Systematic Investigation of Binders for Silicon Anodes: Interactions of Binder with Silicon Particles and Electrolytes and Effects of Binders on Solid Electrolyte Interphase Formation

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• 作者：Cao Cuong Nguyen ; Taeho Yoon ; Daniel M. Seo ; Pradeep Guduru ; Brett L. Lucht
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：May 18, 2016
• 年：2016
• 卷：8
• 期：19
• 页码：12211-12220
• 全文大小：854K
• 年卷期：0
• ISSN：1944-8252

文摘

The effects of different binders, polyvinylidene difluoride (PVdF), poly(acrylic acid) (PAA), sodium carboxymethyl cellulose (CMC), and cross-linked PAA–CMC (c–PAA–CMC), on the cycling performance and solid electrolyte interphase (SEI) formation on silicon nanoparticle electrodes have been investigated. Electrodes composed of Si–PAA, Si–CMC, and Si–PAA–CMC exhibit a specific capacity ≥3000 mAh/g after 20 cycles while Si–PVdF electrodes have a rapid capacity fade to 1000 mAh/g after just 10 cycles. Infrared spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS) reveal that PAA and CMC react with the surface of the Si nanoparticles during electrode fabrication. The fresh Si–CMC electrode has a thicker surface coating of SiO_x than Si–PAA and Si–PAA–CMC electrodes, due to the formation of thicker SiO_x during electrode preparation, which leads to lower cyclability. The carboxylic acid functional groups of the PAA binder are reactive toward the electrolyte, causing the decomposition of LiPF₆ and dissolution of SiO_x during the electrode wetting process. The PAA and CMC binder surface films are then electrochemically reduced during the first cycle to form a protective layer on Si. This layer effectively suppresses the decomposition of carbonate solvents during cycling resulting in a thin SEI. On the contrary, the Si–PVDF electrode has poor cycling performance and continuous reduction of carbonate solvents is observed resulting in the generation of a thicker SEI. Interestingly, the Lewis basic −CO₂Na of CMC was found to scavenge HF in electrolyte.