How Does A Rechargeable Battery Work?
Rechargeable batteries behave like ordinary batteries when they are being discharged. An electrical circuit is created when one material oxidizes, or gives up electrons, while another material immersed in an electrolyte becomes reduced, or gains electrons. The key to a rechargeable battery, however, is that it can reverse this flow of electrons when it is plugged into an electrical outlet (see image above). The material that oxidizes during discharge gains electrons, while the other material gives up electrons.
"All batteries, both rechargeable and nonrechargeable, undergo electrochemical reactions. When a battery is discharged, an electrochemical oxidation reaction proceeds at the negative electrode, and an electrochemical reduction reaction occurs at the positive electrode. When one attempts to recharge a battery by reversing the direction of electric current flow, the opposite takes place: a reduction reaction proceeds at the negative electrode, and an oxidation reaction takes place at the positive electrode.
-Frank McLarnon, staff scientist/principal investigator in the Energy & Environment Division of Lawrence Berkeley National Laboratory.
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