Rechargeable metal hydrides alloy

Hydrogen-storage alloys (18,19) are commercially available from several companies in the United States, Japan, and Europe. A commercial use has been developed in rechargeable nickel—metal hydride batteries which are superior to nickel—cadmium batteries by virtue of improved capacity and elimination of the toxic metal cadmium (see BATTERIES, SECONDARYCELLS-ALKALINe). Other uses are expected to develop in nonpolluting internal combustion engines and fuel cells (qv), heat pumps and refrigerators, and electric utility peak-load shaving. 

One of the problems with early hydride systems was decrepitation of the alloy. Each time the metal hydride storage tank was recharged the particles would break down and eventually the particles became so small that they began to pass through the 5-p.m sintered metal filter which kept the hydride inside the tank. Addition of 0.5% manganese, which caused the decrepitation process to cease once the particles reached a size of about 10 p.m, solved this problem. 

A nickel-metal hydride battery (Ni-MH), which is a type of rechargeable battery comparable to a nickel-cadmium (Ni-Cd) battery, uses a hydrogen-absorbing alloy for the negative electrode... 

B) The nickel-metal hydride (NIMH) rechargeable secondary electrochemical cell, introduced by Beccu87 in 1967, has a nickel oxyhydroxide NiO(OH) electrode and a hydrogen-adsorbing alloy M (e.g., Ti2Ni) at the other electrode in the discharge mode the reaction is... 

According to Pearson s Handbook, this crystal structure is commonly known as the CaCus-type structure. The parent LaNis alloy is well known for its unique hydrogen storage properties, and many closely related alloys with the same crystal structure have been commercialized as electrode materials in rechargeable nickel-metal hydride batteries. 

Goodell, P.D., Stability of rechargeable hydriding alloys during extended cycling. Journal of the Less-Common Metals, 1984, 99(1) p. 1-14. 

Nickel is used extensively in alloys, notably in stainless steel, other corrosion-resistant alloys such as Monel metal, and coinage metals. Electroplated Ni provides a protective coat for other metals. Nickel has widespread use in batteries recently, this has included the production of environmentally friendly nickel-metal hydride batteries (see Box 9.5) which out-perform NiCd cells (equation 21.5) as rechargeable sources of power in portable appliances. 

Cobalt is used in various types of rechargeable batteries. In the Ni-Cd batteries, cobalt represents 1-5% of the weight of nickel hydroxide at the cathode. In the nickel metal hydride battery (Ni/MH), cobalt is moreover employed at the anode as a hydrogen storage alloy such as mischmetal (NiCoAlMn (5-15% Co). Finally, in the Li-ion batteries, the cathode could be LiCo02 where cobalt could represent 50% of the weight (6, 7). 

The rechargeable sealed nickel-metal hydride battery is a relatively new technology with characteristics similar to those of the sealed nickel-cadmium battery. The principal difference is that the nickel-metal hydride battery uses hydrogen, absorbed in a metal alloy, for the active negative material in place of the cadmium used in the nickel-cadmium battery. 

Besides the application of solid hydrogen storage, MH alloys also play a very important role in nickel/metal hydride (Ni/MH) rechargeable battery as the negative electrode. The chemical reaction during charge/ discharge is ... 

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