Future NASA missions aimed at exploring the Moon, Mars, and the outer planets require rechargeable batteries that can operate over a wide temperature range (–60 to +60 ºC) to satisfy the requirements of various applications including landers, rovers, penetrators, CEV, CLV, etc. This work addresses the need for robust rechargeable batteries that can operate well over a wide temperature range.
The Department of Energy (DoE) has identified a number of technical barriers associated with the development of Li-ion rechargeable batteries for PHEVs. For this reason, DoE has interest in the development of advanced electrolytes that will improve performance over a wide range of temperatures, and lead to long life characteristics (5,000 cycles over a 10-year life span). There is also interest in improving the high-voltage stability of these candidate electrolyte systems to enable the operation of up to 5 V with high specific energy cathode materials.
Currently, the state-of-the-art lithium-ion system has been demonstrated to operate over a wide range of temperatures (–40 to +40 ºC); however, the rate capability at the lower temperatures is very poor. In addition, the low-temperature performance typically deteriorates rapidly upon being exposed to high temperatures.
A number of electrolyte formulations were developed that incorporate the use of electrolyte additives to improve the high-temperature resilience, low-temperature power capability, and life characteristics of methyl propionate (MP)-based electrolyte solutions. These electrolyte additives include mono-fluoroethylene carbonate (FEC), lithium oxalate, vinylene carbonate (VC), and lithium bis(oxalate borate) (LiBOB), which have previously been shown to result in improved high-temperature resilience of all carbonate-based electrolytes. These MP-based electrolytes with additives have been shown to have improved performance in experiments with MCMB-LiNiCoAlO2 cells.
A number of lithium-ion electrolytes having improved temperature range of operation were demonstrated. LiPF6-based mixed carbonate electrolyte formulations that contain ester cosolvents have been optimized for operation at low temperature, while still providing reasonable performance at high temperature. In earlier work [see “Optimized Carbonate and Ester-Based Li-Ion Electrolytes” (NPO-44974) NASA Tech Briefs, Vol. 32, No. 4 (April 2008), p. 56], ester co-solvents, including methyl propionate (MP), ethyl propionate (EP), methyl butyrate (MB), ethyl butyrate (EB), propyl butyrate (PB), and butyl butyrate (BB), were investigated in multi-component electrolytes of the following composition: 1.0 M LiPF6 in ethylene carbonate (EC) + ethyl methyl carbonate (EMC) + X (20:60:20 v/v %) [where X = ester co-solvent]. Focusing upon improved rate capability at low temperatures (i.e., –20 to –40 ºC), this approach was optimized further [see “Li-Ion Cells Employing Electrolytes With Methyl Propionate and Ethyl Butyrate Co-Solvents” (NPO-46976), NASA Tech Briefs, Vol. 35, No. 10 (October 2011), p. 47], which resulted in the development of 1.20M LiPF6 in EC+EMC+MP (20:20:60 v/v %) and 1.20M LiPF6 in EC+EMC+EB (20:20:60 v/v %), which were demonstrated to operate well over a wide temperature range in MCMB-LiNiCoA1O2 and Li4Ti5O12-LiNiCoA1O2 prototype cells. In the current work, improved high temperature resilience, low temperature power capability, and life characteristics have been provided with methyl propionate-based electrolyte solutions [i.e., 1.20M LiPF6 in EC+EMC+MP (20:20:60 v/v%)] possessing the additives described above.
This work was done by Marshall C. Smart and Ratnakumar V. Bugga of Caltech for NASA’s Jet Propulsion Laboratory.
In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:
Innovative Technology Assets Management NPO-47538
JPL
Mail Stop 321-123
4800 Oak Grove Drive
Pasadena, CA 91109-8099
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Improved Wide Operating Temperature Range of Li-Ion Cells
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Overview
The document titled "Improved Wide Operating Temperature Range of Li-Ion Cells" (NPO-47538) presents advancements in lithium-ion battery technology developed at the Jet Propulsion Laboratory (JPL), California Institute of Technology. The research focuses on the use of methyl propionate-based electrolytes, which have been shown to significantly enhance the operational temperature range of lithium-ion cells, allowing them to function effectively between -60°C and +60°C.
The report outlines the novelty of the research, emphasizing the development of these new electrolytes that can withstand extreme temperatures, which is crucial for applications in aerospace and other demanding environments. The work was supported by NASA and funded through a DOE-BATT-ABR program, highlighting its significance in the context of government-sponsored research.
The document includes a comprehensive overview of the electrolyte development process, detailing various performance tests conducted on cells with these new electrolytes. Key areas of investigation include discharge rate characterization at low temperatures, variable temperature cycling (ranging from -40°C to +70°C), and 100% depth of discharge (DOD) cycling at elevated temperatures (+50°C). The performance of the methyl propionate-based electrolytes is evaluated in both 0.25Ah and 12Ah cells, providing insights into their efficiency and reliability under different conditions.
Additionally, the report discusses the incorporation of additives into the electrolytes, which further enhances their performance. The electrochemical characterization of electrodes, such as MCMB (Mesocarbon Microbeads) and LiNiCoAlO2, is also presented, showcasing the compatibility and effectiveness of the new electrolytes in various configurations.
The conclusions drawn from the research indicate that the methyl propionate-based electrolytes not only improve the temperature range of operation but also maintain high performance in terms of discharge rates and cycling stability. This advancement has significant implications for the future of lithium-ion battery technology, particularly in applications that require reliable performance in extreme conditions.
Overall, the document serves as a technical support package that encapsulates the findings and methodologies of the research, aiming to disseminate knowledge that could lead to broader technological, scientific, and commercial applications. It underscores the importance of continued innovation in battery technology to meet the evolving demands of various industries.
