall into the anode and react with the Zn).

The above issues are, in my opinion, quite insurmountable from a DIY perspective - especially without incurring very high costs to test more elaborate sequestering agents - so I've decided to focus on more friendly chemistries.

The perbromide sequestration and hydrogen evolution problems are issues with no obvious practical DIY solution - at least to me - and compromises lead to batteries with high self-discharge, low capacities, low energy densities or low energy efficiencies. In my view, there is no point in making a battery if you cannot at least do as well as Li-Fe-PO4 batteries from an economic perspective (either by having much longer cycle life or better energy density or capacity).

Also some notes for those who might be interested and have done some online reading but don't want to read my whole blog or this thread:

1. This Chinese paper, has serious issues and should NOT be considered a substantial breakthrough in Zn-Br batteries. The capacity values reported are based on the mass of active cathode material (3mg per battery), while the entire cathode mass is likely 10x that and the total battery mass - including electrolyte - is likely 50-100x more. The capacities are therefore entirely misleading, since capacity in Zn-Br batteries comes from the mass of electrolyte, NOT the mass of the cathode. The power densities do not account for the mass of the water, anode or entire cathode either, so they are also extremely misleading. The Zn-Br concentration is also kept quite low (0.5M) this is because of a very good reason, TPABr is not soluble in ZnBr2 solutions above this threshold. When accounting for entire battery mass, this is orders of magnitude below lithium ion in terms of power density or capacity.
2. Robert Murray Smith has done several videos about Zn-Br batteries, but these batteries represent a compromise that is unacceptable in practice. The series resistance of these batteries is directly proportional to the distance between the electrodes and all the batteries he has shown have very large distances and likely suffer from huge internal resistance. Although he might have quite high Coulombic efficiency values - what he often quotes as being above 85% - the energy efficiency, or how much energy you get out for energy you put in, is likely extremely low, around 10-15%. Be prepared to put 10kWh for every 1kWh you want to get out if you intend to follow his geometries and advice on these batteries. A high energy efficiency Zn-Br battery should have a cathode-anode distance of around 3-5mm if using 1-2.5M ZnBr2 solutions.
3. The Princeton minimal architecture papers show some of the issues I've discussed above. They run into issues with unacceptable cell discharge and anode deactivation due to hydrogen evolution. If you look into the PhD theses from this research group, you will find theses dedicated to the scaling of these batteries, these show how these issues completely precluded the use of these batteries at any significant scale.

While the Zn-Br chemistry might seem a pretty obvious and clear option for DIY, reality shows why companies and researchers decided to switch to flow batteries and how - even when doing this - some pretty hard problems still remain.

The devil is clearly in the details when it comes to Zn-Br batteries. ?

The above is also not meant to discourage others who might want to pursue this technology, but just a list of issues so that you can go into this chemistry with eyes wide open.

@danielfp248
Still biting the bullet for zn-br cells?
Well i can not leave it behind me also, it keeps on rambling in my mind........on and on.
When i finished rebuilding my house, i also will give it another go.
Thank you VERY much for your efforts, very helpful and constructive ideas!
(we met on a different forum btw)
Matter a fact i was cleaning my shed last month and found some of my old experiments, but not the data that i promest you, sorry.

Thanks for keeping up, with best regards Igor aka 100kwh hunter.
Time sure flies.....

Anyone still getting after it with this battery research? I came to the same conclusion as @danielfp248 that Zn Br cells are not a viable or safe homemade solution. Zn I2 is a logical next step. Here are some other ideas to consider:

1) Zinc Iodine: Use of propylene carbonate as complexing agent (https://www.sciencedirect.com/science/article/abs/pii/S0013468619312939?via=ihub)
2) Zinc Iodine: Use of Ammonium Chloride as electrolyte enhancer (https://www.sciencedirect.com/science/article/abs/pii/S2405829720302531?via=ihub)

There seem to be some irreversible reactions related to the ZnI2 battery on the iodine side, especially if the battery is over charged, so keep that in mind.

Zinc Nickel
I went down the rabbit hole with Zinc Nickel batteries, and I can tell you that getting an electrochemically active version of Nickel Hydroxide - Ni(OH)2 is an extremely finicky process involving PH / temperature / proper precursor matching / mix rate / drip rate.... I got it done once! and could not repeat the process. Nickel compounds are also expensive and I've put this one on the shelf

Zinc Mn3O4
I've moved on to testing Zinc Manganese based chemistries. I am keeping with the Zinc anode theme because it's cheap, available, offers great voltages and well studied (even with potential dendrite issues). Manganese is also very cheap ( Just look at the price of a 5lb back of MnSO4 on amazon... and compare that to a 5lb bag of NiSO4)

This is a good overview to help guide research: https://onlinelibrary.wiley.com/doi/10.1002/inf2.12042

Best of luck! and I definately understand what @Juptron is saying about keeping his own research protected. I've also encountered similar problems in the literature, especially with chinese type papers, and I think there are plenty of mistakes in a tremendous amount of battery related articles (both accidental and possibly deliberate...)

I've attached some files. Spending money on all these articles is expensive, maybe we can share the load here a little bit hopefully I start a trend.

@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.

@danielfp248

I’m curious to hear your views on this article regarding an Australian ZnBr cell, or indeed your opinion on the viability of the gelion battery

toms said:

@danielfp248

I’m curious to hear your views on this article regarding an Australian ZnBr cell, or indeed your opinion on the viability of the gelion battery

'A scientist's dream': Safe, affordable storage batteries to be manufactured in western Sydney

It's hoped the manufacture of a "breakthrough" energy storage battery in Sydney's west will join a market worth more than $100 billion, creating jobs and cost-effective technology able to run safely at high temperatures.

www.abc.net.au

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You can read the gelion patents to get a better idea about this technology. This likely works, but it is going to be quite expensive - the gels are expensive ionic liquid electrolytes - so these are unlikely to ever be able to compete against Li-ion or to be available for someone to build in a DIY manner. Ionic liquids are expensive, despite a ton of research on ionic liquids in batteries we have no large scale commercial applications in the battery area.

Thanks for that. It will be interesting to see where they go with their technology.