Certain metals have a strong ability to capture hydrogen. Under certain temperature and pressure conditions, these metals can "absorb" a large amount of hydrogen, react to form metal hydrides, and release heat at the same time. After that, heating these metal hydrides will decompose them, releasing the hydrogen stored in them. These metals that "absorb" hydrogen are called hydrogen storage alloys.

　　Hydrogen storage alloys have strong hydrogen storage capacity. The density of hydrogen storage per unit volume is 1000 times that of gaseous hydrogen under the same temperature and pressure conditions, which is equivalent to storing 1000 atmospheres of high-pressure hydrogen.

　　Because the cadmium in the nickel-cadmium batteries (Ni-Cd) used in large quantities is toxic, the waste battery processing is complicated and the environment is polluted, so it will gradually be replaced by nickel-hydrogen rechargeable batteries (Ni-MH) made of hydrogen storage alloys. .

　　In terms of battery power, nickel-metal hydride rechargeable batteries of the same size are about 1.5 to 2 times higher than nickel-cadmium batteries, and are free of cadmium pollution. They are now widely used in various small portable electronic devices such as mobile communications and notebook computers. . Larger capacity Ni-MH batteries have begun to be used in gasoline/electric hybrid vehicles. Ni-MH batteries can be used to quickly charge and discharge. When the car is running at high speed, the electricity generated by the generator can be stored in the on-board Ni-MH battery. When a car is running at a low speed, it usually consumes a lot of gasoline than a high-speed running state. Therefore, in order to save gasoline, the on-board nickel-hydrogen battery can be used to drive the electric motor to replace the internal combustion engine. This not only ensures the normal running of the car, but also saves A large amount of gasoline, therefore, hybrid vehicles have greater market potential than traditional cars, and countries around the world are stepping up research in this area.