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Kita-ku, Japan

Yamagata M.,Kansai University | Yamagata M.,IElectrolyte LLC | Tanaka K.,Graduate University for Advanced Studies | Tsuruda Y.,University of Tokyo | And 7 more authors.
Electrochemistry | Year: 2015

A prototype lithium-ion battery with a bis(fluorosulfonyl)imide (FSI)-based ionic liquid electrolyte was developed. The prototype was mounted on a demonstration module of the Hodoyoshi-3 microsatellite, which was successfully launched on June 20, 2014. Qualification tests for space application, including radiation tolerance and vacuum tests, revealed negligible degradation of the ionic liquid-based lithium-ion battery (IL-LIB) cell. According to the flight data, the IL-LIB cell can exist stably in an ultra-high vacuum environment despite its thin and flexible pouch casing without any rigid anti-vacuum reinforcements. Furthermore, the power unit showed the same charge-discharge performance as that predicted by the charge-discharge behavior of an identical cell on the ground, suggesting that the IL-LIB cell maintains performance in high vacuum a microgravity environment. These results prove that LIB cells with FSI-based ionic liquids can be used as a power source for space applications. © The Electrochemical Society of Japan, All rights reserved. Source

Matsui Y.,Kansai University | Yamagata M.,Kansai University | Yamagata M.,IElectrolyte LLC | Murakami S.,Dai ichi Kogyo Seiyaku Co. | And 6 more authors.
Journal of Power Sources | Year: 2015

We evaluate the effects of lithium salt on the charge-discharge performance of a graphite negative electrode in 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMImFSI) ionic liquid-based electrolytes. Although the graphite negative electrode exhibits good cyclability and rate capability in both 0.43 mol dm-3 LiFSI/EMImFSI and LiTFSI/EMImFSI (TFSI- = bis(trifluoromethylsulfonyl)imide) at room temperature, only the LiFSI/EMImFSI system enables the graphite electrode to be operated with sufficient discharge capacity at the low temperature of 0 °C, even though there is no noticeable difference in ionic conductivity, compared with LiTFSI/EMImFSI. Furthermore, a clear difference in the low-temperature behaviors of the two cells composed of EMImFSI with a high-concentration of lithium salts is observed. Additionally, charge-discharge operation of the graphite electrode at C-rate of over 5.0 can be achieved using of the high-concentration LiFSI/EMImFSI electrolyte. Considering the low-temperature characteristics in both high-concentration electrolytes, the stable and rapid charge-discharge operation in the high-concentration LiFSI/EMImFSI is presumably attributed to a suitable electrode/electrolyte interface with low resistivity. These results suggest that optimization of the electrolyte composition can realize safe and high-performance lithium-ion batteries that utilize ionic liquid-based electrolytes. © 2015 Elsevier B.V. Source

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