Better together: integrating adhesion and ion conductivity in composite binders for high-performance silicon anodes

Abstract

Despite the numerous advantages of silicon as an anode material for high-energy-density lithium-ion batteries, its immense expansion during lithiation challenges commercial applications. Herein, a composite binder based on poly(acrylic acid) (PAA) and a tailored terpolymer, poly(sodium 4-styrenesulfonate-co-ureido-pyrimidinone methacrylate-co-hydroxyethyl methacrylate) (PSUOH), is developed to address this issue. Unlike typical copolymer binders, which often suffer from trade-offs between functions, x-PAA/PSUOH combines the strong adhesion provided by PAA with the structural integrity and ionic conductivity provided by the terpolymer without trade-offs. Owing to the synergistic action of both polymers, the resulting silicon anode exhibits a high initial discharge capacity of 3572 mA h g⁻¹ and capacity retention of 71% over 300 cycles while featuring an excellent rate capability at current rates of up to 8 A g⁻¹. The potential of x-PAA/PSUOH for the production of high-energy-density lithium-ion batteries is demonstrated by the fabrication of a full cell with a silicon–graphite anode and LiNi_0.6Mn_0.2Co_0.2O₂ cathode. Thus, our study can provide a useful guideline for developing multifunctional binders for high-performance silicon anodes.