Britannica Sources used in this answer

How does a lead-acid storage battery produce an electric current?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Crystal growth — electrochemical reaction Different mechanisms of crystal growth.

A lead-acid storage battery produces an electric current through a series of electrochemical reactions that convert chemical energy into electrical energy.1

During discharge, the battery utilizes two separate processes occurring at its electrodes:

Positive Electrode: The active material, lead dioxide, reacts with the sulfuric acid electrolyte to produce lead sulfate and water. This process involves the reduction of lead dioxide.21
Negative Electrode: The constituent lead combines with sulfuric acid ions to produce lead sulfate and hydrogen ions. This process involves the oxidation of lead.21

These simultaneous reactions create a driving force, or electrical potential, that causes electricity to flow through an external circuit connecting the two electrodes. As the reaction proceeds, the electrolyte carries the electric current via the migration of ions, and the consumption of sulfuric acid causes the density of the electrolyte to decrease.12