Dear Bidhan Pandit,

for simple capacitors and electrochemical capacitors there is NO difference in capacitance (within 2*SD[1]) values measured from the CV, CD and EIS. Supercapacitors present more complex behavior, each system having specific reasons for possible differences in values measured from the CV, CD and EIS. So,

1) Is it possible, please, to show us capacitance values measured from the CV, CD and EIS for an example of a simple supercapacitor electrode ?

2) In EIS, note, please, the VDC polarization value(s), also.

1.  SD is the standard deviation.

Generally people go with  Cyclic voltammetry (CV) and Charge-discharge (CD) measurements to determine Sp capacitance. EIS is used to determine internal resistance, solution resistance and resistance between active material and the electrode, ie charge transfer resistance.

The most authentic one is the charge/discharge measurements. 

dear Minoj Samuel,

EIS is used to determine internal resistance, solution resistance. I agree.

but, capacitance can be calculated from EIS also. go through the attached paper.

http://pubs.rsc.org/en/content/articlelanding/2012/cs/c2cs35026b#!divAbstract

Dear Muhammad Sajjad,

can you please give the reasons or references???

Dear B pandit, I said in general about EIS. 

Dear Minoj Samuel,

but my question is that why the results differ for the three analysis techniques and why?

regards,

Dear Pandit

All the three measurements are different.  In CV, we measure current against fixed potential window and scan rate(time).  But In the case of charge-discharge, we measure time against fixed potential and current.

My suggestion is  record CV for a fixed potential and calculate the average current.  Then perform charge-discharge giving specific current what we get from CV curve.  This specific capacitance results may be comparable.

Dear Subbukalai Vijayakumar,

How can I calculate average current from CV?

Can u some refer some papers?

regards,

Specific capacitance(S.C) can be calculated by cyclic voltammetry measurements.

S.C= I/S*M, I is the current density, S is the scan rate, M is the mass of the electrode

Dear Vasanth Raj sir,

I know the formulas to calculate SC from CV,CD and EIS.

But I'm concerning about the reliability and physical interpretation of them. 

regards,

Hello,  

The most widely used techniques for electrochemical analysis which measures current vs voltage response of materials at variable potentials. Depending on the experiment, the CV is cycled between initial and final points as it reached its final potential may reverse to its initial point as a results I-E curves obtained in cyclic called cyclic voltammetry.

CV is used to measure the charge storage ability of materials for double layer capacitors and electrochemical energy storage devices. As, from the shape of CV one can conclude whether the processes are reversible or not which occurred on the working electrodes. In addition, the area under the CV curves will be integrated one can get the electrode capacitance.

Dear Bidhan Pandit,

for simple capacitors and electrochemical capacitors there is NO difference in capacitance (within 2*SD[1]) values measured from the CV, CD and EIS. Supercapacitors present more complex behavior, each system having specific reasons for possible differences in values measured from the CV, CD and EIS. So,

1) Is it possible, please, to show us capacitance values measured from the CV, CD and EIS for an example of a simple supercapacitor electrode ?

2) In EIS, note, please, the VDC polarization value(s), also.

1.  SD is the standard deviation.

Dear Muhammad Sajjad  sir,

Capacitance can also be calculated charge-discharge (CD) as well using the formula

Itd/m∆V

From EIS, we can also calculate capacitance. we can calculate C' and C'' from EIS. and can get the modulus as capacitance value at specific frequency.

But, there are deviations in the results. I'm concerning about that. 

regards,

Dear Ioannis Samaras sir, 

SC from CV is 270 F/g at 2 mV/s.

CD- 201 F/g at 2 mA/cm2

from EIS, 42.93 F/g at even such low frequency of 0.01 Hz.

should I go for more low frequency.? but It will be very time consuming then.

VDC polarization is gven zero.

regards,

Dear Bidhan Pandit,

at least 0.01 Hz, should be OK. However, for a reliable calculation of the capacitance C from EIS  :

1) VDC polarization should be at NON zero values. Apply VDC near Vmax (from CV), and a minor (2nd step) correction,

2) Capacitance C from EIS, should be calculated from a reliable equivalent circuit model[1,2].

1. A universal equivalent circuit for carbon-based supercapacitors  [Open Access]  http://link.springer.com/article/10.1007/s10008-013-2328-4

2. Murata Supercapacitor Technical Note   http://www.murata.com/~/media/webrenewal/products/capacitor/edlc/techguide/electrical/c2m1cxs-053.ashx?la=en

Dear Pandit,

As majorly discussed and point out here by other this is a matter of technique only if there are no mixed capacitive phenomena, but there are an advantage of using EIS as this is a spectrally resolved technique. For more information and technical details on this refer to "Mesoscopic behavior of multi-layered graphene: the meaning of supercapacitance revisited (10.1039/C6CP07775G)." In this paper, the capacitance is obtained either by impedance-derived EIS and CV, but the phenomena was better understood thanks to impedance/capacitance spectroscopically resolved methodology

There are already many good answers from others which I generally agree. In addition, I will use data from relatively slow scan rate in CV (with a good rectangular shape), low current in GCD (with good linearity and negligible iR drop) and low frequency range in EIS (vertical or nearly vertical linear portion on the spectrum) to derive the capacitance values so that kinetic influences can be minimised.

Dear Ioannis Samaras sir,

let I have set voltage window of CV is 0 to 1 V.

so Vmax be 1 V. so can I fix VDC at 1 V?

and the minor means what kind of value? here ?? V?

and thanks for ur superb suggestions and recommended articles.

will go through them and will apply in my future work.

regards,

Dear Bidhan Pandit,

measure EIS, please, having a VDC near 1V, down to a low frequency, near 1mHz.

Dear Paulo Roberto Bueno sir,

tahnks for article you suggested. It's the paper of your group. so, any further doubts, I will ask you for sure.

regards,

Dear George Zheng Chen sir,

thank you so much for your reply. I have some questions.

what are the kinetic influences and why they arise for high scan CV, high current GCD or high frequency EIS? 

regards,

There is nothing in science which is an ultimate best due to human limitations. Some experience researchers have recommended cyclic chronopotentiometry (galvanostatic charge discharge measurement) to be the technique of choice for various reasons. Scientific cumminty is somehow satisfied on these recommendations. Are they best? No. Is it a norm? Yes.

For Reference: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.604.7608&rep=rep1&type=pdf

Dear Ioannis Samaras sir,

whenever EIS is measured under VDC value  of almost maximum potential value (here 1 V mentioned ), charge transfer resistance is minimised. and we get maximum capacitance value. why?

and why can't we give more potential than maximum operational potential (here I mean more than 1 V)?

regards,

Dear Bidhan Pandit,

update, please, a newer set of your capacitance CT(=CTechnique) values[1].

1.  Let us remind you an initial set of CT : {CV, CD, EIS} --> {270, 201, 43} F/g.

dear Umair Gulzar sir, 

thanks for ur reply. article is really good for understanding  the whole EIS.

Dear Ioannis Samaras sir,

new set {SC, CD, EIS} --> {270, 201, 193} F/g.

remind you, EIS at Vdc value at near 1 volt for freq. 0.01 Hz.

So, dear Bidhan Pandit,

remeasuring (2nd time) your capacitance CEIS,1V with the same technique, using the proposal modification of DC-polarization value in EIS (Vdc~1V), showed an almost fivefold (~4.5 *) increase[1] over your initial value of CEIS,0V (Vdc~0V).  In other words, the difference among the two common EIS measurements is,  o n l y,   the value of  the polarization (Vdc) parameter.

1. It will be more than fivefold, if you calculate C(1V) using an (equivalent circuit) model technique[2]. So, the new CEIS(1V) will be more close to the higher value of the CCV (270F/g), Cyclic voltammetry (CV) technique.

2. A universal equivalent circuit for carbon-based supercapacitors  [Open Access]  http://link.springer.com/article/10.1007/s10008-013-2328-4

dear Ioannis Samaras sir,

yes, indeed. the difference among the two common EIS measurements is, o n l y, the value of the polarization (Vdc) parameter. 

now I'm concerning about why? I've circulating the question. lets hope to get the answer soon.

Fine, so far, for the acquirement of this critical difference, mostly ignored in the related bibliography for the (specific capacitance of) supecapacitors, till today.

Produced by Rs value (series resistance) from electrode/electrolyte interfaces.

Thank you so much Ioannis Samaras and Mohamed Elsayed Harb sir.