Unveiling the roles of alumina as a sintering aid in Li‐Garnet solid electrolyte. (29th May 2020)

• Record Type: Journal Article
• Authors: Zhang, Kangkang; Xu, Tao; Zhao, Hailei; Zhang, Saisai; Zhang, Zijia; Zhang, Yang; Du, Zhihong; Li, Zhaolin
• Is Part Of: International journal of energy research. Volume 44:Number 11(2020)
• Page Start: 9177
• Page End: 9184
• Publication Date: 2020-05-29
• Subjects: alumina additive -- ionic conductivity -- Li7La3Zr2O12 garnet electrolyte -- sintering; Power resources -- Periodicals; Power (Mechanics) -- Periodicals; Power resources -- Research -- Periodicals; 621.042
• DOI: 10.1002/er.5562
• Languages: English
• ISSNs: 0363-907X

Abstract

Summary: The superiority of garnet‐type solid electrolyte makes it one of most promising candidates for all‐solid‐state lithium batteries. Several studies show that introduction of alumina during synthesis can greatly improve the density and ionic conductivity of garnet electrolyte Li7 La3 Zr2 O12 (LLZO), but the reason of poor sinterability of LLZO is still unclear. In this study, we reveal that lithium carbonate, which has a high decomposition temperature and covers on the particle surface of LLZO, is the underlying reason that handicaps the sinterability of Li‐Garnet electrolyte in air. The addition of alumina promotes the decomposition of Li2 CO3 (down to 400°C) and the concomitant product LiAlO2, as a fast Li‐ion conductor, facilitates the sintering process and bulids a fast Li‐ion conducting network along the grain‐boundaries, significantly increasing the ionic conductivity of Li‐Garnet electrolyte. By the conventional solid state sintering, the 10 mol% Al2 O3 modified Li6.4 La3 Zr1.4 Ta0.6 O12 (LLZT‐10Al2 O3 ) electrolyte reaches a relative density of 96% and shows a conductivity of 0.31 mS cm −1 at room temperature. The prepared LLZT‐10Al2 O3 electrolyte exhibits a good wetting property toward metallic Li electrode with an interfacial resistance of 59 Ω cm 2 compared to 1270 Ω cm 2 for LLZT/Li. This work provides a fundamental understanding and a valuable strategy for developing high performance garnet‐type electrolyte for all‐solid‐state lithium batteries. Abstract : Al2 O3 promotes the decomposition of Li2 CO3 formed on Li‐Garnet particle surface, and the elimination of Li2 CO3 boosters the sintering of Li‐Garnet electrolyte. The reaction of Al2 O3 with Li2 CO3 produces a Li‐ion conductor, LiAlO2, and the product LiAlO2 decreases grain‐boundary resistance. Al2 O3 addition significantly increases the total conductivity of electrolyte.