In our work, we successfully design boron (B) and nitrogen (N) co-doped porous carbon tube bundle (B/N-PCTB) electrode materials which are directly derived from the biomass of dandelion fluff. The low-tortuosity, and open and porous structures contribute to electron transport along the tube wall and unimpeded ion diffusion inside the carbon tubes. The incorporation of heteroatoms into PCTBs can bring extra pseudocapacitance and double layer capacitance to enhance the overall capacitance. Benefiting from the hollow and open microstructure and heteroatom doping, the optimized B/N-PCTB electrode (active materials: 2.6 mg cm⁻²) possesses an impressive specific capacitance of 355 F g⁻¹ at 1 A g⁻¹. Even with an ultrahigh loading mass of 40 mg cm⁻², the electrode still has a relatively high specific capacity of 216 F g⁻¹ at 1 A g⁻¹. The assembled symmetric cell with an active material loading of 80 mg cm⁻² (cathode: 40 mg cm⁻²; anode: 40 mg cm⁻²) shows a superior volumetric energy density of 12.15 W h L⁻¹ at the power density of 699.84 W L⁻¹. The facile yet high-performance porous carbon tube bundle is a promising material which can be applied in many other fields such as lithium ion batteries, hydrogen evolution reaction, and heavy metal ion adsorption.

Sodium ion hybrid capacitors (SHCs) using battery-type and capacitor-type electrodes are designed to obtain both high energy and power densities. However, anode materials commonly cannot meet the high capacity and rapid charging/discharging stability requirements. With the help of sandwiched design, herein novel porous carbon microtubes are sandwiched by vertical ultrasmall-sized SnS nanosheets (SnS/aCMT) via combined solvothermal and thermal-treatment approaches. The three-dimensional interconnected SnS nanosheet network grown on both sides of the hollow carbon microtubes could greatly prevent their aggregation and facilitate ion transport, which endows the anode material with improved specific capacity and structural stability. As a result, the SnS/aCMT electrode presents high capacity (517 mA h g⁻¹ at 0.1 A g⁻¹) and remarkable rate capability (306 mA h g⁻¹ even at 5 A g⁻¹) as well as long-term cycling stability with 88.7% retention over 500 cycles. Furthermore, a SHC, assembled by using SnS/aCMT as the anode and aCMT as the cathode, presents a high energy density of 115 W h kg⁻¹ in the voltage range of 0.5–4.0 V and stable long-term cycling performance.