Hi all respected researchers,
I want to do a study focused on studying the electrochemical properties of polymer composite samples. The current method I have used is by the conventional method, which is 3 electrode system,
where;
i) reference electrode = Ag / AgCl system,
ii) counter electrode = glassy carbon,
iii) working electrode is my solid sample.
These electrodes are then immersed into an electrolyte solution containing 1M LiClO4 in a mixture of 1:1 EC:THF solvent.
However, I have been doubting about the data (Nyquist Plot) of my solid sample that I will include in the Attachment. This is because the data seems to have so high in resistance, which I suspected due to liquid electrolyte used.
So, can you tell me if the technique I'm using suits my solid sample condition? If not suitable, please suggest a suitable technique so that accurate data can be obtained for my polymer electrolyte sample.
Hi dear friend
The method you use depends on the type of polymer you have and whether it is solid or semi-solid.
If your sample is completely solid, it should be analyzed in a two-electrode setup like a coin cell.
So that the sample does not contain any organic solvents and is placed between two conductors which are stainless steel.
In case you have a quasi-solid; First, the polymer film is placed in the electrolyte solution so that the electrolyte is completely trapped in its tissue, and then the battery is assembled as in the previous case.
It should be noted that these items are used to calculate electron conductivity.
If you want to assess the ionic conductivity of the polymer membrane, a two-electrode setup can be employed, where the polymer is sandwiched between silver or platinum electrodes with connected wires (Ag/Polymer/Ag or Pt/Polymer/Pt). This setup is used without any liquid medium, and measurements are conducted using an electrochemical workstation employing techniques like PEIS with a perturbed amplitude ranging from 20 to 10 mV.
It's worth noting that a three-electrode configuration is typically not used to determine the conductivity of the polymer in this context. This setup is designed to facilitate the study of the electrode-electrolyte interfacial reactions between the polymer and the electrolyte used. The resistance measured in a three-electrode setup typically represents the solution resistance between the electrode and the electrolyte rather than the intrinsic conductivity of the polymer.
When you say you're interested in the electrochemical properties of the electrolyte, do you really mean the ionic conductivity? That's the value most people declare in publication, even though it's not often very meaningful, and there are many other electrochemical properties that could be analysed.
For EIS measurements with either 3 or 2 electrodes, have you considered simply pressing contact pins against your electrolyte and connecting to instruments cables? As long as you establish contact pressure between pins and the polymer surface, this works for EIS on solid electrolyte. You can also quantify ionic conductivity as the resistance measured by a high-sensitivity ohmmetre, like a Keithley or a four-point probe. I wouldn't mess around with coin cells, that will only introduce more interfaces and noise.
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