Charging-Discharging Voltage, V
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
V
o
cell
2I cell R esr
V
o
sc – I cell R esr
Charging
Discharging
–1.0
1.0
3.0
5.0
7.0
9.0
11.0
Charging-Discharging Time, s
293
Characterization and Diagnosis Techniques
FIGURE 7.8
Charging–discharging curves recorded using symmetric supercapacitor cell with geometric
area of 4.0 cm 2 for each electrode in 0.5 M Na 2 SO 4 aqueous solution at ambient conditions.
Charging and discharging current density = 0.025 A.cm –2 . Total BP 2000 carbon loading of electrode layers = 3.8 mg.cm –2 . Note that the R esr in the figure should be the sum equivalent series
resistances of both positive and negative electrodes. (Source: Ban, S. et al. 2012. Electrochimica
Acta, in press. With permission.)
C T is 0.127 F.cm –2 or 0.509 F for the entire cell with an electrode area of 4 cm 2 .
The specific capacitance is 34 F.g –1 for the carbon loading of 0.015 g, the maximum cell voltage (V cell ) is 0.991 V, and the equivalent series resistance R
max
esr
= 0.806 Ω.cm 2 or 0.202 Ω for the entire cell. Using these values, the maximum
energy and power densities ((E )
and (P ) , respectively) can be calcum max
m max
lated according to the equations presented in Chapter 2:
1
2
( )
E
= C (V ) ,
m max
T
c e l l max
2
and
1 (V )
2
cell max
( )
P
=
.
m max
4m R esr
The obtained (E m ) max and (P m ) max are 4.6 Wh.kg –1 , and 8.1 × 10 4 W.kg –1 ,
respectively.
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
V
o
cell
2I cell R esr
V
o
sc – I cell R esr
Charging
Discharging
–1.0
1.0
3.0
5.0
7.0
9.0
11.0
Charging-Discharging Time, s
293
Characterization and Diagnosis Techniques
FIGURE 7.8
Charging–discharging curves recorded using symmetric supercapacitor cell with geometric
area of 4.0 cm 2 for each electrode in 0.5 M Na 2 SO 4 aqueous solution at ambient conditions.
Charging and discharging current density = 0.025 A.cm –2 . Total BP 2000 carbon loading of electrode layers = 3.8 mg.cm –2 . Note that the R esr in the figure should be the sum equivalent series
resistances of both positive and negative electrodes. (Source: Ban, S. et al. 2012. Electrochimica
Acta, in press. With permission.)
C T is 0.127 F.cm –2 or 0.509 F for the entire cell with an electrode area of 4 cm 2 .
The specific capacitance is 34 F.g –1 for the carbon loading of 0.015 g, the maximum cell voltage (V cell ) is 0.991 V, and the equivalent series resistance R
max
esr
= 0.806 Ω.cm 2 or 0.202 Ω for the entire cell. Using these values, the maximum
energy and power densities ((E )
and (P ) , respectively) can be calcum max
m max
lated according to the equations presented in Chapter 2:
1
2
( )
E
= C (V ) ,
m max
T
c e l l max
2
and
1 (V )
2
cell max
( )
P
=
.
m max
4m R esr
The obtained (E m ) max and (P m ) max are 4.6 Wh.kg –1 , and 8.1 × 10 4 W.kg –1 ,
respectively.