Electrolytes comprising LiPF6 dissolved at a concentration of 1.0 M in three different mixtures of alkyl carbonates have been found well suited for use in rechargeable lithium-ion electrochemical cells at low temperatures. These and other electrolytes have been investigated in continuing research directed toward extending the lower limit of practical operating temperatures of Li-ion cells down to –60 °C. This research at earlier stages was reported in numerous previous NASA Tech Briefs articles, the three most recent being "Ethyl Methyl Carbonate as a Cosolvent for Lithium-Ion Cells" (NPO-20605), Vol. 25, No. 6 (June 2001), page 53; "Alkyl Pyrocarbonate Electrolyte Additives for Li-Ion Cells" (NPO-20775), Vol. 26, No. 5 (May 2002), page 37; and "Fluorinated Alkyl Carbonates as Cosolvents in Li-Ion Cells (NPO-21076), Vol. 26, No. 05 (May 2002), page 38. The present solvent mixtures, in terms of volume proportions of their ingredients, are 1 ethylene carbonate (EC) + 1 diethyl carbonate (DEC) + 1 dimethyl carbonate (DMC) + 3 ethyl methyl carbonate (EMC); 3EC + 3DMC + 14EMC; and 1EC + 1DEC + 1DMC + 4EMC. Relative to similar mixtures reported previously, the present mixtures, which contain smaller proportions of EC, have been found to afford better performance in experimental Li-ion cells at temperatures <–20 °C.
This work was done by Marshall Smart, Ratnakumar Bugga, and Subbarao Surampudi of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Materials category. NPO-30226
This Brief includes a Technical Support Package (TSP).
Low-EC-Content Electrolytes for Low-Temperature Li-Ion Cells
(reference NPO-30226) is currently available for download from the TSP library.
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Overview
The document is a NASA Technical Support Package detailing advancements in low-ec-content electrolytes for lithium-ion (Li-ion) cells, particularly aimed at improving their performance at low temperatures, down to -60 °C. This research is crucial for applications in aerospace, such as the Mars Exploration Program, which requires reliable rechargeable batteries for landers, rovers, and penetrators operating in extreme conditions.
The work, conducted by Marshall Smart, Ratnakumar Bugga, and Subbarao Surampudi at the Jet Propulsion Laboratory (JPL), focuses on developing new electrolyte formulations that enhance the functionality of Li-ion cells in cold environments. The document outlines various solvent mixtures that have been tested, including combinations of ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC). These mixtures have been found to perform better than previous formulations, particularly at temperatures below -20 °C, by utilizing smaller proportions of EC.
The document also emphasizes the importance of controlling fiber orientation in composite materials, which is critical for maximizing the performance of composite parts. Traditional methods of verifying composite designs involved costly and time-consuming physical prototyping. However, advancements in specialized software integrated into CAD environments allow designers to simulate and predict the behavior of composite materials more accurately. This software enhances the design process by providing features specific to composites, such as defining ply orientations and simulating material drapability, thus reducing the need for over-designing and minimizing weight and costs.
Overall, the document highlights the ongoing research and development efforts to create more efficient and reliable energy storage solutions for space applications, addressing the challenges posed by extreme temperatures. The findings and innovations presented are expected to significantly contribute to the future of aerospace technology, ensuring that Li-ion cells can operate effectively in the harsh conditions of space exploration. For further details, the document encourages accessing the Technical Support Package online under the Materials category on the NASA Tech website.
