SBIR-STTR Award

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.

Keywords:
Li Battery Rechargeable Ionic Liquid Electrolyte Extreme Temperature

Advanced Li battery technology remains beset with performance deficiencies at low/high temperatures/extreme environments (high vacuum, radiation, vibration/shock), primarily from poor conductivity/mobility in organic electrolytes used under such conditions. In this respect, electrolytes using ionic liquids, with large liquidus ranges, no vapor pressure, non-flammability, have been much studied recently, but remain unviable. Now in entirely unrelated work, in electrochromics for spacecraft thermal control operating at -80 to +100 C, this firm developed unique ionic liquids with very high conductivity and ion mobility at low temperatures and space durability. Phase I work further modified these electrolytes specifically for reentry vehicle Li batteries. Performance demonstrated included: Specific energy > 339 Wh/kg at low (-40 C), room, high (+60 C) temperature; >85% capacity retention in multiple cycles; reversible capacity > 145 mAh/g. The key/most important component of the new, reentry-vehicle Li battery, the electrolyte, was successfully arrived at. Phase II work will focus on: Refinement of other battery components compatible with this electrolyte, including correct anodes/cathodes; packaging suitable for reentry vehicles; further increase in performance (specific energy, capacity, peak specific power, etc.); extensive testing in reentry vehicle conditions (long-term dormancy, high-g/radiation). Commercial tie-ups with several Li battery manufacturers have been initiated, will be pursued.

Benefit:
The resulting wide-operating-temperature Li battery technology may be considered a breakthrough. Applications will be in all extreme-temperature environments where conventional Li battery (including Li ion and polymer electrolyte) technology is unable to function. Military applications would be as original equipment in military vehicles and portable field-use power sources for extreme environments. The larger commercial market, would include, e.g., laptops, cell phones or tablet computers for field use applications in extreme cold or hot. Potential extensions include hybrid and electric vehicles and recreational equipment. A recent, authoritative study estimates the Li ion battery market, using existing technology, at ca. $8b/year by 2015.

Keywords:
Reentry, Vehicle, Lithium, Battery, Ionic, Liquid, Electrolyte