Silvera Scaccia

A New Synthetic Route for Preparing LiFePO4 with Enhanced Electrochemical Performance

Nanocrystalline LiFePO 4 was obtained by heating amorphous nanosized LiFePO 4 . The amorphous material was obtained by lithiation of FePO 4 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 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 LiFePO 4 showed very good electrochemical performance delivering about the full theoretical capacity (170 Ah kg -1 ) when cycled at the C/10 rate. A capacity fade of about 0.25% per cycle affected the material upon cycling.

Synthesis of Hydrophobic Ionic Liquids for Electrochemical Applications

In this work is described an improved synthesis of hydrophobic room-temperature ionic liquids (RTIL) composed of N-methyl-N-alkylpyrrolidinium (or piperidinium) cations and (perfluoroalkylsulfonyl)imide, [(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 bis(trifluoromethansulfonyl)imide (PYR 14 TFSI) 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.

Synthesis and Characterization of Amorphous Hydrated FePO4 and Its Electrode Performance in Lithium Batteries

Amorphous iron(III) 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 lired at 400°C showed the best electrochemical performance, delivering about 0.108 Ah g -1 when cycled at C/10 rate. The capacity fade upon cycling was found as low as 0.075% per cycle.

Long-term cyclability of nanostructured LiFePO4

Amorphous LiFePO4 was obtained by lithiation of FePO4 synthesized by spontaneous precipitation from equimolar aqueous solutions of Fe(NH4)2(SO4)2·6H2O and NH4H2PO4, using hydrogen peroxide as oxidizing agent. Nano-crystalline LiFePO4 was obtained by heating amorphous nano-sized LiFePO4 for different periods of time. The materials were characterized by TG, DTA, X-ray powder diffraction, scanning electron microscopy (SEM) and BET. All materials showed very good electrochemical performance in terms of energy and power density. Upon cycling, a capacity fading affected the materials, thus reducing the electrochemical performance. Nevertheless, the fading decreased upon cycling and after the 200th cycle the cell was able to cycle for more than 500 cycles without further fading.

Investigation on the Stability of the Lithium‐Polymer Electrolyte Interface

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 (90°C) 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.

Development and characterization of novel cathode materials for molten carbonate fuel cell

Abstract In the development of molten carbonate fuel cell (MCFC) technology, the corrosion of materials is a serious problem for long-term operation. Indeed, slow dissolution of lithiated-NiO cathode in molten carbonates is the main obstacle for the commercialization of MCFCs. In the search of new, more stable, cathode materials, alternative compounds such as LiFeO2, Li2MnO3, and La1−xSrxCoO3 are presently under investigation to replace the currently used lithiated-NiO. The aim of the present work was to investigate the possibility to produce electrode based on LiCoO2, a promising cathode material. At first, LixCoO2 power samples (0.8

Investigation on lithium–polymer electrolyte batteries

Abstract Lithium–polymer batteries using vanadium oxide-based composite electrodes and operating at moderate temperatures (∼90°C) have been investigated. The work was developed within the advanced lithium–polymer batteries for electric vehicles (ALPE) project, an Italian integrated project, devoted to the realization of lithium–polymer batteries for electric vehicle applications.

Development of molten carbonate fuel cell using novel cathode material

The slow dissolution of lithiated-NiO cathodes in molten carbonates is the main obstacle for the commercialization of molten carbonate fuel cells. The aim of the present work was to investigate the possibility of producing an electrode based on LiCoO2. The LixCoO2 powder samples (0.8 < x < 1.1) were obtained by thermal decomposition of carbonate, acetate and oxide precursors, in air. The syntheses were monitored by thermal analysis (TGA, DTA). The calcined and sintered powder samples were characterized by X-ray diffraction and atomic absorption spectroscopy The porous electrodes were prepared with different pore-formers by cold pressing and sintering. A bi-modal pore size distribution was observed in all the materials. Conductivity measurements were carried out in the temperature range 500–700 °C. The solubility in molten carbonates was measured. To test the cathodic performance of the materials under study, electrochemical impedance spectroscopy measurements were carried out to investigate the porous electrode/molten carbonate interface.

Sequential determination of platinum, ruthenium, and molybdenum in carbon-supported Pt, PtRu, and PtMo catalysts by atomic absorption spectrometry

A simple accurate and precise analytical method for the determination of platinum, ruthenium, and molybdenum in Pt, PtRu, and PtMo nanoparticles catalysts deposited on high-surface area carbon by flame atomic absorption spectrometry (FAAS) and graphite furnace atomic absorption spectrometry (GFAAS) is described. The complete digestion of samples (0.010-0.020g), which contain noble metals (NMs) in the range between 0 and 30% in combination among them or with other non-NMs, is obtained under mild conditions using both concentrated HCl and HCl+HNO(3) (1+1 (v/v)) mixture to boiling for 30min in an open vessel. Carbon is separated from the solution by filtering it. Under optimized conditions of the flame, the poor sensitivity of platinum is enhanced 50-fold in presence of 1% (mV(-1)) ascorbic acid, whereas the analytical signal of ruthenium increased by the presence of co-existing platinum. Any kind of interference is observed on the analytical signal of molybdenum. Recovery test obtained by analyzing commercial powder catalysts ranged from 99 to 101%. The precision, expressed as relative standard deviation of five measurements, is better than 1%. Electrode catalysts, made by using the carbon-supported platinum-based powder catalysts, have been analyzed for the metal loadings onto the electrode by GFAAS after dissolution under the same conditions used for the powder catalysts. The precision, expressed as relative standard deviation of three measurements, is better than 2%.

Sensitive Determination of Oxygen Solubility in Alkali Carbonate Melts

The solubility of O 2 in Li-K and Li-Na eutectic carbonate melts has been estimated in the range 600-700°C using a highly precise chemical titration method. In general, oxygen solubility is found to be distinctly higher in the Li-K than in the Li-Na eutectic with a tendency for such a solubility difference to disappear at 600°C. The precise determination of O 2 solubility values at different O 2 and CO 2 partial pressures allowed evaluation of plausible oxygen dissolution mechanisms by a data fitting procedure. Our results support the assumption of a predominant superoxide formation at 650 and 700°C in both melts, with the difference that in Li-Na carbonate oxygen appears to dissolve also through formation of peroxymonocarbonate ions. At 600°C, molecular oxygen is found to be the major oxygen component.