Synergistic Role of Viscoelasticity and Amphiphilicity in Binder Design for High-Performance Silicon Electrodes

Silicon is a promising anode material for lithium-ion batteries because of its high theoretical capacity. However, their practical application is hindered by substantial volume expansion during lithiation/delithiation, which leads to mechanical degradation and capacity fading. To address this challenge, we propose a stress-dissipative binder system based on UV-induced cross-linking of viscoelastic poly(dimethyl siloxane) (PDMS) with rigid linear poly(acrylic acid) (PAA). The resulting PAA–PDMS binder can reversibly deform and recover in response to external stress due to the flexible siloxane backbone in PDMS, thereby accommodating the substantial volume expansion of Si electrode. Furthermore, the amphiphilic nature of the PDMS molecule increases its affinity for both carbon and Si particles, resulting in enhanced mechanical integrity of the Si electrode. These inherent characteristics of PDMS can effectively compensate for the rigidity of PAA, resulting in a well-balanced binder system tailored for Si electrodes. Consequently, the PAA–PDMS electrode exhibited a discharge capacity of 2072.68 mAh g⁻¹ after 100 cycles at 0.5 C−rate, whereas the PAA−based electrode reached failure after only 70 cycles. Post-mortem analyses reveal that the improved electrochemical performance of the PAA–PDMS electrode arises from its ability to mitigate Si electrode degradation by suppressing volume expansion and stabilizing the electrode–electrolyte interface.