Preparation of Silk Fibroin–Carboxymethyl Cellulose Composite Binder and Its Application in Silicon-Based Anode for Lithium-Ion Batteries

Abstract

The molecular structure and mechanical resilience of the binder are crucial for mitigating volume expansion, maintaining electrode structural integrity, and enhancing the cycling stability of silicon-based anode materials in lithium-ion batteries. In this study, from the perspective of binder molecular structural design, commercial carboxymethyl cellulose (CMC) was modified with silk protein (SF), which has good mechanical properties and abundant surface functional groups, to address issues such as high brittleness, poor compliance and easy cracking of the electrode structure during charge and discharge cycles, and to enhance the mechanical properties of the CMC-based binder and its interaction with silicon particles, so as to improve the cycle stability of silicon-based materials. The mechanical properties of the CMC binder were significantly improved and the interaction between the binder and the surface of the silicon particles was enhanced by the addition of SF. When the SF content was optimized at 6 wt%, the electrode exhibited the best electrochemical performance, delivering a specific capacity of 1182 mAh/g at a high current density of 5000 mA/g, and retaining a capacity of 1138 mAh/g after 50 cycles at 1000 mA/g, demonstrating excellent electrochemical durability.