cathodeselectrodes

Cathode electrodes are the electrodes in an electrochemical cell at which reduction occurs. In galvanic cells, the cathode is the positive terminal; in electrolytic cells, it is the negative terminal. The term cathode is defined by the redox change taking place at the surface, not by the sign of the external connection.

Materials vary by application. Inert electrodes, such as platinum or graphite, are used when the electrode should not participate in the reaction. For metal deposition or plating, the cathode is the surface where metal ions gain electrons and deposit as metal.

In batteries, cathodes are active materials that accept ions during discharge; examples include LiCoO2, LiMn2O4, and LiFePO4 in lithium-ion chemistries. The choice of cathode material influences voltage, capacity, and cycle life.

Common applications include electroplating, electrorefining, and cathodic protection, where the cathode participates in reduction or receives deposited metal. In cathodic protection, external current makes the structure a cathode to prevent corrosion.

The term cathode refers to the function rather than a fixed polarity in a circuit, and the concept is central to electrochemistry and energy storage technology.