In this work is described an improved synthesis of hydrophobic room-temperature ionic liquids ͑RTIL͒ composed of N-methyl-N-alkylpyrrolidinium ͑or piperidinium͒ cations and ͑perfluoroalkylsulfonyl͒imide, ͓͑C n F 2n+1 SO 2 ͒͑C m F 2m+1 SO 2 ͒N − ͔, anions. The procedure described allows the synthesis of hydrophobic ionic liquids with the purity required for electrochemical applications such as high-voltage supercapacitors and lithium batteries. This new synthesis does not require the use of environmentally unfriendly solvents such as acetone, acetonitrile, and alogen-containing solvents that are not suitable for industrial applications. Only water and ethyl acetate are used throughout the entire process. The effect of the reaction temperature, time, and stoichiometry in the various steps of the synthesis has been investigated. With an iterative purification step performed at the end of the synthesis, ultrapure, clear, colorless, inodorous RTILs were obtained. The final vacuum drying at 120°C gave RTILs with a moisture content below 10 ppm. Details for the synthesis of N-butyl-N-methylpyrrolidinium bis͑trifluoromethansulfonyl͒imide ͑PYR 14 TFSI͒ are reported. The overall yield for the synthesis of this ionic liquid was above 86 wt %. Electrochemical tests performed on this material are also reported.

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In this paper is reported an investigation on the stability of the interface formed by polyethene oxide (PEO)-based polymer electrolytes in contact with lithium metal anodes. In particular, the investigation was oriented to determine the effect of the composite electrolyte preparation procedure and environment and the filler addition as well as the cell assembly procedure on the interfacial properties of PEO-LiCF 3 SO 3 /Li half cells. The stability investigation was performed at the operative temperature (90ЊC) of the electrolyte (PEO 20 LiCF 3 SO 3 ) in rest condition as well as during continuous lithium plating/stripping cycles. The results indicate that the preparation procedure and the environment play major roles with respect to the addition of the filler.

Amorphous iron͑III͒ phosphate was synthesized by spontaneous precipitation from equimolar aqueous solutions of Fe(NH 4 ) 2 (SO 4 ) 2 •6H 2 O and NH 4 H 2 PO 4 , using hydrogen peroxide as the oxidizing agent. The material was characterized by chemical analysis, thermogravimetrical analysis, differential thermoanalysis, X-ray powder diffraction, and scanning electron microscopy. The material was tested as a cathode in nonaqueous lithium cells. Galvanostatic intermittent titration technique was used to follow the lithium intercalation process. The effect of firing on the specific capacity was also tested. The material fired at 400°C showed the best electrochemical performance, delivering about 0.108 Ah g Ϫ1 when cycled at C/10 rate. The capacity fade upon cycling was found as low as 0.075% per cycle.

Nanocrystalline LiFePO4 was obtained by heating amorphous nanosized LiFePO4. The amorphous material was obtained by lithiation of FePO4 synthesized by spontaneous precipitation from equimolar aqueous solutions of normalFefalse(NH4)2false(SO4)2⋅6H2O and NH4H2PO4, using hydrogen peroxide as the oxidizing agent. The materials were characterized by chemical analysis, thermogravimetric and differential thermal analysis, X-ray powder diffraction, and scanning electron microscopy. The Brunauer- Emmett-Teller method was used to evaluate the specific surface area. Nanocrystalline LiFePO4 showed very good electrochemical performance delivering about the full theoretical capacity false(170 Ah kg−1false) when cycled at the C/10 rate. A capacity fade of about 0.25% per cycle affected the material upon cycling. © 2002 The Electrochemical Society. All rights reserved.

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