Problems with Iron-Chromium Redox Flow Battery

If Iron Chromium Redox Flow Battery is so cheap, abundant, simple and elegant...... Why isn't it everywhere ? Why was Vanadium even needed in the first place ? Why hasn't anyone commercialized it yet ?

Well..... because it has its own set of problems. Physics and economics aren't really best friends, the more money you spend the better battery you get, the cheaper you get, your efficiency takes a plunge. And trust me you DON'T want a shitty battery. The way I see it for flow batteries-

  • Vanadium is expensive but simple and has good efficiency
  • Iron Chromium is cheaper than Vanadium, but more expensive than Iron, so it has Hydrogen problem of Iron but manufacturing simplicity and efficiency of Vanadium.
  • Iron is dirt cheap, but I would personally not buy it, I don't want a battery that wastes half its energy, because you have to pay for every unit you put in.
This is my take on viable redox flow battery chemistries. Don't get me wrong, there are many newer more amazing chemistries, but they are largely research based. Maybe I'll write another post about them later.

So back to problems of Iron- Chromium, there are primarily 3, let's dive straight into electrochemistry then -

1. Hydrogen Evolution Reaction - 
Similar to All Iron battery, Iron Chromium battery also produce Hydrogen at negative electrode, because Cr3+ to Cr2+, this reaction is very close to water splitting and splits water into hydrogen and loses H+ ions, this eventually leads to chromium ions precipitating out of the solution and ultimately destroying the battery.

2. Chromium Chemical Kinetics -
Chromium in solution form like to bond with water and go into highly stable Cr 6+ form, which prevents it from reacting to anything at room temperature. Good for chromium, bad for our battery, in order to overcome this the battery has to be HEATED, to react quickly, otherwise the battery will take forever to charge.

3. Membrane Selection- 
Remember the daramic membrane we used to make all iron battery ? Yeah that gives a terrible efficiency for Iron chromium battery, because the liquid flowing in the battery can cross over from one terminal to another, Ion exchange membranes are too expensive, and cost cutting is the whole point of the battery.

This is the Trident that has killed Iron-Chromium battery from commercializing. In order to make a commercially viable battery, we have to solve these problems in order to make a flow battery that is DRASTICALLY cheaper than Vanadium.

So now I'll be focusing solely on how I am trying to solve these issues and how I built a Iron-Chromium battery proof of concept. What worked, what didn't and how I actually LIT AN LED, despite the battery failing twice.

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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