SBIR Phase II: Liquefied Gas Electrolytes for High Energy Density Energy Storage Devices

This Small Business Innovation Research (SBIR) Phase II project is focused on the development of a lithium metal battery using a novel Liquefied Gas Electrolyte. While there is an intense global effort to advance electrolyte chemistry for next-generation lithium batteries, these efforts focus almost entirely on liquid and solid-state electrolytes. In contrast, this project aims to further develop the use of a novel class of electrolytes which use solvents that are typically gaseous at room temperature and liquefied under moderate pressures. Phase I work demonstrated world-record cycling lithium metal with an average plating/stripping coulombic efficiency of >99.5% over 400 cycles with (0.5 mA/cm2 and 0.5 mAh/cm2 each cycle) with smooth and highly dense lithium deposition as observed through cryogenic focused-ion-beam characterization. Further, a world-record low temperature electrolytic conductivity of 3 mS/cm at -80 ?C for lithium-based electrolytes was obtained, far exceeding the state-of-art. Lastly, a reversible high temperature shut-down at +40 ?C, due to a decrease in electrolyte conductivity from salt precipitation, was demonstrated. This high temperature shut-down essentially eliminates thermal runaway reaction from occurring, making for a significantly safer battery. Further development of these electrolytes through this NSF Phase II grant will enable further work to increase battery specific energy to 450 Wh/kg, expand operating temperatures from -60 to +60 ?C, and increased safety with no thermal runaway while maintaining power and cycle life comparable to conventional Li-ion. This will be accomplished with further development of the electrolyte chemistry to improve lithium metal coulombic efficiency to >99.8% over 1000 cycles, increase the high temperature shut-down to +60~70 ?C, increasing cathode performance to higher voltages and cycle life, and the development of a high throughput R&D line which will offer high precision addition of electrolyte components to fine tune the chemistry. Because the electrolyte chemistry may use several common materials and manufacturing methods, there should be low cost barrier to entry and it is expected there will be significant cost reduction in volume production down to the goal of $100/kWh. The developed technology will be especially well suited for low temperature applications such as high-atmosphere, defense, and aerospace which frequently endure extreme temperatures and require high specific energy. Because of the superior performance at low temperatures compared to the incumbent, South 8 Technologies will first focus on developing the technology in these areas. As the technology matures, an eventual move into grid storage and transportation markets will follow, leading to a substantial decrease in emissions and reliance on imported fuels. The underlying fundamental chemistry with these new materials is a relatively new field and may potentially lead to significant advances in next-generation energy storage devices and broader technologies, leading to new industries, job growth and beyond. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.