“The lack of progress in the development of next generation lithium ion batteries is largely due to a failure to develop improved electrolytes. Any benefits of new high voltage cathode materials are seldom realized due the limited electrochemical stability of organic carbonate based electrolytes. Ionic liquids have properties that address many of the concerns with classic organic electrolytes.”
~Lin et a. 2011
Ultracapacitors with ionic liquids and wide operating temperature. Lin demonstrated operation of ultracapacitors over a very wide temperature range, from −50 to +100 °C. “Onion-like carbon” and ionic liquid mixtures allowed operation at low temperatures while maintaining high rates at room temperature. PC/TEABF is limited to <3.2V at 20 °C.
Lin et al. 2011
~Krause and Balducci 2011
High power and high voltage ultracapacitors. Krause reported on results of testing an electrolyte of propylene carbonate and PYR14 TFSI (1:1 mixture by weight). Over testing of 100,000 cycles at 3.5V, they measured a capacitance loss of only 5%. They conclude “the use of PC/PYR14 TFSI as electrolyte not only allows high operative voltage, high energy and high power, but it also guarantees an excellent cycling stability.”
Krause and Balducci 2011
~Zhu et al. 2011
The highest performance ultracapacitor ever built? Zhu measured 200 F/g with neat EMIM TFSI as the electrolyte on a graphene oxide electrode at 3.5 V. To our knowledge, this is among the highest performance ultracapacitors ever demonstrated in the laboratory. At a constant current of 0.7 A/g, the energy density and power density were estimated as 85 Wh/kg and 122 kW/kg, when normalized with the total weight of the two a-MEGO electrodes. Operating with BMIM BF4, they measured 97% capacitance retention at 10,000 cycles. The cells had low time constants, with purely capacitive behavior observed with frequencies as high as 3 Hz.
Zhu et al. 2011
~Mastragostino and Soavi 2007
Asymmetric ultracapacitors with polymer electrodes. Mastragostino built and tested ultracapacitors with PYR14 TFSI electrolytes. They demonstrated a cycle-life over 16,000 cycles at 60 °C with a cell voltage >3.4 V using PYR14 TFSI electrolytes, with both activated carbon and poly(3-methylthiophene) (pMeT) electrodes.
Mastragostino and Soavi 2007
~Best, Bhatt and Hollenkamp 2010
FSI-based ionic liquid yield high performance lithium-ion electrolytes. Best, in seminal work on ionic liquids with the FSI anion, stated New “high voltage” cathode materials have been described regularly over the years; yet any benefits are seldom realized due to the limited electrochemical stability of organic carbonate-based electrolytes. These systems are also compromised by poor thermal stability, appreciable volatility (and flammability), and significant toxicity. Certain members of the vast family of compounds known as room temperature ionic liquids (RTILs) have properties that address many of the concerns with classic organic electrolytes. Best’s results clearly establish the ability of FSI-based ionic liquids to provide stable SEI layers in lithium-ion capacitors.
Best, Bhatt, and Hollenkamp 2010
~Han et al. 2011
Li FSI as a replacement for Li PF6. Han, in a recent paper, demonstrated the high potential of Li FSI as a replacement for Li PF6 in lithium ion batteries. His paper showed that Li FSI shows far superior stability towards hydrolysis than Li PF6, yields higher conductivity electrolytes, and is compatible with aluminum current collectors. His work showed the importance of purity in this salt, with aluminum corrosion occurring with Li FSI contaminated with trace amounts of Li Cl (50 ppm), but not with high purity Li FSI. Boulder Ionics is now producing Li FSI with Cl and F contents under 1 ppm on an experimental basis.
Han et al. 2011
~Sugimoto et al. 2010
Neat ILs with silicon-based anodes. Sugimoto was one of the first authors to report on the successful use of neat ionic liquids with silicon-based anodes. His work showed that a neat ionic liquid (EMIM FSI) could provide very stable performance and capacity exceeding 800 mAh/g for a silicon-nickel-carbon composite anode. This paper is among several recent papers that have shown ionic liquid based electrolytes with performance as good, if not better, than the best organic electrolytes. It still stands out for its results with a neat IL without organic additives.
Sugimoto et al. 2010
~Guerfi et al. 2010
IL-based electrolytes for high-safety and high-cycle life batteries. Guerfi, from Hydro Quebec, has reported on non-flammable, ionic liquid-based electrolytes for lithium-ion batteries. His work showed that by mixing ILs and organic electrolytes, it was possible to make non-flammable electrolytes with similar or better performance than standard carbonate-based electrolytes. Using titanate anodes and iron phosphate cathodes, this work suggests that very safe batteries capable of high power and very high cycle life (>10,000 cycles) can be built. Best performance in these tests was obtained with EMIM TFSI-based electrolytes. Fort this electrolyte, performance superior to carbonate electrolytes was obtained up to a 2C rate, while maintaining non-flammability.
Guerfi et al. 2010
Best, A. S., A. I. Bhatt, and A. F. Hollenkamp. 2010. “Ionic Liquids with the Bis(fluorosulfonyl)imide Anion: Electrochemical Properties and Applications in Battery Technology.” Journal of The Electrochemical Society 157 (8): A903–A911. doi:10.1149/1.3429886.
Guerfi, A., M. Dontigny, P. Charest, M. Petitclerc, M. Lagacé, A. Vijh, and K. Zaghib. 2010. “Improved Electrolytes for Li-ion Batteries: Mixtures of Ionic Liquid and Organic Electrolyte with Enhanced Safety and Electrochemical Performance.” Journal of Power Sources 195 (3): 845–852.
Han, Hong-Bo, Si-Si Zhou, Dai-Jun Zhang, Shao-Wei Feng, Li-Fei Li, Kai Liu, Wen-Fang Feng, Jin Nie, Hong Li, and Xue-Jie Huang. 2011. “Lithium Bis(fluorosulfonyl)imide (LiFSI) as Conducting Salt for Nonaqueous Liquid Electrolytes for Lithium-ion Batteries: Physicochemical and Electrochemical Properties.” Journal of Power Sources 196 (7): 3623–3632. doi:10.1016/j.jpowsour.2010.12.040.
Krause, A., and A. Balducci. 2011. “High Voltage Electrochemical Double Layer Capacitor Containing Mixtures of Ionic Liquids and Organic Carbonate as Electrolytes.” Electrochemistry Communications 13 (8) (August): 814–817. doi:10.1016/j.elecom.2011.05.010.
Lin, Rongying, Pierre-Louis Taberna, Sébastien Fantini, Volker Presser, Carlos R. Pérez, François Malbosc, Nalin L. Rupesinghe, Kenneth B. K. Teo, Yury Gogotsi, and Patrice Simon. 2011. “Capacitive Energy Storage from −50 to 100 °C Using an Ionic Liquid Electrolyte.” The Journal of Physical Chemistry Letters 2 (19) (October 6): 2396–2401. doi:10.1021/jz201065t.
Mastragostino, Marina, and Francesca Soavi. 2007. “Strategies for High-performance Supercapacitors for HEV.” Journal of Power Sources 174 (1) (November 22): 89–93. doi:10.1016/j.jpowsour.2007.06.009.
Sugimoto, T., Y. Atsumi, M. Kono, M. Kikuta, E. Ishiko, M. Yamagata, and M. Ishikawa. 2010. “Application of Bis (fluorosulfonyl) Imide-based Ionic Liquid Electrolyte to Silicon-nickel-carbon Composite Anode for Lithium-ion Batteries.” Journal of Power Sources.
Zhu, Y., S. Murali, M. D. Stoller, K. J. Ganesh, W. Cai, P. J. Ferreira, A. Pirkle, et al. 2011. “Carbon-Based Supercapacitors Produced by Activation of Graphene.” Science 332 (6037) (May): 1537–1541. doi:10.1126/science.1200770.