National Laboratory of Solid State Microstructures, College of Engineering and Applied Sciences, Jiangsu Key Laboratory of Artificial Functional Materials, Nanjing University, Nanjing 210093, P. R. China.
Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA.
Sci Adv. 2019 Nov 15;5(11):eaax0651. doi: 10.1126/sciadv.aax0651. eCollection 2019 Nov.
Silicon demonstrates great potential as a next-generation lithium ion battery anode because of high capacity and elemental abundance. However, the issue of low initial Coulombic efficiency needs to be addressed to enable large-scale applications. There are mainly two mechanisms for this lithium loss in the first cycle: the formation of the solid electrolyte interphase and lithium trapping in the electrode. The former has been heavily investigated while the latter has been largely neglected. Here, through both theoretical calculation and experimental study, we demonstrate that by introducing Ge substitution in Si with fine compositional control, the energy barrier of lithium diffusion will be greatly reduced because of the lattice expansion. This effect of isovalent isomorphism significantly reduces the Li trapping by ~70% and improves the initial Coulombic efficiency to over 90%. We expect that various systems of battery materials can benefit from this mechanism for fine-tuning their electrochemical behaviors.
硅由于其高容量和元素丰度，在下一代锂离子电池阳极中显示出巨大的潜力。然而，为了实现大规模应用，需要解决初始库仑效率低的问题。在第一个循环中，锂的损失主要有两个机制：固体电解质界面的形成和电极中锂的捕获。前者已经得到了深入的研究，而后者在很大程度上被忽视了。在这里，通过理论计算和实验研究，我们证明了通过在硅中引入精细成分控制的锗取代，可以大大降低锂扩散的能垒，因为晶格膨胀。这种同价同构的效应显著减少了约 70%的锂捕获，并将初始库仑效率提高到 90%以上。我们期望各种电池材料系统都能从这种微调其电化学行为的机制中受益。
