Thermally and Electrochemically Driven Topotactical Transformations in Sodium Layered Oxides NaxVO2

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• 作者：Christophe Didier ; Marie Guignard ; Matthew R. Suchomel ; Dany Carlier ; Jacques Darriet ; Claude Delmas
• 刊名：Chemistry of Materials
• 出版年：2016
• 出版时间：March 8, 2016
• 年：2016
• 卷：28
• 期：5
• 页码：1462-1471
• 全文大小：762K
• ISSN：1520-5002

文摘

Phase diagrams and structural transformations in the complex Na_xVO₂ system have been studied using electrochemical (de)intercalation and in situ and operando high resolution synchrotron powder diffraction. Starting from O′3-Na_1/2VO₂ obtained by sodium electrochemical deintercalation of O3-NaVO₂, the structural details of irreversible and reversible thermally driven transformations to P′3 and P3 type structures are presented. Subsequently, these P′3-Na_xVO₂ phases provide a platform for operando studies exploring the Na_xVO₂ phase diagram as a function of sodium electrochemical (de)intercalation. In this system, three single phase domains have been found: a line phase P′3-Na_1/2VO₂, one solid solution for 0.53 ≤ x ≤ 0.55 characterized by an incommensurate modulated structure, and a second solid solution for 0.63 ≤ x ≤ 0.65 with a defective structure resulting from a random stack of O′3 and P′3 layers. With further sodium intercalation (x > 0.65), the structure irreversibly transforms to the starting parent phase O3-NaVO₂. This work reveals new details about the diverse structural polymorphs found in sodium layered oxides used as electrode battery materials and the transitional pathways between them as a function of temperature and composition.