Interplay of Wall Number and Mechanochemical Response in Carbon Nanotube Networks Reveals the Mechanism for Durable Silicon Anodes in Lithium-Ion Batteries.

Abstract

Carbon nanotubes (CNTs) represent a fascinating class of conductive additives for silicon anodes, combining a high aspect ratio with an excellent electrical conductivity. However, their agglomeration hinders stable dispersion and uniform electrode formation. Here, single-walled (SWCNTs), thin-walled (TWCNTs), and multi-walled CNTs (MWCNTs) are harnessed to assess electrosteric debundling, interfacial adhesion, and defect formation in electrodes, thereby establishing a more resilient conductive network. We propose a mechanistic framework that links the CNT wall number, dispersant chemistry, and mechanochemical state. In situ (operando) Raman spectroscopy reveals a wall-number-dependent stress pathway during lithiation. SWCNT networks remain tensile and conformal and deliver a stable performance. TWCNT networks transition from compressive to tensile through interwall shear and show intermediate stability, whereas MWCNT networks remain predominantly compressive with interfacial slip and decoupling. We propose selecting flexible, low-wall-number CNTs to sustain a tensile conformal state during lithiation and to maximize rate capability and capacity retention.