化学
粉末衍射
正交晶系
拉曼光谱
相(物质)
结晶学
插层(化学)
衍射
堆积
分析化学(期刊)
电化学
X射线晶体学
离子
电极
晶体结构
无机化学
物理化学
光学
物理
有机化学
色谱法
作者
Benoît Mortemard de Boisse,Dany Carlier,Marie Guignard,Lydie Bourgeois,Claude Delmas
出处
期刊:Inorganic Chemistry
[American Chemical Society]
日期:2014-09-25
卷期号:53 (20): 11197-11205
被引量:213
摘要
The electrochemical properties of the P2-type NaxMn1/2Fe1/2O2 (x = 0.62) phase used as a positive electrode in Na batteries were tested in various voltage ranges at C/20. We show that, even if the highest capacity is obtained for the first cycles between 1.5 and 4.3 V, the best capacity after 50 cycles is obtained while cycling between 1.5 and 4.0 V (120 mAh g–1). The structural changes occurring in the material during the (de)intercalation were studied by operando in situ X-ray powder diffraction (XRPD) and ex situ synchrotron XRPD. We show that a phase with an orthorhombic P′2-type structure is formed for x ≈ 1, due to the cooperative Jahn–Teller effect of the Mn3+ ions. P2 structure type stacking is observed for 0.35 < x < 0.82, while above 4.0 V, a new phase appears. A full indexation of the XRPD pattern of this latter phase was not possible because of the broadening of the diffraction peaks. However, a much shorter interslab distance was found that may imply a gliding of the MO2 slab occurring at high voltage. Raman spectroscopy was used as a local probe and showed that in this new phase the MO2 layers are maintained, but the phase exhibits a strong degree of disorder.
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