2.5.4.4 Discharging Supercapacitor Cell at

Constant Voltage ..................................................... 73

2.5.4.5 Discharging Supercapacitor Cell at

Constant Current .................................................... 74

2.5.4.6 Charging and Discharging Curves at

Constant Current .................................................... 76

2.5.4.7 AC Impedance Equivalent Circuit ....................... 79

2.6 Energy and Power Densities of Electrochemical
Supercapacitors .................................................................................... 79

2.6.1
Energy Densities .................................................................... 79

2.6.2 Power Densities ...................................................................... 81

2.6.3 Ragone Plot: Relationship of Energy Density and
Power Density ........................................................................ 86

2.7 Supercapacitor Stacking ..................................................................... 89

2.7.1 Stacking in Series ................................................................... 89

2.7.2 Stacking in Parallel ................................................................90

2.8 Double-Layer Supercapacitors versus Batteries.............................. 91

2.9 Applications of Supercapacitors ........................................................ 93

2.10 Summary .............................................................................................. 95

References ....................................................................................................... 95

3. Fundamentals of Electrochemical Pseudocapacitors ............................ 99

3.1
Introduction ......................................................................................... 99

3.2 Electrochemical Pseudocapacitance of Electrode–Electrolyte
Interface .............................................................................................. 102

3.2.1 Fundamental Electrochemistry of Pseudocapacitance .. 102

3.2.2 Pseudocapacitance Induced by Underpotential

Deposition ............................................................................. 108

3.2.3 Pseudocapacitance Induced by Lithium Intercalation ... 112

3.2.4 Pseudocapacitance Induced by Redox Couples ............... 113

3.2.4.1 Pseudocapacitance Induced by Dissolved
Couples .................................................................. 113

3.2.4.2 Pseudocapacitance Induced by Undissolved

Redox Couples ...................................................... 115

3.2.5 Pseudocapacitance Induced in Electrically

Conducting Polymer (ECP) ................................................ 120

3.2.6 Coupling of Differential Double-Layer and
Pseudocapacitance ............................................................... 121

3.3 Electrochemical Impedance Spectroscopy and Equivalent

Circuits ............................................................................................... 124

3.4 Materials, Electrodes, and Cell Designs ........................................ 126

3.4.1 Electrode Materials.............................................................. 126

3.4.2 Cell Designs (Symmetric versus Asymmetric) ................ 129

3.5 Summary ............................................................................................ 131

References ..................................................................................................... 132

Contents
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