No abstract

High lithium ion conductivity solid electrolytes of Li 1+x Fe x Ti 2-x (PO 4) 3 and Li 1.4 Fe x Al 0.4-x Ti 1.6 (PO 4) 3 (x=0-0.4) with the NASICON-type structure were synthesized using a precursor prepared by the sol-gel method. The highest electrical conductivity was obtained for the Li 1.4 Fe 0.25 Al 0.15 Ti 1.6 (PO 4) 3 (LFATP) composition sintered at 1040 °C for 7 h in air. The total, grain boundary, and bulk conductivities of the pellet were stable after storage for one month and were 1.01×10-3 , 2.17×10-3 and 1.81×10-3 S cm-1 at 25 °C, respectively. The contribution of electron (or hole) conductivity to the total conductivity was negligibly small. LFATP was unstable in water, but stable in saturated LiOH and LiCl aqueous solution.