Low Temperature Electrolytes in High Specific Energy 18650 Li-Ion Cells for Future NASA Missions
Authors: Smart Marshall C. , Krause Frederick C. , Jones John-Paul , Whitcanack Larry D. , Ratnakumar Bugga V. , Brandon Erik J. , Shoesmith Mark 
Published: February 2020

NASA continues to have an interest in developing robust, high specific energy, rechargeable batteries that can operate well at low temperatures. Improvements in battery specific energy translates into reduced launch costs and/or enhanced mission capability. Improved low temperature performance results in reduced thermal management complexity and reduced allocation of energy to heaters. There is current interest in exploring some of the distant icy moons of Jupiter and Saturn, since these bodies are believed to have liquid oceans beneath the icy surface that may harbor life. In particular, NASA is considering surface missions to Europa, which would benefit from improved high specific energy, low temperature batteries. To address these mission needs, the Electrochemical Technologies Group (ETG) at the Jet Propulsion Laboratory (JPL) is engaged in developing ultra-low temperature rechargeable batteries with high specific energy and enhanced low temperature capability for icy moon surface missions.1 The performance goals of this program include operation over the temperature range of +40oC to -60oC (delivering up to 100 Wh/kg at -40oC and 75 Wh/kg at -60oC). In addition, continuous operation at low temperatures is desired, so the cells should possess good charge characteristics without undesirable lithium plating.
E-One Moli Energy Ltd.’s commercially available 18650-size lithium-ion cells have been identified to be especially attractive, due to their high specific energy (>200 Wh/kg at ambient temperatures) and reasonably wide temperature range of operation. 1 Given the desire for enhanced performance at low temperatures, E-One Moli has fabricated advanced prototype cells containing JPL-developed low temperature electrolytes. These electrolytes have been developed under previous programs and included all-carbonate-based low EC-content electrolytes formulations, as well as methyl propionate (MP)-based electrolytes with various additives. 2-5

To assess the performance of these cells, we have performed discharge rate characterization over a wide temperature range (down to -70oC). In addition, we have evaluated the cells during long term cycling continuously at very low temperatures, especially at -40oC. These results have been compared to baseline commercial off the shelf (COTS) cells.In an attempt to characterize the likelihood of lithium plating when charging at low temperatures, the charge current and charge voltage has been systematically studied. Impedance measurements have also been performed as a function of temperature in an attempt to more fully understand the impact of electrolyte type upon the low temperature performance.
ACKNOWLEDGEMENT
The work described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA) and supported by the NASA Game Changing Development Program.
REFERENCES

1. F. C. Krause, A. Lawrence, M. C. Smart, S. F. Dawson, A. Ulloa-Severino, and B. V. Ratnakumar, “Evaluation of Commercial High Energy Lithium-Ion Cells for Aerospace Applications”, 227thMeeting of the Electrochemical Society, Chicago, Illinois, May 25-29, 2015 (Abstract #47580).

2.
M. C. Smart, B. V. Ratnakumar, K. B. Chin, and L. D. Whitcanack, J. Electrochem. Soc., 157(12), A1361-A1374 (2010).

3.

M. C. Smart, B. V. Ratnakumar, F. C. Krause, L. D. Whitcanack, E. A. Dewell, S. F. Dawson, R. B. Shaw, S. Santee, F. J. Puglia, A. Buonanno, C. Deroy, and R. Gitzendanner, NASA Aerospace Battery Workshop, Huntsville, Alabama, November 17-19, 2015.

4.M. C. Smart, B. V. Ratnakumar, M. R. Tomcsi, M. Nagata, V. Visco, and H. Tsukamoto, 2010 Power Sources Conference, Las Vegas, NV, June 16, 2010, Pages 191-194.

5. (a) M. C. Smart, B.V. Ratnakumar, A. S. Gozdz, and S. Mani, 214th Meeting of the Electrochemical Society, Honolulu, HI, Oct. 12-17, 2008. (b) M. C. Smart, A. S. Gozdz, L. D. Whitcanack, and B. V. Ratnakumar, 220thMeeting of the Electrochemical Society, Boston, MA, October 11, 2011.