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Solid Polymer Electrolyte Lithium Batteries

This promising lithium rechargeable technology is using a polymer electrolyte in a solid state cell in which a polymer electrolyte is sandwiched between a lithium metal film and a metal film. By dissolving lithium, not into a liquid electrolyte but into a really thin polymer (plastic), a high-power battery is realized that is light, yet durable. The laminate construction of such cells offer flexibility of shape and size, which is advantageous for portable power source applications. However, at the present time, the conductivity of these batteries is very low at room temperature, compared with those of liquid electrolytes: these batteries are normally operated in the 60-120oC range. Research is being aimed at increasing conductivity through the use of plasticizers and new polymers.

This new technology offers the potential of future low manufacturing costs. It is environmentally benign, it avoids electrolyte leakage to damage electronic components, and can fit any casing shape. It can be used either as a rechargeable system for training or peacetime exercises, or as a primary battery in emergency or wartime situations. More recently, the development of "Polymer-In-Salt" materials, in which superionic glass electrolytes are mixed with small quantities of the polymers, has been suggested. Dissolution of the polymer into these melt-glass-electrolytes produces a rubbery version of a glassy electrolyte with a thousand-fold increase in lithium ion mobility. A way has been opened to a new generation of lithium batteries with the prospect of a high power density application. Much work remains to be done before this discovery can be fully exploited.

Under a United States Advanced Battery Consortium (USABC) contract, 3M, Hydro-Québec, and Argonne National Laboratory joined technologies to develop and test the first solid electrolyte lithium battery. The Lithium Polymer battery relies on thin-film technology, with composite films that are only 100 microns thick. It’s a solid state battery that can be wound and shaped to suite the application. It uses a plastic electrolyte. 3M expects that a typical EV battery pack would weigh on the order of 500 pounds (224 kg), which could provide as much as 45 kW-h of energy. In comparison, EV1’s lead-acid battery pack weighs over 1000 pounds (480 kg) and provides 16 kW-h of energy.

This unique battery contains a solid, dry, polymer electrolyte with a metallic lithium anode. The cathode is a vanadium oxide composite. Features include built-in electronic control and battery management systems, and the ability to adapt in shape to various sized battery compartments. The battery has a 150-200 mile range per charge, and over 100,000 miles useful life. It is the first advanced battery to achieve performance and cost statistics approaching the USABC's goals for commercial use.