Cotton fabric-derived hybrid carbon network with N-doped carbon nanotubes grown vertically as flexible multifunctional electrodes for high-rate capacitive energy storage

The emerging electronic textiles (e-textiles) with various functionalities urgently demand the flexible textile-based supercapacitors (TSCs) as reliable power sources. The textiles used for energy storage generally serve as supports/current-collectors and thus hardly contribute capacitance in contrast to electrochemically active materials. Herein, ultralong N-doped carbon nanotubes (NCNTs) are grown directly on the hollow textile carbon (TC) fibers to yield highly conductive TC-NCNTs hybrid network (20.4 S cm−1) through a facile one-pot heating strategy, allowing rapid ion and electron kinetics along this 3D interlaced backbone. Electrochemical oxidation of TC-NCNTs for 20 min yields the EATC-NCNTs-20 electrode with an enhanced areal capacitance of 1279 mF cm−2 due to the introduction of tremendous oxygen functional groups. Meanwhile, electrodeposition of CoS nanosheets on TC-NCNTs offers large accessible surface area for pseudocapacitive redox reactions, leading the TC-NCNTs@CoS-8 electrode to achieve an areal capacitance of 2240 mF cm−2 at 5 mA cm−2, together with a remarkable rate performance (92.6 % capacitance retention at 100 mA cm−2 with CoS mass loading of 10.8 mg cm−2). A flexible asymmetric supercapacitor fabricated with the two electrodes delivers an energy density of 2.30 mWh cm−3 at 24.27 mW cm−3. These results could promote the development of advanced textile-based electrochemical energy storage devices.