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

Abstract

Phosphate lithium‐ion conductors are outstanding electrolyte materials for solid‐state lithium batteries. As polycrystalline ceramics, they must be sintered at high temperatures. Lithium tungstate Li2WO4 (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, Li1.5Al0.5Ti1.5(PO4)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 are 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.

Enabling High-Performance Hybrid Solid-State Batteries by Improving the Microstructure of Free-Standing LATP/LFP Composite Cathodes

“…LWO, a material with a low melting temperature of 742 °C, has already been recognized as a very efficient sintering aid for densifying pure LATP, lowering the sintering temperature by more than 100 °C. 31 In this work, we show that LWO can also be added to the composite cathode, lowering the sintering temperature without affecting the phase composition of the LATP and LFP materials and resulting in mechanically stable, self-supporting cathodes with a smooth, homogeneous surface. The advantages of the optimized cathode microstructure are demon-strated in cell fabrication, which enables the deposition of a thin polymer separator layer without a supporting ceramic sheet 15 and a cell assembly that operates with lithium metal anodes without short-circuiting.…”

Synergistic Effect of Calcination and Sintering on the Reduction of Grain Boundary Resistance of LATP Solid Electrolyte

“…As a result of the comparison of the impurity removal time during the calcination process, it was found that the impurity phase did not appear in the LA_900 °C sample, from which the impurities were sufficiently removed. However, the LSC_900 °C and LWC_900 °C samples were found to contain small amounts of the LiTiPO 5 impurity phase, which has the potential to reduce the ionic conductivity, as shown in Figure d …”

“…However, the LSC_900 °C and LWC_900 °C samples were found to contain small amounts of the LiTiPO 5 impurity phase, which has the potential to reduce the ionic conductivity, as shown in Figure 2d. 45 As all samples were crystallized and the peaks were clearly distinguishable, the crystallinity of the samples was confirmed by two methods. The first method estimated the crystallinity based on the angle of XRD reflection expressed as the full width at half maximum (fwhm) of the XRD diffraction peak, while the second method estimated crystallinity based on the area of the XRD peak using eq 1.…”

Recent Advances of LATP and Their NASICON Structure as a Solid‐State Electrolyte for Lithium‐Ion Batteries

“…The ionic conductivity of MAUST–LATP is 0.10 mS cm −1 , and the MAUST–LLZTO‐based lithium symmetric battery demonstrates good cycle stability over 5000 h at a current density of 0.1 mA cm −2 . The other scheme proposes that the addition of some sintering aids like Li 2 O, [ 67 ] Li 2 B 4 O 7 , [ 68 ] TeO 2 , [ 69 ] LiF, [ 70 ] and Li 2 WO 4 [ 71 ] can improve the ionic conductivity while reducing the sintering temperature. Usually, sintering aids reduce the activation energy of grain boundary lithium migration and increase the density of LATP [ 72 ] to boost electrical conductivity.…”