P. C. Barbosa

Application of di-ureasil ormolytes based on lithium tetrafluoroborate in solid-state electrochromic displays

In this study the sol–gel synthetic strategy was used to prepare organic–inorganic hybrid electrolyte systems composed of a di-urea cross-linked poly(ethylene oxide) (PEO)/siloxane (di-ureasil) matrix with a wide concentration range of lithium tetrafluoroborate (LiBF4). The assembly and preliminary characterization of a prototype solid-state electrochromic device based on a four-layer sandwich structure incorporating these hybrid electrolytes doped with controlled quantities of LiBF4 are reported. The composition of hybrid xerogels was indicated using the notation d-U(900)nLiBF4 and d-U(600)nLiBF4. In this representation the average molecular weight of the host di-ureasil framework is identified as d-U(900) or d-U(600) and the subscript n expresses the salt content in terms of the number of ether oxygen atoms per Li+ cation. The most conducting electrolyte of these hybrid systems is the d-U(900)35LiBF4 composition (1.70 × 10−4 S cm−1 at about 95 °C). The lowest decomposition temperature was observed at a composition of n = 2.5 in both the d-U(900)nLiBF4 and the d-U(600)nLiBF4 electrolyte systems (250 °C and 243 °C, respectively). Electrochromic devices assembled with d-U(900)nLiBF4 and d-U(600)nLiBF4 electrolytes with compositions of 20 ≤ n ≤ 35 presented good color contrast, a maximum optical density of 0.23 and an encouraging performance in the coloring/bleaching process. The average transmittance in the visible region of the spectrum was above 74% for all the bleached samples analyzed.

Synthesis and thermal behaviour of an amorphous solid polymer electrolyte

In this study the synthesis of an amorphous polymer network, poly[oxymethylene-oligo(oxyethylene)], designated as aPEO, is described. This polymer has been characterized by gel permeation chromatography, thermal analysis, conductivity measurements, evaluation of electrochemical stability and nuclear magnetic resonance spectroscopy. The synthetic procedure developed permits partial fractionation of the product of the polymerization reaction. This linear macromolecule appears to be a promising polymer for application in batteries and electrochromic devices since it provides access to an amorphous polymer structure with good mechanical properties and promising electrochemical behaviour.

Interpenetrating Polymer Networks Based on Poly(trimethylene carbonate) and poly(ethylene oxide) Blends Doped with Lithium Salts

Fundacao para a Ciencia e a Tecnologia (FCT) - POCI/QUI/59856/2004, POCTI/SFA/3/686), bolsa SFRH/BD/22707/2005 and SFRH/BD/38616/2007

Characterization of Lithium-based Solid Polymer Electrolytes

Fundacao para a Ciencia e Tecnologia (FCT) - contracto POCI/QUI/59856/2004, POCTI/SFA/3/686, bolsa SFRH/BD/22707/2005, SFRH/BD/38616/2007