Monoclinic Phase Na3Fe2(PO4)3: Synthesis, Structure, and Electrochemical Performance as Cathode Material in Sodium-Ion Batteries

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• 作者：Yao Liu ; Yirong Zhou ; Junxi ZhangYongyao Xia ; Tong ChenShiming Zhang
• 刊名：ACS Sustainable Chemistry & Engineering
• 出版年：2017
• 出版时间：February 6, 2017
• 年：2017
• 卷：5
• 期：2
• 页码：1306-1314
• 全文大小：865K
• ISSN：2168-0485

文摘

Sodium iron phosphate (Na₃Fe₂(PO₄)₃) as cathode material for sodium-ion batteries has been synthesized through a simple method of a solid state reaction. It crystallizes in a monoclinic structure in the space group C2/c. The morphology of the as-prepared sample has been investigated by scanning electron microscopy and transmission electron microscopy. The charge/discharge curves show a very flat plateau at about 2.5 V (vs Na/Na⁺). The initial specific discharge capacity is 61 mAh g^–1 and remains at 57 mAh g^–1 after 500 cycles at a current rate of 1 C. X-ray photoelectron spectroscopy measurements indicate that not all of the Fe³⁺ of Na₃Fe₂(PO₄)₃ is reduced during the electrochemical process. The ex-situ X-ray diffraction measurements were applied to research the mechanism of sodium-ion storage; the results indicated that the Na₃Fe₂(PO₄)₃ compound partly transformed into Na₄Fe₂(PO₄)₃ and Na_3+xFe₂(PO₄)₃ compound. These results testify to the potential of monoclinic Na₃Fe₂(PO₄)₃ as a cathode material in sodium-ion batteries.