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중심금속 혼성을 이용한 리튬금속인산염의 단결정 합성 및 구조분석
- Alternative Title
- Yongho Kee
- Author(s)
- 기용호
- Alternative Author(s)
- Yongho Kee
- Advisor
- 윤호섭
- Department
- 일반대학원 에너지시스템학부
- Publisher
- The Graduate School, Ajou University
- Publication Year
- 2013-02
- Language
- kor
- Keyword
- Lithum
- Alternative Abstract
- New mixed-metallic phosphates, Lix(V/Nb)2(PO4)3 , Lix(V1-yNby)PO5 (y= 0.4 or 0.6) and Li2Ti2(PO4)3 have been prepared and their crystal structures have been determined through single crystal X-ray diffraction techniques. I. Lix(V/Nb)2(PO4)3 Li metal phosphates, Li3M2(PO4)3 , have been widely investigated for secondary Li batteries. The positions and stoichiometries of Li ions in this phase play crucial roles to determine the efficiency of the system. In our group we have focused on the systematic approach toward the synthesis of new members of this family via partial substitution of metal sites with different oxidation states. As a result of our effort, we report here the synthesis and structural characterization of the new mixed-metal phosphates, Lix(V/Nb)2(PO4)3. Although they have various Li contents and positions, they share the common framework structure. The compounds in this phase, Lix(V/Nb)2(PO4)3 are isostructural and they crystallize in the space group Pbcn of the orthorhombic system with the channels in which Li ions stay. The title compounds consist of infinite chains of trans-corner-sharing VO6 octahedra, which are linked together by tetrahedral PO4 groups. Although the structure of (V/Nb)2(PO4)3 is comprised of the usual V/Nb-centered octahedra and P-centered tetrahedra, The stoichiometry of each metal can vary, [Lix(V/Nb)2(PO4)3 : x = 2.55, 2.48, 2.35, 2.22, 2.18, 1.86, 1.66, 0.96] and they seem to be adjusted by the sum of the oxidation states of each metal. Therefore, the classical charge balance of the title compound can be represented as [Li+]x[V3+]2-2y[Nb5+]2y[P5+]3[O2-]12. II. Lix(V1-yNby)PO5 (y= 0.4 or 0.6) Lithium vanadyl(IV) orthophosphate, LiVPO5, has been known. In attempts to design a new mixed-metallic phosphate from the known phase, the new mixed-metallic phases, Lix(V1-yNby )PO5, have been prepared as single crystals and they have been characterized through X-ray diffraction. The title compound consists of infinite chains of trans-corner-sharing VO6 octahedra, which are linked together by tetrahedral PO4 groups. In this compound the metal sites are occupied by statistically disordered V and Nb atoms. Although the structure of Lix(V1-yNby)PO5 is comprised of the usual V/Nb-centered octahedra and P-centered tetrahedra, its space group seems to be changed from Pnma to C2/c as the stoichiometry of Nb atom, y, decreases. The polyhedra share O atoms to form three-dimensional frameworks with large empty channels. The Li ions stay in these spaces and their stoichiometries seem to be adjusted by the sum of the oxidation states of each metal. Therefore, the classical charge balance of the title compound can be represented as [Li+]x[V4+]1-y[Nb5+]y[P5+][O2-]5. Appendix. Li2Ti2(PO4)3 Li metal phosphates, Li3M2(PO4)3 , have been widely investigated for secondary Li batteries. The positions and stoichiometries of Li ions in this phase play crucial roles to determine the efficiency of the system. In our group we have focused on the systematic approach toward the synthesis of new members of this family via partial substitution of metal sites with different oxidation states. As a result of our effort, we report here the synthesis and structural characterization of the new mixed-metal phosphates, Li2Ti2(PO4)3. The title compound is isostructural with Li2TiM(PO4)3 (M = Fe, Cr) and Li2FeZr(PO4)3 and has the same [Ti2(PO4)3]2 framework as the previously reported Li3-xM2(PO4)3 phases. The framework is built up from corner-sharing TiO6 octahedra and PO4 tetrahedra, one of which has 2 symmetry. The Li+ ions are located on one crystallographic position and reside in the vacancies of the framework. They are surrounded by four O atoms in a distorted tetrahedral coordination. The classical charge-balance of the title compound can be represented as [Li+]2[Ti4+][Ti3+][P5+]3[O2-]12. Appendix. Li3V2(PO4)3 The structure of trilithium divanadium(III) tris(orthophosphate), Li3V2(PO4)3 has been reinvestigated based on single-crystal data. The title compound adopt the Li3Fe2(PO4)3 structure type and the structure is composed of VO6 octahedra and PO4 tetrahedra connected by sharing O atoms to form the anionic three-dimensional framework, ∞3[V2(PO4)3]3-. The positions of the Li+ ions in the empty channels can be varied and bond valence calculations studies showed that structures similar to our work seem to be more stable compared with others. The classical charge balance of the title compound can be represented as [Li+]3[V3+]2[P5+]3[O2-]12.
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- Graduate School of Ajou University > Department of Energy Systems > 3. Theses(Master)
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