Nickel-metal hydride battery
A nickel-metal hydride battery, also known as NiMH, is a secondary cell, meaning it is a rechargeable battery.  They are used in cameras and other electronic devices.  They are made in several sizes; AA is the most common.  They are similar to nickel-cadmium batteries but store twice as much energy. They have a voltage of 1.2 V, the same as the nickel-cadmium battery. They do not contain toxic chemicals like the nickel cadmium battery does.  They work by the oxidation of hydrides, such as lanthanum hydride, by nickel(III) oxide.