Nickel-metal hydride batteries are a type of rechargeable battery with an electrochemistry similar to nickel cadmium batteries, but the eliminate the toxic cadmium metal.
The older nickel cadmium battery uses nickel oxide hydroxide and metallic cadmium as electrodes, while the newer nickel-metal hydride battery keeps the nickel oxide hydroxide electrode it uses a complex alloy that readily absorbs hydrogen atoms forming a metal hydride, it is the absorbed hydrogen within this hydride that actually functions as the active electrode in the battery. In addition to eliminating the toxic cadmium (making recycling or disposal easier and cheaper) this change also provides other advantages: higher battery capacity, no memory effect, etc.
Some of the different alloys used in the metal hydride electrode are:
- titanium nickel
- lanthanum neodymium nickel cobalt silicon
- cerium lanthanum neodymium praseodymium nickel cobalt silicon
