A nickel cadmium battery is a secondary cell. It is also known as Nicad or Ni-Cd. It was used for many applications, such as rechargeable phones, flashlights, and other things. Now the nickel metal-hydride battery is being used. Nickel cadmium batteries contain toxic cadmium metal in them. It works by the oxidation of cadmium by nickel(III) oxide. Potassium hydroxide is used as an electrolyte.