Lithium Diffusion in Amorphous LixSi (x ≤ 0.4) Materials
Lithium Diffusion in Amorphous LixSi (x ≤ 0.4) Materials
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DOI：
10.4028/www.scientific.net/ddf.391.88
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发表时间：
2019-02
影响因子：
--
通讯作者：
F. Strauss;H. Schmidt
中科院分区：
文献类型：
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作者：
F. Strauss;H. Schmidt
锂硅化合物是一种很有前途的锂离子电池负极材料。Li在电极材料中的扩散对于充电/放电速率、最大比容量和可能的副反应是重要的。为了进一步开发用于锂离子电池的新型负极材料，理解原子输运的基本原理是非常重要的。研究了用离子束共溅射法制备的Li_xSi薄膜。在LixSi上进行了Li示踪自扩散实验|用二次离子质谱分析了退火前后的6LixSi异质结和6Li、7 Li同位素深度分布。通过比较实验的深度分布的扩散方程的解析解的扩散系数。LixSi中低Li浓度x < 0.1时的扩散系数在140至325 °C之间遵循阿克里尼乌斯定律，活化能为1.4 eV。一个陷阱限制扩散机制的建议，氢扩散氢化非晶硅。相反，对于x ≤ 0.4，在室温下沉积后直接观察到完全的同位素相互扩散。这些结果表明，随着Li含量的增加，扩散显著加速，如文献中通过理论计算所建议的[1]。
Lithium-silicon compounds are promising materials as negative electrodes in Li-ion-batteries. The diffusion of Li in electrode materials is important for charging/discharging rates, maximum specific capacity and possible side reactions. In order to further the development of novel negative electrode materials for lithium-ion batteries, understanding the basic principles of atomic transport is of high importance. Thin LixSi films were investigated, which were produced by reactive ion-beam co-sputtering of segmented elemental Li and Si targets. Li tracer self-diffusion experiments were done on LixSi|6LixSi heterostructures and 6Li and 7Li isotopes depth profiles were analysed by secondary ion mass spectrometry before and after annealing. Diffusivities were extracted by comparing the experimental depth profiles to analytical solutions of the diffusion equation. The diffusivities for low Li concentrations x < 0.1 in LixSi follow the Arrhenius law between 140 and 325 °C with an activation energy of 1.4 eV. A trap-limited diffusion mechanism is suggested, comparable to hydrogen diffusion in hydrogenated amorphous silicon. In contrast, for x ≈ 0.4 complete isotope interdiffusion is observed directly after deposition at room temperature. These results indicate a significant acceleration of diffusion with increasing Li content as suggested in literature by theoretical calculations [1].