Achieving Cyclic Structural Stability in 20% Si/C Anodes via a Hydroxyl-Rich Ternary Copolymer Binder

Silicon (Si) is a promising anode material for high-energy-density lithium-ion batteries owing to its high theoretical specific capacity of ~3600 mAh g⁻¹. However, its large volume change during cycling causes severe mechanical degradation and rapid capacity fading. Herein, we developed a series of functional binders by terpolymerizing acrylic acid and acrylonitrile with different functional monomers to improve the mechanical stability of Si/carbon (Si/C) anodes. In particular, hydroxyl-containing 2-hydroxyethyl acrylate (HEA) and 2-hydroxypropyl acrylate (HPA) promote hydrogen bonding with the Si surface and impart self-healing capability to the resulting PAHEA and PAHPA binders, whereas ethoxyethoxyethyl acrylate (EEA), without hydroxyl functionality, does not exhibit this behavior. The 20% SiC anodes with PAHEA and PAHPA deliver discharge capacities of 650.91 and 644.13 mAh g⁻¹, respectively, at 0.1C. Corresponding 1 Ah pouch cells retain 81.26% and 78.22% of their initial capacities after 600 cycles at 1C. These results demonstrate that hydroxyl-functionalized copolymer binders can effectively enhance the structural stability and cycling durability of Si/C anodes, providing a practical strategy for the development of high-performance silicon-based batteries.