Development and Application of a Poly(acrylic acid)-Grafted Styrene–Butadiene Rubber as a Binder System for Silicon-Graphite Anodes in Li-Ion Batteries

Silicon anodes require polymer binder systems that are both mechanically robust and electrochemically stable, to accommodate the dramatic volume expansion experienced during cycling operation. Herein, we report the use of a poly(acrylic acid)-grafted styrene–butadiene rubber (PAA-g-SBR) with 80% partially neutralized Na-PAA as the binder system for silicon-graphite anodes. The PAA-g-SBR graft copolymer was synthesized by grafting tert-butyl acrylate onto SBR and treating the intermediate with H3PO4. The PAA-g-SBR/Na-PAA binder system was found to provide superior electrochemical performances to that of a Na-PAA/SBR system. The Na-PAA/PAA-g-SBR system had a stable capacity retention of 673 mAh g–1 for 130 cycles, while the capacity retention of the Na-PAA/SBR system was found to decline immediately. The Na-PAA/PAA-g-SBR system also displayed more preferable mechanical properties, with a lower Young’s modulus value and a larger strain at failure compared to that of the Na-PAA/SBR system. Overall, these findings indicate a promising and robust polymer binder system for the application of silicon anodes in the next generation of lithium-ion batteries.