Abstract
Lithium ion solid electrolytes with different compositions”Li1+x(AlxTi2-x)(PO4)3, Li1+x(InxTi2-x)(PO4)3, Li1+x(AlxZr2-x)(PO4)3 and Li1+x(InxZr2-x)(PO4)3 (x = 0.2, 0.3, 0.4 and 0.5)” were synthesized in bulk form by solid-state reactive sintering method in this paper. The ionic conductivity of Li1+x(AlxTi2-x)(PO4)3 (x = 0.3) is 1.69074 10-3 S/cm measured by EIS. The change of crystal structure resulted from different atomic radii of doping and compositions have been studied by XRPD and Rietveld method, and the relationship between crystal phase and ionic conductivity is presented. Possible defect chemistry and thermodynamic aspect in explanation of why ionic conductivity being increased dramatically by doping these solid solutions are also proposed in this paper. The ionic conductivity was calculated theoretically with the data of lithium ion concentration by ICP-AES, longitudinal relaxation time by NMR, and jumping distance of lithium ion by XRPD and Rietveld method. These theoretical values of ionic conductivity were compared with the experimental values from EIS.Besides, the sputtering target of 2 in. diameter for Li1+x (AlxTi2-x)(PO4) 3(x = 0.3) with optimized ionic conductivity was made by solid-state reactive sintering method. The thin films of solid electrolyte on Si wafer were deposited by RF magnetron sputtering. The composition, ionic conductivity, crystal phase and vibrational spectroscopy of these electrolyte films with and without annealing at 700℃ were identified by ICP-MS, EIS, XRPD and FT-IR.