Effect of intercalated and exfoliated montmorillonite clay on the structural, dielectric and electrical properties of plasticized nanocomposite solid polymer electrolytes

•Plasticized nanocomposite solid polymer electrolytes are prepared by different methods.•Dielectric and electrical properties are investigated in the frequency range over 20 Hz to 1 MHz.•Effect of intercalated and exfoliated montmorillonite clay nanofiller on ionic conductivity has been explored.•These materials are suitable for lithium ion batteries and electrochromic devices.

Plasticized nanocomposite solid polymer electrolyte (PNSPE) films, consisted of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) polymer blend matrix (50/50 wt%) with lithium tetrafluoroborate (LiBF4) as dopant ionic salt (10 wt%), ethylene carbonate (EC) as plasticizer (10 wt%) and montmorillonite (MMT) clay as nanofiller (3 wt%), have been prepared by classical solution-cast (SC) and the ultrasonic-microwave irradiated (US-MW) solution-cast methods. X-ray diffraction (XRD) study confirms that these PNSPE films are predominantly amorphous and contain very small amount of PEO crystallites. The SC method prepared PNSPE film bears highly ordered intercalated MMT structures, whereas, the US-MW method prepared PNSPE film has large amount of disordered exfoliated MMT structures. Dielectric relaxation spectroscopy (DRS) from 20 Hz to 1 MHz has been employed for characterization of complex dielectric permittivity, alternating current electrical conductivity and complex impedance spectra of the films. Three relaxation processes corresponding to the electric double layers dynamics, polymer chain segmental motion and ionic conductivity have been explored. It has been observed that the dielectric and electrical properties of the PNSPE films change notably with the film preparation methods. Results reveal that the exfoliated MMT decreases the dielectric polarization and creates hindrance to the polymer chain segmental dynamics which causes decrease of ionic conductivity in comparison to the ion-dipolar complexes containing intercalated MMT. The room temperature dc ionic conductivity of the PNSPE films have been found about 10−5 S cm−1, which confirms these materials as potential candidate for design and development of flexible-type all-solid-state lithium-ion conducting electrochromic devices.