Maria Carewska

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.

Nanoscale organization in piperidinium-based room temperature ionic liquids

Here we report on the complex nature of the phase diagram of N-alkyl-N-methylpiperidinium bis(trifluoromethanesulfonyl)imide ionic liquids using several complementary techniques and on their structural order in the molten state using small-wide angle x-ray scattering. The latter study indicates that the piperidinium aliphatic alkyl chains tend to aggregate, forming alkyl domains embedded into polar regions, similar to what we recently highlighted in the case of other ionic liquids.

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.

A novel intrinsically porous separator for self-standing lithium-ion batteries

γ-LiAlO2, Al2O3 and MgO were used as fillers in a PVdF-HFP polymer matrix to form self-standing, intrinsically porous separators for lithium-ion batteries. These separators can be hot-laminated onto the electrodes without losing their ability to adsorb liquid electrolyte. The electrochemical stability of the separators was tested by constructing half-cells with the configuration: Li/fibre-glass/filler-based separator/electrode. MgO-based separators were found to work well with both positive and negative electrodes. An ionic conductivity of about 4×10−4 S cm−1 was calculated for the MgO-based separator containing 40% 1 M solution of LiPF6 in an EC/DMC 1:1 solvent. Self-standing, lithium-ion cells were constructed using the MgO-based separator and the resulting battery performance evaluated in terms of cyclability, power and energy density.

Electrical conductivity and 6,7Li NMR studies of Li1 + yCoO2

Abstract The battery cathode material LiCoO2 was synthesized with a deliberate excess of Li, according to Li1 + yCoO2, where y = 0.08 and 0.35 (nominally). The effect of divalent doping with Mg2+ was also explored for some samples, with y values of 0.0 (stoichiometric) and 0.08. Electrical conductivity measurements of the stoichiometric material, without Mg, as functions of oxygen partial pressure and temperature exhibit p-type semiconducting behaviour and suggest that the defects primarily responsible for the generation of holes are cobalt ion vacancies. Excess Li increases the electrical conductivity, while the incorporation of Mg leads to a more dramatic enhancement in conductivity, the latter interpreted as a transition to metallic behaviour. NMR spectroscopic measurements of both 6,7Li isotopes suggest that only a small fraction (

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.

Characterization of PEO‐Based Composite Cathodes. I. Morphological, Thermal, Mechanical, and Electrical Properties

This report describes the fabrication and characterization of polymer-based composite cathode membranes intended for use in polymer-electrolyte batteries operating at moderate temperatures (60--100 C). The present work is focused on the determination of morphological, thermal, mechanical, and electrical properties of PEO-based composite cathodes. The work was developed within the Advanced Lithium Polymer Electrolyte project (ALPE), an Italian integrated project devoted to the realization of lithium polymer batteries for electric vehicle applications.

Lithium iron oxide as alternative anode for li-ion batteries

Lithium–iron oxide Li–Fe–O was synthesized by solid state reaction between Li2CO3 and Fe2O3. The sample was characterized by X-ray powder diffraction. The XRD patterns showed well defined reflections corresponding to α-LiFeO2 and the spinel LiFe5O8 in a molar ratio of 9:1. The material was tested as alternative anode for lithium-ion batteries. It exhibited good cyclability delivering about 120 mAh/g after 500 deep charge/discharge cycles. Unlikely, the use of the material as intercalation anode in practical cells is hindered by the irreversible uptake of lithium that takes place during the first lithium insertion. X-ray diffraction pattern showed that during this step a reduction of the lithium iron oxide occurs leading to the formation of lithium oxide and iron metal.