IEEE Power Electronics Magazine - September 2023 - 57

Table 3. Performance comparison of commercially available supercapacitor types and Li-ion battery [1], [11].
Device type
-
Voltage
(V)
Standard EDLC
High-temp. EDLC
LMO hybrid
LTO hybrid
High-energy
battery type
High-power
battery type
Li-ion battery
2.7
2.5
2.7
2.8
2.7
2.7
3.7
Capacitance/
mAh capability
3,000 F
2,200 mAh
3,000 F
2,000 mAh
6,000 F
2,600 mAh
7,500 F
2,800 mAh
70,000 F
19,000 mAh
40,000 F
12,000 mAh
2,600 mAh
1.1
0.7
55
810
710
50
56.7
37
192
2,045
3,667
1,245
T -able 4. Comparing temperature range, cyclic life, and energy/power density of different SC families.
SC type
Standard
EDLC
−20 to 60
1,000,000
cycles
High-temp.
EDLC
−40 to 80
500,000 cycles
LMO hybrid
−20 to 50
LTO hybrid
Rated Voltage (V) 2.7 V dc [2.8 V] 2.5 V dc [2.6 V] 2.7 V dc [2.8 V] 2.7 V dc [2.8 V]
Temp. range (°C)
Cycle life (25 °C)
−20 to 40
40,000-50,000 cycles
Shelf-life
Energy-density
(Wh/kg)
Power-density
(Wh/kg)
After 1,000 hrs no-load test same
as endurance (2.7 V:60 °C)
>5 ~ 8
>8,000
After 1,000 hrs no-load test same
as endurance
10 ~ 14
2,500 ~ 4,000
High-energy
battery type
2.7 V dc [2.8 V]
−20 to 50
15,000 cycles
High-power
battery type
2.7 V dc [2.8 V]
−20 to 50
20,000 cycles
After 1,000 hrs no-load test same as
endurance
50 ~ 120
1,600 ~ 3,200
ESR
(mΩ)
0.29
0.3
0.7
0.8
Weight
(g)
525
525
670
560
Energy-density
(Wh/kg)
5.7
4.9
8
9.8
Power-density
(Wh/kg)
11,970
9,921
3,886
4,375
Ragone plot shown in Figure 5 compares various energy
storage device families in general. In the following section,
we calculate the energy density and power density of the
device families we detailed in Tables 4 and 5, creating a
detailed Ragone plot to compare their relative performance.
For the Ragone plot analysis, the energy density and the
power density of a device are calculated using the following
formulas.
Energy density
RatedAh capabilityNominal DC voltage
Wei
=
()*
Ah
ghg torvolumeofthe packaged device
()
V
(4)
The maximum power capability is estimated by the following
relationship considering the maximum power delivery
criteria occurring where the ESR is equal to the load resistance
[9], [17].
Maximum power capability()=
Pmax
V
2
4 * ESR
(5)
Then the power density is estimated by,
Powerdensity
Weight or volume of thepackaged device
Pmax
=
Figure 9, is a specifically created Ragone plot based on the
above relationships, to compare Li-ion batteries and different
SC types, using datasheet values available for the SC
devices from Samwha [11].
Combined SC and Batteries in Hybrid
Energy Storage Systems (HESS)
As Table 4 indicates, supercapacitors have the specific
advantage of very high power density, which is the opposite
case for Li-ion batteries. Given this situation, hybridization
of batteries and SCs helps to overcome the
limitations of SCs or batteries as they have power or
energy restrictions when taken individually. Thus, such
hybrid systems are vital for applications that require both
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