Estudo físico-químico da interface eletrólito polimérico/nanotubos de carbono.

Abstract

A study of interface between carbon nanotubes (CNT) and polymer electrolytes by electrochemical impedance and cyclic voltammetry was accomplished. These two components were investigated independently before the interface was build. Thermal, electrical and morphological properties of a double-walled carbon nanotube functionalized with carboxylic groups (DWCNT-COOH) were characterized. The nanotubes showed high purity and electrodes constructed from this material revealed interesting properties for applications in interface systems with polymer electrolytes, such as electrical conductivity of 10-2 Scm-1 and porous morphology. Polymer electrolytes based on a block copolymer with poly(ethylene-b-ethylene oxide) and a salt of lithium, LiN(CF3SO2)2, were produced with three different concentrations. Thermal and electrical characteristics correlate well with the increase of salt concentration on the electrolyte. Electrolytes revealed values of conductivity, at room temperature, among the best ones described in literature for these solid systems, reaching 10-4 Scm-1. Two different thicknesses of electrolyte layer were used to produce interfaces CNT/polymer electrolyte. The formation of nanocomposite was observed in the system where the electrolyte layer thickness was of the same order of magnitude as the layers of CNT. Conductivity of the order of 10-2 Scm-1 was attained, due to infiltration of electrolyte in nanotube electrodes. The second system was prepared using electrolyte layer two orders of magnitude greater than nanotube layers. Accumulation of charges in the electric double layer, formed by the interface CNT/polymer electrolyte, was observed in this case with total capacitance of 2,6 F/g, at room temperature.