Nickel-metal hydride (NiMH) is a type of rechargeable battery that uses nickel oxide hydroxide and a hydrogen-absorbing alloy as its electrodes. It is known for its higher energy density compared to older battery technologies, such as nickel-cadmium (NiCd), making it suitable for various applications, including portable electronics and hybrid vehicles. NiMH batteries are environmentally friendlier than some alternatives, as they do not contain toxic heavy metals like cadmium. They also have a lower self-discharge rate, allowing them to retain charge longer when not in use. However, they can be sensitive to overcharging and require proper management to ensure longevity.