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Which substances react in a lead-acid storage battery?

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Crystal growth — electrochemical reaction Different mechanisms of crystal growth.

In a lead-acid storage battery, the electrochemical reactions involve the following substances:

Positive Electrode: Lead dioxide ( $P b O_{2}$ ) acts as the active material.1
Negative Electrode: Spongy lead ( $P b$ ) serves as the constituent material.12
Electrolyte: A solution of sulfuric acid ( $H_{2} S O_{4}$ ) and water ( $H_{2} O$ ) participates in the reactions.12

During discharge, the lead dioxide at the positive electrode combines with the sulfuric acid to produce lead sulfate ( $P b S O_{4}$ ) and water. Simultaneously, at the negative electrode, the lead combines with sulfate ions from the electrolyte to form lead sulfate and release electrons. This process consumes sulfuric acid and produces water, which dilutes the electrolyte and lowers its specific gravity, providing a way to measure the battery's state of charge. When the battery is recharged, these chemical reactions are reversed.12