| This thesis describes the synthesis and characterization of polyphosphazenes as polymer electrolytes for secondary lithium battery applications. The polyphosphazenes that were synthesized include (a) species with linear and branched oligo(oxyethylene) side groups, (b) examples which incorporate crown ethers of various sizes, and (c) polymers which include sulfone or sulfoxide functional groups. Additional work involved the investigation of the factors that limit the cycle life of lithium-polymer secondary batteries.; New polymers that contain either linear or branched oligo(oxyethylene) side-chains were synthesized. The polymers that bear linear side-chains have low glass transition temperatures and poor physical properties. The polymers with branched side-chains have similar glass transition temperatures, but have significantly improved bulk dimensional stabilities. The two systems have comparable ionic conductivities.; Phosphazene polymers, bearing either 12-crown-4, 15-crown-5, or 18-crown-6 groups, either as single-substituent polymers or with 2-(2{dollar}spprime{dollar}-methoxyethoxy)ethoxy cosubstituents, were synthesized. The polymers in which all the side groups are crown ether units generate relatively low ionic conductivities at ambient temperatures. The ambient temperature ionic conductivity of the cosubstituent polyphosphazenes, as well as of MEEP, when complexed with MClO{dollar}sb4{dollar} (M = Li, Na, K, Rb, Cs), was measured. The ionic conductivity is reduced when a favorable 1:1 or 2:1 crown ether-cation complex is formed. There is an increased glass transition temperature when a favorable 2:1 complex is formed.; A synthetic method for the introduction of sulfone or sulfoxide functional groups into polyphosphazenes has been developed. This procedure involves the prior introduction of thioether groups followed by oxidation by {dollar}rm Hsb2Osb2{dollar} or m-chloroperbenzoic acid. Oxidation of the sulfur atom results in polymers with relatively high glass transition temperatures. The potential of these materials as polymer electrolytes, both in the solid state or in systems with added propylene carbonate, was explored.; The compatibility of polyphosphazene electrolytes with manganese (IV) oxide-based cathodes was investigated. Laminates of a solid polymer electrolyte (SMEP) between two MnO{dollar}sb2{dollar}-based intercalation cathodes were constructed. The cathodes were fabricated by solvent-casting and compression techniques. Both {dollar}lambda{dollar}-MnO{dollar}sb2{dollar} and {dollar}gamma{dollar}-MnO{dollar}sb2{dollar} were used. MEEP was the cathode binder material. Charge cycling was carried out and cell performance monitored by electrochemical impedance spectroscopy. |
