Li+ transport properties of W substituted Li7La3Zr2O12 cubic lithium garnets

Abstract

Lithium garnet Li7La3Zr2O12 (LLZ) sintered at 1230 °C has received considerable importance in recent times as result of its high total (bulk + grain boundary) ionic conductivity of 5 × 10−4 S cm−1 at room temperature. In this work we report Li+ transport process of Li7−2xLa3Zr2−xWxO12 (x = 0.3, 0.5) cubic lithium garnets. Among the investigated compounds, Li6.4La3Zr1.7W0.3O12 sintered relatively at lower temperature 1100 °C exhibits highest room temperature (30 °C) total (bulk + grain boundary) ionic conductivity of 7.89 × 10−4 S cm−1. The temperature dependencies of the bulk conductivity and relaxation frequency in the bulk are governed by the same activation energy. Scaling the conductivity spectra for both Li6.4La3Zr1.7W0.3O12 and Li6La3Zr1.5W0.5O12 sample at different temperatures merges on a single curve, which implies that the relaxation dynamics of charge carriers is independent of temperature. The shape of the imaginary part of the modulus spectra suggests that the relaxation processes are non-Debye in nature. The present studies supports the prediction of optimum Li+ concentration required for the highest room temperature Li+ conductivity in LixLa3M2O12 is around x = 6.4 ± 0.1

W-Doped Li7La3Zr2O12 Ceramic Electrolytes for Solid State Li-ion Batteries

“…In addition, W (normally W 6+ ) substitution for Zr 4+ may lead to more Li vacancies in LLZWO, which is beneficial to enhancement of ionic conductivity. However, there are few reports on W-doped LLZO previously [17]. The role of W dopant playing on ionic conduction improvement of grain and grain boundary is not clear.…”

Estimation of the concentration and mobility of mobile Li+ in the cubic garnet-type Li7La3Zr2O12

“…1,2 These garnet materials are also stable against reactions with metallic lithium electrodes and are stable in air at ambient and high temperatures. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] The most extensively studied members of the lithium conducting garnets are the cubic Li 7 La 3 Zr 2 O 12 (LLZ) based materials due to their high ionic conductivity >10 À4 S cm À1 at RT. [1][2][3][4][5] Extensive work has been devoted to optimize the ionic conductivity of garnet materials, which could be achieved by chemical substitutions and structural modications.…”

Formation and Stability of Interface between Garnet-Type Ta-doped Li7La3Zr2O12 Solid Electrolyte and Lithium Metal Electrode

“…However, high conductivity above 10 −4 S cm −1 at a room temperature range is only obtained in the former, densified by high temperature sintering. Partial substitution of the Zr 4+ site in LLZ by other higher valence cations, such as Nb 5+ [13,14], Ta 5+ [15][16][17][18][19][20][21][22][23], W 6+ [24,25], and Mo 6+ [26], is effective at stabilizing the cubic phase, and the conductivity at room temperature is greatly improved to 1 mS cm −1 by controlling the dopants content and optimizing Li + concentration in the garnet framework. Although a solid-state battery with an Nb-doped LLZ as SE has already been demonstrated [13,27,28], a Ta-doped LLZ showed much better chemical stability against a Li metal electrode than when Nb-doped [29,30].…”