Solid-state polymer nanocomposite electrolyte of TiO2/PEO/NaClO4 for sodium ion batteries

Abstract

A free-standing transparent film for sodium-ion conduction in PEO-based solid polymer electrolyte (additionally comprising NaClO4 and nano-sized TiO2) has been fabricated for use in Na-ion batteries by using a solution casting technique. The crystallinity of the solid polymer electrolyte and the interactions between PEO and the Na-ions is characterized by X-ray diffraction (XRD) and Fourier transformed infra-red (FTIR) spectra, which reveals the degree of Na+ ion solvation by PEO oxygen atoms (EO:Na). The ionic conductivities of the films are investigated by impedance analysis from 1 MHz to 1 Hz within the temperature range 303–363 K. A solid polymer electrolyte with anatomic ratio EO:Na = 20 exhibits a maximum ionic conductivity of 1.35 × 10−4 S cm−1, which increases to 2.62 × 10−4 S cm−1 by the addition of TiO2 (3.4 nm, 5 wt%) at temperature 60 °C. The performance of a Na2/3Co2/3Mn1/3O2 half cell with a polymer electrolyte is compared to a similar cell with a liquid electrolyte.