The "metal" part of the pouch-type nickel-metal hydride battery is actually an intermetallic compound. Many types of intermetallic compounds have been used in the manufacture of nickel-metal hydride batteries, mainly divided into two categories. The most common type is AB5, A is a mixture of rare earth elements (or) plus titanium (Ti); B is nickel (Ni), cobalt (Co), manganese (Mn), (or) and aluminum (Al ). The electrodes of some high-capacity batteries "contain multiple components" are mainly composed of AB2, where A is titanium (Ti) or vanadium (V), B is zirconium (Zr) or nickel (Ni), plus Some chromium (Cr), cobalt (Co), iron (Fe), and / or manganese (Mn).

All these compounds play the same role: reversibly forming metal hydrides. When the battery is charged, hydrogen ions (H) in the potassium hydroxide (KOH) electrolyte will be released and absorbed by these compounds to avoid the formation of hydrogen (H2) to maintain the internal pressure and volume of the battery. When the battery is discharged, these hydrogen ions will return to the original place through the reverse process