The Plasticizer Effect On The Performance Of PEO (LiClO₄)-Li_1.3Al_0.3Ti_1.7(PO₄)₃ Solid Polymer Electrolytes

The polymer electrolytes, as ionic conductors, which consist of a salt dissolved in a polymer host, in applications such as rechargeable lithium batteries and other electrochemical devices have attracted more and more interest. The most investigated systems consist of poly(ethylene oxide), PEO, with dissolved salts. Ionic transport in these systems is highly coupled to the relaxation processes of the polymer backbone and has been determined to occur predominantly in the amorphous phase for polymer electrolytes. Because of high crystallinity, these electrolytes with PEO and dissolved salts suffer from low conductivity values at room temperature so that the applications are restricted for the polymer electrolytes which result in fast ion mobility and therefore high conductivities with low crystallinity.In this paper, I primarily focused my work on adding different percent mass of EC PC or the mixture of them to the trinomial system PEO-LiClO₄ -Li1.3Al0.3Ti1.7(PO4)3 with E0/Li=8 and 15wt.% -Li1.3Al0.3Ti1.7(PO4)3 content which carefully selected from the scientific research of Doctor Yan-Jie Wang. The polymer electrolyte films was prepared by by a solution-cast method. Several techniques including X-ray diffraction (XRD), DSC, SEM and electrical impedance (El) measurement were used to investigate the structure, thermal property, morphology and conductivity of these polymer electrolytes. It is found by study that the amorphous phase dominated in the prepared (PEO/plasticizer-LiClO4)-Li1.3Al0.3Ti1.7(PO4)3 polymer electrolyte system, where the temperature dependence of conductivity follows Vogel-Tamman-Fulcher (VTF) equation while the conductivity increase with the increasing temperature. Additionally the migration of lithium cations depends mainly on the segmental movements of the polymer chain in the amorphous region. Both the pre-exponential factor (A) andthe pseudo activation energy (Ea) monotonously increase with the increase of plasticizer content in the polymer electrolyte (PEO/plasticizer-LiC104)-Li1.3Al0.3Ti1.7(PO4)3), suggesting that ion migration easily happen and the increase of pre-exponential factor agrees with the increase of conductivity of the polymer electrolyte films with EC PC or the mixture of them. At 40wt. % plasticizer content, the conductivity, when the pre-exponentialfactor (A) and the pseudo activation energy (Ea) respectively have a maximum, is optimal, and the conductivity value is 10-3 S cm-11 at room temperature.