2
Fundamentals of Electrochemical
Double-Layer Supercapacitors
2.1 Introduction
The early concept of an electrochemical supercapacitor (ES) was based on
the electric double-layer existing at the interface between a conductor and its
contacting electrolyte solution. The electric double-layer theory was first proposed by Hermann von Helmholtz and further developed by Gouy, Chapman,
Grahame, and Stern. The electric double-layer theory is the foundation of electrochemistry from which the electrochemical processes occurring at an electrostatic interface
between a charged electrode material and an electrolyte are investigated.
Based on this knowledge, many electrochemical theories and technologies
including electrochemical supercapacitors, batteries, and fuel cells have been
invented and established since the double-layer theory was put forward.
As discussed in Chapter 1, electrostatic and electrolytic capacitors are considered the first and second generation capacitors. These early capacitors were
developed for use as primary circuit elements in holding microfarad to picofarad charges of direct current or to filter the frequencies for alternating current circuits. With the rapid developments in materials, the third generation
known as the supercapacitor was invented. The earliest supercapacitor with
unusually high capacitance was invented by Becker at SOHIO in 1957, and
intended to serve as an electrolytic capacitor for low voltage operation. Carbon
material served as its electrodes. With further modifications, the first practical supercapacitor was developed by Boos [1],[2] as described in a 1970 patent.
The rapid growth of mobile electronics and alternative energy vehicles created a need for advanced electrochemical energy storage devices with high
power capabilities. This need led to substantial research and development of
supercapacitors. In the early 1990s, the United States Department of Energy
(DOE) strongly advocated funding for battery and supercapacitor research,
creating international awareness of the potential of the supercapacitor. Since
then, great effort has focused on supercapacitor research and development
in terms of electrode materials, composites, hybridizations, and suitable electrolytes to improve performance and reduce costs.
37
Fundamentals of Electrochemical
Double-Layer Supercapacitors
2.1 Introduction
The early concept of an electrochemical supercapacitor (ES) was based on
the electric double-layer existing at the interface between a conductor and its
contacting electrolyte solution. The electric double-layer theory was first proposed by Hermann von Helmholtz and further developed by Gouy, Chapman,
Grahame, and Stern. The electric double-layer theory is the foundation of electrochemistry from which the electrochemical processes occurring at an electrostatic interface
between a charged electrode material and an electrolyte are investigated.
Based on this knowledge, many electrochemical theories and technologies
including electrochemical supercapacitors, batteries, and fuel cells have been
invented and established since the double-layer theory was put forward.
As discussed in Chapter 1, electrostatic and electrolytic capacitors are considered the first and second generation capacitors. These early capacitors were
developed for use as primary circuit elements in holding microfarad to picofarad charges of direct current or to filter the frequencies for alternating current circuits. With the rapid developments in materials, the third generation
known as the supercapacitor was invented. The earliest supercapacitor with
unusually high capacitance was invented by Becker at SOHIO in 1957, and
intended to serve as an electrolytic capacitor for low voltage operation. Carbon
material served as its electrodes. With further modifications, the first practical supercapacitor was developed by Boos [1],[2] as described in a 1970 patent.
The rapid growth of mobile electronics and alternative energy vehicles created a need for advanced electrochemical energy storage devices with high
power capabilities. This need led to substantial research and development of
supercapacitors. In the early 1990s, the United States Department of Energy
(DOE) strongly advocated funding for battery and supercapacitor research,
creating international awareness of the potential of the supercapacitor. Since
then, great effort has focused on supercapacitor research and development
in terms of electrode materials, composites, hybridizations, and suitable electrolytes to improve performance and reduce costs.
37