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Why do alkaline batteries have a higher capacity than zinc-carbon batteries?

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Cross-section diagram of an alkaline-manganese dioxide battery showing labeled internal components, including the steel-plated covers, cathode, anode gel, current collector, separator, steel can, and brass rivet. — battery Cutaway view of an alkaline–manganese dioxide power cell.

Alkaline batteries provide a higher capacity than zinc-carbon batteries primarily due to their distinct construction and chemical composition, which allow for a higher power density.1

While zinc-carbon batteries (or Leclanché cells) rely on a traditional design with an ammonium chloride electrolyte, alkaline batteries utilize a potassium hydroxide electrolyte. This alkaline electrolyte enables a completely different, more efficient internal structure. Specifically, alkaline batteries feature a cathode composed of a high-purity manganese dioxide and graphite mixture, paired with an anode made of a powdered zinc alloy.1

This configuration, housed within a steel can, allows alkaline cells to deliver significantly more energy for devices such as flashlights, toys, and radios compared to zinc-carbon or zinc chloride systems. Additionally, the use of an alkaline electrolyte helps decrease the corrosion of the cell, contributing to its longer-lived performance.12