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In this work, a novel flexible electrode material for supercapacitor is prepared by electrodeposition of Ni-Co-S interconnected nanosheet arrays on N-doped hierarchical porous carbon nanofibers (Ni-Co-S@N-pCNFs). The electrode exhibits a remarkable specific capacitance of 520.2 F g -1  at the current density of 0.2 A g −1 and 670 F g -1  at 2 mV s −1 . The activated charcoal (AC) loaded N-doped porous carbon nanofibers (AC@N-pCNFs) as electrode is also prepared which exhibits a specific capacitance of 257.2 F g -1  at 0.2 A g −1 , as well as excellent cycling stability with a capacitance retention of 92.6% after 5000 cycles. Furthermore, the Ni-Co-S@N-pCNFs as the positive electrode, active carbon loaded N-doped hierarchical porous carbon nanofibers (AC@N-pCNFs) as negative electrode, and KOH/NKK hybrids as both the electrolyte and separator are assembled into flexible asymmetric supercapacitor. The assembled supercapacitor device without using any current collectors or binders shows a high energy density of 21.6 Wh·kg −1 at a power density of 134.9 W kg −1 and robust long-term cycling stability retaining over 90.0% after 3000 cycles at 1.0 A g −1 . The as-assembled asymmetric supercapacitors (ASCs) have an outstanding mechanical flexibility and electrochemical stability and no significant attenuation occurred during cycling under different bending states. [ABSTRACT FROM AUTHOR]

Flexible supercapacitors with both high energy and high power densities are critical for flexible electronics. In this paper, hybrid flexible carbon nanofibers decorated with NiCo 2 S 4 nanoparticles are successfully prepared by combination of electrospinning, carbonization and hydrothermal treatments. The obtained hybrid carbon nanofibers display remarkable specific capacitance (527.8 F g −1 at the current density of 0.2 A g −1 and 622.5 F g −1 at 2 mV s −1 ), good rate capability (310.5 F g −1 at 4.0 A g −1 ) and excellent cycle stability (retaining 90.0% after 3000 cycles). The flexible asymmetric supercapacitors based on carbon nanofibers decorated with NiCo 2 S 4 and porous carbon nanofibers coated with activated charcoal are fabricated. The combined unique properties of each of these components enable highly flexible and mechanically strong films that can serve as electrodes directly without using any current collectors or binders. The fabricated device shows an energy density of 32.1 Wh kg −1 at power density of 67.6 W kg −1 and cycle stability retaining 88.5% after 1500 cycles at 1.0 A g −1 . Therefore, the novel flexible asymmetric device with perfect flexibility and stability can be applied as one of the most promising power supplies. [ABSTRACT FROM AUTHOR]

In this paper, a hollow sulfur@graphene oxide core–shell composite is synthesized for high-performance lithium-sulfur batteries through a facile two-step solution method with the assistance of polyvinylpyrrolidone. Scanning electron microscope observation shows that the hollow sulfur sphere is coated by the homogeneous graphene oxide nanolayer, and thermogravimetric analysis demonstrates the composite holds sulfur loading as high as 92 wt%. The composite served as cathode in lithium-sulfur batteries shows its capacity as high as 745 mAh g −1 at 0.2C after 20 cycles. It also has an excellent cycling stability even at a high current density of 1C (73% retention and 96% coulombic efficiency after 150 cycles), implying that the diffusion of the polysulfides into electrolyte can be greatly inhibited. It is believed that the structure design of graphene oxide coated hollow sulfur sphere can be developed for the practical application of high-performance lithium-sulfur batteries. [ABSTRACT FROM AUTHOR]

• Sericin acts as a biosorbent to anchor iron ions (Fe3+) by coordination. • Fe 3 C is uniformly dispersed in sericin-derived carbon (SC) by in-situ synthesis. • The modification of Fe 3 C to SEI film is confirmed by ex-situ EIS analysis. • Fe 3 C/SC presents high reversible capacity, rate capability and stable cyclability. • The strategy can be used to design other carbon-based materials for energy storage. [Display omitted] Biomass-derived carbon is considered a promising alternative to commercial graphite anode because of its renewability and tunable physical/chemical properties. However, the specific capacity and rate capability of biochar anode materials must be further enhanced to satisfy the increasing energy demand. Here, we report a facile strategy to synthesize uniform Fe 3 C inserted sericin-derived porous carbon (Fe 3 C/SC) via coordination with Fe3+ ions to the carboxylate radicals of sericin protein. The obtained composite retains a hierarchical pore structure with an interconnected carbon scaffold. In particular, the embedded Fe 3 C nanoparticles (NPs) in the carbon matrix will serve as a catalyst for the modification of the solid electrolyte interphase (SEI) layer during the cycles, which effectively enhance reversible capacity. The resulting anode provides high reversible capacity (584.0 mAh g−1 at 0.1 A g−1 after 150 cycles), superior rate capability (259.0 mAh g−1 at 2 A g−1) and remarkable cycling stability under high current density (219.7 mAh g−1 retention at 2 A g−1 after 600 cycles). This composite is expected to be one of the most potential anode materials for lithium-ion batteries, owning to its cost-effective, facile synthesis and efficient performance with excellent electrochemical properties. [ABSTRACT FROM AUTHOR]