Preparation, characterization and conductivity of NASICON-type Li1+xM(III)xTi2-x(PO4)3 (M(III) = Al, Cr, Fe; 0.5 ≤ x ≤ 2.0) materials via modern, scalable synthesis routes

Abstract

Lithium-conducting NASICON materials are frequently researched for their high ionic conductivity and possible application in solid state batteries. The highest ionic conductivities are found for M(III) cation substituted LiTi2(PO4)3 derivates. While aluminum substituted compositions are mostly researched as electrolyte-materials, the chromium and iron containing compounds are mixed conductors and thus suitable materials for cathodes. Conventional synthesis routes of these materials include the highly energy consuming solid-state reaction and the sol-gel method in organic solvents. In this work, the compositions Li1+xM(III)xTi2-x(PO4)3 (M(III) = Al, Cr, Fe; 0.5 ≤ x ≤ 2.0) were synthesized by two rather new synthetic routes in an aqueous solution that requires a reduced number of educts. Stoichiometry, crystal- and microstructure, density and conductivity were investigated. The ionic conductivities of the resulting NASICON-materials are mostly within the range of comparative literature and the applied synthesis methods can be considered as suitable for these compositions.

Keywords

• Application of two recent, scalable and low cost synthesis routes for NASICON materials
• Full substitution series for Li1+xM(III)xTi2-x(PO4)3 (M(III) = Al, Cr, Fe
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• Thorough sample characterization including phase chemistry, density and stoichiometry