A lithium-ion conductive Li1.5Al0.25Ga0.25Ti1.5(PO4)3 solid electrolyte for electrochemical device

Lithium-ion solid electrolyte disc with high conductivity even at low temperature for electrochemical devices were designed using Li1+x+yAlxGayTi2-x-y (PO4)(3) (x + y = 0-0.5) with NASICON-type structure. The solid-electrolyte discs were synthesized by a solution method at 900-1000 degrees C. Effects of Al and/or Ga dopants and crystal structures on ionic conductivity of the solid electrolytes were investigated. Almost single phase of Li1+x+yAlxGayTi2-x-y (PO4)(3) + y = 0-0.5) systems could be synthesized at sintering temperatures above 900 degrees C up to x = 0.5, y = 0.25. An ionic conductivity as high as 9.3 x 10(-4) S/cm at 30 degrees C and activation energy of 0.29 eV were obtained with the trivalent-cation double-doped Li1.5Al0.25Ga0.25Ti1.5(PO4)(3) disc sintered at 900 degrees C.