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How does a battery keep the electric potentials at its electrodes different?

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density current: descent to the ocean floor — density current Diagram showing the behaviour of a density current as it descends to the seafloor.

A battery maintains a potential difference between its electrodes by using chemical reactions to continuously replenish excess positive and negative charges at its terminals. These reactions occur at separate locations within the battery, typically involving an anode that undergoes oxidation (releasing electrons) and a cathode that undergoes reduction (accepting electrons).123

Because these reactions are physically separated, the electrons are forced to travel through an external circuit to balance the charge, creating a flow of electricity. An electrolyte inside the battery completes the internal circuit by allowing ions to migrate between the electrodes, which balances the flow of current and maintains the chemical equilibrium necessary to sustain the potential difference.123

Essentially, the battery acts as a source of electromotive force by performing work to move charges in a direction opposite to the electric force that would otherwise naturally neutralize the potential difference. This process continues as long as the chemical reactants are available to sustain the oxidation-reduction reactions.13