This section provides overview, applications, and principles of electric double layer capacitors. Also, please take a look at the list of 10 electric double layer capacitor manufacturers and their company rankings.
An electric double layer capacitor is a capacitor that uses the electric double layer formed at the interface between the electrode and the electrolyte to store an electric charge and is characterized by its exceptionally high energy density.
Because of their high energy density, they are often compared to rechargeable batteries such as nickel-metal hydride batteries and lithium-ion batteries. Still, while batteries involve chemical reactions during charging and discharging, electric double layer capacitor involve only physical charge adsorption and no chemical reaction.
For this reason, electric double layer capacitor is inferior to rechargeable batteries in terms of energy density (the amount of energy stored per unit weight or volume). Still, on the other hand, they have the advantage of output density (the amount of power that can be extracted instantaneously) and extremely low-performance degradation (life span) due to repeated charging and discharging. However, the power density (the amount of instantaneous power that can be extracted) and the performance degradation (life span) due to repeated charging and discharging are advantages.
Electric double layer capacitors are used as energy storage devices. While rechargeable batteries are suitable for applications that require a large amount of energy, electric double layer capacitors are selected for applications that require rapid charging and discharging and where durability is required.
Specifically, they are used in backup power supplies for electronic circuits in mobile devices, printers, copiers, electric toothbrushes, solar-powered watches, etc. They are also used in the robotic power system of the asteroid probe Hayabusa and in energy regeneration during the deceleration of automobiles.
The electrolytic double-layer capacitor uses the electric double layer generated at the interface of active materials to make a capacitor. Capacitance C is defined by the formula "C=εS/d." The following measures are necessary from this formula to increase the capacitance C.
The electrolyte is made by dissolving electrolytes such as quaternary ammonium salts and imidazolium salts in organic solvents, and activated carbon is used as the active material for the cathode and anode, and the following measures are necessary to increase the capacitance C.
The capacitors' charging and discharging use an increase in charge at the interface between the electrolyte and electrode so that the positive and negative ions in the electrolyte are paired when they are adsorbed on their respective electrodes. When the stored charge is discharged, the ions are desorbed from the electric double layer. Electric double layer capacitors can be cylindrical or stacked. The cylindrical type has the advantage of being easy to produce: the positive electrode, negative electrode, and separator are stacked, rolled up, and placed in a cylinder, which is then filled with electrolyte.
Unlike batteries, electric double layer capacitors do not undergo a chemical reaction during charging and discharging. For this reason, while the capacity of a rechargeable battery decreases significantly from the initial stage after about 1,000 cycles, the performance of electric double layer capacitors are said, in principle, to be almost unaffected even after 1 million charge-discharge cycles. In reality, however, the capacity of electric double layer capacitors decreases due to the following factors.
When using electric double layer capacitors, it is necessary to consider the effect on life expectancy and pay attention to temperature rise and bias of voltage and current when used in series or parallel.
Disadvantages of electric double layer capacitors include the following.
This is caused by the evaporation of the electrolyte from the sealing section of the electric double layer capacitors to the outside. This disadvantage can be suppressed by using an electrolyte with a high boiling point or by making the sealing section smaller.
Leakage can occur when the butyl rubber used for sealing deteriorates. This can be controlled by reducing the size of the sealing section to prevent moisture, which causes rubber deterioration, from penetrating the inside.
AC Circuit Incompatible
Since this product is intended for secondary electrical use, such as power backup in DC circuits, it cannot be used in AC circuits.
*Including some distributors, etc.
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