Fabrication and characterizations of lithium aluminum titanate phosphate solid electrolytes for Li-based batteries

Demands for electric vehicles and flexible electronics have escalated research in developing high-performance lithium batteries based on solid-state chemistry. The present work is to develop highly-conductive and flexible solid electrolyte for such applications. Lithium aluminum titanate phosphate (LATP or Li1.3Al0.3Ti1.7(PO4)3), both in ceramic pellets and free-standing composite membranes, have been fabricated. The crystal structure, surface morphology, and ionic conductivity are systematically studied. LATP pellets are prepared using solid state reaction approach. The results indicate that calcine temperature has significant impacts on the phase impurity and sintering temperature and duration have more impacts on the grain size and porosity of LATP pellets. At the optimal conditions, the highest bulk conductivity of LATP electrolyte reaches 1.5*10-3 S/cm at room temperature with an activation energy of 0.206 eV. The as-prepared LATP has high conductivities comparable with liquid electrolytes, which is feasible for applications to all-solid-state lithium batteries. Ceramic electrolyte can be composited with polymer electrolyte to enable flexible battery design. In this study, LATP-based electrolyte membranes are fabricated in composite with a lithiated polymer, i.e. polyvinylidene fluoride (PVDF) dissolved with lithium perchlorate (LiClO4), via the casting method. It is found curing temperature has influences on ionic conductivities of the composite membrane and high casting temperature can cause the decomposition of PVDF. Appropriate LATP composition can increase the ionic conductivity, mechanical strength while maintaining the flexibility of the composite membrane. Raman spectroscopic analysis suggests there exists certain interactions among the three components in the composite membrane.