2. + + + + + + The following reactions occur at the electrodes when the battery is producing electricity, i.e. during d dd discharge. +++ + In a battery:

3. During c cc charging the chemical reactions are reversed. The following reactions occur at the electrodes when the battery is being charged. + + + + + + +++ + The first small rechargeable battery produced for appliances, used a reaction between c cc cadmium and a compound of n nn nickel (nickel oxyhydroxide NiOOH) to produce a current. More advanced rechargeable batteries such as l ll lithium-ion batteries have been developed. The main advantage of these batteries is they are much lighter.

4. + PEM + +

5. + + +2+ + + +