Deciphering the Critical Role of the CNT–Binder Interface in the Stress-Tolerant Capability of Si Anodes

Silicon (Si) stands as a premier anode candidate for next-generation lithium-ion batteries, yet its commercialization is impeded by substantial volume expansion and concomitant side reactions. Carbon nanotubes (CNTs), leveraging their high aspect ratio and exceptional conductivity, form long-range conductive networks that mitigate electrode bulk variation, suppress repetitive SEI formation, and accelerate electrochemical kinetics. However, the critical role of the interaction between CNTs and binders is normally neglected in previous studies. In this work, we first decipher that the weak interfacial adhesion between rigid CNTs and binders, coupled with insufficient bonding sites, is a significant factor causing mechanical failure of Si anodes. Furthermore, we design a reinforced CNT-binder interface via robust interfacial hydrogen bonds between carboxylated CNTs (COOH-CNTs) and lithiated poly(acrylic acid) (Li-PAA) binders, achieving a mechanically resilient Si electrode. The resultant electrode exhibits an enhanced strain tolerance and reduced impedance during fast charging. Consequently, the COOH-CNT-modified nano-Si anode delivers significantly enhanced electrochemical performance, retaining 68.8% capacity after 300 cycles at 2 A g^-1. This work establishes interfacial chemistry engineering of CNT additives as a critical strategy for developing high-energy-density lithium-ion batteries.