I synthesized graphene by chemical method and I have taken CV (for supercapacitor application). For taking CV, I used three electrode (sample coated Glassy carbon, Pt and Ag/Agcl) configuration method and using Na2SO4 as a electrolyte. Then I found the specific capacitance using the formula [half of the area divided by multiplication of mass, scan rate and potential window]. But I don't know how to calculate the energy density and power density using cyclic voltammetry and what formula is used to calculate the above things?
Dear yongfeng bu, I think this formula for charge-discharge cycle not for CV. Ok if it is not like that means please tell me, what is ΔU and t means? Because for CV data finding specific capacitance i use the above mentioned formula in question such as finding the area of the curve in software itself and take the half area and divided by mass, scan rate and potential window... Is there any formula used to calculate the energy density and power density with the help of CV curves. And please mention the reference paper also.. Thank you very much for your kind reply...
C = i*t /m*ΔU, i(A), t(s), m(g)，ΔU(V)
dE (Wh/kg) = 0.5*C*(ΔU)2
dP (kW/kg) = (dE/1000)/(t/3600) =3.6 dE/t
Dear yongfeng bu, I think this formula for charge-discharge cycle not for CV. Ok if it is not like that means please tell me, what is ΔU and t means? Because for CV data finding specific capacitance i use the above mentioned formula in question such as finding the area of the curve in software itself and take the half area and divided by mass, scan rate and potential window... Is there any formula used to calculate the energy density and power density with the help of CV curves. And please mention the reference paper also.. Thank you very much for your kind reply...
ΔU is potential window, t is discharge time.
Energy density and power density are not directly calculated for CV data. However, you can use the above equation (dE = 0.5*C*(ΔU)^2) to calculate the dE, because you have calculated the specific capacitance.
Ok thank you very much Mr. Yongfeng bu.... And can i know the reference please?
Dear Yongfeng bu, thank you for your answer to the question of Asiq, however I have doubt about the formula of dE. You have mentioned formula of C, in which you consider mass in grams, and at the same time you expect value of dE with units per Kg. How do you explain this?
Thank you in advance.
the, factor 3.6 is used as correcting the unit form gram and second into kilogram and hour respectively
Regardless of the methods (CV, galvanostatic charge-discharge, EIS), energy density and power density can only be derived from full cell (2-electrode) experiments.
Some authors even request a full package cell for derivation of energy and power densities.
References:
Best practice methods for determining an electrode material’s performance for
ultracapacitors, Meryl D. Stoller and Rodney S. Ruoff, Energy Environ. Sci., 2010, 3, 1294–1301
Capacitive Energy Storage in Nanostructured CarbonElectrolyte Systems
P. SIMON, Y. GOGOTSI, Vol. 46, No. 5 ’ 2013 ’ 1094–1103 ’ ACCOUNTS OF CHEMICAL RESEARCH
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