Room-temperature miscibility gap in LixFePO4
Room-temperature miscibility gap in LixFePO4
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DOI：
10.1038/nmat1634
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发表时间：
2006-05
期刊：
影响因子：
41.2
通讯作者：
A. Yamada;Hiroshi Koizumi;S. Nishimura;N. Sonoyama;R. Kanno;M. Yonemura;Tatsuya Nakamura;Yo Kobayash
中科院分区：
文献类型：
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作者：
A. Yamada;Hiroshi Koizumi;S. Nishimura;N. Sonoyama;R. Kanno;M. Yonemura;Tatsuya Nakamura;Yo Kobayash
可充电锂离子电池是一种先进的储能系统。然而，高成本、安全隐患和化学不稳定性阻碍了其在大规模应用中的使用。另一种阴极材料LiFePO4解决了这些问题，但存在涉及强烈电子/空穴局部化的动力学问题。其中一个原因被认为是LixFePO4中固定的单价Fe3+PO4/Life2+PO4两相电极反应中的有限载流子密度。在这里，我们提供了实验证据，在室温下，Li_xFePO_4可以描述为Fe~(3+)/Fe~(2+)混价中间体LiαFePO_4和Li_1-−β_FePO_4相的混合物。用粉末中子衍射法对锂在各相中的占位数进行了修正，分别为α=0.0 5和1−β=0.89。通过构型熵的反常以及开路电压与恒定平衡电势的偏差，检测到了混溶间隙(0<；x<；α，1−β<；x<；1)以外的相应固溶体范围。这些发现鼓励在环境温度下进一步改进这类重要的化合物。
The rechargeable lithium-ion cell is an advanced energy-storage system. However, high cost, safety hazards, and chemical instability prohibit its use in large-scale applications. An alternative cathode material, LiFePO4, solves these problems, but has a kinetic problem involving strong electron/hole localization. One reason for this is believed to be the limited carrier density in the fixed monovalent Fe3+PO4/LiFe2+PO4two-phase electrode reaction in LixFePO4. Here, we provide experimental evidence that LixFePO4, at room temperature, can be described as a mixture of the Fe3+/Fe2+mixed-valent intermediate LiαFePO4and Li1−βFePO4phases. Using powder neutron diffraction, the site occupancy numbers for lithium in each phase were refined to beα=0.05 and 1−β=0.89. The corresponding solid solution ranges outside the miscibility gap (0<x<α,1−β<x<1) were detected by the anomaly in the configurational entropy, and also by the deviation of the open-circuit voltage from the constant equilibrium potential. These findings encourage further improvement of this important class of compounds at ambient temperatures.