Safer Electrolytes for Lithium-Ion Cells

NASA Tech Briefs, Jun 2004

John H. Glenn Research Center,

Cleveland, Ohio

A number of nonvolatile, low-flammability liquid oligomers and polymers based on aliphatic organic carbonate molecular structures have been found to be suitable to be blended with ethylene carbonate to make electrolytes for lithium-ion electrochemical cells. Heretofore, such electrolytes have often been made by blending ethylene carbonate with volatile, flammable organic carbonates. The present nonvolatile electrolytes have been found to have adequate conductivity (nbout 2 mS/cm) for lithium ions and to remain liquid at temperatures down to -5 °C. At normal charge and discharge rates, lithiumion cells containing these nonvolatile electrolytes but otherwise of standard design have been found to operate at current and energy densities comparable to those of cells now in common use. They do not perform well at high charge and discharge rates - an effect probably attributable to electrolyte viscosity. Cells containing the nonvolatile electrolytes have also been found to be, variously, nonflammable or at least self-extinguishing. Hence, there appears to be a basis for the development of safer high-performance lithium-ion cells.

This work was done by Joe Kejha, Novis Smith, and Joel McCloshey of LithChem for Glenn Research Center. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Maleriah category.

Inquiries concerning rights for the commercial use of this invention should be addressed to NASA Glenn Research Center, Commercial Technology Office, Attn: Steve Fedor, Mail Stop 4-8, 21000BrookparkRoad, Cleveland, Ohio 44135. Refer to LEW-17398.