Next-generation Li1.3+xAl0.3AsxTi1.7-x(PO4)3 NASICON electrolytes with outstanding ionic conductivity performance

Abstract

NASICON-type solid electrolytes feature prominently in the improved safety and energy density of solid-state lithium batteries (ASSLBs). Achieving high ionic conductivity in these electrolytes is key to optimizing their performance. In this study, we introduced a new class of NASICON-type materials by doping arsenic into the Li1.3Al0.3Ti1.7(PO4)3 framework, creating a series of Li1.3+xAl0.3AsxTi1.7-x(PO4)3 phases with varying arsenic content (x = 0, 0.1, 0.2, 0.3), synthesized using the standard solid-state reaction method. X-ray diffraction confirmed the successful formation of the Li1.3+xAl0.3AsxTi1.7-x(PO4)3 phases, which was further validated by Rietveld refinement. Structural analyses through FT-IR, Raman spectroscopy, NMR, and ICP-AES studies validate the effective incorporation of arsenic into the lattice. Among the different compositions, Li1.5As0.2Al0.3Ti1.5(PO4)3 phase stood out due to its high relative density of 89% and its pore-free microstructure, as observed through scanning electron microscopy results, revealing the largest grain and crystallite size. Notably, doping with arsenic resulted in a significant enhancement in ionic conductivity, increasing from 5.34×10-5 Ω-1.cm-1 for Li1.3Al0.3Ti1.7(PO4)3 to 8.57×10-4 Ω-1.cm-1 for the Li1.5As0.2Al0.3Ti1.5(PO4)3 at 25°C. With a lithium transference number of 0.99, and a conduction mechanism largely unaffected by changes in temperature or composition, demonstrating its suitability as a promising candidate for solid electrolyte applications