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[Display omitted] • The vacancy-defective graphene sheets are constructed successfully through polyacrylonitrile thermally mediated. • Vacancy defects on graphene sheets can enhance electrons/ions transport kinetics • The assembled aqueous zinc-ion hybrid supercapacitors exhibit a high energy density and outstanding cycling stability. The electrochemical behavior of graphene sheets in energy storage system is closely related to its electronic structures. Specifically, structural vacancy defects can expose more active sites and enhance the electrochemical performance. However, it is still a challenging problem to realize valid defect regulation on improving the reaction kinetics of electrode materials. Herein, vacancy-defective graphene sheets were constructed through the thermal mediated method via intercalation of polyacrylonitrile nanofibers. The vacancy defects were generated from the NH 3 gas resulting from polymer decomposition at gradient carbonization temperature. The obtained composites of the graphene sheets and carbon nanofibers demonstrate that the vacancy defects benefit to charge transport, allowing more electrons to pass through the interlayered structure, and enhance the adsorption capacitance during the reversible electrochemical process. In addition, the as-assembled Zn ion hybrid supercapacitors exhibit a high energy density of 129.9 Wh kg−1 and outstanding cyclic stability (99.8 % after 10,000 cycling). The confined polymer-mediated thermal modification strategy can afford abundant vacancy defective sites and exhibit promising outlook for constructing high-performance graphene-based electrode materials for Zn ion hybrid supercapacitors. [ABSTRACT FROM AUTHOR]

[Display omitted] • PVP/ZIF-7/PAN nanofibers carbonized at 900 °C yielded flexible ZnO P /C. • A capacitance of 382.5 mF cm−2 was obtained at a current density of 1 mA cm−2. • ZnO P /C demonstrated a capacitance retention of ∼ 101 % over 10,000 cycles. • ZnO P /C delivered an energy density of 49 μWh cm−2 at a power density of 2 mW cm−2. This study investigates the carbonization of electrospun fibers derived from zeolitic imidazolate framework (ZIF)-7/polyacrylonitrile solutions containing urea or polyvinylpyrrolidone (PVP). The carbonization yields highly flexible composites comprising nitrogen-doped carbon nanofibers and ZnO. Notably, using PVP as a nitrogen source generates a composite exhibiting excellent electrochemical performance. Specifically, it delivers a high capacitance of 382.5 mF cm−2 at a current density of 1 mA cm−2. Furthermore, this composite demonstrates capacitance retentions of approximately 101 % and 80 % after 10,000 cycles and a 90° bending test, respectively. The charge-storage capability of the PVP-based ZnO P /C composite surpasses that obtained without PVP by 1.4 times. Additionally, a composite fiber mat of ZnO P /C obtained via one-step electrospinning exhibits exceptional electrical conductivity and an energy density of 49 μWh cm−2 at a power density of 2 mW cm−2. These findings highlight the potential of this material as an electrode for 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]

[Display omitted] • ● A dual network organohydrogel based asymmetric supercapacitor exhibits temperature tolerance from −20 to 80 °C. • ● High operation voltage of 1.7 V and a high energy density of 51.1Wh kg−1 is obtained with the supercapacitor. • ● Over the repeated cycles of heating and cooling between –20 and 80 °C, 94% of the initial capacitance is retained. • ● The supercapacitor exhibits mechanical stability over bending regardless of the temperature. It is highly desirable for supercapacitors to achieve mechanical flexibility and temperature tolerance, as well as high energy density, to fully utilize their superior characteristics of high-power density and long cycle stability to realize their potential as practical wearable energy storage devices. We devise a novel strategy to fabricate a flexible asymmetric supercapacitor based on dual network organohydrogel, exhibiting high energy density and electrochemical stability over a wide temperature range spanning 100 ℃. A three-dimensional core–shell NiCo 2 O 4 @MnO 2 nanostructure is selected as the positive electrode to supply multiple ion diffusion channels through its mesoporous structure, and nano structured N-doped carbon nanofibers as the negative electrode to increase the contact area with electrolyte, and 6 M KOH based organohydrogel as electrolyte. The resulting supercapacitor exhibits high electrochemical performance including a high operation voltage of 1.7 V and high energy density of 51.1 Wh kg−1 at a power density of 850 W kg−1 and is stable over temperature changes between –20 and 80 ℃. This work demonstrates a high-performance supercapacitor designed with 3D asymmetric electrodes and a dual network organohydrogel, suitable as a practical energy storage device, requiring mechanical stability and stability against temperature change. [ABSTRACT FROM AUTHOR]

[Display omitted] • Direct laser writing carbonization and heating treatment are used to manufacture carbon fibers. • Heat treatment can increase the specific surface area of carbonized lignin fiber. • A flexible supercapacitor constructed of carbon fibers has the qualities of being light, thin, and breathable. Electrode materials significantly impact supercapacitor performance and developing high-performance electrode materials is crucial in energy storage. Commonly used laser-induced electrode materials are currently limited by severe contamination and hard-to-change intrinsic properties. This paper proposes a method for fabricating high-performance supercapacitors by laser carbonizing the lignin composite fiber membranes with heating treatment. Lignin fiber can achieve superior tensile strength, stiffness, and carbonization degree under suitable heat treatment temperatures. Heat treatment at 450 °C has been proven to be the ideal temperature for supercapacitor performance. At a current density of 1 A/g, the supercapacitor can reach the highest specific capacitance of ∼391.2F/g. In addition, doping MoS 2 boosted the device's performance to a specific capacitance of ∼527.8F/g, a power density of ∼500 W/kg, and an energy density of ∼73 Wh/kg at the same current density. In addition, lignin fibers are ideal materials in electronic textiles due to their soft, thin, and breathable properties. This study provides supportive evidence and technical guidance for improving the performance of flexible wearable supercapacitors. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mn-doped PAN nanofibers were decorated with ZIF-67. • Oriented attachment of PVP/ZIF-67 occurred on Mn-doped PAN-2MI nanofibers. • PVP/ZIF-67/Mn-fibers carbonized at 900 ℃ resulted in flexible C/Co-CoO x /Mn-CNF. • The areal capacitance of 1263 mF·cm−2 was obtained at a current density of 0.25 mA·cm−2. • The energy density of 0.18 mWh·cm−2 was obtained at a power density of 0.5 mW·cm−2. Electrodes for flexible supercapacitors were fabricated from manganese-doped carbon nanofibers (Mn-CNF) decorated with carbon-coated Co-CoO x (C/Co-CoO x) nanotubes. The Mn-doped polyacrylonitrile (PAN)–2-methylimidazole (2MI) solution was electrospun using optimized Mn concentrations and ZIF-67 was then surface loaded by wet impregnation with added polyvinylpyrrolidone (PVP). These ZIF-67 loaded Mn-fibers, when annealed, resulted in carbon-coated C/Co-CoO x nanotubes on the Mn-CNF surface. In the presence of PVP, ZIF-67 oriented attachment occurs, forming evenly dispersed CoO x particles even after high temperature annealing. XRD spectra exhibit the formation of metallic Co nanoparticles (NPs), whereas Raman spectra and XPS indicate Co particle oxidation. A carbon coating limits the oxidation of Co; thus, the particles are called C/Co-CoO x. A symmetric supercapacitor cell prepared using the CNFs decorated with C/Co-CoO x using an aqueous electrolyte has a capacitance of 1263 mF⋅cm−2 at a current density of 0.25 mA⋅cm−2 and a wide potential window of 1.4 V for the optimal case. Long-term cycling showed 110 % capacitance retention after 10,000 cycles. Moreover, bending tests and powering LEDs demonstrated the flexibility and improved charge storage of the prepared nanofiber electrodes. [ABSTRACT FROM AUTHOR]

• The δ-MnO 2 @Fe-CNFs with various morphology were fabricated by varying pH and Fe ratio. • The δ-MnO 2 @Fe-CNF-5% at pH = 2 shows tubular structure with uniform MnO 2 nanosheet assembly. • The δ-MnO 2 @Fe-CNF-5% has excellent supercapacitor performance. • The δ-MnO 2 @Fe-CNF-5% achieves a high salt adsorption of 20 mg/g in CDI device. • The δ-MnO 2 @Fe-CNF-5% has high stability, superior to δ-MnO 2 @CNF. Birnessite-type MnO 2 (δ-MnO 2) nanosheet assembly with various structures were achieved by redox reaction of KMnO 4 under acidic condition with Fe regulation on Fe-doping carbon nanofibers (Fe-CNFs). The Fe-CNFs with various Fe contents were conveniently obtained by carbonization of the electrospun ferric acetylacetonate-polyacrylonitrile (AAI-PAN) fiber with various AAI ratios. X-ray diffraction and transmission electron microscopy demonstrated the formation of δ-MnO 2 on the Fe-CNFs. pHs of KMnO 4 solution and Fe content in the fiber affected the morphology of δ-MnO 2. At pH = 2, the uniform δ-MnO 2 nanosheet assembly was transferred into a tubular structure by adjusting Fe content in the Fe-CNFs template (AAI = 5%, mass ratio). The obtained δ-MnO 2 @Fe-CNF-5% exhibited the highest aspect ratio, large surface area and best charge-transfer behavior. The δ-MnO 2 @Fe-CNF-5% electrode delivered a specific capacitance of 210 F/g (0.3 A/g) and a superior cycling stability with 94% capacitance retention in 4500 cycles. The δ-MnO 2 @Fe-CNF-5%, as a negative electrode presented an excellent performance both in supercapacitor with high energy density (20 Wh/kg) and in capacitive deionization cell with the salt adsorption capacity of 20 mg/g. The unique nanostructure and excellent electrochemical performance render the δ-MnO 2 @Fe-CNF-5% composite as a much promising material for charge storage and deionization applications. [ABSTRACT FROM AUTHOR]

• NPCNFs/PANI with Integrated architecture has been well designed. • 3D continuous and conductive network can reduce internal resistance effectively. • Large surface areas and hierarchical porosity decrease the ion diffusion length. • The all-solid-state flexible device exhibits desirable electrochemical properties. Electrode materials with rationally designed architecture are crucial to achieve high-performance supercapacitors. However, there is still a great challenge for integrating the features of large accessible surface areas, fast electron/ion transport kinetics and favorable mechanical flexibility within a single electrode. Herein, we propose a facile approach to fabricate high-performance freestanding carbon-based electrode of polyaniline modified nitrogen-doped hierarchical porous carbon nanofibers, which effectively combine the merits of highly conductive electrospun carbon nanofibers with hierarchical porous structure, suitable nitrogen content as well as pseudocapacitive materials. Benefiting from the well-designed architecture, the as-assembled symmetric all-solid-state flexible device exhibits a high specific capacitance of 260 F g−1 at 0.5 A g−1 and high rate capability with a capacitance retention of 60% at 16 A g−1. Furthermore, the device also displays a desirable energy density of 8.9 Wh kg−1 with power density of 0.27 kW kg−1 and excellent cycling stability with 80.1% capacitance retention after 10,000 charge-discharge cycles at 2 A g−1. Eventually, the as-designed composite electrodes open up new avenues for facile construction of high-performance supercapacitor electrodes. [ABSTRACT FROM AUTHOR]