Al₂O₃辅助烧结LLZO基固体电解质的制备与表征

Preparation and Characterization of LLZO-Based Solid Electrolytes by Al₂O₃-Assisted Sintering

摘要: 锂离子电池市场的快速增长，使得人们对于锂离子电池性能和稳定性的要求变得更高。传统的液态有机电池容易短路引发爆炸和火灾，存在严重的安全隐患。与使用液态电解质的传统锂离子电池相比，全固态锂离子电池具有很好的稳定性和安全性，因而受到了广泛的关注。石榴石型固体电解质Li₇La₃Zr₂O₁₂(LLZO)具有较高的离子电导率，被认为是一种很有前景的固体电解质。然而，LLZO的合成往往需要较高的温度，但高温又会导致锂大量挥发，从而使得样品的离子电导率下降。因此，如何降低LLZO的合成温度和提高其电导率是一个重要的课题。本文中，我们通过引入Al₂O₃作为烧结助剂，利用传统的固相法合成了具有石榴石型结构的固体电解质Li_6.1Ga_0.3La₃Zr₂O₁₂。与未引入Al₂O₃的样品相比，在引入Al₂O₃后，不仅降低了烧结温度，而且显著提高了离子电导率。我们发现添加少量的Al₂O₃作为助烧剂可以将烧结温度从1100℃降低到1050℃左右。最后，当Al₂O₃含量为2 wt%时，室温离子电导率最高，为1.28 mS/cm。

Abstract: The rapid growth of the lithium-ion battery market has led to higher requirements for the performance and stability of lithium-ion batteries. Traditional liquid organic batteries are prone to short-circuits and cause explosions and fires, posing serious safety hazards. Compared with traditional Li-ion batteries using liquid electrolytes, all-solid-state Li-ion batteries have received extensive attention due to their good stability and safety. Garnet-type solid electrolyte Li₇La₃Zr₂O₁₂ (LLZO) has high ionic conductivity and is considered to be a promising solid electrolyte. However, the synthesis of LLZO often requires high temperature, but the high temperature could lead to a large amount of lithium evaporation, thus reducing the ionic conductivity of the LLZO-based samples. Therefore, how to reduce the synthesis temperature of LLZO and improve its ionic conductivity is an important topic. Here, we synthesized solid electrolytic Li_6.1Ga_0.3La₃Zr₂O₁₂ with garnet-type structure by traditional solid-phase method and introducing Al₂O₃ as a sintering aid. Compared with the samples without sintering aid, the introduction of Al₂O₃ not only reduces the sintering temperature, but also significantly increases the ionic conductivity. It is found that adding a small amount of Al₂O₃ as an additive can reduce the sintering temperature from 1100°C to around 1050˚C. Finally, we found, when the Al₂O₃ content is 2 wt%, the room-temperature ionic conductivity is the highest at 1.28 mS/cm.