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Structure - Electrode Activity Relationship in Triphyllite - Related Compounds

闪石相关化合物的结构-电极活性关系

基本信息

批准号：
16350108
负责人：
YAMADA Atsuo
金额：
$ 10.18万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

项目摘要

A series of synthetic (Mn_yFe_<1-y_)PO_4(y<0.8) phases were obtained by chemical oxidation of crystallized isotypic Li(Mn_yFe_<1-y>)PO_4 under optimized conditions. All samples exhibit antiferromagnetism but the decrease in Neel temperature is more than 7 times larger in (Mn_yFe_<1-y>)PO_4 than in Li(Mn_yFe_<1-y>)PO_4. This was discussed in terms of the asymmetric superexchange interaction by an unusual synergetic effect of Jahn-Teller distortion and edge-shared interconnection with PO_4 tetrahedra.We provide firm experimental evidence that Li_xFePO_4 at room temperature can be described as a mixture of the Fe^<3+>/Fe^<2+> mixed-valent intermediate Li_αFePO_4 and Li_<1-β>FePO_4 phases with surprisingly large values of α and β. Using powder neutron diffraction, the site occupancy numbers for lithium in each phase were refined to be α=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 … More 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.Rietveld analysis for the powder neutron diffraction profile for LiFePO_4 was performed. Tensor elements of the unisotropic thermal factor showed the principal axis of the lithium vibration is toward the face shared vacant tetrahedral space. This is consistent with the theoretical prediction ; lithium ions diffuse along curved one-dementional chain along b-axis. Impact of temperature on the phase diagram of LixFePO_4 with > 200nm particle size was slight under the unmixing line around 200 C. While the reduction in particle size down to <100 nm seems to have significant effect to the room temperature miscibility gap. The thermodynamic concepts for the extended solution in smaller particles are discussed, followed by a very high rate capability observed for the small spherical particles <80nm. Less

在优化条件下，通过晶化的同型Li(MnYFe&lt；1-y&gt；)PO4的化学氧化，得到了一系列合成的(MnYFe&lt；1-y)PO4(y&lt；0.8)相。所有样品都表现出反铁磁性，但(Mn_yFe_&lt；1-y&gt；)PO_4的Neel温度降幅是Li(Mn_yFe_&lt；1-y&gt；)PO_4的7倍以上。通过Jahn-Teller扭曲和与PO_4四面体的边共享互连的不对称超交换作用，讨论了这一现象。我们提供了确凿的实验证据，证明室温下Li_xFePO_4可以描述为Fe^&lt；3+&gt；/Fe&lt；2+&gt；混价中间体Li_αFePO_4和Li_β&GT；FePO_4相，α和β值大得惊人。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α中的异常检测到了混溶间隙(0&lt；x&lt；β，1-…&lt；x&lt；1)以外的相应固溶体范围更多的熵，以及开路电压与恒定平衡电势的偏差。这些发现鼓励了这类重要化合物在常温下的进一步改进。对LiFePO_4的粉末中子衍射谱进行了Rietveld分析。张量单元的各向同性热因子表明，锂振动的主轴是朝向表面共享的空位四面体空间。这与理论预测是一致的，锂离子沿着弯曲的一维链沿b轴扩散。在200℃附近的分解线上，温度对LixFePO_4的相图影响不大，但当粒径减小到&lt；100 nm时，对室温混溶间隙有明显的影响。讨论了在较小颗粒中扩展溶液的热力学概念，然后在较小的球形颗粒中观察到非常高的速率能力&lt；80 nm。较少

项目成果

期刊论文数量（25）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Electrochemical, magnetic, and structural investigation of the Li_<1-x>(Mn_yFe_<1-y>)PO_4 olivine phases

Li_<1-x>(Mn_yFe_<1-y>)PO_4橄榄石相的电化学、磁性和结构研究

DOI：
发表时间：
2006
期刊：
Chem. Mater. 18
影响因子：
0
作者：
A.Yamada;Y.Takei;et al.
通讯作者：
et al.

Magnetic properties of Li(Mn_yFe_<l-y>)PO_4 and its delithiated phases

Li(Mn_yFe_<l-y>)PO_4及其脱锂相的磁性

DOI：
发表时间：
2005
期刊：
Appl. Phys. Lett 87
影响因子：
0
作者：
A.Yamada;Y.Takei;et al.
通讯作者：
et al.

電池革新が拓く次世代電源

电池创新引领的下一代电源

DOI：
发表时间：
2006
期刊：
影响因子：
0
作者：
N.Arimitsu;A.Nakajima;K.Katsumata;T.Shiota;N.Yoshida;T.Watanabe;Y.Kameshima;K.Okada;M.K.I.Senevirathna;G.R.A.Kumara;G.R.A.Kumara;B.Onwona-Agyeman;辰巳国昭他
通讯作者：
辰巳国昭他

Magnetic properties of Li(Mn_yFe_<i-y>)PO4 and its delithiated phases

Li(Mn_yFe_<i-y>)PO4及其脱锂相的磁性