Studies on spinel cobaltites, FeCob>2b>Ob>4b> and MgCob>2b>Ob>4b> as anodes for Li-ion batteries

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• 作者：Yogesh Sharma ; N. Sharma ; G.V. Subba Rao ; B.V.R. Chowdari
• 关键词：Spinel ; FeCob>2b>Ob>4b> ; MgCob>2b>Ob>4b> ; Anode materials ; Li-ion batteries
• 刊名：Solid State Ionics
• 出版年：2008
• 期刊代码：96_01672738
• 类别：ch
• 出版时间：30 June 2008
• 卷：179
• 期：15-16
• 页码：587-597
• 文件大小：1148 K

摘要

The compounds, FeCob>2b>Ob>4b> and MgCob>2b>Ob>4b> are synthesized by the urea combustion and oxalate decomposition method, respectively. Powder X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED) and X-ray photoelectron spectroscopy (XPS) have been used to characterize the phases. Scanning electron microscopy (SEM) showed the distinct features in the morphology, submicron-size of FeCob>2b>Ob>4b> and needle-shaped particles of MgCob>2b>Ob>4b>. Galvanostatic cycling was carried out in the voltage range 0.005–3.0 V vs. Li at a current of 60 mA g^{− 1} (~ 0.08 C) up to 50 cycles. The observed first-cycle charge capacities are, FeCob>2b>Ob>4b>: 827 mA h g^{− 1} (corresponding to theoretical 7.3 mol of Li per mole of FeCob>2b>Ob>4b>) and MgCob>2b>Ob>4b>: 736 mA h g^{− 1} (5.7 Li). At the end of 50 cycles, FeCob>2b>Ob>4b> retained ~ 90%of the first-charge capacity, and a coulombic efficiency of ~ 99%is noted between 20 and 50 cycles. MgCob>2b>Ob>4b> showed extensive capacity-fading and retained only 0.9 mol of cyclable Li in the range 28–50 cycles. These results show that Fe is a better counter ion than Mg. The average charge and discharge voltages are ~ 2.0 V and ~ 1.2 V, respectively, for both the compounds. Cyclic voltammograms, up to 12 cycles on FeCob>2b>Ob>4b> complement the galvanostatic cycling results. Impedance studies were carried out on FeCob>2b>Ob>4b> at various voltages during the first cycle and after 10 cycles, and the data have been interpreted.