Lithium Ion‐Conducting Glass–Ceramics of Li_1.5Al_0.5Ge_1.5(PO₄)₃–xLi₂O (x=0.0–0.20) with Good Electrical and Electrochemical Properties

Abstract

NASICON‐type structured Li1.5Al0.5Ge1.5(PO4)3–xLi2O Li‐ion‐conducting glass–ceramics were successfully prepared from as‐prepared glasses. The differential scanning calorimetry, X‐ray diffraction, nuclear magnetic resonance, and field emission scanning electron microscope results reveal that the excess Li2O is not only incorporated into the crystal lattice of the NASICON‐type structure but also exists as a secondary phase and acts as a nucleating agent to considerably promote the crystallization of the as‐prepared glasses during heat treatment, leading to an improvement in the connection between the glass–ceramic grains and hence a dense microstructure with a uniform grain size. These beneficial effects enhance both the bulk and total ionic conductivities at room temperature, which reach 1.18 × 10−3 and 7.25 × 10−4 S/cm, respectively. In addition, the Li1.5Al0.5Ge1.5(PO4)3–0.05Li2O glass–ceramics display favorable electrochemical stability against lithium metal with an electrochemical window of about 6 V. The high ionic conductivity, good electrochemical stability, and wide electrochemical window of LAGP–0.05LO glass–ceramics suggest that they are promising solid‐state electrolytes for all solid‐state lithium batteries with high power density.

Recent Advances in Inorganic Solid Electrolytes for Lithium Batteries

“…Besides, NASICON-type SEs can have high electrochemical oxidative voltage. For example, LiGe 2 (PO 4 ) 3 -based SEs were reported to show high electrochemical oxidative voltage of about 6 V (vs. Li/Li + ) (Xu et al, 2007), as shown in Figure 11. However, similar to LLTO, LiTi 2 (PO 4 ) 3 -based SEs are instable toward Li metal, with the reduction of Ti 4+ to Ti 3+ (Hartmann et al, 2013).…”

Aqueous Lithium-Air Batteries

“…The conductivity is highly dependent on the preparation method because this type of electrolyte has a high grain boundary resistance. An extremely high conductivity of 4.62 × 10 −3 S cm −1 at 25°C was reported for the Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 glass ceramic [33]; however, the electrical conductivity at 25°C of the same composition glass ceramic was reported to be 4 × 10 −4 S cm −1 by Fu [34] and 7.25 × 10 −4 S cm −1 by Wen and coworkers [35]. The conductivity of glass ceramics may be dependent on the preparation method and the effect of ageing on the conductivity should also be considered.…”

PREPARATION OF Li_1.5Al_0.5Ge_1.5(PO₄)₃ SOLID ELECTROLYTE BY SOL-GEL METHOD

“…Li 1+x Al x Ge 2-x (PO 4 ) 3 (LAGP) solid electrolyte is a member of Li ion conductive ceramics with NASION (Na super ion conductor) type structure. The total ionic conductivities of LAGP are 4.22 × 10 -3 S cm -1 5 , that is comparative to Li 1+x Al x Ti 2-x (PO 4 ) 3 (LATP) 6,7 and Li 0.35 La 0.55 TiO 3 (LLT) 8,9 which are anticipated to be applied to the all-solid-state battery. The electrochemical windows of LATP and LLT are limited by facile reduction of Ti 4+ at 2.4 V vs. Li/Li .…”