Zinc-Iodide
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Starting a thread to keep track of our zinc-iodide development. Background in this blog post: https://fbrc.dev/posts/progress-update-dev-kit/#preliminary-results-from-first-chemistry-zinc-iodide
Current electrolyte composition is roughly 2M KI, 1M ZnCl2, 2M NH4Cl, 5% triethylene glycol, with a Daramic separator and graphite felt on both sides, no spacer.
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This is why we can't use BPT tubing in the peristaltic pumps of the dev kit for this chemistry:
anolyte (right) and catholyte (left) tubings. They are both exact same external and internal diameters. The catholyte one is obviously slashed and the catholyte pump had a lot of iodine inside. So, lastest longer but definitely not impervious to it
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Updates from @danielfp@chemisting.com during today's meeting:
I started a test with 2M KI, 1M ZnCl2, 2M NH4Cl, 5% Trieg with Daramic and felt on both sides. Going to charge to 1.6V at 10mA/cm2, see if it makes any difference regarding stability with Trieg on subsequent cycles.
I did one cycle at 10mA/cm2, charged to around 240mAh (noticed a dip indicating start of solid I2 buildup, so cut it there), discharged 180mAh. I am now charging to 150mAh at 30mA/cm2, normally I would see drops in capacity with cycling with Trieg at this level, we'll see if they happen.
Seems to be stable now at 30mA/cm2. I will leave it cycling here longer, see if it starts decaying.
ok, went for 9 cycles with no issues at all. I am now going to cycle it to 1.65V, to the Nernst limit, see if it continues working equally well.
Charging to 1.65V showed the weird start for the discharge curve, although with no apparent deterioration of the cycle characteristics after the first cycle. No evidence for solid iodine formation was present, so the solution is very well behaved.
Test at 15mA/cm2 of the same cell. Some deterioration is now evident, charging to 1.55 V
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K kirk referenced this topic