Ce掺杂的石榴石固态电解质改性研究

Research on Modification of Ce-Doped Garnet Solid-State Electrolyte

摘要: 在众多无机固态电解质材料中，石榴石型Li₇La₃Zr₂O₁₂ (LLZO)因具备宽电化学稳定窗口、优异的化学稳定性及热稳定性，被广泛认为是最具产业化应用潜力的候选材料之一。尽管LLZO拥有诸多优势，但仍存在显著短板：较低的室温离子电导率限制了其实际产业化应用进程，需通过晶界改性等针对性调控手段加以解决。在此通过Ce元素掺杂的LLZTO形成双掺杂石榴石固态电解质Li_6.6Ce_xLa₃Zr_1.6−xTa_0.4O₁₂ (Ce_xLLZTO, x = 0.08, 0.1, 0.2, 0.3, 0.4)，探究了Ce元素的掺杂含量对于Ce_xLLZTO的影响。锂过量15%、预烧结温度在850℃下有助于提升石榴石固态电解质的离子电导率和降低体相阻抗与晶界阻抗。随着Ce元素掺杂含量的增加，Ce_xLLZTO逐渐由四方相转变为立方相，当x = 0.3时达到最高离子电导率4.2 × 10⁻⁴ S∙cm⁻¹。

Abstract: Among a variety of inorganic solid-state electrolytes, garnet-type Li₇La₃Zr₂O₁₂ (LLZO) is recognized as one of the most promising candidates for industrial application owing to its wide electrochemical stability window, superior chemical stability and thermal stability. Although LLZO has many advantages, it possesses obvious deficiencies. Its low room-temperature ionic conductivity hinders its practical industrialization, which can be ameliorated via targeted modification approaches such as grain boundary regulation. In this study, dual-doped garnet solid-state electrolytes Li_6.6Ce_xLa₃Zr_1.6−xTa_0.4O₁₂ (Ce_xLLZTO, x = 0.08, 0.1, 0.2, 0.3, 0.4) were synthesized by cerium doping into LLZTO, and the influence of cerium doping content on the performance of Ce_xLLZTO was systematically investigated. A 15% excess of lithium combined with pre-sintering at 850˚C can enhance the ionic conductivity and reduce the bulk impedance and grain boundary impedance of the garnet electrolytes. With the increase in Ce doping amount, the crystalline phase of Ce_xLLZTO gradually transforms from tetragonal to cubic. The optimal ionic conductivity of 4.2 × 10⁻⁴ S∙cm⁻¹ is achieved at x = 0.3.