Xie Wei, Pang Chunlei, He Peng, Xiao Chengmao, Koyama Michihisa, Wang Jiantao, Qi Xiaopeng, Ren Jianguo, He Xueqin
BTR New Material Group Co. Ltd, Xitian High-Tech Industrial Park, Guangming New District, Shenzhen 518106, China.
Global Research Centre for Environment and Energy Based on Nanomaterials Science, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.
Phys Chem Chem Phys. 2022 Mar 23;24(12):7405-7414. doi: 10.1039/d2cp00498d.
Silicon monoxide is a potentially viable anode material for high-performance lithium-ion batteries (LIBs). However, a low initial coulombic efficiency and large volume expansion limit its commercial application. Pre-lithiation is an efficient solution, but is expensive because of limited "pre-lithiation" sources. In this work, we theoretically investigated a novel multiple pre-doping SiO system (Li-NaMg-SiO). By comparing its lithiation behavior to that of the traditional Li-doping system (Li-SiO), we revealed the different doping effects during lithiation. Similar to the traditional Li-doping system, the insertion of Na and Mg disintegrates the Si-O host matrix to form Na-O and Mg-O bonds and active Si clusters. At the end of lithiation, the O-Li coordination number (CN) tends to saturate at CN ≈ 5 in Li-Na-SiO, Li-Mg-SiO, and Li-NaMg-SiO systems, while the value of CN in the Li-SiO system is more than 6, which suggests that there are reorganizations between Li, Na, and Mg in the silicate matrix. Doping sources of both Na and Mg can prevent the active Li ions from being trapped by O-Li bonds and increase the initial coulombic efficiency. From the density of states (DOS), we notice that all the different pre-doping systems have similar electronic structures, and they can be expected to undergo the same lithiation process. Furthermore, the higher ion-conductivity and smaller volume expansion during the lithiation process characterized by root mean square deviation (RMSD) and volume analysis prove the advantages of the binary doping system (Li-NaMg-SiO) for the improvement of cycle stability for Si-based materials. These advantages benefit from the loose and amorphous structures of doping systems during lithiation. Our work highlights the doping effects of multiple sources and the promotion of "inert compounds" on the entire lithiation process, which provide valuable insight for high-performance anode design.
一氧化硅是高性能锂离子电池（LIBs）一种潜在可行的负极材料。然而，低初始库仑效率和大体积膨胀限制了其商业应用。预锂化是一种有效的解决方案，但由于“预锂化”源有限而成本高昂。在这项工作中，我们从理论上研究了一种新型的多重预掺杂SiO体系（Li-NaMg-SiO）。通过将其锂化行为与传统锂掺杂体系（Li-SiO）的锂化行为进行比较，我们揭示了锂化过程中不同的掺杂效应。与传统锂掺杂体系类似，Na和Mg的插入会使Si-O主体基质解体，形成Na-O和Mg-O键以及活性Si簇。在锂化结束时，Li-Na-SiO、Li-Mg-SiO和Li-NaMg-SiO体系中O-Li配位数（CN）趋于在CN≈5时饱和，而Li-SiO体系中的CN值大于6，这表明在硅酸盐基质中Li、Na和Mg之间存在重新排列。Na和Mg的掺杂源都可以防止活性Li离子被O-Li键捕获，并提高初始库仑效率。从态密度（DOS）来看，我们注意到所有不同的预掺杂体系都具有相似的电子结构，并且可以预期它们会经历相同的锂化过程。此外，通过均方根偏差（RMSD）和体积分析表征的锂化过程中较高的离子电导率和较小的体积膨胀证明了二元掺杂体系（Li-NaMg-SiO）在提高硅基材料循环稳定性方面的优势。这些优势得益于锂化过程中掺杂体系的松散和非晶结构。我们的工作突出了多源掺杂效应以及“惰性化合物”对整个锂化过程的促进作用，这为高性能负极设计提供了有价值的见解。
