期刊
CHEMISTRY OF MATERIALS
卷 25, 期 9, 页码 1699-1705出版社
AMER CHEMICAL SOC
DOI: 10.1021/cm400150u
关键词
NaxNbS2; Na/vacancy ordering; sodium ion battery
资金
- Robert A. Welch Foundation [F-1066]
- China Scholarship Council
- NNSFC-NSFGP [U1134002]
- NSFGP [10351063101000001]
- program Understanding Charge separation and Transfer at Interfaces in Energy Materials (EFRC:CST), an Energy Frontier Research Center
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-SC0001091]
A layered sulfide, Na0.5NbS2 (space group: P6(3)/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 NaxNbS2 (0 <= x <= 1.0) operating on the Nb(IV)/Nb(III) redox couple. Although the system shows a high specific capacity of 143.6 mAh g(-1), 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 NaxNbS2 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 Na0.5NbS2. Although layered NaMS2 systems allow full sodium intercalation, the strong Na+-Na+ intralayer interaction induces layer gliding and Na+-ion ordering that create undesirable steps in the voltage profile.
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