Jacob Johnston:

You raised an interesting question that I also thought about a few years ago. My conclusion is that increasing the electrolyte conductivity will not alter the theoretically available capacity, as it is determined by the electrodes and electrolytes. However, it will affect the rate capability and can change the experimental capacity at a certain charging or discharging rate. Rapid electron diffusion is definitively beneficial for achieving high capacity at fast charging or discharging rates.

Another point is that increasing the conductivity of the electrolyte can diminish the electrolyte resistance, which reduces ohmic drop and also good for capacity enhancement.

Jacob Johnston:

You raised an interesting question that I also thought about a few years ago. My conclusion is that increasing the electrolyte conductivity will not alter the theoretically available capacity, as it is determined by the electrodes and electrolytes. However, it will affect the rate capability and can change the experimental capacity at a certain charging or discharging rate. Rapid electron diffusion is definitively beneficial for achieving high capacity at fast charging or discharging rates.

Another point is that increasing the conductivity of the electrolyte can diminish the electrolyte resistance, which reduces ohmic drop and also good for capacity enhancement.

I agree with Tianyu, with lower electrolyte conductivity the cell runs into transport issues, namely higher ohmic loses which correspond to higher voltage drops. The lower cutoff voltage is then reached faster and one would then observe a lower capacity. To reduce this effect you 'll need to discharge at a slower rate or even better do the experiment in a quasi-equilibrium way (e.g., GITT).

Best,

Arman

I agree with the previous answers and I would add that your observation about "lower viscosity electrolytes make the cathode material perform better" is explained by a higher conductivity of the electrolyte. Ionic conductivity is associated with mobility of ions. Then, if viscosity is high, ion mobility is reduced and the same happens with conductivity.

I agree with Tianyu Liu, and I would add some my literature study about "lower viscosity electrolytes make the cathode material perform better", this statement is relate to process of SEI forming in electrolyte filling process, if we use the lower one, it will help the SEI forming to be uniform and increase the ion mobility, so that the capacity will increase.

I could answer this question from a fuel cell perspective. The voltage losses that occur in a fuel cell are 3 types : activation, Ohmic, and mass transport. The Ohmic losses are caused by the resistance to the flow of charged species in the electrodes, electrolyte, inerconnectors, and flow channels. Since such conductivity is very high in metals and carbons, the electrolyte resistance is the main contributor to the overall Ohmic losses. Therefore, reducing the Ohmic losses is mainly an area of electrolyte development which means either increasing the ion conductivity or decreasing the membrane thickness to decrease the electrolyte resistance. The higher voltage losses wold mean a lower working efficiency for a fuel cell operation but a small voltage loss would mean a small overall power output. That is why the typical working fuel cell suffers from a very big voltage loss (quite low efficiency).

Hope this helps.

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PS: I have recently passed my PhD examination at the University of Sheffield, UK and my topic is the development of Pt-free trimetallic catalysts for direct ethanol oxidation in fuel cells. My supervisor and I are looking for collaboration to pursue further testing and potentially alternative application on the powders I have prepared.

For anyone interested, please, contact me on ([email protected] & [email protected])