Insights into the Li Diffusion Mechanism in Si/C Composite Anodes for Lithium-Ion Batteries,ACS Applied Materials & Interfaces

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Insights into the Li Diffusion Mechanism in Si/C Composite Anodes for Lithium-Ion Batteries
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2021-04-30 , DOI: 10.1021/acsami.1c03366
Xiang Gao _{1,

2} , Wenquan Lu ₃ , Jun Xu _{1,

2}

Affiliation

Recently, Si/C composite materials have attracted enormous research interest as the most promising candidates for the anodes of next-generation lithium-ion batteries, owing to their high energy density and mechanical buffering property. However, the fundamental mechanism of Li diffusion behavior in various Si/C composite materials remains unclear, with our understanding limited by experimental techniques and continuum modeling methodologies. Herein, the atomic behavior of Li diffusion in the Si/C composite material is studied within the framework of density functional theory. Two representative structural mixing formats, that is, simple mixture mode and core–shell mode, are modeled and compared. We discover that the carbon material increases Li diffusion in silicon from 7.75 × 10^–5 to 2.097 × 10^–4 cm²/s. The boost is about 50% more obvious in the mixture mode, while the core–shell structure shows more dependence on the atomic structures of the carbon layer. These results offer new insights into Li diffusion behavior in Si/C composites and unlock the enhancing mechanism for Li diffusion in Si/C. This understanding facilitates the modeling of batteries with composite anodes and will guide the corresponding structure designs for robust and high-energy-density batteries.

中文翻译：

锂离子电池Si / C复合阳极中Li扩散机理的见解

近年来，由于其高能量密度和机械缓冲性能，Si / C复合材料作为下一代锂离子电池负极的最有希望的候选物而引起了巨大的研究兴趣。然而，由于我们的理解受到实验技术和连续建模方法的限制，在各种Si / C复合材料中Li扩散行为的基本机理仍不清楚。在此，在密度泛函理论的框架内研究了Li扩散在Si / C复合材料中的原子行为。对两种代表性的结构混合形式进行了建模和比较，即简单的混合模式和核-壳模式。我们发现，碳材料将Li在硅中的扩散从7.75×10 ^–5增加到2.097×10 ^–4厘米² /秒。在混合模式下，助推作用更明显约50％，而核-壳结构显示出对碳层原子结构的更多依赖性。这些结果为Si / C复合材料中Li的扩散行为提供了新的见解，并揭示了Si / C中Li扩散的增强机制。这种理解有助于对具有复合阳极的电池进行建模，并将指导用于坚固和高能量密度电池的相应结构设计。

更新日期：2021-05-12

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