Iron compounds, batteries

A number of researchers, ° ° particularly in Japan, have been pursuing the oxides of iron as potential cathode materials for lithium cells. However, materials of the type LiFeOz have shown little ability for lithium removal. A number of other iron compounds have been studied over the years, including FeOCl, ° FePS3, ° KFeSz, and FeSz, but none showed much reversibility. Although metal phosphates have been studied for more than 20 years since the discovery of fast ion transport in NASICON, it is only recently that they have been considered as cathodes or anodes " of lithium batteries. 

The iron compounds used in this battery are much less expensive than the current Mn02 compounds and the products are more environmentally friendly (Fe203 is a form of rust). 

Iron has conventionally been used as the anode or negative active material in batteries but iron compounds have also been used as the cathode or positive active material. The use of iron sulfides (FeS and FeS2) in lithium primary and in high temperature batteries is covered in Chapters 14 and 41. 

Multiple bimetallic sulfates with the formula Li2M(S04)2 (M = Fe, Mn, Co) have been proposed as new polyanionic Li-ion battery cathode compounds since the discovery of LiFePOa as a promising positive electrode material [5, 95, 96]. The Fe-based Li2Fe(S04)2 exhibits an open circuit voltage of 3.83 V versus Li /Li°, which is the highest potential ever obtained for the Fe /Fe redox couple in an iron-based, fluorine-free compound, and is only matched by the triplite phase of LiFe(S04)F [97, 98]. This finding has not only paved the way for the development of a totally new class of fluorine-free compounds but could also reveal fundamental structure-property relationships in Li-ion cathode materials. 

Lead-acid, nickel-iron (Ni-Fe), nickel-cadmium (NiCd), and nickel-metal hydride (NiMH) batteries are the most important examples of batteries with aqueous electrolytes. In lead-acid batteries, the overall electrochemical reaction upon discharge consists of a comproportionation of Pb° and Pb4+ to Pb2+. All nickel-containing battery reactions are based on the same cathodic reduction of Ni3+ to Ni2+, but utilize different anodic reactions providing the electrons. Owing to toxicity and environmental concerns, the formerly widely used Cd°/Cd2+ couple (NiCd cells) has been almost entirely replaced by H/H+, with the hydrogen being stored in a special intermetallic compound (NiMH). 

A promising new battery now under development employs unusual iron(VI) compounds at the anode. Because iron(VI) is such a strong oxidizing agent, its compounds are normally very unstable, but these problems seem to have been solved by removing contaminants such as cobalt and nickel. These so-called super-iron batteries reportedly can furnish 50% more energy than conventional dry cell batteries. 

Use Aluminum alloys for structural parts, die-cast auto parts, missiles, space vehicles powder for pyrotechnics and flash photography, production of iron, nickel, zinc, titanium, zirconium antiknock gasoline additives magnesium compounds and Gri-gnard syntheses cathodic protection reducing agent desulfurizing iron in steel manufacture precision instruments optical mirrors dry and wet batteries. 

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