Table 4.

Key metrics used for the characterization of a supercapacitor

Parameters (Unit)	Information obtained	Measurement formula	Equation
Capacitance [F]	Ability to collect and store energy in the form of electrical charge	${\displaystyle \mathrm{C}=\frac{\int I\mathrm{d}V}{\mathrm{V}}}$ ${\displaystyle \mathrm{C}=\frac{i\mathrm{\Delta }V}{\mathrm{\Delta }t}}$ ${\displaystyle 2\pi \mathrm{C}=\frac{\mathrm{d}(-Z^{\prime \prime })}{\mathrm{d}\left({\displaystyle \frac{1}{f}}\right)}}$	(1) (2) (3)
Gravimetric capacitance [F g−1]	Charge storage ability per unit mass	${\displaystyle {\mathrm{C}}_{\mathrm{m}}=\frac{A}{2smV}}$ ${\displaystyle {\mathrm{C}}_{\mathrm{m}}=\frac{i\mathrm{\Delta }t}{m\mathrm{\Delta }V}}$	(4) (5)
Lengthwise capacitance [F cm−1]	Charge storage ability per unit length	${\displaystyle {\mathrm{C}}_{\mathrm{l}}=\frac{A}{2slV}}$ ${\displaystyle {\mathrm{C}}_{\mathrm{l}}=\frac{i\mathrm{\Delta }t}{l\mathrm{\Delta }V}}$	(6) (7)
Areal capacitance [F cm−2]	Charge storage ability per unit area	${\displaystyle {\mathrm{C}}_{\mathrm{A}}=\frac{A}{2saV}}$ ${\displaystyle {\mathrm{C}}_{\mathrm{A}}=\frac{i\mathrm{\Delta }t}{a\mathrm{\Delta }V}}$	(8) (9)
Volumetric capacitance [F cm−3]	Charge storage ability per unit volume	${\displaystyle {\mathrm{C}}_{\mathrm{v}}=\frac{A}{2svV}}$ ${\displaystyle {\mathrm{C}}_{\mathrm{v}}=\frac{i\mathrm{\Delta }t}{V\mathrm{\Delta }V}}$	(10) (11)
Energy density [Wh kg−1]	Amount of energy able to deliver	${\displaystyle \mathrm{E}=\frac{1}{2}{\mathrm{CV}}^2=\frac{QV}{2}}$	(12)
Power density [W kg−1]	How faster is the energy to deliver	P = VI ${\displaystyle \mathrm{P}=\frac{E}{t}}$ ${\displaystyle \mathrm{P}=\frac{V^2}{4R}}$	(13) (14) (15)
Coulombic efficiency	Reversible capacity	${\displaystyle \%\mathrm{E}=\frac{C_{\mathrm{charging}}}{C_{\mathrm{discharging}}}\times 100}$	(16)

[C = capacitance, I = current density, V = voltage window, i = discharging current, ∆v = discharge voltage, ∆t = discharge time, −Z′ = imaginary part of the impedance, A = integrated area of the CV curve, s = scan rate (mV s⁻¹), m = mass of the electroactive material on both electrodes, l = length of the electrode, v = volume of the SC, R = resistance].