In liquid-filled batteries, the liquid electrolytes may escape or present a fire hazard and an inert spacer is needed to separate the electrodes. Alternative polymer-based electrolytes are of current technological interest. Solid polymer electrolytes are non-volatile, non-corrosive materials, which can readily be processed into any shape or size. However, despite possessing the required mechanical properties, they have inherently lower conductivity. Gel-based systems are an attempt to strike a balance between the high conductivity of organic liquid electrolytes and the dimensional stability of a solid polymer.
Rectorite was modified with dodecyl benzyl dimethyl ammonium chloride to form organic-modified rectorite (OREC). OREC was used as a filler additive to modify gel polymer electrolytes (GPEs) and prepare composite gel polymer electrolytes (CPEs) which consisted of polymethyl methacrylate (PMMA) used as a polymer matrix, propylene carbonate (PC), used as a plasticizer, and LiClO4, used as a lithium ion producer. A variety of physical and chemical techniques was used to characterize the CPEs. The interlayer d spacing of OREC was much larger than that of the initial rectorite (2.22 nm). OREC also possesses a fine microscopic structure, and has a hydrophobic surface. Molau and XRD analysis of CPEs indicate that OREC has good compatibility with the components of CPEs and can be dispersed well. The effects of temperature and OREC dose on properties were studied. The temperature dependence of ionic conductivity of CPEs is well fitted by the VTF (Vogel-Tamman-Fulcher) relation. OREC doses of 5 phr gave the greatest ionic conductivity. This amount also greatly increased the plasticizer maintenance levels. Due to the occupancy of free volume space in the polymer matrix of CPEs by OREC, the bulk resistance of the CPEs was lowered and the glass transition temperature (T
g) increased. The sheet structure of OREC is thought to improve the decomposition temperature of CPEs.