Organic-inorganic hybrid electrolytes by in-situ dispersion of silica nanospheres in polymer matrix

Abstract

In the present study, an organic-inorganic hybrid electrolyte based on a polymer (PEO) and silica (SiO2) matrix containing different amounts of lithium salt (LiTf) is being reported. The synthesized hybrid electrolytes are freestanding flexible films with good mechanical stability. The interaction/complexation of the cation (Li+) with the polymeric chain has been confirmed by the ATR-IR spectroscopic measurements. TEM images of these hybrid electrolytes clearly show the appearance of in-situ formed silica nanospheres within the PEO matrix while the FESEM analysis confirms the layered morphology of such systems. DSC results show that the melting temperature (Tm) of the hybrid electrolytes decreases with the increase in the concentration of lithium salt which, in turn, is responsible for the increase in the ionic conductivity due to the enhancement in the flexibility of the polymer backbone. It is evident from the TGA that these hybrid electrolytes are thermally stable upto 200°C. The ionic conductivity obtained by complex impedance spectroscopy technique has been found to increase with increasing concentrations of LiTf and reaches a value of 1.24×10−6S/cm at 30°C and 1.15×10−4S/cm at 100°C for the loading of 20wt% of LiTf in the matrix. Temperature dependence of ionic conductivity has been found to be typical of thermally activated process as well as phase transition behavior of PEO both at T>Tm and T<Tm. These results indicate that the prepared organic-inorganic hybrid electrolyte films could be a promising alternative as an electrolyte for all solid state rechargeable lithium-ion batteries.