Sodium Intercalation Behavior of Layered NaxNbS2 (0 鈮?x 鈮?1)

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• 作者：Youhao Liao ; Kyu-Sung Park ; Penghao Xiao ; Graeme Henkelman ; Weishan Li ; John B. Goodenough
• 刊名：Chemistry of Materials
• 出版年：2013
• 出版时间：May 14, 2013
• 年：2013
• 卷：25
• 期：9
• 页码：1699-1705
• 全文大小：459K
• 年卷期：v.25,no.9(May 14, 2013)
• ISSN：1520-5002

文摘

A layered sulfide, Na_0.5NbS₂ (space group: P6₃/mmc), was synthesized by a conventional solid-state reaction as an electrode material for a Na-ion battery. Galvanostatic Na insertion/extraction was performed to characterize the system Na_xNbS₂ (0 鈮?x 鈮?1.0) operating on the Nb(IV)/Nb(III) redox couple. Although the system shows a high specific capacity of 143.6 mAh g^鈥?, the voltage profile is not suitable with a signature of Na/vacancy ordering at x = 0.5. First-principles calculation was applied to reveal possible structures of Na_xNbS₂ and describe the corresponding electrochemical properties. The calculated Na binding energies and voltages are in good agreement with experimental charge/discharge voltages. We also found a possible atomic arrangement of Na/vacancy ordering in Na_0.5NbS₂. Although layered NaMS₂ systems allow full sodium intercalation, the strong Na⁺鈥揘a⁺ intralayer interaction induces layer gliding and Na⁺-ion ordering that create undesirable steps in the voltage profile.

Keywords:

Na_xNbS₂; Na/vacancy ordering; sodium ion battery