Example Data Table
| Input |
Example Value |
Meaning |
| Scan rate | 10 mV/s | Instrument sweep speed |
| Voltage window | 0.8 V | Usable potential range |
| Average current | 2.3 mA | Mean CV current magnitude |
| Active mass | 5 mg | Mass loaded on electrode |
| Area | 1 cm² | Exposed electrode surface |
| Volume | 0.02 cm³ | Active layer or device volume |
Formula Used
Scan rate conversion: ν = scan rate ÷ 1000.
Average current method: C = Iavg ÷ ν.
Integrated CV method: C = ∫|I(V)|dV ÷ (ν × ΔV × k).
Specific capacitance: Cs = C ÷ m.
Areal capacitance: Ca = C ÷ A.
Volumetric capacitance: Cv = C ÷ volume.
Energy density estimate: E = 0.5 × Cs × ΔV² ÷ 3.6.
Here, ν is V/s, I is amperes, ΔV is volts, k is the sweep basis factor, and m is grams.
How To Use This Calculator
Enter the scan rate from the CV test. Use millivolts per second. Enter the working voltage window in volts. Add anodic and cathodic current values in milliamps. If you have raw CV points, paste voltage and current pairs into the data box.
Enter mass, area, and volume for normalized outputs. Select full loop when pasted data includes forward and reverse sweeps. Select single sweep when only one branch is used. Use the multiplier only when your reporting convention requires it.
Press Calculate. The result appears above the form and below the header. Download the result as CSV or PDF for records.
CV Capacitance Analysis Guide
Basic Idea
Cyclic voltammetry is widely used for early supercapacitor testing. A rectangular CV curve usually shows ideal capacitive behavior. A tilted curve can show resistance, slow ion movement, or poor contact. This calculator helps convert curve current into capacitance values. It supports simple average current and integrated curve data. Both methods can help when raw instrument software is not available.
What The Result Means
Capacitance shows how much charge is stored for each volt. A higher value means more stored charge. Specific capacitance divides the result by active material mass. Areal capacitance divides it by electrode area. Volumetric capacitance divides it by material or device volume. These views are useful because electrode size changes reported performance.
Using CV Data Correctly
Scan rate has a strong effect on the result. A slow scan usually gives higher capacitance because ions have more time to enter pores. A fast scan can lower the value and reveal rate limits. Use the same voltage window when comparing samples. Also use the same mass basis, area basis, and electrolyte conditions.
Average Current Method
The average current method is quick. It uses the mean of anodic and cathodic current. This is useful for nearly rectangular curves. It is less accurate for curves with peaks or sloped shapes. For faradaic materials, the integration method is usually better. It includes the full curve area.
Integration Method
The integration method sums the absolute current over voltage. A full CV loop should be divided by two. That avoids counting forward and reverse scans twice. The calculator accepts voltage and current pairs. Current should be entered in milliamps. Voltage should be entered in volts.
Reporting Better Values
Always report scan rate, voltage window, electrode mass, and curve source. State whether the result is cell capacitance or single electrode capacitance. For symmetric two electrode devices, some papers multiply the cell result by four for single electrode comparison. Use that convention only when it matches your study design.
Practical Notes
CV based capacitance is an estimate. Confirm important values with charge discharge testing. Check baseline drift before using integration. Remove unstable cycles from the data. Good records make results easier to review, compare, and repeat. Use calibrated instruments for final reporting.
FAQs
What is capacitance from a CV curve?
It is the estimated charge storage ability derived from current response during a voltage sweep. The result shows how many farads the electrode or device provides under the entered scan rate and voltage window.
Should I use average current or integration?
Use average current for nearly rectangular curves and quick checks. Use integration when the curve has peaks, sloping regions, or uneven current. Integration better represents the full current response.
Why is the full loop divided by two?
A full CV loop includes forward and reverse scans. Dividing by two avoids double counting both sweeps. Use the single sweep option only when your pasted data contains one branch.
What scan rate unit should I enter?
Enter scan rate in millivolts per second. The calculator converts it to volts per second before using the capacitance formula.
What does specific capacitance mean?
Specific capacitance is capacitance divided by active mass. It is commonly reported in farads per gram. It helps compare materials with different loadings.
When should I use the multiplier value four?
Use four only for symmetric two electrode devices when your convention reports single electrode capacitance from full cell capacitance. Do not use it for every test.
Can this replace charge discharge testing?
No. CV calculations are useful estimates. Important supercapacitor reports should also include galvanostatic charge discharge results, cycling stability, and resistance data.
Why do results change with scan rate?
Fast scans reduce ion access to small pores. Slow scans allow more complete charge storage. That is why capacitance often falls as scan rate increases.