Self-Healable Poly(Acrylic Acid) Binder toward Optimized Electrochemical Performance for Silicon Anodes: Importance of Balanced Properties

Si is a promising anode for high-energy lithium-ion batteries, but its severe capacity decay due to volume changes remains a challenge. To address this, we synthesized a series of acrylic copolymer binders with randomly distributed carboxylic acid (CA) and n-butyl carbamate (BC) groups. CA groups ensure good adhesion to the Si surface, while BC groups provide self-healing as well as a wide range of thermal and mechanical properties. By fine-tuning the content of these functional groups, we optimize the mechanical, adhesion, and self-healing properties, and electrolyte uptake of the binders to maximize their electrochemical performance. The Si electrode with a binder containing 68 mol % CA groups and 32 mol % BC groups achieves a high initial discharge capacity of 3628 mA h g–1, with an initial Coulombic efficiency (ICE) of 84%. This electrode also displays a discharge capacity of 2334 mA h g–1 after 100 cycles at 0.5 A g–1, surpassing the performance of a Si-poly(acrylic acid) electrode (3171 mA h g–1 at the first cycle, ICE of 86%, and 1367 mA h g–1 at the 100th cycle at 0.5 A g–1). Through a systematic investigation of the structure–property–electrochemical performance relationship, we prioritize the desired properties of the binder to enable the development of high-performance Si anodes.