Highly conductive, ionic liquid-based polymer electrolytes

In this manuscript is reported a thermal and impedance spectroscopy investigation carried out on quaternary polymer electrolytes, to be addressed as separators for lithium solid polymer batteries, containing large amount of the N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide ionic liquid. The target is the development of Li+ conducting membranes with enhanced ion transport even below room temperature. Polyethylene oxide and polymethyl methacrylate were selected as the polymeric hosts. A fully dry, solvent-free procedure was followed for the preparation of the polymer electrolytes, which were seen to be self-consistent and handled even upon prolonged storage periods (more than 1 year). Appealing ionic conductivities were observed especially for the PEO electrolytes, i.e., 1.6 × 10-3and 1.5 × 10-4 S cm-1 were reached at 20 and -20°C, respectively, which are ones the best, if not the best ion conduction, never detected for polymer electrolytes

A lithium-ion battery based on LiFePO4 and silicon/reduced graphene oxide nanocomposite

In this paper, the preparation and chemical–physical characterization of a composite material made of silicon nanoparticles (nSi) and reduced graphene oxide (RGO) for using as an anode for lithium-ion batteries are report- ed. The nSi/RGO composite was synthesized by microwave irradiation followed by a thermal treatment under reducing atmosphere of a mixture of nSi and graphene oxide, and characterized by XRD, SEM, and TGA. The nano- structured material was used to prepare an electrode, and its electrochemical performance was evaluated in a lithium cell by galvanostatic cycles at various charge rates. The electrode was then coupled with a LiFePO4 cathode to fabricate a full lithium-ion battery cell and the cell performance evaluated as a function of the discharge rate and cycle number

Ionic Liquid Electrolytes for Safer Lithium Batteries – I. Investigation around Optimal Formulation

In this paper we report on the investigation of ionic liquid-based electrolytes with enhanced characteristics. In particular, we have studied ternary mixtures based on the lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt and two ionic liquids sharing the same cation (N-methyl-N-propyl pyrrolidinium, PYR13), but different anions, bis(trifluoromethanesulfonyl)imide (TFSI) and bis(fluorosulfonyl)imide (FSI). The LiTFSI-PYR13TFSI-PYR13FSI mixtures, found to be ionically dissociated, exhibit better ion transport properties (about 10−3 S cm−1 at −20°C) with respect to similar ionic liquid electrolytes till reported in literature. An electrochemical stability window of 5 V is observed in carbon working electrodes. Preliminary battery tests confirm the good performance of these ternary electrolytes with high-voltage NMC cathodes and graphite anodes

Magnetism and structure of LixCoO2 and comparison to NaxCoO2

The magnetic properties and structure of LixCoO2 for x between 0.5 and 1.0 are reported. Co4+ is found to be high-spin in LixCoO2 for x between 0.94 and 1.0 and low-spin for x between 0.50 and 0.78. Weak antiferromagnetic coupling is observed, increasing in strength as more Co4+ is introduced. At an x value of about 0.65, the temperature-independent contribution to the magnetic susceptibility and the electronic contribution to the specific heat are largest. Neutron diffraction analysis reveals that the lithium oxide layer expands perpendicular to the basal plane and the Li ions displace from their ideal octahedral sites with decreasing x. A comparison of the structures of the NaxCoO2 and LixCoO2 systems reveals that the CoO2 layer changes substantially with alkali content in the former but is relatively rigid in the latter. Further, the CoO6 octahedra in LixCoO2 are less distorted than those in NaxCoO2. We postulate that these structural differences strongly influence the physical properties in the two systems

Ricerca e sviluppo di materiali e processi per la realizzazione di materiali anodici con prestazioni migliorate. Test elettrochimici su anodi compositi

Il presente rapporto descrive la preparazione e la caratterizzazione elettrochimica di anodi che utilizzano TiO2 (ossido di titanio), in qualità di materiale attivo. L’ossido di titanio, preparato per via elettrochimica è stato confrontato con TiO2 preparato sia mediante tecnica laser (ENEA) che commerciale

Effect of milling and doping on decomposition of NH3BH3 complex

In this work we considered three different samples: borane ammonia (BA) complex as received, ball milled BA and, finally, BA subjected to ball milling and doped with 1 mol% of hydrogen hexachloroplatinate hydrate. Their crystalline structure was described by XRD and morphology was investigated using SEM and EDS techniques. In order to describe samples behaviour in hydrogen release we plotted TGA curves and thermal decomposition tests were realized. We verified that ball milling increases the BA cristallinity and changes its morphology enhancing the amount of evolved gas. Both the milled and the doped samples show an increase of the pre-exponential factor in the Arrhenius equation. The activation energy remains almost unchanged for the doped sample and it increases for the milled one. As result it was found that the decomposition of 1 mol% doped sample could be provided by waste heat coming from a PEM fuel cell

A new Sinthetic Rout to Prepare LiFePO4 with Enhanced Electrochemical Performance.

Paris, Franci