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ELECTRIC VEHICLE BATTERIES to absorb and release lithium ions, has resulted in lower specific power and limited cycle life for lithium-polymer batteries. The current collector for lithium-polymer batteries is typically made of either copper or aluminum foil surrounded by a low thermal conductivity material such as polyurethane. The battery case is made of polypropylene, reinforced polypropylene, or polystyrene. Lithium-polymer batteries are considered solid-state batteries since their electrolyte is a solid. The most common polymer electrolyte is polyethylene oxide complexed with an appropriate electrolyte salt. The polymers can conduct ions at temperatures above about 60°C (140°F), allowing for the replacement of flammable liquid electrolytes by polymers of high molecular weight. Since the conductivity of these polymers is low, the batteries must be constructed in thin films ranging from 50 to 200 mm thick. There is, however, a great safety advantage to this type of battery construction. Because the battery is solid-state by design, the materials will not flow together and electrolyte will not leak out in case there is a rupture in the battery case during an EV accident. Because the lithium is intercalated into carbon anodes, the lithium is in ionic form and is less reactive than pure lithium metal. Another major advantage of this type of battery construction is that a lithium-polymer battery can be formed in any size or shape, allowing vehicle manufacturers considerable flexibility in the manner in which the battery is incorporated into future vehicle designs.
FUEL CELL TECHNOLOGY The oil crisis in 1973 led to the development of the alternative automotive power sources. This development of alternative power sources prompted EV for urban transportation. During this period, the primary concern was to gain independence from foreign oil sources. The two primary commercially available battery types were the Pb-acid and the NiCd batteries. This prompted research into the development of fuel cells. In the case of the battery, chemical energy is stored in the electrode, while in the case of the fuel cell, the energy is stored outside the electrodes. Thus there is no physical limit to the amount of fuel stored. This is analogous to the gasoline cars with internal combustion engines. Renewable energy-based hydrogen vehicles used in place of conventional and diesel-fueled internal combustion engines will reduce automotive air pollution significantly. Dating back to the developments in 1839, Sir William Graves first demonstrated the fuel cell principle. Since 1987, the DOE has awarded
