液相辅助烧结LLTO基固体电解质的制备与表征

Preparation and Characterization of LLTO-Based Solid Electrolytes by Liquid-Phase-Assisted Sintering

摘要: 在传统的电池系统中，有机液态电解液存在诸多安全问题，于是更安全高效的固态电解质成为了当前研究的热点。但全固态电池的发展与应用仍存在许多瓶颈，还存在着比如固体电解质的室温离子导电率比传统液体有机电解质的低两个数量级、研究者对充放电过程中的电极–电解质界面了解不够充足等问题。钛酸镧锂(Li_3xLa_2/3-xTiO₃)是目前被国内外广泛关注的全固态电池离子导体之一，x = 0.10时其晶粒电导率与有机液锂电解质的性能相近，可达到10⁻³ S/cm；然而只有10⁻⁵ S/cm数量级的晶界电导，成为了影响其总离子导电率的主要因素。本文探究了不同煅烧温度所制备的LLTO性能，并探究了加入不同比例的Li₂CO₃作为液相烧结助剂时，LLTO的烧结及离子电导率改善行为。实验结果表明，在1300℃烧结的Li_0.33La_0.57TiO₃总电导率取得最高的2.29 × 10⁻⁵ S/cm。添入1.0 wt%的Li₂CO₃对LLTO电学性能的影响最好，在烧结温度为1300℃时，总电导率达到4.92 × 10⁻⁵ S/cm，在1200℃烧结的样品总电导率为2.89 × 10⁻⁵ S/cm，均高于不加助烧剂时LLTO样品的总电导率。

Abstract: Compared with liquid electrolyte lithium-ion batteries, all-solid-state batteries have great po-tential in improving safety and obtaining high performance. However, there are still many bot-tlenecks in the development of all-solid-state batteries. The insufficient room-temperature ionic conductivity (10⁻⁵~10⁻³ S/cm) when compared to those of conventional organic liquid electro-lytes (10⁻² S/cm), the difficulty in informing an effective electrode-electrolyte interface and in-sufficient fundamental understanding of the interfacial process after charge/discharge all hin-der the practical application of such devices. Lithium strontium titanate (Li_3xLa_2/3-xTiO₃, repre-sented as LLTO) is a good kind of ionic conductor for all-solid-state batteries. Its bulk conductiv-ity at room temperature can reach 10⁻³ S/cm when x = 0.10, which is close to the conductivity of organic liquid lithium-ion conductor. In this work, LLTO solid electrolyte materials were synthe-sized at different temperatures and Li₂CO₃ was used as a liquid-phase sintering aid to improve the sintering behavior of LLTO and to enhance the ionic conductivity. The experimental results show that the optimum sintering temperature of Li_0.33La_0.57TiO₃ is 1300˚C and the total conduc-tivity at this temperature is 2.29 × 10⁻⁵ S/cm. The addition of Li₂CO₃ has a positive effect on the electrical properties of LLTO. When 1.0 wt% Li₂CO₃ is added, the total conductivity of LLTO reaches 4.92 × 10⁻⁵ S/cm and 2.89 × 10⁻⁵ S/cm at the sintering temperature of 1300 and 1200˚C, respectively, both of which are significantly higher than that of LLTO samples sintered at the same temperatures without the sintering aid.