SiO44-对Li3Sc2(PO4)3快离子导体的阴离子替代效果研究

Li3Sc2(PO4)3因具有有利的离子传导通道、低的电子电导率和高的稳定性而成为全固态锂离子电池用固体电解质最具竞争力的材料之一,然而这一化合物只有在245℃以上的γ相才具有快离子传导特性。人们主要采用Zr4+、Ti4+等阳离子部分取代其中的Sc3+以改善材料的室温电导率,有关该化合物PO43-阴离子替代的报道还很少。本研究试图利用机械研磨技术,通过向Li3Sc2(PO4)3原料混合物中加入适量SiO2,以期能够实现对该化合物的部分阴离子替代。研究结果表明:所制备的Li3+xSc2(PO4)3-x(SiO4)x(x=0~0.6)系列化合物在x=0.15时电导率达到最大值,σ298=9.55×10-4 S.m-1,离子传导激活能达到最小值45.06 kJ.mol-1。29Si MAS-NMR测试结果证实所加入的SiO2主要以SiO4]四面体形式存在替代Li3Sc2(PO4)3中部分PO4]四面体。

Effect of Anion Substitution of SiO44- for Li3Sc2(PO4)3 Superion Conductor

Li3Sc2(PO4)3 was one of the most powerful solid state electrolytes for lithium ion batteries because of its favourable channels for ion conduction,very low electronic conductivity and high stability in air.However,the compound only presented superionic conductivity at temperatures higher than 245 ℃.Cation substitution of Zr4+,Ti4+ and so on for partial Sc3+ was generally adopted in order to increase its room-temperature ionic conductivity,and researches on anion substitution for PO43-in the Li3Sc2(PO4)3 compound were little.In this research,we introduced some SiO2 into starting-materials mixture of the Li3Sc2(PO4)3 ceramics by mechanical milling,and tried to substitute for partial PO43-.Our results proved that the prepared Li3+xSc2(PO4)3-x(SiO4)x(x=0～0.6) compounds showed the highest ion conductivity of 9.55×10-4 S·m-1 at 298 K,as well as the lowest activation energy of 45.06 kJ·mol-1.Furthermore,the 29Si MAS-NMR spectrum indicated that the added SiO2 mainly existed in the form of tetrahedra substituting for tetrahedra in the compound.