The role of a battery in an electrochemical cell depends on whether the cell is galvanic (voltaic) or electrolytic:
1. In a Galvanic (Voltaic) Cell
- The cell itself acts like a battery.
- A spontaneous redox reaction occurs, and the chemical energy is directly converted into electrical energy.
- The “battery” (galvanic cell) provides a flow of electrons through an external circuit, which can power devices.
- Example: The Daniell cell, where zinc is oxidized and copper ions are reduced, producing electricity.
Role: To supply electric current by using chemical reactions.
2. In an Electrolytic Cell
- A separate battery is connected to the cell.
- Here, the battery forces a non-spontaneous redox reaction to occur by supplying electrical energy.
- The battery pushes electrons into the cathode and pulls them from the anode, driving reactions that would not normally happen.
- Example: Electrolysis of water, where the battery drives the decomposition of water into hydrogen and oxygen gases.
Role: To provide external energy to drive non-spontaneous reactions.
In short:
- In a galvanic cell, the battery is the electrochemical cell itself, producing current.
- In an electrolytic cell, the battery acts as an external power source to make reactions occur.