Electrochemical capacitors also called supercapacitors or ultracapacitors are mainly classified into three types : electric double layer capacitors, pseudocapacitors, and asymmetric capacitors assembled with faradic and nonfaradic electrodes. Recently, they have received a great attention as electrical storage devices with high power density and long cycle life compared with secondary batteries, and have been extensively researched and developed. They have played an important role as power sources in various electric devices, regenerating system of vehicles, and so on. Their contribution to leveling output fluctuation of renewable powers is also expected. They would develop more and more as essential power sources in the future. In this article, fundamental principles, characteristics, constituent materials and so on for electrochemical capacitors are described.

Electric double layer capacitor (EDLC) is an electric energy storage device, which operates through charging and discharging dielectric layer (electric double layer) formed on interface between nanoporous carbon electrode and electrolyte. The EDLC has excellent power density and cyclability, but the energy density is smaller than rechargeable battery. The energy density of the EDLC is proportional to capacitance and square of maximum charge voltage. This review addresses the basic concept to design the nanostructure of porous carbon electrode to improve the energy density.

Electrical energy storage (EES) devices, in conjunction with technologies such as electric vehicles and renewable power sources, are crucial tools for efficient utilization of electric power in sustainable societies. Among different EES devices, electrochemical capacitors, and specifically supercapacitors (SCs), are considered as promising thanks to its high-power, safe and long-lived characteristics. In order to enhance the voltage and energy density of SCs while maintaining its high power, a synthesis of nanocomposites of active materials with homogeneous particle sizes and dispersibility is required. In this article, we introduce examples of synthesis of such nanocomposites with conductive nanocarbons which enable ultrafast electrochemical response, using in situ synthesis method based on the ultracentrifugation process.

Electric double layer capacitor is used for various applications because of its unique characteristics, such as high reliability, less environmentally-load and high rate capability. The present paper describes a basic principle, constitution, characteristics, applications and future prospects of electric double layer capacitor.

Based on the “Sustainable Zoom-Zoom” plan, Mazda's long-term vision for technology development, we have been advancing what is called a “Building Block Strategy”.

With use of a new-generation technology called “SKYACTIV TECHNOLOGY”, we intend to thoroughly improve Mazda's base technologies with an eye to improving the powertrain efficiency, reducing the vehicle weight, and eventually combining them with electric device technologies in a phased manner so as to reduce total CO₂ emissions.

As the second step of this approach, Mazda has developed a new regenerative braking system called “i-ELOOP”, where the energy generated during deceleration is recovered and reused as electric energy necessary for a vehicle to move.

This paper introduces the Electric Double Layer Capacitor (hereinafter referred to as EDLC) and as device technologies of the “i-ELOOP”, a regenerative braking technology developed as the second step of the Building Block Strategy.

In order to put organic light emitting diodes (OLEDs) into practical use, high barrier films with 10^－6 g m^－2 day^－1 level of water vapor transmission rate (WVTR) are required. Allthough various techniques for evaluating high gas barrier properties have been proposed, WVTR measurement methods with the detection limit of 10^－6 g m^－2 day^－1 or less have not been developed so far. The author succeeded to develop a WVTR measurement unit to measure 10^－6 g m^－2 day^－1 or less by applying ultra-high vacuum technologies. The measurement result of two gas barrier films with 10^－6 g m^－2 day^－1 and 0.1 cc m^－2 day^－1 level of oxygen transmission rate (OTR), respectively, are shown.