锆酸镧锂固态电解质合成过程多因素影响  

The influences of multifactors in the synthesis progress on the characteristics of lithium lanthanum zirconate solid electrolytes

作　　者：雷蕾[1] 高鹏[1] 冯娜娜 蔡坤鹏[1] 张海[1] 张扬[1,2] LEI Lei;GAO Peng;FENG Nana;CAI Kunpeng;ZHANG Hai;ZHANG Yang(Key Laboratory for Thermal Science and Power Engineering of Ministry of Education,Department of Energy and Power Engineering,Tsinghua University,Beijing 100084,China;Shanxi Research Institute for Clean Energy Tsinghua University,Taiyuan 030000,Shanxi,China)

机构地区：[1]清华大学能源与动力工程系,热科学与动力工程教育部重点实验室,北京100084 [2]清华大学山西清洁能源研究院,山西太原030000

出　　处：《储能科学与技术》2023年第5期1625-1635,共11页Energy Storage Science and Technology

基　　金：国家自然科学基金项目(52176116);清华大学山西清洁能源研究院创新种子基金。

摘　　要：本工作采用化学共沉淀方法合成石榴石型Li_(7)La_(3)Zr_(2)O_(12)(LLZO)固态电解质,借助扫描电子显微镜(SEM)、X射线衍射(XRD)、电化学阻抗谱分析等系统研究了制备过程中烧结工艺、球磨、Al元素掺杂及压片压力等参数对样品颗粒尺寸、立方相稳定、致密化行为以及最终固态电解质锂离子电导率的影响。研究结果表明,热压烧结或湿法球磨均有利于提高固态电解质片的致密度,但样品的最终离子电导率受晶相结构影响表现不佳,相比而言干法球磨、常压烧结能够很好地合成立方相c-LLZO且结构中的杂相随温度升高而减少。为了解决随温度升高产生的颗粒粗化问题,由两步烧结代替一步烧结获得小粒径、高致密度固态电解质,同时增强了Al掺杂离子的稳定结构作用。最终,干法球磨、经750 MPa冷压成型、1100℃×6 h^-1200℃×20 h两步烧结获得的Al掺杂LLZO电解质离子电导率最高,达1.52×10^(-4)S/cm,这是其稳定立方结构和高致密度形貌共同作用的结果。本研究有助于推动陶瓷材料的制备与应用,为固态电池技术研发提供指导。Lithium lanthanum zirconate(Li_(7)La_(3)Zr_(2)O_(12),LLZO)solid-state electrolytes were synthesized using the chemical coprecipitation method.The effects of the operation parameters of the sintering process,ball milling,Al doping,and compression force on the grain boundary,phase,densification,and final Li+ion conductivity were evaluated using various characterization techniques,e.g.,scanning electron microscopy(SEM),powder X-ray diffraction(XRD),and electrochemical impedance spectroscopy(EIS)analyses.Wet ball milling using isopropanol as a grinding aid or hot-pressed sintering is beneficial for improving the density of LLZO pellets.However,the Li+ion conductivities at room temperature of the samples is low due to their poor structures.The cubic phase structure(c-LLZO)was synthesized via dry ball milling and pressure less sintering,and the crystal structures became pure as the sintering temperature increased.To solve the subsequent problem of the grain coarsening,a two-step sintering was proposed instead of one-step sintering to synthesize LLZO electrolytes with small particle sizes and high relative density.At the same time,the effect of Al doping in stabilizing the cubic structure was also enhanced using the two-step sintering.Finally,the as-prepared Al-doped LLZO solidstate electrolyte obtained via dry ball milling,cold pressing at 750 MPa,and two-step sintering of 1100℃for 6 h and 1200℃for 20 h exhibited the highest ionic conductivity(1.52×10^(-4)S/cm),mainly owing to its cubic garnet structure and the highest relative density.This research will shed light on preparing and applying LLZO-related ceramic materials,providing a solid basis and guidance for developing solid-state battery technology.

关 键 词：固态电解质 化学共沉淀 高温烧结 铝掺杂 球磨 

分 类 号：TM911.3[电气工程—电力电子与电力传动]