The button Fara capacitor, also known as the electric double layer capacitor, is a brand new capacitor based on the interface electric double layer theory proposed by the German physicist Helmholtz. It is known that an excessive charge having a sign opposite to the surface of the metal electrode inserted into the electrolyte solution and the liquid surface causes a potential difference between the phases.
Then, if two electrodes are simultaneously inserted in the electrolyte, and a voltage less than the decomposition voltage of the electrolyte solution is applied therebetween, the positive and negative ions in the electrolyte will rapidly move toward the two poles under the action of the electric field, and respectively in two The surface of the upper electrode forms a tight charge layer, ie, an electric double layer, and the electric double layer formed by the electric double layer and the dielectric in the conventional capacitor are similar in polarization charge generated by the electric field, thereby generating a capacitive effect and a close electric double layer approximation. In the case of a plate capacitor, however, since the tight charge layer spacing is much smaller than the distance between the charge layers of a conventional capacitor, it has a larger capacity than a conventional capacitor.
The electric double layer capacitor has a larger internal resistance than the aluminum electrolytic capacitor. Therefore, it can be directly charged without load resistance. In the case of overvoltage charging, the electric double layer capacitor will open without damaging the device. The overvoltage breakdown of aluminum electrolytic capacitors is different.
At the same time, the electric double layer capacitor can be charged in an unrestricted manner compared with the rechargeable battery, and the number of times of charging can reach 10^6 times or more. Therefore, the electric double layer capacitor not only has the characteristics of capacitance but also has battery characteristics, and is a New special components between battery and capacitor
The basic principle is that when charging the electrode, the surface charge of the electrode in the state of the ideal polarized electrode will attract the opposite ions in the surrounding electrolyte solution, so that these ions are attached to the surface of the electrode to form an electric double layer, which constitutes an electric double layer capacitor. Since the distance between the two charge layers is very small (generally 0.5 nm or less), and the special electrode structure is used, the surface area of the electrode is increased by 10,000 times, thereby generating a large capacitance.