Rechargeable batteries - Nickel oxide batteries

We call them "nickel-cadmium" or "nickel-iron" or "nickel-zinc" batteries... In fact, the positive active material is nickel oxyhydroxide NiO(OH), where nickel is in oxidation state 3. During discharge, this compound is transformed into nickel hydroxide Ni(OH) ₂ where nickel is in oxidation state 2. Nickel, which undergoes reduction during discharge, is therefore a positive electrode material. It is associated with various negative materials. Historically, the first were cadmium and iron in 1900, zinc in 1930, hydrogen after 1960, and hydride materials after 1985. The Ni-Cd and Ni-Fe systems are dealt with in paragraphs 1 and 2 respectively. To date, the Ni-Zn system has not enjoyed any real commercial success, due to the limited lifespan of the zinc electrode. This situation could change as a result of efforts to promote electric vehicles. The Ni-H ₂ sealed battery is a hybrid device that implements two technologies, that of the battery at the nickel oxide electrode and that of fuel cells at the hydrogen electrode. Finally, the nickel-metal hydride (Ni-MH) system is covered in 3 . These negative materials outperform nickel in that they exchange two electrons, while hydrogen is lighter. However, nickel has established itself as a positive material because of the robustness of the electrodes to which it leads. These have exceptional lifetimes, reaching several thousand cycles.