Synergistic Effect of Calcination and Sintering on the Reduction of Grain Boundary Resistance of LATP Solid Electrolyte

The NASICON-type Li1.4Al0.4Ti1.6(PO4)(3) (LATP)solid electrolyte isa promisingcandidate for next-generation lithium-ion batteries due to its highstability in air and moisture, as well as high bulk ion conductivity.However, the grain boundary resistance of LATP limits its overallionic conductivity, which remains a major obstacle to the commercializationof all-solid-state batteries. In this study, we made efforts to solvethe problem by promoting the minimization of voids and the formationof well-defined grain boundaries by controlling the temperature oftwo heat treatments during the synthesis process. The crystallizationtemperature was confirmed through thermogravimetric analysis/DTA analysis,and the degree of crystallization was confirmed using XRD analysis.The formation of grain boundaries and the presence of voids were evaluatedby cross-sectional SEM images after sintering. After sintering, theLA_900 degrees C sample, characterized by a high degree of crystallizationand well-formed grain boundaries without voids, demonstrated a lowbulk and grain boundary resistance, which was confirmed by electrochemicalimpedance spectroscopy analysis. The result was an ionic conductivityof 1.72 x 10(-4) S/cm. These results providevaluable insights into the facile synthesis of LATP.