An electrolytic capacitor is a polarized capacitor whose anode or positive plate is made of a metal that forms an insulating oxide layer through anodization.
This oxide layer acts as the dielectric of the capacitor. A solid, liquid or gel electrolyte covers the surface of this oxide layer and acts as the cathode or negative plate of the capacitor. Due to their very thin dielectric oxide layer and enlarged anode surface, electrolytic capacitors have a much higher product of capacitance voltage (CV) per unit volume than ceramic capacitors or film capacitors, so they can have large capacitance values. There are three families of electrolytic capacitors: aluminum electrolytic capacitors, tantalum electrolytic capacitors, and niobium. Any of the three types of dielectric material is used to manufacture this type of capacitor.
The large capacity of electrolytic capacitors makes them especially suitable for passing or avoiding low-frequency signals and for storing large amounts of energy. They are widely used to decouple or filter noise in power supplies and DC link circuits for variable frequency drives, to couple signals between amplification stages, etc.
They are polarized components due to their asymmetric construction and must operate with a higher voltage (that is, more positive) at the anode than at the cathode at all times. For this reason, the anode terminal is marked with a plus sign and the cathode with a minus sign. Applying a reverse polarity voltage, or a voltage that exceeds the maximum rated working voltage of just 1 or 1.5 volts, can destroy the dielectric and therefore the capacitor. Electrolytic capacitor failure can be dangerous and lead to explosion or fire
