Study on disordered structure and ionic diffusion in amorphous solids with non linear ultrasonic resonance

非线性超声共振研究非晶固体中的无序结构和离子扩散

• 批准号: 18540321
• 负责人: NAKAMURA Koichi
• 金额: $ 2.22万
• 依托单位: The University of Tokushima
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2006
• 资助国家: 日本
• 起止时间: 2006 至 2007
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18540321/
• 关键词: Lithium ion secondary battery; Piezoelectric material; Mechanical milling; NMR; Electrical conductivity; LiCoO_2; LiNbO_2

lithium cobalt oxide has been used as a cathode material of lithium ionic rechargeable battery so far and advanced cathode material with higher charge/discharge properties has been expected. In this study, our aim is to obtain new insights into structural change and ionic diffusion in amorphous like lithium compounds by using fly-AIRS-Al milling (MM) method to control disorder of crystal structure. Electrical resistivity of milled lithium cobalt oxide is analyzed by a Delve model on the basis of a single ion hopping process The results indicate that in lithium cobalt oxide prepared by MM the moderate MM condition with short milling time stimulates the lithium ionic diffusion through the defects, while the excessive MM condition with long milling time degrades the lithium ionic diffusion becalm a large number of defects induced by excessive MM effectively cut off diffusion path fir migrating lithium ions In lithium cobalt oxide, it hind that the NMR line width of ^7Li NMR spectrum becom … More es broader with increasing milling time. The MM process changes magnetic state of cobalt which is primitively a low spin configuration in the CoO_6 octahedron so that the line broadening is ascribed to the magnetic width due to tee magnetic moment of cobalt induced by MM.On the other hand, piezoelectric material LiNbO_3 and LiTaO_3 milled fir several hours show the motional narrowing of ^7Li-NMR line width at mom temperature. This means that disordered crystal structure induces a fast ionic diffusion in these materials. From the NMR spectrum analysis by decomposing spectrum, it hind that several percent of lithium in the materials would diffuse with much lower activation energy of 0.3 eV than primitive activation energy of 1.6 eV in non-milled LiNbO_3 from the analysis by decomposing NMR spectrum, consisting of a narrow and broad spectrum.Echo decay time, T_2 of propagating wave in a SiO_2 particle was measured over the temperature range from room temperature to 500 K by two-pulse phonon echo technique. The values of T_2 are temperature independent so that SiO_2 might be a standard material to detect energy loss out of particles contacting other fine powder samples. Phonon echo of SiO_2 particles is strongly affected by mixing fine particles. Only 0.5 mol% of LiNbO_3 fine powder suppresses phonon echo intensity at room temperature in the air, because the wet fine powder prevent from vibration of SiO_2 particles. Phonon echo intensity increases due to dehydrating fine powder at 393K because it makes vibration of SiO_2 particles better. However, a large amount of mixed fine powder has suppressed phonon echo intensity even at high temperatures so that disappearance of phonon echo does not depend only on humidity. A further study will plan to study an origin of disappearance of phonon echo in mixed particle system. Less

迄今为止，钴酸锂已被用作锂离子可充电电池的正极材料，并且期望具有更高充电/放电性能的先进正极材料在本研究中，我们的目的是获得对非晶结构变化和离子扩散的新见解。通过使用 Fly-AIRS-Al 铣削 (MM) 方法来控制铣削的钴酸锂的电阻率，通过 Delve 模型分析了类似锂化合物的情况。结果表明，在通过 MM 制备的钴酸锂中，适度的 MM 条件和较短的研磨时间会刺激锂离子通过缺陷的扩散，而过度的 MM 条件和较长的研磨时间会降低锂离子扩散的平静度。过量的MM引起的大量缺陷有效地切断了锂离子迁移的扩散路径。在钴酸锂中，这表明NMR线宽^7Li NMR 谱随着研磨时间的增加而变得更宽，MM 过程改变了钴的磁性状态，钴原本是 CoO_6 八面体中的低自旋构型，因此谱线变宽归因于 T 形磁矩造成的磁宽度。另一方面，压电材料LiNbO_3和LiTaO_3研磨几个小时后显示出运动变窄^7Li-NMR 在室温下的线宽，这意味着无序的晶体结构会在这些材料中引起快速的离子扩散。通过分解谱进行的 NMR 谱分析表明，材料中百分之几的锂会以低得多的活化率扩散。通过分解NMR谱分析，未研磨的LiNbO_3的能量为0.3 eV，比原始活化能1.6 eV高，由窄谱和宽谱组成。回波衰减时间，通过双脉冲声子回波技术在室温至 500 K 的温度范围内测量了 SiO_2 粒子中传播波的 T_2。T_2 的值与温度无关，因此 SiO_2 可能是检测能量损失的标准材料。 SiO_2 颗粒的声子回波受到混合细颗粒的强烈影响，仅 0.5 mol% 的 LiNbO_3 细粉就抑制了声子回波强度。室温空气中，由于湿细粉阻止了SiO_2颗粒的振动，393K下细粉脱水使SiO_2颗粒的振动更好，声子回波强度增加，但大量混合的细粉抑制了声子。即使在高温下，声子回声的消失也不仅仅取决于湿度，进一步的研究将计划研究混合粒子系统中声子回声消失的起源。

项目成果

NMR Study on Lit Ionic Motion in Li_xV_2O_5 (0.4

Li_xV_2O_5 (0.4<x<1.4)中锂离子运动的NMR研究

• 发表时间: 2008
• 作者: D. Nishioka; et. al.
• 通讯作者: et. al.

Li^+ ionic diffusion and vacancy ordering in 8-LiGa

8-LiGa 中的 Li^ 离子扩散和空位排序

• 发表时间: 2007
• 作者: Koichi; Nakamura; et. al.
• 通讯作者: et. al.

NMR Study on Lit Ionic Motion in Li_XV_20_5(0.4

Li_XV_20_5(0.4<x<1.4)中锂离子运动的NMR研究

• 发表时间: 2008
• 作者: D. Nishioka; et. al.
• 通讯作者: et. al.

Ionic diffusion and structural changes in lithium compounds

锂化合物中的离子扩散和结构变化

• 发表时间: 2007
• 作者: K. Nakamura; et. al.
• 通讯作者: et. al.

Changes of the structure and electrical conductivity in LiCoO_2 prepared by mechanical milling

机械球磨制备LiCoO_2结构和电导率的变化

• 发表时间: 2007
• 作者: H. Hirano; et. al.
• 通讯作者: et. al.