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You know I have been wrong before, but never so pleasantly surprised. I spent the last two months trying to copy VRFB........ well, not exactly. I wanted to make an Iron-Chromium Redox Flow Battery that was just as good as VRFB. That means its power density, efficiencies and performance should match closely with VRFB. 

But as I have stated many times earlier, Fe-Cr batteries have a fundamental flaw, they can't operate at room temperature, which is the fundamental reason why they have not been commercialized yet.

In my previous post I wrote about a paper that I had recently found, it added salt to the battery in order to enable it to operate  at room temperature. Let's understand how 

The paper used salt to increase the kinetics of chromium at room temperature. This happened because the lithium (or in my case sodium) chloride increased the concentration of chloride ions in the electrolyte solution. This causes excessive Cl⁻ ions in the electrolyte solution and increased concentration of Cr⁵⁺ and Cr⁴⁺ ions in the solution. But this paper comes very close to the solubility limit of chloride ions in the solution at room temperature, which is noted by the authors that if any more chloride was added than 0.4 M, the solution would start precipitating. .

solution precipitating due to excessive salts
Source

Moreover looking more closely at the current densities at which the paper high efficiencies  achieved, they were around 40 mA/cm² which is closer to All Iron Batteries than VRFBs. That means your stack is as big as the Iron batteries. 

Now here's the kicker. This paper has a strictly controlled temperature atmosphere of 25°C ± 0.5°C. That's a bit odd to me, because if you know anything about physics, any kind of battery releases heat. You know it when you charge your phone. You know it when you keep your laptop on your lap. Moreover, the LFP batteries that are used currently are deliberately liquid cooled because even 1-2% percent of their waste energy becomes heat which can be catastrophic since it can lead to thermal runaway which can degrade the battery severely.

LFP battery pack heating up
Source

That's interesting, because Chromium Chloride and Iron Chloride do not precipitate at elevated temperatures, instead they react faster and gain efficiency, getting close to VFBs.

So me trying to engineer a room temperature battery would be going one step backwards instead of utilizing one of the biggest perks of my battery.

And modern VFBs also rely on cooling systems and heat exchangers to cool the battery down. I have actually talked to a manufacturer of VFBs in India, and they put heat sinks on their stack to cool the electrolyte down because Vanadium precipitates out of water above 40°C.

But you'd say that I am not accounting for heating costs of the battery. I will......in my next post

None of this is AI generated, so feel free to fact check me and looking forward to your views and help. 


Mayank Jately


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