Lithium-Conducting Self-Assembled Organic Nanotubes

Abstract

Supramolecular polymers are compelling platforms for the design of stimuli-responsive materials with emergent functions. Here, we report the assembly of an amphiphilic nanotube for Li-ion conduction that exhibits high ionic conductivity, mechanical integrity, electrochemical stability, and solution processability. Imine condensation of a pyridine-containing diamine with a triethylene glycol functionalized isophthalaldehyde yields pore-functionalized macrocycles. Atomic force microscopy, scanning electron microscopy, and in solvo X-ray diffraction reveal that macrocycle protonation during their mild synthesis drives assembly into high-aspect ratio (>10³) nanotubes with three interior triethylene glycol groups. Electrochemical impedance spectroscopy demonstrates that lithiated nanotubes are efficient Li⁺ conductors, with an activation energy of 0.42 eV and a peak room temperature conductivity of 3.91 ± 0.38 × 10^-5 S cm^-1. ⁷Li NMR and Raman spectroscopy show that lithiation occurs exclusively within the nanotube interior and implicates the glycol groups in facilitating efficient Li⁺ transduction. Linear sweep voltammetry and galvanostatic lithium plating-stripping tests reveal that this nanotube-based electrolyte is stable over a wide potential range and supports long-term cyclability. These findings demonstrate how the coupling of synthetic design and supramolecular structural control can yield high-performance ionic transporters that are amenable to device-relevant fabrication, as well as the technological potential of chemically designed self-assembled nanotubes.