Effects of vanadium substitution on the cycling performance of olivine cathode materials

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• 作者：Mao-Sung Chen ; She-huang Wu ; Wei Kong Pang
• 关键词：Cathode material ; Lithium iron phosphate ; Olivine structure ; Vanadium substitution
• 刊名：Journal of Power Sources
• 出版年：2013
• 出版时间：1 November, 2013
• 年：2013
• 卷：241
• 期：Complete
• 页码：690-695
• 全文大小：2106 K

文摘

V-substituted LiFePO₄ (LiFe_1?xV_xPO₄, 0?¡Ü?x?¡Ü?0.10) powders are prepared via a solution method. The compositions, crystalline structure, morphology of the prepared powders are systemically investigated with inductive couple plasma-option emission spectrometry (ICP-OES), synchrotron radiation X-ray diffraction (s-XRD), X-ray Absorption Spectroscopy (XAS) and field emission-transmission electron microscopy (FE-TEM). Results of s-XRD and Rietveld analysis reveal that olivine phase is observed exclusively for LiFe_1?xV_xPO₄ (x?¡Ü?0.05) samples, whereas a minor amount of monoclinic Li₃V₂(PO₄)₃ is detected in the prepared LiFe_0.93V_0.07PO₄ and LiFe_0.90V_0.10PO₄ samples. It is also found that the lattice parameters of olivine structure and average Li-O and M-O (M?=?Fe or V) bond lengths slightly increase and decrease with the amount of V substitution, recommending an enhanced lithium diffusivity in the structure. Results of XAS study suggest that V ions occupy octahedral sites (4c) of Fe in LiFePO₄ structure with valence of 3+, showing good agreement with shortened M-O bonds determined in Rietveld analysis. As a result of V substitution, LiFe_1?xV_xPO₄, (0?¡Ü?x?¡Ü?0.10) cathodes exhibit better electrochemical performance, such as discharge capacity, rate capability, and cycling performance at both room and elevated temperatures.