Active Material-Free Continuous Carbon Nanotube Fibers with Unprecedented Enhancement of Physicochemical Properties for Fiber-Type Solid-State Supercapacitors

Abstract

Fiber-type solid-state supercapacitors (FSSCs) are gaining traction as wearable energy storage devices, given their adaptability akin to traditional fibers. Carbon nanotube fibers (CNTFs) generated via a liquid crystalline (LC) wet-spinning process demonstrate outstanding electrical conductivity, mechanical strength, and flexibility. However, their intrinsic "defect-free" sp2 carbon surface restricts immediate FSSC application, limited by lower specific surface area and scant pseudocapacitive sites. This study develops LC-spun CNTFs with inherent electrochemical activity, eliminating the need for post-processing or additional active materials, a requirement typically essential in most previous research. This advancement arises from the wet-spinning of functionalized CNTs from a LC solution with an exceptionally high concentration of 160 mg mL-1, facilitated by the manipulation of the LC phase transition range. The resultant CNTFs exhibit a refined internal structure, yielding an electrical conductivity of 1.9 MS m-1 and a mechanical strength of 0.93 GPa. Simultaneously, they demonstrate inherent electrical energy storage capabilities with a specific capacitance of 139.4 F g-1 and a volumetric capacitance of 192.4 F cm-3 at 0.5 A g-1. This innovation signifies a step forward in the potential for mass production without the burden of additional materials and steps. A high-performance, fiber-type, solid-state supercapacitor is developed using functionalized CNTFs, which are fabricated by the wet-spinning of their liquid crystal phase. These fibers not only possess exceptional physical properties but also exhibit inherent electrochemical activity. The active-material-free energy storage device in this study underscores the potential for efficient mass production of fiber-type energy storage electrodes.image