Non-Destructive Interfacial Engineering Using PDA–PPY-Coated SWCNTs and Tannic Acid for Synergistically Stabilized Silicon Anodes

Abstract

Silicon is a promising high-capacity anode material for next-generation lithium-ion batteries, but its severe volume expansion and low intrinsic conductivity induce interfacial instability, crack formation, and conductive-network failure. Herein, we present a non-destructive interfacial engineering strategy using single-walled carbon nanotubes (SWCNTs) conformally coated with a polydopamine–polypyrrole (PDA–PPY) copolymer and integrated into a tannic acid (TA)-reinforced carboxymethyl cellulose (CMC) binder matrix. The PDA–PPY coating improves SWCNT dispersion, hydrophilicity, and interfacial adhesion while preserving the integrity of the graphitic sp² framework. TA further establishes a multidentate hydrogen-bonding network among PDA–PPY, Si, and the CMC backbone, reinforcing conductive-network cohesion and suppressing structural degradation during repeated cycling. The coating chemistry and hydrogen-bonding network collectively regulate interfacial wettability, conductive-network morphology, and SEI evolution. As a result, the optimized Si@CMCTA PDA–PPY SW electrode retains 71.09% of its capacity after 100 cycles at 1 A g^–1 and 61.06% after 200 cycles at 2 A g^–1. Notably, it delivers 1148.95 mA h g^–1 even at 8 A g^–1, approximately 1.65 times that of the conventional CMC–SWCNT counterpart. Post-cycling XPS depth-profiling analysis further demonstrates suppressed crack formation and the formation of a thin, compact, LiF-rich interphase, indicating effective stabilization of the electrode/electrolyte interface.