Enrique Morales

Synthesis and characterization of novel urethane cross-linked ormolytes for solid-state lithium batteries

Abstract A novel family of Li + -based organic/inorganic materials obtained by the sol–gel process is proposed. The compounds, named urethanesils , are obtained as thin, transparent, elastomeric and amorphous monolithic films. They incorporate solvating pendant methyl end-capped short poly(oxyethylene) chains which are covalently bonded to the silica backbone by means of urethane cross-links. The urethane linkages are formed by reacting 3-isocyanatepropyltriethoxysilane with hepta(ethylene glycol) methyl ether (HEGME). Li + has been introduced in the urethanesils as lithium triflate (LiCF 3 SO 3 ). Two compositions of salt have been considered: n =100 and 8, where n represents the molar ratio of (OCH 2 CH 2 ) units per lithium ion. Infrared spectroscopy provides conclusive evidence that, although the oligopolyether chains of HEGME become less disordered upon formation of the inorganic network, the addition of salt induces disorder. The FTIR spectrum of the most concentrated urethanesil strongly suggests that the triflate ions are essentially coordinated in the material. The thermal and mechanical properties of the undoped and doped urethanesils have been investigated by DSC and DMTA. At 90°C, the highest ionic conductivity (approximately 10 −6 Ω −1 cm −1 ) is observed for composition n =8. The electrochemical stability domain of the least concentrated urethanesil spans 5 V.

Structural, morphological and electrical characterization of polymer electrolytes based on PEO/PPO blends

As an alternative to PEO based solid polymer electrolytes, we have synthesized via physical route solid polymer electrolyte films, formed by blends of PEO and PPO, as a way to improve lithium transport and the mechanical properties of the films. In this way different binary blends of the polymers mentioned above were prepared, studying their crystalline and amorphous structure by means of differential scanning calorimetry, optical microscopy and FTIR and X-ray spectrometry. In addition, ionic conductivity of the samples was measured as a function of temperature.

Ionic conductive polymer systems based on polyether and polyphosphazene blends

Several polymer electrolytes have been obtained, based on binary blends of polyethylene oxide (PEO), polypropylene oxide, and polyphosphazene by means of solvation with lithium triflate. The different samples were studied both as to their microstructure and for their electrical properties, either through the determination of their respective glass transition temperatures and melting enthalpies or by means of complex impedance spectroscopy. When comparing the results obtained for the synthesized binary systems with those known for PEO, the former systems prove to possess a better dimensional stability and a higher conductivity than PEO in itself.

Synthesis and characterisation of poly(methylalkoxysiloxane) solid polymer electrolytes incorporating different lithium salts

Abstract Two comb polymers with oligo-oxyethylene side chains of the type O(CH 2 CH 2 O) n CH 3 were prepared from poly(methylhydrosiloxane) (PMHS). Homogeneous polymer electrolytes were made from the two synthesised polymers and four lithium salts having different chemical structures, such as lithium perchlorate (LiClO 4 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), lithium hexafluorophosphate (LIPF 6 ) and lithium bis(trifluoromethane sulfonylimide) (LiN(SO 2 CF 3 ) 2 ) by solvent casting method, and their thermal, electrical and electrochemical properties measured as a function of temperature. Results indicate that polymer electrolyte complexes are amorphous materials, and that its properties depend on the oligo-oxyethylene chain length as well as on the chemical nature of the lithium salt.

Thermal and electrical characterization of plasticized polymer electrolytes based on polyethers and polyphosphazene blends

Abstract The effect of four different plasticizers on the thermal properties, lithium ion conduction and electrochemical stability of polymer electrolytes based on blends of poly(ethylene oxide), poly(propylene oxide) and a fluorinated polyphosphazene has been investigated using DSC, impedance spectroscopy and cyclic voltammetry techniques. The addition of 80 wt% of plasticizer increases the conductivity various orders of magnitude, depending on the chemical nature of the plasticizers, lowering the glass transition and melting temperatures of the complexes, maintaining good electrochemical (stable up to 4 V) and cyclability properties after 10 cycles.

Synthesis and characterization of polymeric electrolytes for solid state magnesium batteries

In this work the synthesis and structural and electrical characterisation are described regarding new polymeric electrolytes for magnesium batteries on the basis of polyether blends [poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO) and poly(phosphazene) (PPz)]. For the microstructural characterisation we used X-ray spectroscopy, Fourier-transform IR spectroscopy (FTIR), as well as differential scanning calorimetry (DSC). Electrical characterisation was conducted by means of complex impedance spectroscopy. The results obtained confirm the formation of complex magnesium salts by solvation of the oxygen of the polyether chain with the magnesium ion from the magnesium salt [magnesium trifluoromethanesulphonate, (CF 3 SO 3 ) 2 Mg]. As a consequence high conductivities are obtained at temperatures around 100°C. This conductivity is significantly enhanced when the polymers are plasticized.

Acid/base characterization of sepiolite by inverse gas chromatography

SummaryThe surface properties of sepiolite were investigated by inverse gas chromatography. It is shown that the value of the dispersive component change uniformly with temperature, while the values obtained for the parameters KA and KD indicate an acidic character for the sepiolite surface.

Conductivity and electrochemical stability of composite polymer electrolytes

Abstract In this work the synthesis together with the electrical and electrochemical characterization of new composite polymer electrolytes on the basis of poly(ethylene oxide) blend with a perfluorinated polyphosphazene, and γ-LiAlO2 as a ceramic filler are reported. The effect of the addition of a plasticizer, like propylene carbonate, on the properties of the composite polymer electrolyte has also been analyzed. Ionic conductivity was evaluated by complex impedance analysis, and electrochemical behaviour by cyclic voltammetry. Results indicate that the incorporation of the ceramic filler at low levels decreases the ionic conductivity of the system, while at the higher concentration tested, there is an improvement on the ionic conductivity at high temperatures resulting from the inhibition of the PEO crystallization processes. Cyclic voltammetry results suggest that γ-LiAlO2 addition has a little effect on polymer electrolyte electrochemical stability.

Electrochemical synthesis of poly(3‐methylthiophene): A kinetic study

Poly(3-methylthiophene) (P3MT) films were electrogenerated on both platinum and carbon-felt working electrodes. The kinetic equation was determined by the monomer and electrolyte concentrations being changed for different reaction times. For each sample, the weight of the polymer obtained was measured along with the polymerization charge, the oxidation charge, the ratio (R) between the two magnitudes, the charge storage efficiency (SE), and the doping level. The results obtained from the kinetic study indicate significant electrolyte participation in the electropolymerization process. The SE and the doping level decreased inversely proportionately to both the reaction time and the concentrations of the monomer and electrolyte. The ratio R increased with reaction time as well as with monomer or electrolyte concentrations for all P3MTs generated on the carbon-felt electrodes, whereas for those films generated on platinum electrodes, the highest values were obtained for the lowest monomer and electrolyte concentrations.

Morphological properties of composite solid polymer electrolytes based on polyethylene oxide

Morphological properties of polymer electrolytes based on blends of polyethylene oxide and a perfluorinated polyphosphazene solvated with LiCF 3 SO 3 with and without the addition of dispersed γ-LiAlO 2 are reported. The effect exerted on the morphology of the complex electrolytes by the addition of a plasticizer-like propylene carbonate has also been studied. Results indicate the incorporation of γ-LiAlO 2 leads to changes on the morphology of the complex electrolyte, as verified by X-ray diffraction analysis. The major effect observed by plasticizer addition was a decrease on the crystallinity of the system together with a displacement of the T g towards lower temperatures.