As fossil fuels become less and less in the context of large-scale development and utilization by human beings, in recent years, the development and use of hydrogen energy have received increasing attention. Ni-mh battery has been paid more and more attention as an essential direction of hydrogen energy application. Although the NIMH battery is indeed a good-performance battery, the nickel-metal hydride battery for aerospace is a high-voltage nickel-metal hydride battery. Such ni-mh battery pack is high-pressure hydrogen is quickly exploded when stored in a thin-walled container, and the Nimh battery also requires precious metals as catalysts to make it The cost has become costly, which is challenging to be accepted by civilians. Therefore, foreign countries have begun to explore civilian low-voltage nickel-metal hydride batteries since the 1970s. Ni-MH cells are divided into high-voltage Ni-MH batteries and low-voltage Ni-MH batteries. The high-voltage nickel-metal hydride battery was first developed by M.Klein and J.F.Stockel of the United States in the early 1970s. The trend of replacing NiCh batteries with Nimh batteries and applying them to various satellites has formed.
Structure and principle
Nimh battery positive electrode active material is Ni (OH) 2 (called NiO electrode), negative electrode active material is metal hydride, also called hydrogen storage alloy (electrode called hydrogen storage electrode), and the electrolyte is a 6mol / L potassium hydroxide solution. The active material forms the electrode pole pieces mainly by sintering type, slurry type, foam nickel type, fibre nickel type, and infiltration type. Electrodes prepared by different processes have large differences in capacity and high current discharge performance. Generally, Production of batteries according to different conditions of use. Communications and other civilian batteries are mostly battery-pulled anodes and foamed nickel anodes. The charge-discharge chemical reaction is as follows :
Positive electrode: Ni (OH) 2 + OH- = NiOOH + H2O + e-
Anode: M + H2O + e- = MHab + OH-
Total reaction: Ni (OH) 2 + M = NiOOH + MH
Note M: hydrogen alloy; Hab: adsorption of hydrogen; the process from the left to the right of the reaction is the charging process; the process from right to left is the discharge process.
During charging, Ni (OH) 2 and OH- in the positive electrode react to form NiOOH and H2O, and at the same time e- is released to form MH and OH-. The total reaction is that Ni (OH) 2 and M form NiOOH, and the hydrogen storage alloy stores hydrogen; In contrast, MHab releases H +, H + and OH- to form H2O and e-, and NiOOH, H2O and e- to form Ni (OH) 2 and OH- again. The standard electromotive force of the battery is 1.319V.