Scalable Interfacial Design of CNT/MXene Hybrid Yarns for Durable and Flexible Supercapacitors

Yarn-type solid-state supercapacitors hold immense promise for integration into wearable electronics, yet their development is often hindered by limited energy density and poorly defined nanoscale architectures. Conventional architecture typically involves random mixtures of 1D and 2D materials or film-based designs, which lack interfacial uniformity and mechanical compliance. Here, a dimensionally programmed assembly strategy is reported in which 1D carbon nanotubes (CNTs) and 2D titanium carbide (MXene) are alternately deposited in a layer-by-layer fashion onto bio-derived mulberry fiber paper (Korean traditional paper, KTP) via a scalable, binder-free bar-coating process. This design enables precise modulation of interlayer spacing, promotes structural integrity, and prevents MXene aggregation while preserving high charge mobility. The resulting CNT/MXene@KTP electrodes are motor-twisted into yarn structures and integrated with a solid-state PVA/H₂SO₄ gel electrolyte to fabricate two-ply all-solid-state supercapacitors with exceptional flexibility. Optimization of MXene deposition cycles led to a volumetric capacitance of 14 801 mF cm^-3 and an energy density of 2.06 mWh cm^-3 at 73.94 mW cm^-3. Beyond electrochemical metrics, the ordered 1D-2D heterostructure imparts superior mechanical durability and scalability, offering a compelling platform for next-generation, textile-integrated, self-powered electronic systems.