  We propose a dynamical theory of how the chemical energy stored in a battery
generates the electromotive force (emf). In this picture, the battery's
half-cell acts as an engine, cyclically extracting work from its underlying
chemical disequilibrium. We show that the double layer at the
electrode-electrolyte interface can exhibit a rapid self-oscillation that pumps
an electric current, thus accounting for the persistent conversion of chemical
energy into electrical work equal to the emf times the separated charge. We
suggest a connection between this mechanism and the slow self-oscillations
observed in various electrochemical cells, including batteries, as well as the
enhancement of the current observed when ultrasound is applied to the
half-cell. Finally, we propose more direct experimental tests of the
predictions of this dynamical theory.
