A Super High Lithium Ion Conducting Solid Electrolyte of Grain Boundary Modified Li1.4Ti1.6 Al0.4(PO4)3

Abstract: A single phase NACICON-type lithium conducting solid electrolyte, Li1.4Ti1.6 Al0.4(PO4)3 (LTAP), was synthesized from the precursor prepared by a sol-gel method with citric acid. The bulk and grain boundary conductivity of the LTAP sintered at 950 °C was estimated to be 1.8x10-3 S cm-1 and 1.3x10-3 S cm-1 at 25 °C, respectively, from the impedance profile analysis. The grain boundary resistance was almost diminished by immersion in a saturated LiCl aqueous solution at 50 °C for one week, and the total conductivity at 25 °C increased from 7.5x10-4 S cm-1 to 9.2x10-3 S cm-1. The high conductivity has not changed for a long period in open air. The conductivity enhancement was explained by the formation of a low resistance LiCl-xH2O phase trapped in the grain boundaries of LTAP nanoparticles.

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