Chamidah Nur, Suzuki Akito, Shimizu Takeshi, Zhong Chengchao, Shimoda Keiji, Okazaki Ken-Ichi, Yaji Toyonari, Nakanishi Koji, Nishijima Motoaki, Kinoshita Hajime, Orikasa Yuki
Department of Applied Chemistry, Graduate School of Life Sciences, Ritsumeikan University 1-1-1 Nojihigashi Kusatsu Shiga 525-8577 Japan
Research Organization of Science and Engineering, Ritsumeikan University 1-1-1 Nojihigashi Kusatsu Shiga 525-8577 Japan.
RSC Adv. 2023 Jun 7;13(25):17114-17120. doi: 10.1039/d3ra02554c. eCollection 2023 Jun 5.
Silicon has been considered to be one of the most promising anode active materials for next-generation lithium-ion batteries due to its large theoretical capacity (4200 mA h g, LiSi). However, silicon anodes suffer from degradation due to large volume expansion and contraction. To control the ideal particle morphology, an experimental method is required to analyze anisotropic diffusion and surface reaction phenomena. This study investigates the anisotropy of the silicon-lithium alloying reaction using electrochemical measurements and Si K-edge X-ray absorption spectroscopy on silicon single crystals. During the electrochemical reduction process in lithium-ion battery systems, the continuous formation of solid electrolyte interphase (SEI) films prevents the achievement of steady-state conditions. Instead, the physical contact between silicon single crystals and lithium metals can prevent the effect of SEI formation. The apparent diffusion coefficient and the surface reaction coefficient are determined from the progress of the alloying reaction analyzed by X-ray absorption spectroscopy. While the apparent diffusion coefficients show no clear anisotropy, the apparent surface reaction coefficient of Si (100) is more significant than that of Si (111). This finding indicates that the surface reaction of silicon governs the anisotropy of practical lithium alloying reaction for silicon anodes.
由于硅具有较大的理论容量（4200 mA h g，LiSi），它被认为是下一代锂离子电池最有前景的负极活性材料之一。然而，硅负极会因体积的大幅膨胀和收缩而退化。为了控制理想的颗粒形态，需要一种实验方法来分析各向异性扩散和表面反应现象。本研究利用电化学测量和对硅单晶进行的Si K边X射线吸收光谱，研究了硅 - 锂合金化反应的各向异性。在锂离子电池系统的电化学还原过程中，固体电解质界面（SEI）膜的持续形成阻碍了稳态条件的实现。相反，硅单晶与锂金属之间的物理接触可以防止SEI形成的影响。通过X射线吸收光谱分析合金化反应的进程来确定表观扩散系数和表面反应系数。虽然表观扩散系数没有明显的各向异性，但Si（100）的表观表面反应系数比Si（111）的更显著。这一发现表明，硅的表面反应决定了硅负极实际锂合金化反应的各向异性。
