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[Display omitted] • Acetylated sugarcane bagasse is blend electrospun with polyacrylonitrile successfully. • Hierarchically porous structure of carbon nanofiber is introduced without any activation. • As-prepared carbon nanofiber is flexible, porous, and with high capacitive performance. The biomass-based carbon nanofibers (CNFs) have been regarded as promising electrode materials for supercapacitors. However, the preparation of biomass-based hierarchically porous CNFs by electrospinning without any chemical and physical activation is still challenging, especially when using the whole components of lignocellulose. Herein, a feasible way to synthesize a hierarchically porous CNF by electrospinning of the blends of acetylated sugarcane bagasse (ASCB) and polyacrylonitrile (PAN) followed by carbonization is proposed. Degradation of ASCB during carbonization induced multiscale defects that led to the formation of hierarchical pores and introduced flexibility for the CNFs. The specific capacitance and areal capacitance of CNFs respectively were 289.5 F g−1 and 64.2 μF cm−2. The flexible all-solid-state symmetric supercapacitor (ASSC) derived from the CNFs showed high power density (1.26 kW kg−1) and energy density (56.0 W h kg−1), as well as high capacitance retention and great cycling stability. This synthetic strategy provides a practicable way to utilize the whole components of lignocellulosic biomass and explore its application on high-performance flexible electrode materials. [ABSTRACT FROM AUTHOR]

• We first put forward the concept: a precursor fiber is a tree. It not only has good thermal stability of lignin, but also has flexibility of cellulose. • With the introduction of covalent-bond connection, the precursor fibers exhibit a large molecular weight, uniform molecular weight distribution, excellent thermal stability, and good spinnability. • The properties of resulting pure biomass-based carbon fibers are effectively improved by controlling the formation of covalent-bonds between lignin and cellulose-acetate. • The resulting pure biomass-based carbon fibers show independent filamentous morphology, uniform diameter, large surface area, excellent mechanical property and power storage capacity. • This work is a very valuable reference to the preparation of renewable and low-cost controllable fiber supercapacitor. The morphological collapse of pure biomass-based carbon nanofibers (CNFs) is due to the poor thermal stability of cellulose. Inspired by nature, cellulose and lignin are linked by covalent-bonds in trees made wood extensible and stable. In this work, an effective strategy was presented to mimic this biological structure for the preparation of biomass-based CNFs. Epichlorohydrin (ECH) is used to form the covalent-bonds between lignin and cellulose-acetate (CA) for a novel precursor material. With the introduction of covalent-bonds, precursor materials not only exhibit the spinnability of cellulose, but also possess the thermal stability of lignin. After carbonization, the pure biomass-based CNFs are successfully prepared and exhibit independent filamentous morphology, uniform diameter, large surface area, and power storage capacity. The specific capacitance of 320.3 F/g is obtained by using the CNFs-6 (prepared with 10 % ECH content) as super-capacitor. Simultaneously, the biomass-based CNFs super-capacitor device delivers a high energy density of 30.2 Wh/ kg at the power density of 400 W/kg. These results indicate that the introduction of covalent-bonds can effectively increase the energy storage properties significantly. This novel strategy showed a successful route for the preparation of high quality and low cost biomass-based CNFs. [ABSTRACT FROM AUTHOR]