Wang Guoqing, Xu Bo, Shi Jing, Wu Musheng, Su Haibin, Ouyang Chuying
Department of Physics, Laboratory of Computational Materials Physics, Jiangxi Normal University, Nanchang 330022, PR China.
Department of Chemistry, Hongkong University of Science and Technology, Hongkong, PR China.
Nanoscale. 2019 Aug 7;11(29):14042-14049. doi: 10.1039/c9nr03986d. Epub 2019 Jul 16.
Li ion transport is very important to the rate capability of electrode materials in Li ion batteries. For Si anodes, due to huge structural changes of Si structures during the process of charging and discharging, Li ion transport is essentially affected by the Si internal microstructures. Herein, we studied the effect of Si microstructures on Li ion diffusion in Li-Si alloys using first-principles molecular dynamics calculations. Our results demonstrate that the Li diffusion coefficients are closely related to the aggregation degree of Si atoms, regardless of whether it is the low Li concentration phase LiSi or the high Li concentration phase LiSi under consideration. Furthermore, through counting the number of Si microstructures, such as rings, chains and small clusters, the relationship between the aggregation degree of Si atoms and the number of Si microstructures is established. A large number of Si microstructures corresponds to the low aggregation degree of Si atoms, thus resulting in small Li diffusion coefficients due to the strong interaction between Li and Si atoms. Conversely, a small number of Si microstructures originates from the high aggregation degree of Si atoms, consequently leading to large Li diffusion coefficients. Our study provides a deep insight into the relationship between the Li ion diffusion and the Si distribution, which facilitates the performance improvement of future Si anode materials.
锂离子传输对锂离子电池中电极材料的倍率性能非常重要。对于硅负极，由于硅结构在充放电过程中发生巨大的结构变化，锂离子传输本质上受到硅内部微观结构的影响。在此，我们使用第一性原理分子动力学计算研究了硅微观结构对锂 - 硅合金中锂离子扩散的影响。我们的结果表明，无论考虑的是低锂浓度相LiSi还是高锂浓度相LiSi，锂扩散系数都与硅原子的聚集程度密切相关。此外，通过计算硅微观结构（如环、链和小簇）的数量，建立了硅原子聚集程度与硅微观结构数量之间的关系。大量的硅微观结构对应于硅原子的低聚集程度，由于锂与硅原子之间的强相互作用，导致锂扩散系数较小。相反，少量的硅微观结构源于硅原子的高聚集程度，从而导致较大的锂扩散系数。我们的研究深入洞察了锂离子扩散与硅分布之间的关系，这有助于未来硅负极材料性能的提升。
