Abstract:
To meet the increasing global demands for energy and allow for the depletion of fossil fuel supplies in the coming years, alternate clean energy sources, which do not depend on conventional energy sources must be developed. To use renewable sources effectively, reliable ways of storing energy are needed. One alternative energy storage technology that has already taken off in a big way is the rechargeable lithium-ion battery. This technology has become a commercial reality through the efforts of the Sony Corporation and others, and is used widely today in portable computer and telecommunications devices, which is also receiving considerable attention in applications for electric vehicles, especially as these devices are becoming smaller and more efficient. Demand and competition are driving the quest for higher storage capacity, longer operating times, faster recharging times, and other performance optimizations. The three primary functional components for lithium ion battery are the anode, cathode and electrolyte, for all of which a variety of materials may be used. Steady progress has been made by using improved materials for the anode, cathode, electrolyte and the interfaces between them. The cathode used is generally one of three materials viz, an oxide layered structure, such as LiCoO2, polyanion based oxide, LiFePO4 type, or a spinel structure, such as LiMn2O4. Electrolyte used in lithium ion batteries consists of lithium salts, such as LiPF6, LiBF4, or LiCIO4 dissolved in an organic solvent, namely ethylene carbonate and di-ethyl carbonate. A liquid electrolyte conducts the Li ions, which are acting as carriers between the cathode and the anode when current is passed through an external circuit. Typical conductivity of liquid electrolyte at room temperature (i.e., 20 °C) is in the range of 10 mS/cm. The choice of material for the anode, cathode, and electrolyte depends on the voltage, capacity, life and safety of lithium ion battery can change dramatically.
