Solid Electrolyte Interphase Growth and Capacity Loss in Silicon Electrodes

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• 作者：Alison L. Michan ; Giorgio Divitini ; Andrew J. Pell ; Michal Leskes ; Caterina Ducati ; Clare P. Grey
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：June 29, 2016
• 年：2016
• 卷：138
• 期：25
• 页码：7918-7931
• 全文大小：957K
• 年卷期：0
• ISSN：1520-5126

文摘

The solid electrolyte interphase (SEI) of the high capacity anode material Si is monitored over multiple electrochemical cycles by p>7p>Li, p>19p>F, and p>13p>C solid-state nuclear magnetic resonance spectroscopies, with the organics dominating the SEI. Homonuclear correlation experiments are used to identify the organic fragments −OCH₂CH₂O–, −OCH₂CH₂–, −OCH₂CH₃, and −CH₂CH₃ contained in both oligomeric species and lithium semicarbonates ROCO₂Li, RCO₂Li. The SEI growth is correlated with increasing electrode tortuosity by using focused ion beam and scanning electron microscopy. A two-stage model for lithiation capacity loss is developed: initially, the lithiation capacity steadily decreases, Lip>+p> is irreversibly consumed at a steady rate, and pronounced SEI growth is seen. Later, below 50% of the initial lithiation capacity, less Si is (de)lithiated resulting in less volume expansion and contraction; the rate of Lip>+p> being irreversibly consumed declines, and the Si SEI thickness stabilizes. The decreasing lithiation capacity is primarily attributed to kinetics, the increased electrode tortuousity severely limiting Lip>+p> ion diffusion through the bulk of the electrode. The resulting changes in the lithiation processes seen in the electrochemical capacity curves are ascribed to non-uniform lithiation, the reaction commencing near the separator/on the surface of the particles.