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The combination of multiple electrode materials and their reasonable structural design are conducive to the preparation of composite electrodes with excellent performance. In this study, based on carbon nanofibers grown with Ni(OH)2 and NiO (CHO) prepared by electrospinning, hydrothermal growth, and low-temperature carbonization, five transition metal sulfides (MnS, CoS, FeS, CuS, and NiS) were hydrothermally grown on their surfaces, exhibiting that CHO/NiS had the optimal electrochemical properties. Subsequently, the effect of hydrothermal growth time on CHO/NiS revealed that the electrochemical performance of CHO/NiS-3h was optimal, with a specific capacitance of up to 1717 F g−1 (1 A g−1), due to its multistage core–shell structure. Moreover, the diffusion-controlled process of CHO/NiS-3h dominated its charge energy storage mechanism. Finally, the asymmetric supercapacitor assembled with CHO/NiS-3h as the positive electrode demonstrated an energy density of 27.76 Wh kg−1 at a maximum power density of 4000 W kg−1, and it still maintained a power density of 800 W kg−1 at a maximum energy density of 37.97 Wh kg−1, exhibiting the potential application of multistage core–shell composite materials in high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Supercapacitors are considered as important energy conversion and storage devices, and one‐dimensional carbon nanofibers derived from electrospinning have been widely applied for supercapacitor electrode materials. The integration of carbon and metal hydroxide materials has become particularly important in order to pursue their higher electrochemical properties. In this paper, a one‐dimensional core‐shell electrode with Ni(OH)2 as shell and carbon nanofibers as core (Ni/CNFs@Ni(OH)2) was fabricated by electrospinning, high‐temperature carbonization and hydrothermal synthesis. This electrode exhibited high energy storage performance (785 F g−1 (1 A g−1)), good coulombic efficiency and cycling stability. Furthermore, the asymmetric supercapacitor (ASC) assembled with activated carbons as negative electrode and Ni/CNFs@Ni(OH)2 as positive electrode demonstrated a good energy storage performance (62.5 F g−1 (1.6 V)). Meanwhile, this ASC displayed a significant energy density of 22.2 Wh kg−1 at 800 W kg−1 and an outstanding rate capability, indicating that Ni/CNFs@Ni(OH)2 had a high potential application value in supercapacitors. [ABSTRACT FROM AUTHOR]

[Display omitted] • The NB-PCNF and MnO 2 /Co 3 O 4 /NB-PCNF were successfully fabricated via needleless electrospinning. • The co-doping of multiple non-metallic atoms enhances the electrochemical capability of carbon nanofibers. • The heterogeneous structure in MnO 2 /Co 3 O 4 /NB-PCNF can effectively improve the electrical conductivity. • A flexible asymmetric solid-state supercapacitor (FASS-SC) exhibits excellent electrochemical performance. Rational design of an electrode material with high flexibility and electrochemical performance is the key to wearable energy storage devices. Herein, a facile and productive needleless electrospinning method was introduced to prepare self-supported and flexible nanofibrous electrode materials for asymmetric capacitor. The MnO 2 nanoclusters and ZIF67-derived Co 3 O 4 nano-sheets were sequentially deposited on the surface of N, B-doped carbon nanofibers (hetero-junction MnO 2 /Co 3 O 4 /NB-PCNF). Attributing to the constructed multi-pathway for redox reactions on electrode, the specific capacitance of NB-PCNF and MnO 2 /Co 3 O 4 /NB-PCNF can reach up to 204.2F/g and 141.43F/g at a small current density of 0.1 A/g, respectively. In long-term cycling tests, the electrode materials exhibited excellent cycling stability and good rate capability. The electrodes were assembled with Potassium-ion hydrogel electrolyte to form a flexible asymmetric solid-state supercapacitor (FASS-SC). FASS-SC can reach a voltage window of 1.6 V. It provided 28.2 W h/kg at an energy density of 600 W/kg and a specific capacitance retention of 94.18 % after 10,000 cycles. The FASS-SC offers new research ideas for future flexible devices and wearable technologies. [ABSTRACT FROM AUTHOR]