Phase transformation and grain-boundary segregation in Al-Doped Li7La3Zr2O12 ceramics. Issue 16 (15th August 2021)

• Record Type: Journal Article
• Authors: Zhuang, Libin; Huang, Xiao; Lu, Yang; Tang, Jiawen; Zhou, Yongjian; Ao, Xin; Yang, Yan; Tian, Bingbing
• Is Part Of: Ceramics international. Volume 47:Issue 16(2021)
• Page Start: 22768
• Page End: 22775
• Publication Date: 2021-08-15
• Subjects: Li-garnet -- Li7La3Zr2O12 -- Solid electrolyte -- Phase -- DRT analysis -- Grain boundary; Ceramics -- Periodicals; Céramique industrielle -- Périodiques; Ceramics; Periodicals; Electronic journals; 666
• DOI: 10.1016/j.ceramint.2021.04.295
• Languages: English
• ISSNs: 0272-8842

Abstract

Abstract: Cubic phase garnet-type Li7 La3 Zr2 O12 (LLZO) is a promising solid electrolyte for highly safe Li-ion batteries. Al-doped LLZO (Al-LLZO) has been widely studied due to the low cost of Al2 O3 . The reported ionic conductivities were variable due to the complicated Al 3+ -Li + substitution and Li x AlO y segregation in Al-LLZO ceramics. This work prepared Li7−3 x Al x La3 Zr2 O12 ( x = 0.00~0.40) ceramics via a conventional solid-state reaction method. The AC impedance and corresponding distribution of relaxation times (DRT) were analyzed combined with phase transformation, cross-sectional microstructure evolution, and grain boundary element mapping results for these Al-LLZO ceramics to understand the various ionic transportation levels in LLZO with different Al-doping amounts. The low conductivity in low Al-doped (0.12~0.28) LLZO originates from the slow Li + ion migration (1.4~0.25 μs) in the cubic-tetragonal mixed phase. On the other hand, LiAlO2 and LaAlO3 segregation occur at the grain boundaries of high Al-doped (0.40) LLZO, resulting in a gradual Li + ion jump (6.5 μs) over grain boundaries and low ionic conductivity. The Li6.04 Al0.32 La3 Zr2 O12 ceramic delivers the optimum Li + ion conductivity of 1.7 × 10 −4 S cm −1 at 25 °C.