How to Identify Anode and Cathode in a Battery

Identifying the anode and cathode in a battery (which is a galvanic cell, or voltaic cell) is straightforward because it directly relates to the physical positive (`+`) and negative (`-`) terminals marked on the battery.

This rule applies when the battery is discharging (i.e., being used to power a device):

• The Cathode is the Positive (`+`) Terminal. This is the terminal that electrons flow towards from the external circuit. It is the site of reduction (gain of electrons).
• The Anode is the Negative (`-`) Terminal. This is the terminal that electrons flow away from into the external circuit. It is the site of oxidation (loss of electrons).

A Simple Summary for a Discharging Battery:

• Positive (`+`) Terminal = Cathode
• Negative (`-`) Terminal = Anode

Important Note: Charging vs. Discharging

This identification (Anode = Negative) is only true when the battery is providing power (discharging).

When you are recharging a battery, you are applying an external power source, forcing the battery to act as an electrolytic cell. In this case, the roles reverse their polarity:

• The battery's Positive (`+`) Terminal becomes the Anode (where oxidation is forced to occur).
• The battery's Negative (`-`) Terminal becomes the Cathode (where reduction is forced to occur).

However, for general identification "in a battery," the standard discharging rule (Anode is Negative) is the correct answer.