Domi Yasuhiro, Usui Hiroyuki, Ieuji Naoya, Nishikawa Kei, Sakaguchi Hiroki
Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University, 4-101 Minami, Koyama-cho, Tottori 680-8552, Japan.
Center for Research on Green Sustainable Chemistry, Tottori University, 4-101 Minami, Koyama-cho, Tottori 680-8552, Japan.
ACS Appl Mater Interfaces. 2021 Jan 27;13(3):3816-3824. doi: 10.1021/acsami.0c17552. Epub 2021 Jan 15.
We investigated the impact of electrolyte difference on lithiation and delithiation properties of a LiSi electrode to improve the Coulombic efficiency (CE) of Si-based electrodes. The results of X-ray diffraction, Raman spectroscopy, and soft X-ray emission spectroscopy demonstrated that a portion of the Li in LiSi desorbed by simply immersing the electrode in an ionic-liquid electrolyte, that is, the phase transition of LiSi to Si occurred. In contrast, this phenomenon was not confirmed in an organic-liquid electrolyte. Instead, the desorbed Li was consumed for the formation of a surface film; thus, the Li in LiSi did not elute into the electrolyte. The addition of vinylene carbonate (VC) to the ionic-liquid electrolyte suppressed the phase transition of LiSi to Si. Although the LiSi electrode showed a low initial CE and poor cycling performance in a VC-free electrolyte, the electrode exhibited a high CE and a remarkable cycle life in the VC-added electrolyte. It was considered that no desorption of the mechanically added Li in LiSi contributed to the superior cycle life; thus, the characteristic ductility, malleability, and high electrical conductivity of lithium silicide should improve the electrochemical performance.
我们研究了电解质差异对锂硅电极锂化和脱锂性能的影响，以提高硅基电极的库仑效率（CE）。X射线衍射、拉曼光谱和软X射线发射光谱的结果表明，通过将电极简单浸入离子液体电解质中，锂硅中的一部分锂会解吸，即发生了锂硅向硅的相变。相比之下，在有机液体电解质中未观察到这种现象。相反，解吸的锂用于形成表面膜；因此，锂硅中的锂不会洗脱到电解质中。向离子液体电解质中添加碳酸亚乙烯酯（VC）可抑制锂硅向硅的相变。尽管锂硅电极在无VC的电解质中初始CE较低且循环性能较差，但在添加VC的电解质中该电极表现出高CE和显著的循环寿命。据认为，锂硅中机械添加的锂没有解吸有助于其优异的循环寿命；因此，硅化锂的特性延展性、可锻性和高电导率应能改善其电化学性能。
