In NI-MH alkaline rechargeable batteries, the positive electrode active material is mainly made of nickel, and the negative electrode active material is mainly made of hydrogen storage alloy.

The positive active material is mainly made of nickel, and the negative active material is mainly an alkaline storage battery made of hydrogen storage alloy.

Nickel-metal hydride batteries (NiMH) are improved from nickel-cadmium batteries (NiCd batteries), which replace cadmium (Cd) with metals that can absorb hydrogen. It provides a higher capacity than nickel-cadmium batteries at the same price, less obvious memory effects, and lower environmental pollution (no toxic cadmium). Its recycling efficiency is better than that of lithium ion batteries, and it is called the most environmentally friendly battery. But when compared with lithium-ion batteries, it has a relatively high memory effect. The old nickel-metal hydride batteries have a higher self-discharge response, and the new nickel-metal hydride batteries have a relatively low self-discharge (similar to alkaline electricity), and can work at low temperatures (-20 ℃). Nickel-metal hydride batteries have a larger output current than carbon-zinc or alkaline batteries, and are relatively more suitable for high-power consumption products. Some special models even have a larger output current than nickel-cadmium batteries.

At present, the capacity of nickel-metal hydride batteries is generally higher than that of alkaline batteries (in terms of volume). Taking AA batteries as an example, the marked capacity of nickel-metal hydride batteries can reach 2900mAh (milliampere-hours. China generally calls mAh "milliampere hours" ), While alkaline batteries have only ~ 2100mAh, which is of course much higher than 1100mAh of nickel-cadmium batteries, but still not as good as lithium-ion batteries.

Alkaline batteries will leak slightly corrosive and harmful liquids after long-term non-use (it will be harmful to the human body or damage the device using the battery), and lithium batteries may burn or explode when not in use. Relatively speaking, nickel-metal hydride batteries are the safest batteries