Cotton induced graphene-like carbon tubes as electrodes for ultrahigh-energy–density supercapacitors

•Preparation of graphene-like graded porous carbon tubes using long-staple cotton.•The CTOs exhibited superior capacitance and exceptional cycle stability.•The assembled NiCo2S4/CTOs//CTOs ASCs provided ultra-high energy density. Developing a simple, cost-effective method to synthesize carbon tubes with unique physicochemical properties is of great value for energy storage/conversion applications. In this study, cotton-induced O, N-doped graphene-like hierarchically structured porous carbon tubes (CTOs) were fabricated through a facile method and used as a supercapacitor electrode. The CTOs possessed enhanced porosity, a unique pore structure, and a large specific surface area (3,345.4 m2 g−1), and the electrode demonstrated an ultrahigh specific capacitance of 428.2 F g−1 at 1.0 A g−1 and remarkable cycle stability (93.3 % after 10,000 cycles). Density functional theory calculations confirmed that the high-level O, N-doped graphene-like hierarchically porous structures increased ion transfer efficiency and conductivity. When NiCo2S4/CTOs and CTOs were used as the positive and negative electrodes, respectively, the asymmetric supercapacitors (NiCo2S4/CTOs//CTOs) exhibited an extremely high specific capacitance of 180.8 F g−1 and a maximum energy density of 64.3 Wh kg−1. Moreover, two serially connected NiCo2S4/CTOs//CTOs capacitors could power a 9 W alarm clock for 26 min. The proposed approach enables the facile synthesis of superior carbon tubes using long-staple cotton, offering potential energy storage and conversion.