When calculating the energy density for supercapacitor cells we use the following equation .. I wish to know how to calculate the cell voltage (V) which is determined by the thermodynamic stability of an electrolyte.
Emax equal 0.5 Ct V2
knowing that my supercapacitor cell is graphene based and I used PVA solid electrolytes in my flexible unit.
Maximum operating voltage window depends on your mode of measurement i.e., 3-electrode or 2-electrode. Kindly provide more detail about measurement mode and range of voltage that you have chosen, then I can give you more information.
Arvinder
Thanks alot for your cooperative answer ..
Actually i work on 2 electrode system to configure the electrochemical performance of my supercapacitor unit .. I use Versa stat 4 potentiostat and versa studio 2.4 software
in CV measurement my potential window was (0) - (1)
For cc discharge the potential limits 0 - 1
Thanks in Advance
The voltage can be obtained from cyclic voltammetry. You will need to perform a CV at the electrode you are using in the supercapacitor and in the electrolyte you are using. The voltage you seek is the combined anodic and cathodic potential limits within which especially your electrolyte is stable, and you obtain your capacitive current. If you think 0 - 1 V is the maximum voltage you can perform your CV without electrolyte breakdown, then your cell voltage in the same electrolyte is 1V.
In your case it should be V-IR where V is 1V.
IR is the voltage drop that you can estimate from charge-discharge curve.
Your device will loss some energy (voltage drop) at its internal resistance. Rest of the energy it will provide you. So important is the voltage range after excluding IR drop, which should be less that 1V.
Arvinder
If are you using PVA solid electrolytes in aqueous medium the voltage range is 0 to 1 V is needed. A higher voltage causes decomposition of water that in the cathode side can bring at an oxidation of the graphene.
dear Ingy Nagy Ghoniem · 1.31 · 0.46
... in aqueous medium a secure voltage range is 0 to 1 V (or 0 to -1 V). However, this secured voltage window concerns each one of your electrodes (say e1, e2), referred to H-reference electrode (say e3). The best (example) cell is the Pb-battery that pushes the voltage window to the limits [+1+(-1)=2]. The V(e1-e3)=1V, and V(e2-e3)=-1V. So, about ~2V voltage window in (one cell) Pb-battery. In a car Pb-battery you must have ISOLATED (in series) cells. So in each one car battery n-cells (n=6) you apply the condition for a secured voltage window for each one of the electrodes (say e1n, e2n), referred to H-reference electrode. So, if you understand well the concept of voltage window for water cells, you understand why an example of Li-metal-electrode is NOT stable in water [ V(Li-H) ~ -3V
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