In situ synchrotron diffraction study of charge–discharge mechanism of sol–gel synthesized LiM0.5Mn1.5O4 (M = Fe, Co)
In situ synchrotron diffraction study of charge–discharge mechanism of sol–gel synthesized LiM0.5Mn1.5O4 (M = Fe, Co)
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DOI：
10.1016/j.jpowsour.2012.06.032
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发表时间：
2012-11
影响因子：
9.2
通讯作者：
Aiswarya Bhaskar;N. Bramnik;D. Trots;H. Fuess,;H. Ehrenberg
中科院分区：
文献类型：
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作者：
Aiswarya Bhaskar;N. Bramnik;D. Trots;H. Fuess,;H. Ehrenberg
标称成分为 LiM0.5Mn1.5O4(M = Fe, Co) 的样品通过溶胶-凝胶工艺合成，并在 1000 °C 下进行后热处理。与镍类似物相比，钴和铁掺杂样品在 55°C 下表现出快速降解，在 C/2 倍率下 70 个循环后，钴和铁取代样品在室温下的平均容量保留分别为 ∼55% 和 ∼59%。当以截止电流速率 C/5 循环时，Fe 掺杂尖晶石的 PITT 图显示出放电容量的尖峰，这是由于动力学限制而假设的，当以较慢的充放电速率循环时，尖峰消失。检查了这一假设，并通过原位同步加速器衍射详细研究了 Fe 和 Co 掺杂尖晶石的 Li 嵌入/脱嵌机制。在这两种情况下，充放电过程都是通过固溶体机制发生的，尽管铁掺杂尖晶石在放电过程中表现出两相区。
Samples with nominal composition LiM0.5Mn1.5O4(M = Fe, Co) were synthesized via a sol–gel process with a post thermal treatment at 1000 °C. In contrast to the Ni-analogue Co- and Fe-doped samples show a fast degradation at 55 °C with an average capacity retention at RT of ∼55% for the Co- and of ∼59% for the Fe-substituted samples, respectively after 70 cycles for a C/2 rate. The PITT plots of the Fe doped spinel exhibited a sharp peak in the discharge capacity when cycled with a cut-off current rate C/5, which was assumed due to a kinetic limitation, which disappears when cycled at slower charge–discharge rates. This assumption was checked, and the mechanisms of Li-intercalation/-de-intercalation were investigated in detail for the Fe and Co doped spinels by in situ synchrotron diffraction. The charge–discharge processes take place through a solid-solution mechanism in both cases, though the Fe-doped spinel exhibits a two-phase region during the discharge.