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

Abstract

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.

Achievements, challenges, and perspectives in the design of polymer binders for advanced lithium-ion batteries

“…Recently, Kim, Ahn et al synthesized a series of self-healable acrylic copolymer binders with randomly distributed carboxylic acid and n -butyl carbamate groups (Table 3). 273 Varying the ratio between the acid and carbamate side groups allowed the properties of the binder to be balanced. The Si electrode with binder containing 68 mol% carboxylic groups and 32 mol% carbamate groups achieved a high initial discharge capacity of 3628 mA h g −1 , with ICE = 84%, and showed a discharge capacity of 2334 mA h g −1 after 100 cycles at 0.5 A g −1 .…”