Electrolyte additive 4-vinyl-1, 3-dioxolane-2-one has been found to be promising for rechargeable lithium-ion electrochemical cells. This and other additives, along with advanced electrolytes comprising solutions of LiPF6 in various mixtures of carbonate solvents, have been investigated in a continuing effort to improve the performances of rechargeable lithium-ion electrochemical cells, especially at low temperatures. In contrast to work by other researchers who have investigated the use of this additive to improve the high-temperature resilience of Li-ion cells, the current work involves the incorporation of 4-vinyl-1,3-dioxolane-2-one into quaternary carbonate electrolyte mixtures, previously optimized for low-temperature applications, resulting in improved low temperature performance.
The benefit afforded by 4-vinyl-1,3-dioxolane-2-one can be better understood in the light of relevant information from a number of prior NASA Tech Briefs articles about electrolytes and additives for such cells. To recapitulate: The loss of performance with decreasing temperature is attributable largely to a decrease of ionic conductivity and the increase in viscosity of the electrolyte. What is needed to extend the lower limit of operating temperature is a stable electrolyte solution with relatively small low temperature viscosity, a large electric permittivity, adequate coordination behavior, and appropriate ranges of solubilities of liquid and salt constituents. Whether the anode is made of graphitic or non-graphitic carbon, a film on the surface of the anode acts as a solid/electrolyte interface (SEI), the nature of which is critical to low-temperature performance. Desirably, the surface film should exert a chemically protective (passivating) effect on both the anode and the electrolyte, yet should remain conductive to lithium ions to facilitate intercalation and deintercalation of the ions into and out of the carbon during discharging and charging, respectively.
The additives investigated previously include alkyl pyrocarbonates. Those additives help to improve low-temperature performances by giving rise to the formation of SEIs having desired properties. The formation of the SEIs is believed to be facilitated by products (e.g., CO2) of the decomposition of these additives. These decomposition products are believed to react to form Li2CO3-based films on the carbon electrodes.
The present additive, 4-vinyl-1,3-dioxolane-2-one, also helps to improve low temperature performance by contributing to the formation of SEIs having desired properties, but probably in a different manner: It is believed that, as part of the decomposition process, the compound polymerizes on the surfaces of carbon electrodes.
The effectiveness of 4-vinyl-1,3-dioxolane-2-one as a performance-improving additive in several different LiPF6/carbonate-solvent-mixture electrolytes was investigated in a series of charge/discharge tests of rechargeable lithium-ion electrochemical cells containing the electrolytes, at room temperature and at a temperature of –20 °C. In one pair of tests, the electrolyte comprised LiPF6 dissolved at a concentration of 1.0 M in a solvent mixture comprising 1 volume part of ethylene carbonate + 1 volume part of diethyl carbonate + 1 volume part of dimethyl carbonate + 2 volume parts of ethyl methyl carbonate. In one of the tests, no additive was included; in the other test, the electrolyte included 4- vinyl-1,3-dioxolane-2-one in the proportion of 1.5 weight percent. The results of these tests showed that the additive enhanced low-temperature performance: specifically, the results showed that at –20 °C and at any given voltage, the cell containing the additive retained a greater proportion of its room-temperature capacity than did the cell that did not contain the additive (see figure).
This work was done by Marshall Smart and Ratnakumar Bugga 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-40969
This Brief includes a Technical Support Package (TSP).
4-Vinyl-1,3-Dioxolane-2-one as an Additive for Li-Ion Cells
(reference NPO-40969) is currently available for download from the TSP library.
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Overview
The document titled "4-Vinyl-1,3-Dioxolane-2-One as an Additive for Li-Ion Cells" from NASA's Jet Propulsion Laboratory discusses the development and application of a novel electrolyte additive aimed at improving the performance of lithium-ion batteries, particularly under low-temperature conditions. This research is crucial for future NASA missions, such as those exploring Mars and outer planets, where batteries must operate effectively in extreme temperatures ranging from -40°C to 30°C.
The additive, 4-vinyl-1,3-dioxolane-2-one, is incorporated into multi-component electrolyte formulations, specifically quaternary blends of aliphatic carbonates. The document highlights that the use of this additive enhances the solid electrolyte interface (SEI) formation on carbon electrodes, which is vital for battery efficiency and longevity. The SEI is a protective layer that forms on the electrode surface, influencing the battery's performance, especially at low temperatures.
Experimental results demonstrate that lithium-ion cells utilizing this additive exhibit improved efficiency, with first-cycle efficiencies exceeding 82%. This is significant compared to traditional electrolytes, which often yield efficiencies below 80% due to poor film-forming characteristics. The document also notes that the additive contributes to the resilience of the battery, allowing it to maintain performance over extended cycles and under varying temperature conditions.
Additionally, the research references other studies that have identified similar compounds, such as vinyl carbonate, as effective in enhancing the thermal resilience of lithium-ion cells. The findings suggest that the incorporation of 4-vinyl-1,3-dioxolane-2-one not only improves low-temperature performance but also extends the overall life of the battery, making it suitable for long-duration space missions.
In summary, this document outlines the promising potential of 4-vinyl-1,3-dioxolane-2-one as an electrolyte additive, emphasizing its role in advancing lithium-ion battery technology for aerospace applications. The research aims to address the challenges of low-temperature operation and high cycle life, ultimately contributing to the success of future exploratory missions in extreme environments.
