In Situ Preparation of High-Performance Silicon-Based Integrated Electrodes Using Cross-Linked Cyclodextrins.

Area of Science:

• Materials Science
• Electrochemistry
• Green Chemistry

Background:

• Silicon anodes offer high theoretical capacity but suffer from poor cycling stability due to large volume expansion during charging/discharging.
• Conventional binders and material modification strategies for silicon anodes are often costly, complex, and environmentally unfriendly.
• There is a need for green, simple, and effective solutions to overcome the limitations of silicon-based anode materials.

Purpose of the Study:

• To develop a high-performance silicon anode using a novel binder synthesized via in situ thermal cross-linking of citric acid (CA) and beta-cyclodextrin (β-CD).
• To investigate the effect of carbonylation of β-CD (to carbonyl-β-CD, c-β-CD) on binder properties and silicon anode performance.
• To demonstrate a green and straightforward approach for improving the stability and capacity of silicon anodes for lithium-ion batteries.

Main Methods:

• Synthesis of a novel binder through in situ thermal cross-linking of citric acid (CA) and β-cyclodextrin (β-CD) during electrode preparation.
• Preparation of silicon (Si) electrodes utilizing the synthesized CA/β-CD binder.
• Modification of β-CD to carbonyl-β-CD (c-β-CD) to enhance water solubility and cross-linking capabilities.
• Electrochemical testing, including cycling performance and specific capacity measurements at various cycles and current densities (e.g., 0.5 C).
• Analysis of the solid electrolyte interface (SEI) layer formation and its role in accommodating volume variations.

Main Results:

• The Si electrode with the CA/β-CD binder exhibited excellent cycling performance, retaining a specific capacity of 1696 mAh·g^-1 after 200 cycles at 0.5 C.
• Carbonylation of β-CD to c-β-CD improved binder water solubility and facilitated multidimensional connections with CA and Si.
• The Si electrode using the c-β-CD modified binder achieved a significantly enhanced specific capacity of 1941 mAh·g^-1 at 0.5 C.
• The integrated electrode structure effectively promoted the formation of a stable and controllable solid electrolyte interface (SEI) layer.
• The binder successfully accommodated the large, repeated volume variations of the silicon material during electrochemical cycling.

Conclusions:

• The in situ synthesized CA/β-CD binder, particularly with c-β-CD modification, provides a green and effective strategy for stabilizing silicon anodes.
• This approach significantly enhances the cycling stability and specific capacity of silicon anodes, addressing key challenges in their practical application.
• The developed binder facilitates the formation of a robust SEI layer, crucial for accommodating silicon's volume changes and ensuring long-term battery performance.