Construction of carbon nanorods supported hydrothermal carbon and carbon fiber from waste biomass straw for high strength supercapacitor

The development of high-performance flexible supercapacitor using biomass wastes as raw materials to overcome the high manufacturing cost has attracted excellent interest. Herein, a hierarchical structure of carbon nanorods supported hydrothermal carbons and carbon fibers (CNR/HTC/CFs) with superior electrochemical performance as well as high strength is successfully designed for the first-time using waste straw as a sustainable and economic carbon resource. The straw pyrolysis gases after purification are introduced to support the formation of high specific surface area CNRs via a simple vapor phase growth process. The CNR/HTC/CFs exhibit high mass specific capacitance of 269.47 F g⁻¹ under the scan rate of 3 mV s⁻¹ in three-electrode system. A high energy density of 15.54 Wh kg⁻¹ with the power density of 0.49 kW kg⁻¹ was obtained in the as-assembled all solid-state supercapacitor device with gel electrolyte, whose value retains as high as 6.99 Wh kg⁻¹ with the power density of 10.01 kW kg⁻¹. The tensile strength of the finally fibers can reach up to 2743 ± 467 MPa, which is sufficient for many practical industrial applications. This work provides a feasible synthetic strategy using sustainable biomass waste as raw materials to prepare high strength and capacitance energy storage devices.