摘要
长期以来，安全性问题一直是制约锂电池发展和应用的瓶颈，用固体电解质取代液体电解质是克服这一瓶颈最有效的方法之一。高的离子电导率、低的电子电导率、良好的热稳定性是固体电解质应具备的理想性质，固体电解质Li7La3Zr2O12（LLZO）不仅具备这些性能，而且与锂负极接触时具有良好的电化学稳定性和很大的实用潜力，Li7La3Zr2O12一直是电池领域的研究热点。研究了氟化锂对Li7La3Zr2O12陶瓷的晶体结构、微观形貌、烧结温度和离子电导率的影响，XRD图谱表明，加入氟化锂燃料后，LLZO晶体结构没有发生明显变化。样品SEM照片显示，陶瓷材料具有特殊的微观结构，晶粒边界几乎消失，陶瓷微观结构中形成封闭的孔隙，使得晶粒边界几乎消失，总离子电导率较高。在LLZO陶瓷的密度中添加3%（质量分数）的氟化锂，即可实现离子电导率。
关键词： Li7La3Zr2O12；离子电导率；氟化锂；助烧剂
Abstract
For a long time, safety issues have been the bottleneck restricting the development and application of lithium batteries. Replacing liquid electrolytes with solid electrolytes is one of the most effective ways to overcome this bottleneck. High ionic conductivity, low electronic conductivity, and good thermal stability are ideal properties that solid electrolytes should have. The solid electrolyte Li7La3Zr2O12 (LLZO) not only has these properties, but also has good electrochemical stability in contact with Li anode and great practical potential, Li7La3Zr2O12has always been a research hotspot in the field of batteries. The effects of lithium fluoride on crystal structure, micromorphology, sintering temperature and ionic conductivity of Li7La3Zr2O12 ceramics were studied. The XRD pattern showed that the LLZO crystal structure did not change significantly when lithium fluoride fuel was added. Sample SEM photographs show that a special microstructure was found with grain boundaries virtually removed, creating closed pores in the ceramic microstructure, which contributes to negligible grain boundaries and high total ionic conductivity. With the addition of 3% (mass fraction) of lithium fluoride to the density of LLZO ceramics, ionic conductivity can be achieved.
Key words： Li7La3Zr2O12; Ionic conductivity; Lithium fluoride; Burnt aid
参考文献 References
[1] LI Jing, LV Xiaojuan, ZHANG Feng, et al. Research Progress of Solid-State Lithium-ion Electrolytes [J]. Acta Ceramics Sinica, 2021, 42(05): 717-731.
[2] Mu Daobin, Xie Huilin, Wu Borong. Research and progress of solid electrolyte for lithium-ion batteries [J]. Journal of Automotive Safety and Energy Conservation, 2020, 11(04).
[3] A WAKA J, TAKASHIMA A, KATAOKA K, et al. Crystal structure of fast lithium-ion-conducting cubic Li7La3Zr2O12 [J]. Chemistry Letters, 2011, 40(1): 60-62.
[4] I L’INA E A, ANDREEV O L, ANTONOV B D, et al. Morphology and transport properties of the solid electrolyte Li7La3Zr2O12 prepared by the solid-state and citrate–nitrate methods [J]. Journal of Power Sources, 2012, 201: 169-173.
[5] LU Chao, LI Mingming, WU Xiaoqiang, et al. Research Progress on Modification of Solid Inorganic Electrolyte Li7La3Zr2O12 [J]. Inorganic Chemicals Industry, 2021, 5, 3(11): 10-16+113.
[6] TANG Y, ZHANG Q, LUO Z, et al. Effects of Li2O-Al2O3-SiO2 system glass on the microstructure and ionic conductivity of Li7La3Zr2O12 solid electrolyte [J]. Materials Letters, 2017, 193: 251-254.
[7] IL’INA E A, PERSHINA S V, ANTONOV B D, et al. The influence of the glass additive Li2O -B2O3-SiO2 on the phase composition, conductivity, and microstructure of the Li7La3Zr2O12[J]. Journal of Alloys and Compounds, 2018, 765: 841-847.
[8] TADANAGA K, TAKANO R, ICHINOSE T, et al. Low temperature synthesis of highly ion conductive Li7La3Zr2O12-Li3BO3 composites [J]. Electrochemistry Communications, 2013, 33: 51-54.
[9] ANANI N, RAMAKUMAR S, KANNAN S, et al. Optimization oflithium content and sintering aid for maximized Li+ conductivit ductivity and density in Ta-doped Li7La3Zr2O12 [J]. Journal of the American Ceramic Society, 2015, 98(7): 2039-2046.