Cathode

The electrode where reduction occurs in an electrochemical cell. Its polarity depends on the cell: it is positive in a galvanic cell and negative in an electrolytic cell.

Reduction: A chemical process in which a species gains electrons or decreases its oxidation state. Reduction defines the cathode, where reacting species gain electrons.
Galvanic cell: An electrochemical cell that produces electrical energy from a spontaneous chemical reaction. Its cathode is positive because the cell's spontaneous reaction drives electrons toward it.
Lithium-ion battery: A rechargeable battery that transfers lithium ions between electrodes during charge and discharge. Its cathode host material accepts lithium ions during discharge.
Half-reaction: A representation of either the oxidation or reduction part of a redox reaction, including electrons. Cathodic chemistry is written as the reduction half-reaction.
Electrochemical cell: A system that converts chemical energy into electrical energy or uses electrical energy to drive chemical reactions. The cathode is one of the two electrodes in every electrochemical cell.
Electrolytic cell: An electrochemical cell that uses electrical energy to drive a nonspontaneous chemical reaction. Its cathode is negative because an external source supplies electrons to it.
Electroplating: A process that deposits a metal coating by electrochemical reduction from solution. Metal ions gain electrons at the cathode and form a coating.
Oxidation state: A bookkeeping value indicating an atom's assigned electron loss or gain in a compound. Reduction at the cathode lowers the oxidation state of the reacting species.
Anode: The electrode where oxidation occurs in an electrochemical cell. Oxidation occurs at the anode, opposite the cathode's reduction reaction.
Conventional current: The defined direction of electric current, taken as the direction positive charge would move. Its direction through the external circuit is opposite electron flow to the cathode.

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