My adventures building a Zinc-Iodine battery

danielfp248

Battery researcher
For the first experiments I have been using Cu anodes (easily cut from copper tape), which have been easy to adhere to the Titanium electrodes and sand to reveal pristine copper. I also sanded down the Ti electrodes (320 and then 240 papers) before these experiments to ensure they are much more flat as they previously had some small irregularities due to the way in which they were cut.

The results so far have been really good, without any dendrites, when using a fiberglass separator. I was even able to run a cell for 141 cycles at 10mA/cm2 with a single layer of fiberglass separator with no issues (Exp 3b).

However, I am still experiencing substantial capacity decay. The fact that the decay is slower at higher current (10 mA/cm2 Vs 5 mA/cm2) (Exp 3a and 3b), suggest that the decay is related to some species that are generated and diffuse away from the electrodes. Since there is less time for diffusion at higher current, you expect diffusion related decay to be less prominent as electrode cycling becomes faster. This also matches the fact that Coulombic efficiency increased with current (97 at 10 mA/cm2 Vs 93 at 5mA/cm2).

I am now running an experiment (Exp 4) including 1M NaCl in the solution, to see the effect of further reduced water activity. After this is done I will run additional experiments at 2M NaCl and 5M NaCl, to see the effect this additive has on cycling characteristics.
 

danielfp248

Battery researcher
Exp12 is giving some really interesting results. It uses a copper anode, a Spectracarb 2050A-0850 Cathode, 3 layers of fiberglass separator and an electrolyte made of 15m ZnCl2 + 5m KI + 1m NaCl in distilled water. I am testing this at a current density of 10mA/cm2, charging to 1.45V and discharging to 0.5V.

So far the battery has cycled exactly 100 times. This is the first time potential and capacity changes have seemingly stabilized. Coulombic efficiency is also now consistently in the >97% region. No dendrites have appeared yet either.

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The graphs below show the changes in capacity and changes in potential as functions of cycle number:

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Capacity is at around 1.07mAh, given the volume of the battery of 0.1032cm^3 and an average discharge potential of 1.03V, the energy density of this battery is at 10.88 Wh/L. The most exciting aspect of this battery is its stability so far, which I hadn't been able to achieve before. I'm going to run it until it decays to 20% of max capacity, dies due to dendrites or reaches 2000 cycles🤞.
 

Andrew Cote

New Member
Hello Daniel,

I have an interesting design and application for a titanium dioxide-based battery. Do you make and test batteries as a hobby or is it your business?
 

danielfp248

Battery researcher
Hello Daniel,

I have an interesting design and application for a titanium dioxide-based battery. Do you make and test batteries as a hobby or is it your business?

I do it as a hobby, I have no plans or goals to ever make any of this commercial. It is just to learn and share with anyone interested.
 

danielfp248

Battery researcher
This is Exp21, using CCP cathode, 3 layers of fiberglass separator, copper anode and the regular ZnCl2 15m + KI 5m electrolyte. This cell is being cycled between 0.8V and 1.275V at 10mA/cm2. So far 100 cycles and the battery capacity went down and then back up close to max capacity.

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I decided to cycle only to 0.8V because the copper anode seemed to face some deterioration when cycling down to 0.5V. The current capacity of this battery is on the lower side - energy density is around 4Wh/L - I want to see for how long it lasts under these conditions. Mean charge potential seems to be stable for now. Coulombic efficiency is in the 96-97% range, energy efficiency is in the 82-83% range.

Will this battery finally be long term stable?
 
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