Advances in Battery Technologies and Markets: Material Science Aspects
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Mat. Res. Soc. Symp. Proc. Vol. 496 01998 Materials Research Society
The systems and technologies to meet these growing and new markets fall into four main product types; Small Rechargeables for Consumer Electronics [Ni-MH, Lithium ion, Rechargeable MnO2] Advanced Energy Storage Systems: Advanced Lead-Acid, Ni-MIT, Rechargeable Lithium New Manufacturing Techniques: continuous, high speed, environmentally benign, low labor content Consumer primary cells, alkaline MnO2 worldwide, zinc-air hearing aid cells Battery Materials Background The materials of construction and assembly of batteries encompass a great variety of chemical and physical shapes.
They include elements, inorganic and organic
compounds, polymers, ceramics, aqueous and non-aqueous solutions, and films, fibers, and mats. There are six main function categories for materials in batteries; negative active material, positive active material, substrates and conductivity enhancers, electrolytes; separator systems, and packaging materials. These are illustrated in Table II. In several cases, use in batteries constitutes the major application for a particular material e.g. lead, cadmium, electrolytic MnO2. In other cases, batteries constitute a very small fraction of the world use of a material and it is difficult to obtain special material, e.g. cellophane, absorber fabrics. The general requirements for each of these classes of components are shown in Table III. In Table IV, the current status of common consumer size secondary cells is compared. In order to appreciate the role of material science in capacity and performance improvements in cells, the example is shown in Fig. I of the increase in capacity in AA size Nickel-Cadmium and Nickel-MH cells in the period of 1968-1995. In the same volume, the capacity of Ni-Cd cells improved by a factor of 2.5. This was mainly attributable to new substrate materials and in improvements in the packing density of Ni(OH) 2 . The characteristics and improvements in Nickel Hydroxide are a good example of the semiconductor nature of battery materials and pore structure can be modified to provide much improved energy density and performance. Table V illustrates the nickel hydroxide structure and compares the properties of conventional and "spherical" material. The latter is a name coined to reflect the appearance of the high density powder.[1]. Although the chemical structure is the same, the surface areas and pore structures are very different. In essence, the preparation of the spherical material eliminates large, and unnecessary, pores. Further improvements are under study. Reisner et.al. [2] reported that the preparation of nickel hydroxide by nanophase techniques lead to a more catalytic material which can have a higher packing density. Other improvements in nickel electrode active material included the recent development of a uniform foam [3] made by coating polyurethane foam by the carbonyl nickel process. In addition, a variety of nickel powders of high porosity have been developed. These can be used as additives
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