Pseudo-Core/Shell Latex Particles Constructed via Soft/Hard Segment Phase Separation for High-Performance Si/C Anodes

Abstract

Abstract Silicon-based anodes in lithium-ion batteries (LIBs) currently suffer from structural collapse and capacity decay caused by drastic volume expansion in silicon particles. To address this issue, a binder that exhibits strong interfacial interactions and suitable mechanical properties to maintain the structural integrity of the electrode urgently needs to be developed. Herein, a pseudo-core-shell polystyrene-co-acrylate binder (PES) was synthesized via seeded emulsion polymerization, where the polystyrene-rich core serves as a rigid framework and provides sufficient strength to resist the expansion of the active material, while the shell enriched with 2-ethylhexyl acrylate units exhibits good flexibility, which helps to cushion internal stresses within the electrode and prevent the destruction of the Si/C anode. Additionally, compared with the conventional styrene–butadiene rubber (SBR) binder, PES exhibits superior adhesion performance, which effectively enables the formation of a conductive network and maintains stable electrical contact. Benefiting from an appropriate soft-segment content, PES-25 achieves an optimal balance between rigidity and flexibility, which effectively stabilizes the solid electrolyte interphase (SEI) layer and promotes lithium-ion (Li+) transport. The electrode prepared with the PES-25 retains a reversible discharge capacity of 413.9 mAh g–1 after 300 cycles at 1C and 452.0 mAh g–1 after 200 cycles at 0.2C, respectively, which is significantly higher than that of the SBR binder (351.0 mAh g–1 after 300 cycles at 1C and 373.1 mAh g–1 after 200 cycles at 0.2C), demonstrating superior cycling stability. This work is expected to provide guidance for the design of binders compatible for high-capacity silicon-based anodes.