SWCNT/MWCNT binderless hybrid hydrogel: Towards large-scale high-performance EMI shielding coating at commercial level

Abstract

Developing a multiscale hierarchical structure is advantageous for leveraging multiple EMI shielding mechanisms. Here, we present a seldom-reported method for synthesizing highly concentrated and well-dispersed carbon nanotube (CNT) composite materials that can be made into free-standing films without complex processing or binder materials. By combining multi-walled CNTs (MWCNTs) with single-walled CNTs (SWCNTs), we form a unique, highly entangled scaffold referred to as the single-walled nanotube and multi-walled nanotube complex (SMCNT). This self-assembles in the solvent after a proper functionalization process and mechanical mixing. Owing to its hybrid scaffold structure, the SMCNT dispersion can reach concentrations of up to 90 mg/mL, exhibiting viscoelastic rheological properties. This hybrid structure also enhances both the electrical conductivity and mechanical robustness in the resultant CNT films. Moreover, the SMCNT dispersion can be easily applied to large areas via the commercial shear coating method, making it suitable for various practical applications. The SMCNT composites exhibit outstanding EMI shielding effectiveness of up to 15,860 dB/mm and maintain stable shielding performance under 85/85 test conditions for approximately two weeks. This superior EMI shielding behavior is attributed to the dense, interwoven CNT network, which maximizes the air/material interface, as well as the intrinsic electrical conductivity and the chemical stability of CNTs.