L.R.A.K. Bandara

Ionic conductivity of plasticized(PEO)-LiCF3SO3 electrolytes

Many polymer electrolytes used in practical applications contain a low molecular wcight plasticizer. Plasticizers can be used to change the mechanical and electrical properties of polymer electrolytes by reducing the degree of crystallinity and lowering the glass transition temperature T g . In this study the ionic conductivity has been determined for a (PEO) 9 LiCF 3 SO 3 polymer electrolyte with added plasticizers. The samples were in the form of thin films with the thickness 0.1- 0.5 mm and ethylene carbonate (EC), propylene carbonate (PC) or a mixture of ethylene carbonate and propylene carbonate (EC:PC) were used as plasticizers. The ionic conductivity increases with increasing amount of plasticizer but the amount of plasticizer which can be added is limited since the films become too soft for use in practical applications. Without any plasticizer, the complex (PEO) 9 LiCF 3 SO 3 only has a conductivity of 2.5 x 10 -5 S cm -1 at 332 K. Adding 50% of the plasticizers by mol. weight of PEO to the (PEO) 9 LiCF 3 SO 3 complex yielded mechanically stable films with an ionic conductivity of 9.0 x 10 -4 S cm -1 with EC and 5.2 x 10 -5 S cm -1 with PC at the same temperature

A novel gel polymer electrolyte based on polyacrylonitrile (PAN) and its application in a solar cell

A PAN-based gel polymer electrolyte with possible iodide ion conductivity was prepared by incorporating a mixture of Pr4N+I−, iodine, EC and PC in PAN. Out of various compositions prepared and characterised, the sample with composition PAN (13%):EC (31%):PC (45%):Pr4N+I− (7%):I2 (4%) by weight ratio, exhibited the maximum room temperature (25°C) conductivity of 2.95×10−3 S cm−1. The predominantly ionic nature of the electrolyte was established by using the dc polarisation technique. The temperature dependence of ionic conductivity follows the VTF behaviour, indicating the amorphous nature of the electrolyte. Dye-sensitised photoelectrochemical solar cells prepared using this electrolyte exhibited an open circuit voltage (Voc) of 0.69 V, a short circuit current (Isc) of 3.73 mA cm−2 for an incident light intensity of 600 W m−2 yielding an overall quantum efficiency of 2.99%.

Broad band dielectric behaviour of plasticized PEO-based solid polymer electrolytes

The conductivity and dielectric response of poly(ethylene oxide) (PEO) based plasticized polymer electrolyte systems were studied in the broad frequency range from 5 Hz to 1.8 GHz and in the temperature range from 248 K to 353 K. Propylene carbonate (PC) and ethylene carbonate (EC) were used as conventional plasticizers while poly(perfluorinated ethylene methylene oxide) (M03) was used as a new type of plasticizer. PEO-LiN(CF3SO2)2 plasticized with M03 shows high enough conductivity values to be used as electrolyte in rechargeable lithium polymer batteries.At high frequency a dielectric relaxation is observed for pure PEO as well as for the salt containing systems in the GHz region that is assumed to be due to segmental motion of the polymer chains. In the salt containing systems, this relaxation is shifted to lower frequencies relative to that of pure PEO, this is attributed to transient cross-linking. However, at lower frequencies another dielectric response peak was detected in all samples containing salts. The effect of the plasticizer on this relaxation is complex.