Enhanced lithium-ion transport in PEG-based composite polymer electrolyteswith ferroelectric BaTiO3

The ion-conduction properties of a polyethylene oxide (PEO)-based composite polymer electrolyte comprised of PEG, LiClO4, and the ferroelectric materi al BaTiO3 were studied. The addition of BaTiO3 resulted in an increase in c onductivity over the temperature range 25-115 degrees C. The optimum amount of BaTiO3 (purity 99.9%, particle size 0.6-1.2 mu m) was 1.4 wt %, which i s very low in comparison with previously reported composite polymer electro lytes. The ionic conductivity of a composite polymer electrolyte containing 1.4 wt % BaTiO3 was 1 X 10(-5) S cm(-1) at 25 degrees C, which is at least one order of magnitude higher than that of the pristine polymer electrolyt e (4 X 10(-7) S cm(-1)). The transport number of the lithium ion in this co mposite polymer electrolyte was higher than that of the pristine polymer el ectrolyte. The increase in the conductivity and the lithium-ion transport n umber is explained on the basis of the spontaneous polarization of the ferr oelectric material due to its particular crystal structure. The addition of BaTiO3 powder greatly enhanced the lithium/electrolyte interface stability . (C) 1999 The Electrochemical Society. S0013-4651(98)07-024-4. All rights reserved.