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Highly adhesive binders are developed to prolong the cycle life of silicon anodes and accelerate their practical application. A series of poly(N-methacryloyl-3,4-dihydroxy- l -phenylalanine) (PMDOPA) binders, containing ultra-high content of catechol groups, are synthesized through radical polymerization and applied to silicon anodes. The ultra-high content of catechol groups endows the PMDOPA binder superior adhesive strength compared to the carboxyl groups of the polyacrylic acid (PAA) binder. As the molecular weight increases, the flexibility, solvent resistance and adhesive strength of the PMDOPA binders are all enhanced, which effectively alleviates the electrode pulverization during long-term cycling and prolongs the cycle life of batteries. Especially, the PMDOPA-20 binder, which possesses the highest molecular weight of 208 kDa among all the PMDOPA samples, exhibits the longest cycle life of 665 cycles at the current density of 840 mA g−1, even though its molecular weight is lower than PAA. This work demonstrates that both the functional adhesive group and molecular weight are crucial for binder performance, which provides a valuable reference for the future development of high-performance binders. Image 1 • A series of binders containing ultra-high content of catechol groups are synthesized. • Silicon anode performance is improved as the binder molecular weight increases. • The silicon electrodes with catechol-based binders exhibit long cycle lives. • Both functional group and molecular weight are crucial for binder performance. [ABSTRACT FROM AUTHOR]

Using conductive binders, instead of the traditional binders and conductive additives, is an effective way to increase the specific capacity and long cycle life of the silicon (Si) anode. However, the rigid conductive binders of Si anodes tend to form cracks during the repetitive huge volume changes of Si. Here, a novel n-type conductive binder, multi-block polymer of poly(1-pyrenemethyl methacrylate) and polybutadiene (PPy- b -PB) was designed. The polybutadiene (PB) rubber was incorporated into the conductive binder by combining condensation and reversible addition-fragmentation chain transfer polymerization. With high initial coulombic efficiency of 77.9%, the PPy- b -PB/Si anode possesses high reversible capacity (2274 mAh g−1) and capacity retention (87.1%) at the rate of 0.2 C (0.84 A g−1) after 200 cycles. The superior cyclic performance of the PPy- b -PB can be ascribed to the PB rubber, which enhanced the reversible deformation ability, flexibility, and adhesion length scale of the binder, without with a negligible change of the charge-transfer resistance for the anode. The original structure and the preparation method of the multi-block conductive binder provide a new way to manufacture multifunctional binders. A n-type multi-block polymer PPy- b -PB of poly(1-pyrenemethyl methacrylate) (PPy) and polybutadiene (PB) was designed to enhance the reversible deformation ability, flexibility, and adhesion length scale of the conductive binder PPy. With high initial coulombic efficiency of 77.9%, the PPy- b -PB/Si anode possesses high reversible capacity (2274 mAh g−1) and capacity retention (87.1%) at the rate of 0.2 C (0.84 A g−1) after 200 cycles. Image 1 • A novel multi-block binder was prepared by Condensation and RAFT polymerization. • The binder was used as conductive binder for Si anodes in Li-ion batteries. • Reversible deformation ability of the binder was improved with polybutadiene. • High capacity and cycling stability of Si anode was achieved by using the binder. [ABSTRACT FROM AUTHOR]