Hydrogen storage conventional metal hydrides

We have so far described the research and development for nickel-metal hydride batteries in which a hydrogen storage alloy (metal hydride) is used as a negative electrode material. This type of battery has been attracting a great deal of attention as a new non-military battery because it is characterized by several advantages over the conventional secondary batteries ... 

It is clear that conventional metal hydride hydrogen storage is not a feasible option for storage of land or air vehicle propulsion fuel. However, metal hydride hydrogen storage has been successfully employed on the German, Class 212, fuel cell-powered submarine, where very long underwater endurance is not required. 

A wide range of materials are currently being considered as hydrogen storage media, including conventional metal hydrides, complex hydrides, chemical hydrides, carbon-based materials, Zeolites, MOFs, clathrates, and so on. In this section, some well-studied hydrogen storage... 

Two types of fundamental metal hydride electrodes comprising the AB, and ABj classes of alloys are currently of interest. The AB, alloys with A = rare earth or mischmetal, B = Ni and/or other transition metal are investigated. LaNi, has been well-investigated because of its utility in conventional hydrogen storage applications, but it is very expensive and corrodes rapidly. The commercial AB, electrodes use mischmetal, a low-cost combination of rare earth elements, as a substitute for La. The partial substitution of Ni by Co, Ce, Mn and Al increases the thermodynamic stability of the hydride phase, the corrosion resistance and hence the cycle life. However, the substitution reduces the hydrogen storage capacity. 

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