Estudo do transporte de íons Li+ em híbrido orgânico-inorgânico (SPHP) e nanocompósito (NHP) e seu desempenho em dispositivos eletrocrômicos.
Resumen
The main goal of the present work is to describe the lithium ion transport
mechanism in a hybrid (SPHP) and nanocomposite (NHP) polyelectrolyte based
on complex conductivity analysis as a function of temperature. The chemical
synthesis strategy used to produce a helical free-chain configuration of singlephase
hybrid organic-inorganic polymer electrolytes was based on a simple
non-hydrolytic sol-gel route. The SPHP resulting from this strategy showed a Tg
of -79oC and its temperature-dependent ionic conductivity (achieved at
temperatures higher than Tg) displayed an Arrhenius behavior. This remarkable
behavior characterizes a segmental motion-decoupled polymer. An Arrheniustype
behavior for ionic conductivity (σdc) and hopping frequency of charge
carrier (ωp) were observed. The values of activation energy obtained for σdc and
ωp as a function of the temperature was approximately the same (~ 0.2 eV),
indicating that the dispersive conductivity, σ(ω), originates from the migration of
ions. This relevant physical aspect is allied to the fact that the contribution to the
dispersive conductivity appears to be governed by a nearly frequency
independent dielectric loss, ε = A, which correspond to an almost linear
frequency dependent term of the form, σ = ωε ( ω) = Aω, in the real part of the
complex conductivity. Furthermore, we observe a high stability, of SPHP and
NHP when applied in a large EC device (5 x 10 cm2) using WO3
(electrochromic) and CeO2 -TiO2 (counter-electrode ion storage) electrodes,
both optimized and produced by Leibniz-Institut of New Materials (Leibniz-INM,
Germany). The electrochromic device exhibited excellent color and bleach
reversibility, high coloration efficiency (> 35cm2 / C) from the first cycle up to
more than 60000 CA cycles, and a maximum constant rate of deintercalation /
intercalation (Oout / Qin = 1). Its remarkable behavior and high stability render
this material an excellent candidate for application in electrochromic devices.