The positive active material of Ni-MH battery is Ni(OH)2 (called NiO electrode), the negative active material is metal hydride, also known as hydrogen storage alloy (the electrode is called hydrogen storage electrode), and the electrolyte is 6mol/L potassium hydroxide solution. There are mainly sintering type, pulping type, foam nickel type, fiber nickel type, and embedded infiltration type in the active material forming electrode pole pieces. The electrodes prepared by different processes have great differences in capacity and high-current discharge performance. Batteries are produced in different processes according to the conditions of use. Most of the civilian batteries such as communications use a pulp-type negative electrode and a foamed nickel-type positive electrode to form a battery. The charging and discharging chemical reaction is as follows[1]:

Positive electrode: Ni(OH)2+OH-=NiOOH+H2O+e-

Negative electrode: M+H2O+e-=MHab+OH-

Total reaction: Ni(OH)2+M=NiOOH+MH

Note: M: hydrogen alloy; Hab: adsorbed hydrogen; the process from left to right of the reaction formula is the charging process; the process of the reaction formula from right to left is the discharge process.

When charging, the Ni(OH)2 and OH- on the positive electrode react to form NiOOH and H2O, and at the same time release e- to form MH and OH- together. The overall reaction is Ni(OH)2 and M to form NiOOH, and the hydrogen storage alloy stores hydrogen; discharge On the contrary, MHab releases H+, H+ and OH- generate H2O and e-, NiOOH, H2O and e-regenerate Ni(OH)2 and OH-. The standard electromotive force of the battery is 1.319V.