Critical Role of the Crystallite Size in Nanostructured Li4Ti5O12 Anodes for Lithium-Ion Batteries.
Critical Role of the Crystallite Size in Nanostructured Li4Ti5O12 Anodes for Lithium-Ion Batteries.
复制标题
DOI：
10.1021/acsami.8b05057
复制
发表时间：
2018-06
影响因子：
9.5
通讯作者：
Junpei Yue;Felix M Badaczewski;Pascal Voepel;Thomas Leichtweiss;Doreen Mollenhauer;W. Zeier;B. Smarsly
中科院分区：
文献类型：
--
作者：
Junpei Yue;Felix M Badaczewski;Pascal Voepel;Thomas Leichtweiss;Doreen Mollenhauer;W. Zeier;B. Smarsly
钛酸锂Li 4 Ti 5 O 12（LTO）被认为是锂离子电池中碳基负极的有前途的替代品。尽管LTO具有稳定的结构框架，但它也具有缺点，例如锂离子扩散缓慢和电子导电性差。为了改善LTO作为阳极材料的性能，纳米化是一种很有前途的方法，本文通过系统的实验方法研究了纳米化的影响。通过优化的溶剂热方法制备了具有高结晶度和4 - 12 nm晶粒尺寸的纯相多晶LTO纳米颗粒（NPs），并通过高分辨率透射电子显微镜、X射线衍射（XRD）、对分布函数（PDF）分析、拉曼光谱和X射线光电子能谱等技术进行了表征。通过广泛的电化学分析，包括充电/放电曲线，循环伏安法，和电化学阻抗谱，晶粒尺寸约为。7 nm被确定为最佳粒径。这样的NP表现出与具有较大微晶尺寸但具有更显著的界面电荷储存的NP一样好的可逆容量。通过将微晶尺寸减小到约4 nm，界面电荷储存显著增加，然而导致可逆容量的损失。使用从同步加速器XRD数据获得的PDF进行的深入结构表征表明，具有小晶粒尺寸的NP富集Ti，并且这种富Ti结构能够实现更高的Li存储。电化学表征证实了这一结果，并进一步指出了一个合理的原因，为什么在非常小的纳米颗粒（4 nm）中的较高的Li存储导致可逆容量的损失。
Lithium titanate Li4Ti5O12 (LTO) is regarded as a promising alternative to carbon-based anodes in lithium-ion batteries. Despite its stable structural framework, LTO exhibits disadvantages, such as the sluggish lithium-ion diffusion and poor electronic conductivity. To modify the performance of LTO as an anode material, nanosizing constitutes a promising approach and the impact is studied here by a systematical experimental approach. Phase-pure polycrystalline LTO nanoparticles (NPs) with high crystallinity and crystallite sizes ranging from 4 to 12 nm are prepared by an optimized solvothermal protocol and characterized by several state-of-the-art technologies, including high-resolution transmission electron microscopy, X-ray diffraction (XRD), pair distribution function (PDF) analysis, Raman spectroscopy, and X-ray photoelectron spectroscopy. Through a wide array of electrochemical analyses, including charge/discharge profiles, cyclic voltammetry, and electrochemical impedance spectroscopy, a crystallite size of approx. 7 nm is identified as the optimum particle size. Such NPs exhibit as good reversible capacity as the ones with larger crystallite sizes but with a more pronounced interfacial charge storage. By decreasing the crystallite size to about 4 nm, the interfacial charge storage increases remarkably, however resulting in a loss of reversible capacity. An in-depth structural characterization using the PDF obtained from synchrotron XRD data indicates an enrichment in Ti for NPs with the small crystallite sizes, and this Ti-rich structure enables a higher Li storage. The electrochemical characterization confirms this result and furthermore points to a plausible reason as to why a higher Li storage in very small nanoparticles (4 nm) results in a loss in the reversible capacity.