Only Fe system
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I wanted to dedicate this thread to Fe-only systems, in particular systems that have plated Fe on one side and Fe3+ on the other. I am currently waiting on MgCl2 and CaCl2 to carry out some experiments on WiSE electrolytes, but in the meantime I thought I would test a low water activity system containing large amounts of urea. This contains 5mL of H2O, 2g of Fe2Cl2.2H2O, 5g of Urea and 0.3mL of HCl 15%. System is using a non conductive felt on the anolyte side and carbon felt on the catholyte side. Using 900um Daramic as microporous membrane.
Initial single cycle results show that this system can work at relatively high CE but quite low current (which is not surprising given the high amount of urea in the solution). This is one of the highest capacities I have been able to run for an Fe system (10 Ah/L), but energy efficiency is dismal (below 40%). I also don't know if it will actually cycle in a stable manner, we'll have to wait for some additional cycles to see how the system evolves. Perhaps this system will work better with felt on both sides, as metallic Fe is not as dendrite prone as Zn.
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Second cycle already showed heavy degradation, so I stopped the test
Will wait for the Mg, Ca chlorides before doing another test. Just urea doesn't seem to work well enough.