Nickel-hydrogen batteries electrodes

The reaction of hydrogen at the nickel electrode determines the rate of selfdischarge in nickel-hydrogen batteries. 

Developed in the 1960s, it makes use of different technologies for its electrodes NiO(OH) is from nickel cadmium and H2 from fuel-cell systems. Because of its longer cycle life the main use of the nickel-hydrogen battery is in aerospace applications to replace the nickel cadmium cells. For example, the Hubble Space Telescope launched in 1990 was equipped with nickel-hydrogen cells [12]. 

Nickel-hydrogen batteries (Ni/T ) were developed in 1970 for aerospace applications. These batteries are a combination of the Ni-Cd technology (Ni electrode) and the fuel-cell technology (H2 electrode). They use nickel hydroxide as cathode active material, a hydrogen electrode as anode, and an aqueous solution of potassium hydroxide as electrolyte. Asbestos (fuel-cell grade asbestos paper) and Zircar (untreated knit ZYK-15 Zircar cloth) are used... 

Nickel and its alloys are extensively used in electrochemical applications due to its good corrosion resistance. In battery applications, nickel is used as the positive electrode in nickel-cadmium, nickel-iron, nickel-zinc, and nickel-hydrogen batteries, and as anodes in fuel cells, electrolyte cells and electro-organic syntheses . Because of the importance of nickel in battery applications, electrochemical properties of nickel have been studied for more than IOC years since 1887 when Dun and... 

Mostly in batteries the reacting substances are stored within the electrodes (the active material ), but there are also systems where the electrolyte participates, as in lead-acid batteries, or where the reacting substances are stored in separate tanks, e.g. Zn/Cl, Zn/Br, and vanadium redox batteries (Section 1.8.5), or as a gas in the container of nickel-hydrogen batteries (Section 1.8.3). 

The electrolyte is an important component of the cell. Often it is only the medium for electrode reactions and ionic conductivity and does not appear in the cell reaction (e.g., in nickel/cadmium and nickel/hydrogen batteries), sometimes as in lead-acid batteries, it is also a component of the cell reaction. A certain interaction, however, between the electrolyte and the active material usually cannot be prevented and often influences aging of the battery. 

Nickel/hydrogen batteries are closely related to the nickel/cadmium battery, since they employ the same positive electrode and the same electrolyte. They have been developed for aerospace applications and are still the number one energy storage system in many satellite projects 60. 

The packaging approach utilized for tliis battery is similar to that for nickel—hydrogen single cylindrical cells as shown in Figure 23. The sdv er electrode is typically the sintered type used in rechargeable sdv er—zinc cells. The hydrogen electrode is a Teflon-bonded platinum black gas difhision electrode. 

In normal battery operation several electrochemical reactions occur on the nickel hydroxide electrode. These are the redox reactions of the active material, oxygen evolution, and in the case of nickel-hydrogen and nickel-metal hydride batteries, hydrogen oxidation. In addition there are parasitic reactions such as the corrosion of nickel current collector materials and the oxidation of organic materials from separators. The initial reaction in the corrosion process is the conversion of Ni to Ni(OH)2. 

A Ni-H2 ceU may be viewed as a hybrid of the alkaline Ni-Cd ceU with the alkaline hydrogen-oxygen fuel cdl. Simply, the hydrogen electrode from the fud ceU is combined with the nickel oxide positive electrode from the Ni-Cd ceU, thus forming a battery system with two of the most reversible dectrodes. OveraU, the reaction within the Ni-H2 ceU is ... 

Figure 4.2. Schematic of a nickel-hydrogen storage battery (1) electrode block, (2) container, (3) terminal.

The nickel-based systems have traditionally included the following systems -nickel-iron (Ni/Fe), nickel-cadmium (NiCd), nickel metal hydrides (NiMH), nickel hydrogen (Ni/H2), and nickel-zinc (Ni/Zn). Of these, the metal hydride chemistry has been the most successful in the secondary battery market. AU nickel systems are based on the use of a nickel oxide active material (undergoing one valence change from charge to discharge or vice-versa). The electrodes can be pocket type, sintered type, fibrous type, foam type, pasted type, or plastic roll-bonded type. All systems use an alkaline electrolyte, KOH. 

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