Very-Wide-Operating-Temperature Li Batteries Based on Unique Ionic Liquid Electrolytes Originally Developed for Electrochromics in Spacecraft Thermal

ABSTRACT: While secondary Li batteries have advanced significantly in the last 30 years, one of their critical deficiencies remains poor performance seen at low (<-60 C ) and high (>+90 C) temperatures, due primarily to poor conductivity/ion mobility at these temperatures. This work seeks to use a new ionic liquid, developed in entirely unrelated work by this firm (in variable-emittance electrochromics for spacecraft thermal control operating at -80 to +100 C) and demonstrated to be a good Li battery electrolyte. This will be tested neat as well as in combination with stabilized carbonate-based Li battery electrolytes having high thermal stability. Preliminary data (shown herein) obtained specifically for this proposal show excellent Li battery functionality and an operating temperature range of -40 to +100 C. The new ionic liquid possesses large liquidus range (-95 C to +200 C), high conductivity both neat (10 mS/cm) and as a 40:60 mix with a lactone (18 mS/cm). It shows, e.g. 85% of room temperature charge capacity at -40 C and +90 C. Although the focus of the proposed work will be the new, wide-operating-temperature electrolyte, it will also address packaging and manufacturing aspects of Li cells pertaining to low and high temperature durability in aerospace applications. BENEFIT: If successful, a wide-operating-temperature Li battery electrolyte technology will be available, which may be considered a breakthrough in Li battery technology. The military applications would be as original equipment in military vehicles and portable field-use power sources for extreme environments. In the potentially much larger commercial market, applications wherever Li batteries are now used would be extendable to extreme environment and field use. These would include, e.g., electronic and computer equipment, cell phones, hybrid and electric automobiles and other vehicles, gaming equipment and recreational equipment.