Nickel hydroxide is used as a cathode material in nickel-metal hydride batteries. When nickel-metal hydride batteries were first commercialized in Japan in 1990, sales of nickel-metal hydride batteries initially increased rapidly for use in portable electronic devices. Later, however, these were replaced by lithium-ion rechargeable batteries as mobile devices became thinner and lighter. More recently nickel-metal hydride batteries have been used mainly in hybrid vehicles, power tools, electrically power assisted bicycles, along with a variety of other applications.