As fossil fuels are becoming less and less under the condition of large-scale development and utilization of human beings, in recent years, the development and utilization of hydrogen energy has received increasing attention. As an important direction in the application of hydrogen energy, nickel-metal hydride batteries have attracted more and more attention. Although the nickel-hydrogen battery is indeed a kind of battery with good performance, the nickel-hydrogen battery for aerospace is a high-pressure nickel-hydrogen battery. Such high-pressure hydrogen gas is easy to explode when stored in a thin-walled container, and the nickel-hydrogen battery also requires precious metals as a catalyst. This makes it very expensive, which is difficult to accept for civilian use. Therefore, foreign countries have been exploring civilian low-voltage nickel-hydrogen batteries since the 1970s. Ni-MH batteries are divided into high-voltage nickel-hydrogen batteries and low-voltage nickel-hydrogen batteries. The high-voltage Ni-MH battery was first developed by M. Klein and J.F. Stockel in the United States in the early 1970s. The trend of replacing nickel-cadmium batteries with nickel-metal hydride batteries and applying them on various satellites has been formed.
Structure and principleedit
The positive electrode active material of the nickel-hydrogen battery is Ni(OH)2 (called NiO electrode), the negative electrode active material is metal hydride, also called hydrogen storage alloy (the electrode is called hydrogen storage electrode), and the electrolyte is 6mol/L potassium hydroxide solution. The active material forming the electrode pads mainly include sintering, drawing, foaming nickel, fiber nickel and infiltration, etc. Electrodes prepared by different processes have large differences in capacity and high current discharge performance. The battery is produced in different processes according to the conditions of use. Most of the civilian batteries such as telecommunications use drawn-out negative electrodes and foamed nickel positive electrodes. The charge and discharge chemical reaction is as follows:
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 a charging process; the process from right to left of the reaction formula is a discharge process.
When charging, the positive electrode's Ni(OH)2 reacts with OH- to generate NiOOH and H2O, and at the same time releases e- to generate MH and OH- together. The total reaction is Ni(OH)2 and M to generate NiOOH, hydrogen storage alloy stores hydrogen; On the contrary, MHab releases H+, H+ and OH- generate H2O