Thermal behavior and lithium ion conductivity of L sub(2)O-Al sub(2)O sub(3)-TiO sub(2)-SiO sub(2)- P sub(2)O sub(5) glass-ceramics

A lithium ion conductive solid electrolyte, L sub(2)O-Al sub(2)O sub(3)-TiO sub(2)-SiO sub(2)- P sub(2)O sub(5) glass with NASICONtype structure have been synthesized and transformed into glass-ceramic through thermal-treatment at various temperatures from 700 to 1 000 degree C for 12 h. The differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and complex impedance techniques were employed to characterize the samples. The experimental results indicated that the capability of glass forming in this system is superior to that of L sub(2)O-Al sub(2)O sub(3)-TiO sub(2)-P sub(2)O sub(5). The glass has an amorphous structure and resultant glass-ceramic mainly consisting of LiTi sub(2)(PO sub(4)) sub( 3) phases. Impurity phases AlPO sub(4), TiO sub(2), TiP sub(2)O sub(7) and unidentified phase were observed. With the enhanced heat-treatment temperature, grain grew gradually and lithium ion conductivity of glass-ceramics increased accordingly, the related impedance semicircles were depressed gradually and even disappeared, which could be analytically explained by the coordinate action of the 'Constant phase element' (CPE) model and the 'Concept of Mismatch and Relaxation' model (CMR). When the sample is devitrified at 1 000 degree C, the maximum room temperature lithium ion conductivity comes up to 4.110 super(-4) S/cm, which is suitable for the application as an electrolyte of all-solid-state lithium batteries.