EFFECT OF Al2O3 CERAMIC FILLER ON THERMAL AND TRANSPORT PROPERTIES OF POLY(ETHYLENE OXIDE)-LITHIUM PERCHLORATE SOLID POLYMER ELECTROLYTE

Abstract

Polymer electrolytes (PEs) have attracted attention in the last two decades due to their applications in electrochemical devices. At low temperatures, the conductivity of PEs is poor due to the presence of crystalline PEO regions. Low molecular weight liquid plasticizers and ceramic fillers are added to overcome the above problems. In the present work, poly(ethylene oxide) (PEO) was selected as the host polymer and lithium perchlorate (LiClO4) was used as the salt and the effects of adding the inert filler alumina (Al2O3) to PEO-LiClO4 polymer electrolytes have been investigated. Ionic conductivity of PEs was measured using complex impedance analyzer. Maximum ionic conductivity was obtained for the n = 10 sample, (PEO)nLiClO4, out of the five samples (n = 10,20,30,40,60) studied. Al2O3 was added to the n = 10 and n = 30 samples from 2.5% to 15% weight percentages. An increase in ionic conductivity was obtained when the filler percentage was increased and further increase of filler content decreased the conductivity. This is connected with the increase of the amorphous phase content in the polymer with the addition of filler. Differential Scanning Calorimetry results indicate reduction of melting enthalpy and a slight shift in the melting temperature (Tm), towards lower values with the addition of salt concentration as well as with the addition of filler percentage, indicating the increase of amorphous nature of samples. An endothermic peak is observed at 69.7 °C, which corresponding to Tm of pure PEO. The complexation of LiClO4 salt with PEO was confirmed by Fourier Transform Infrared spectroscopy studies. It can be well observed that the increase in salt concentration and the addition of Al2O3 results in decrease of crystalline nature of the polymer electrolytes.