| Based on the study of Lithium fast ion conductive systems of Li3Sc2(PO4)3, LiTi2 and their solid solution Li3-2x(Sc1-xTix)2(PO4)3, Li3-2x(Al1-xTix)2(PO4)3 is expected to have similar performance as a new ionic conductor. By using Al to replace Sc, this thesis started with a systematic investigation on the preparation and characterization of Li3-2x(Al1-xTix)2(PO4)3 (X = 1.0-0.55) ceramics. Among all Li3-2x(Al1-xTix)2(PO4)3 (X = 1.00.55), Li1.3Al0.3Ti1.7(PO4)3 exhibits the most optimal ionic conductivity. For Li1.3Al0.3Ti1.7(PO4)3 prepared, the ionic conductivities 2.435 ×10-6S/cm at room temperature and 9.638 × 10-4S/cm at 613K were obtained.Composite polymer electrolytes, composed of lithium ionic conductive salt (LiX) and semi-crystalline polymer, have been attracting research interests for its potential applications in rechargeable lithium batteries and other electrochemical devices. The most important polymer used as the polymeric host in composite polymer electrolyte is poly(ethylene oxide), and in short, PEO, since it can dissolve and forms complexes with LiX. The ion transport in PEO-LiX systems is highly coupled with the relaxation processes of the polymer backbone and has been determined to occur predominantly in the amorphous phase of PEO. Because the crystallinity of PEO is usually high, PEO-LiX system suffers from low conductivity at room temperature. Non ionic conductor oxides, such as SiO2 and Al2O3, were conventionally added to reduce the crystallinity of polymer matrix and improve the mechanical property as well.. In this work, ionically conductive Li1.3Al0.3Ti1.7(PO4)3 prepared by us was used as a filler in PEO-LiClO4 composite polyer electrolyte system in the expectations of reducing crystallinity and extra contribution to ionic conductivity as well. Investigations have been carried on the structure, the thermal property, the morphology and the conductivity of these composite polymer electrolytes using conventional techniques including IR, XRD, DSC, SEM and electrical impedance (EI) measurement.New ionic conductor, Li1.3Al0.3Ti1.7(PO4)3, was added as a filler in PEO-LiClO4 to form PEO(LiClO4)- Li1.3Al0.3Ti1.7(PO4)3 electrolyte films, in which EO/Li=8 was fixed but the ratio of Li+ from LiClO4 to Li+ from Li1.3Al0.3Ti1.7(PO4)3 was varied. The conductive filler effect is compared with the insulating oxide fillers effect investigated by previous researchers on the performance of the composite polymer electrolyte. It is found that PEO preferably tends to complex with LiClO4 rather than Li1.3Al0.3Ti1.7(PO4)3, and the crystallinity is considerably reduced. The temperature dependence of conductivity of all PEO(LiClO4)-Lii 3Alo.3Ti).7(P04)3 films follows Vogel-Tamman-Fulcher (VTF) equation, instead of Arrhenius relation. As LioAlojTii^PO^ content is 15wt.%, the conductivity is optimal. The pseudo activation energies (Ea) and the pre-exponent constant (^4) changed with the variation of ion transference number (f//). The ionic filler addition contributes to the improvements of ionic conductivity not only through prohibiting crystallization but also the conductivity of the filler itself. |
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