The document discusses different types of batteries, including nickel-cadmium, alkaline, lithium-iodine, mercury, and lead-acid batteries. It provides the chemical reactions, components, and properties of each battery type. In particular, it notes that nickel-cadmium and lead-acid batteries are rechargeable because their reaction products cling to the electrodes, allowing the reactions to be run in reverse when an external voltage is applied. Alkaline batteries are not rechargeable because their reaction products do not remain attached to the electrodes.