My adventures building a Zinc-Bromine battery

[danielfp248]

Funny, I’ve had the same feelings. I smile each time he describes the “3 types of people”. clearly, he’s saying that the least trustworthy of the 3 are those involved in battery development - and yet we accept all things on the channel at face value. Reminiscent of the ”frog and the scorpion”. . That being said, I have no particular reason to doubt him.... I think his primary goal (and he‘s quite successful at it) is to inspire others to experiment. To take the published papers and dare to ask “why?”. After all, Flash Graphene synthesis wasn’t optimized on the basis of some quantum revelation. It was a grad student who said something like this... “if we can produce graphene with the power of high intensity lasers, why not try a simple spark discharge?“. Anyone wanting to look at Graphene seriously is in need of a cheap Raman Spectroscope. My old physchem graduate advisor wrote two books on various spectroscopic measurement systems.... he’d be impressed with what you can do with a 3D printer these days!

I agree, Robert does a great job sharing and getting people excited about chemistry. I support his channel and admire his work in this sense.

However, his Zn-Br battery designs are just not practical or efficient designs. Those foam batteries have huge energy efficiency losses and the jar designs he shared in his last videos about the topic have abysmal energy efficiencies as well. In both of these designs I would estimate you would get 10-15% energy efficiency out of them, which is not acceptable for a battery application.

Also the Chinese paper that started my journey in Zn-Br batteries is just hype, see this post about my comments on their experimental results https://chemisting.com/2020/09/12/zinc-bromine-batteries-can-they-really-be-that-good/

 

[Nitrous]

I don't add any current collector to the carbon, see my Swagelok cell configuration here https://chemisting.com/2020/12/25/zinc-bromine-batteries-about-my-swagelok-cell-for-s9mall-scale-battery-testing/

Thanks for that. I’ve been looking at PVDF as a polymer base for electrodes, especially in the context of bipolar electrodes in higher total voltage per cell. I was surprised to find out that there is information on bipolar configurations for LAB systems. Thanks for the link. Doug (I’ve been looking at the active solders for carbon/metal bonds.... very interesting stuff - see Ben Krasnow’s video on US assisted soldering)

 

[Nitrous]

I agree, Robert does a great job sharing and getting people excited about chemistry. I support his channel and admire his work in this sense.

However, his Zn-Br battery designs are just not practical or efficient designs. Those foam batteries have huge energy efficiency losses and the jar designs he shared in his last videos about the topic have abysmal energy efficiencies as well. In both of these designs I would estimate you would get 10-15% energy efficiency out of them, which is not acceptable for a battery application.

Also the Chinese paper that started my journey in Zn-Br batteries is just hype, see this post about my comments on their experimental results https://chemisting.com/2020/09/12/zinc-bromine-batteries-can-they-really-be-that-good/

You’re referring to the Zinc-Bromine Static Battery Paper, right?

A High-Performance Aqueous Zinc-Bromine Static Battery LujieGao12ZhuxinLi1YipingZou1ShuangfengYin1PengPeng3YuyingShao3XiaoLiang124​

It’s sad when peer review means nothing.....

 

[danielfp248]

You’re referring to the Zinc-Bromine Static Battery Paper, right?

A High-Performance Aqueous Zinc-Bromine Static Battery LujieGao12ZhuxinLi1YipingZou1ShuangfengYin1PengPeng3YuyingShao3XiaoLiang124​

It’s sad when peer review means nothing.....

Yea, exactly that one. They calculate their capacity values with only 3mg of cathode material - which is the activated carbon they add to a whole other bunch of things that make up the cathode - for the specific capacity and energy values they use those 3mg plus the mass of ZnBr2+TPABr, ignoring the mass of the water which is critical since you cannot dissolve these things at higher concentrations. Total scam as you simply cannot build a battery without the other components. In reality, the values are 100x lower when you consider all the materials.

 

[Nitrous]

Yea, exactly that one. They calculate their capacity values with only 3mg of cathode material - which is the activated carbon they add to a whole other bunch of things that make up the cathode - for the specific capacity and energy values they use those 3mg plus the mass of ZnBr2+TPABr, ignoring the mass of the water which is critical since you cannot dissolve these things at higher concentrations. Total scam as you simply cannot build a battery without the other components. In reality, the values are 100x lower when you consider all the materials.

I am a peer reviewer. I remember getting asked by an editor to “rush a paper” through.... the author was very well known.... I refused to do it. The paper was published, but with changes. Peer review should be a critical review, regardless of the “name” or reputation submitting it. Glad I didn’t spend a fortune on TPAB . My other thought was to look at bipolar LAB arrangements.... some interesting methods to explore to increase surface area of the electrodes. Lead acid may be old, but old is ripe for improvement .

 

[Nitrous]

Daniel, have you looked at the technology being developed by e-Tech? It appears to be a plating technology, but the difference is that the metallic zinc is deliberately dislodged from the receiving electrode. Seems like a clever way of preventing discharge and ultimately, do away with dendrite formation (I'm guessing - I've not read the papers yet)

Energy Storage Technology | Renewable Energy Storage

e-zinc.ca

 

[Identernet]

Hi Daniel.
I have been reading through your research/experiments with great interest as static zinc bromide batteries have been my main focus of interest for several years. They seem to be a natural contender for mass energy storage but receive little publicity compared to flow batteies. I have had good results but have never, until recently, been able to overcome the problem of massive self discharge. You do not make any comments regarding this (unless I have missed it), so was wondering how your cells perform in this respect. One thing I noticed is that you used graphite in your swagelock. I tried this initially and always found that the graphite resistance made this method next to useless. I believe the stainless steel, or any other metal for that matter, reduces it's efficiency. I make my test cells from a 3D printed container and get good results.

 

[svetz]

... I make my test cells from a 3D printed container and get good results.

That's interesting, are the results something you can publish here or provide a link to?

 

[Identernet]

That's interesting, are the results something you can publish here or provide a link to?

Hi
I have attached a zip file giving STL files of the top and bottom if anyone wishes to make the part on their 3D printer. I have also attached a jpeg of the assembly in use. I clamp the assembly using 6 small (22mm) binder clips. These are real cheap on Ebay and are great for applications like this and for electrical connectors. Just put a 3mm screw through one of the holes in the clip and connect your wires via the screw. The test jig makes use of grafoil and materials of a similar thickness. It would probably be a good idea to put O rings (sponge not rubber) in both the top and bottom to get a better seal, although this is a personal preference. You still get a slight smell of Bromine, but not too bad with the window open ?. I use grafoil of about 0.1mm thick which I glue to parcel tape before cutting. I also use parcel tape on the other side of the grafoil which is not used for electrical continuity. This gives a much tougher electrode which does not break easily due to bending. The binder clips do not dig in so do not damage the grafoil quickly.
I will give some results on self discharge when I have done more testing, although I only have one of those cheap china electrical loads which are not massively accurate.

 

[svetz]

...I have attached a zip file giving STL files of the top and bottom if anyone wishes to make the part on their 3D printer....

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

 

[Identernet]

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

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.

 

[Identernet]

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.

 

[svetz]

That's pretty impressive, but why no dendrites?

 

[Identernet]

That's pretty impressive, but why no dendrites?

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.

 

[svetz]

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

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.

 

[Identernet]

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.

 

[danielfp248]

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.

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.

 

[Identernet]

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.

 

[danielfp248]

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.

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.

 

[Identernet]

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?