You do need electrodes for electrochemical analyses, but the electrodes do not need to be the same as those used in the device. For example, in a solid state lithium ion battery, the solid electrolyte can be studied for its conductivity and porosity (relative) by sandwiching the electrolyte (membrane) between two inert conductors, instead of the active electrodes used in the battery. The same applies to the solid electrolyte in a supercapacitor.

(Added on 01 June 2020) Regarding electronic conduction through the solid state electrolyte membrane, the sandwich cell together with impedance analysis, can detect the electronic and ionic resistances, respectively.

You do need electrodes for electrochemical analyses, but the electrodes do not need to be the same as those used in the device. For example, in a solid state lithium ion battery, the solid electrolyte can be studied for its conductivity and porosity (relative) by sandwiching the electrolyte (membrane) between two inert conductors, instead of the active electrodes used in the battery. The same applies to the solid electrolyte in a supercapacitor.

(Added on 01 June 2020) Regarding electronic conduction through the solid state electrolyte membrane, the sandwich cell together with impedance analysis, can detect the electronic and ionic resistances, respectively.

Bao, J., Zhang, X., Bai, L., Bai, W., Zhou, M., Xie, J., Guan, M., Zhou, J. and Xie, Y., 2014. All-solid-state flexible thin-film supercapacitors with high electrochemical performance based on a two-dimensional V 2 O 5· H 2 O/graphene composite. Journal of Materials Chemistry A, 2(28), pp.10876-10881.

Dear Prof. Chen and dear Prof. Braun,

Thank you very much for your answers. I highly appreciate it.

I wonder how that sandwich structure is made. Since the geometry and amount of the solid-state electrolyte matters in measuring the ionic conductivity, for instance, how would it be possible to sandwich the solid-state electrolyte between the conductors? Does it necessitate molding of the electrolyte to consolidate its shape and amount prior to the measurement?

Best regards,

Amin

Dear Amin, for electrochemical characterization of solid-state electrolytes you can press them in the form of tablets from powder and apply electrodes either by painting or screenprinting on both sides. The area of these electrodes is important for estimating charge transformations. You can include this area in normalizing impedance values and investigating the resistance in electrochemical impedance spectroscopy (EIS).

Dear Shamim, thanks a lot for your explanation. It completely makes sense to me.

Dear Amin Hodaei , ensure that the solid poly electrolyte that you prepare, has uniform thickness, and is a free standing film, then sandwich the SPE between electronically conducting but ionically blocking electrodes like stainless steel e.g. SS 316 and then you can perform EIS studies. Kindly refer the below paper for better clarity.

https://link.springer.com/article/10.1007/BF02376083

Dear Amin Hodaei,

it would be spurious to characterize SSE (Solid-State Electrolytes) in supercapacitors' cases, when the electrodes are not present, since (most of) the SSEs are, actually, mixed (ionic and electronic) conductors[1].

However, there are specific advantages for the case of SSEs in unipolar supercapacitors; so, you can apply (beneficial[2]) Diode junction(s), biased in the correct (unipolar, p-n) direction of your supercapacitors' polarity, by selecting (two different, but) certain metals, for each one of the current (ionically blocking) collector(s), only.

1. https://www.researchgate.net/post/How_to_distinguish_electronic_conductivity_from_ionic_conductivity_in_mixed_oxide_conductors2

2. The main disadvantage will be a small 'gap', in the low(er) Voltage onset, for a common functioning, due to diode(s); however, this is not a very big problem for unipolar HIGH-Voltage supercapacitors.

Dear Prof. Sindhu K P,

Thank you very mcuh for your explanation. I highly appreciate it.

Dear Prof. Ioannis Samaras ,

Thank so much for your answer to my question. I very much appreciate it.

Dear Prof. Artur Braun , The solid-state electrolyte that is the case of my question is a gel-based electrolyte and it can take a shape based on the configuration of the system. For instance, it can be sandwiched between the electrodes, however, I was wondering if it would be possible to characterize the conductivity values of the electrolyte without necessarily using the targeted electrodes.