Decoupling Mechanical and Interfacial Failure Silicon Anodes via a Rigid-Flexible Binder Design for High-Energy-Density Lithium-Ion Batteries

Abstract

Silicon-based anodes hold immense promise for next-generation lithium-ion batteries with high energy density. Still, they are plagued by severe capacity fading due to immense volume changes and subsequent interfacial instability. While "rigid-flexible" binder designs offer a conceptual solution, their complex synthesis often hinders practical application.Herein, we report a simple, scalable, and highly effective strategy to overcome these bottlenecks by rationally optimizing the mass ratio of commercially available rigid carboxymethyl cellulose (CMC) to flexible styrene-butadiene rubber (SBR). We reveal that an optimal CMC: SBR ratio of 7:3 yields a unique three-dimensional network that synergistically integrates mechanical robustness with elastic deformability. This tailored architecture is key to overcoming both the mechanical and interfacial challenges. Consequently, the optimized Si-7:3 anode delivers an outstanding initial Coulombic efficiency of 92.91% and maintains a high reversible capacity of 1875.3 mAh g ⁻1 after 200 cycles at 2 A g ⁻1 . Crucially, the practical viability is further demonstrated in a full cell with a LiNi0.9Co0.05Mn0.05O2 (Ni90) cathode, which retains 98.2% capacity after 100 cycles.This work provides a facile, industry-compatible binder engineering strategy that not only addresses the critical challenges of silicon anodes but also offers fundamental insights into the interplay between binder micromechanics and interfacial chemistry, paving the way for advanced energy storage systems.