The Impact of Lithium Tungstate on the Densification and Conductivity of Phosphate Lithium Ion Conductors

Phosphate lithium ion conductors are outstanding electrolyte materials for solid-state lithium batteries. As polycrystalline ceramics, they have to be sintered at high temperatures. Lithium tungstate Li 2 WO 4 (LWO) is reported for the first time as an effective sintering aid to reduce the sintering temperature for one of the most common solid-state lithium ion conductors, Li 1.5 Al 0.5 Ti 1.5 (PO 4 ) 3 (LATP). While densification of LATP without sintering aids requires temperatures of at least 950°C to obtain a relative density of 90%, here relative densities of 90-95% are achieved even at 775°C when 5 wt.% of LWO is added. At 800°C the LATP containing 5 - 7 wt.% LWO densifies to a relative density of 97.2%. The ionic conductivity of LWO containing LATP is generally higher than that of pure LATP sintered at the same temperature. LATP containing 7 wt.% LWO shows high ionic conductivity of 4.4 × 10 -4 S/cm after sintering at 825°C. A significant reduction in sintering temperature, an increase in density and in the ionic conductivity of LATP as well as its non toxicity render LWO a very promising sintering aid for the development of LATP-based solid state batteries.