Li ion dynamics in TiO2 anode materials with an ordered hierarchical pore structure--insights from ex situ NMR.
Li ion dynamics in TiO2 anode materials with an ordered hierarchical pore structure--insights from ex situ NMR.
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DOI：
10.1039/c3cp54586e
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发表时间：
2014-01
期刊：
影响因子：
--
通讯作者：
P. Bottke;Yu Ren;I. Hanzu;P. Bruce;M. Wilkening
中科院分区：
文献类型：
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作者：
P. Bottke;Yu Ren;I. Hanzu;P. Bruce;M. Wilkening
非原位核磁共振（NMR）测量进行了研究锂插层介孔氧化物（LixTiO 2）作为可充电锂离子电池的阳极材料的锂离子动力学。如最近所示，分级有序的TiO 2显示出优异的循环性能，并确保高的锂储存容量。(7)Li自旋-晶格弛豫NMR和受激回波NMR作为一种强有力的组合，从原子尺度的观点阐明了Li跳跃过程。为了确定原子Li跳跃率和微观活化能温度可变的SLR NMR测量，在实验室和旋转参考系，以及混合时间依赖的自旋对齐回波NMR测量进行。结果表明，适度的锂扩散率，然而，在锂离子电池中，这是补偿利用纳米结构的材料，大大减少了扩散长度。重要的是，虽然从四方对称到正交对称的相变发生在增加的电荷状态，扩散参数和激活能探测（0.4至0.5 eV）依赖于锂含量x弱于预期。因此，尽管x的值增加，正交相的演变似乎支持Li扩散率，而不是以负面的方式影响输运性质。这个有趣的特征可能对最近观察到的出色的循环行为非常有益。
Ex situ Nuclear Magnetic Resonance (NMR) measurements were carried out to study lithium ion dynamics in lithium intercalated mesoporous anatase (LixTiO2) serving as an anode material for rechargeable lithium-ion batteries. As has been shown recently, hierarchically ordered TiO2 shows excellent cycling performance and ensures a high lithium storage capacity. (7)Li spin-lattice relaxation NMR and stimulated echo NMR serve as a powerful combination to shed light on the Li hopping processes from an atomic-scale point of view. To determine atomic Li jump rates and microscopic activation energies temperature-variable SLR NMR measurements, in both the laboratory and rotating frame of reference, as well as mixing-time dependent spin-alignment echo NMR measurements were carried out. The results point to moderate Li diffusivities; however, in a lithium-ion cell this is compensated for by taking advantage of nm-structured materials with greatly reduced diffusion lengths. Importantly, although a phase transition from tetragonal symmetry to orthorhombic symmetry takes place at increased states of charge, the diffusion parameters and activation energies probed (0.4 to 0.5 eV) do depend weaker on Li content x than expected. Thus, despite the increased value of x, the evolution of the orthorhombic phase seems to support Li diffusivity rather than to affect the transport properties in a negative way. This interesting feature might be highly beneficial for the excellent cycling behavior observed recently.