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Why do batteries eventually run out of power?

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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.

Batteries run out of power because they contain a finite amount of chemical energy available for conversion into electrical energy.1

A battery generates electromotive force through specific chemical reactions occurring at its electrodes—the anode and cathode—which are separated by an electrolyte. These reactions involve a limited supply of active materials that undergo chemical transformations to produce electric current. Once these materials are depleted or the chemical potential is exhausted, the battery can no longer sustain the necessary reactions to provide power.12

While primary batteries are designed to be discarded once this capacity is reached, secondary (storage) batteries are engineered to allow these chemical reactions to be reversed through the application of an external direct current, effectively recharging the device for further use.12