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Compressible and flexible supercapacitors have aroused enormous interest of many scientific researchers for potential applications in wearable electronic products. However, the design and construction of the electrode with superior mechanical as well as electrical properties still face a lot of challenges. In present work, melamine foam/polypyrrole (MF/PPy) electrode with high deformation-tolerance and excellent electrochemical performance is prepared by in-situ interfacial polymerization of polypyrrole on commercial melamine foam, where PPy nanoparticles with size of 700 nm are uniformly anchored on the MF skeletons. The electrochemical characterizations show that the electrode exhibits excellent specific area capacitance of 2.685 F cm−2 at 2 mA cm−2 and good cyclic stability with more than 80% of capacitance remained after 3000 cycles. Furthermore, a symmetrical aqueous supercapacitor is assembled and exhibits an excellent energy density up to 75.95 μWh cm−2 at the power density of 5.82 mW cm−2 and excellent cycling stability as the current density increases by 10 times. Even under a high strain of 70%, about 95.76% of the initial capacitance is retained after 500 consecutive compressions. These outstanding performances enable the MF/PPy composite a promising candidate for potential applications in compressible and flexible electrochemical energy storage devices. [ABSTRACT FROM AUTHOR]

The hollow and spinous NiCo 2 S 4 nanotubes were designed and prepared through hydrothermal sulfurization reaction using the degummed natural cocoon silk as a template. Recently, ternary cobalt nickel sulfide, performing as the promising electrode material for supercapacitors has obtained great interests. Herein, the hollow and spinous NiCo 2 S 4 nanotubes are designed and prepared through a simple hydrothermal reaction using the natural silk as the template. The spinous Ni-Co precursors are grown on the natural silk through a facile hydrothermal strategy and the hollow structure is obtained by decomposing the silk via hydrothermal sulfurization. After the calcination treatment, the hollow and spinous NiCo 2 S 4 nanotubes are applied as the electrode material and exhibit better electrochemical performance than the solely vulcanized samples. In addition, owing to the unique hollow and spinous structure of NiCo 2 S 4 nanotubes, the supercapacitor electrode material shows good specific capacitance (630 F g−1 at 1 A g−1), low internal resistance R s (0.68 Ω) and high capacitance retention (91% after 3000 cycles) at 10 A g−1. Furthermore, an all-solid-state asymmetric supercapacitor is self-assembled with the SC400 composite and exhibits an energy density of 52.34 Wh kg−1 at the power density of 2206.37 W kg−1. Additionally, a blue LED indicator can be powered by connecting two ASCs in series. The prepared hollow and spinous NiCo 2 S 4 nanotubes with excellent electrochemical properties can envision promising applications in energy storage devices and nanotechnology. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Thermally-treated and acid-etched method is utilized to obtain flexible carbon fiber cloth. • N/O-enriched carbon fibers exhibit high surface area and large pore volume. • N- and O-rich functional groups can generate high pseudocapacitance. • The electrode based on N/O-enriched carbon fibers cloth shows prominent area-capacitance and flexibility. Abstract The fast development of portable devices has greatly stimulated the demand for flexible supercapacitors (FSCs). The key to assembling FSCs lies in the development of electrodes with high-performance and good flexibility. In this work, oxygeneous groups modified nitrogen-doped carbon fibers cloth (ONCC) was obtained through annealing the pre-oxidized polyacrylonitrile cloth (PPC), followed by a facile oxidation process using a mixture of concentrated sulfuric acid and concentrated nitric acid. By changing annealing temperature, the nitrogen content can be controlled in the obtained ONCC. It was found that the PPC annealed at 950 °C followed by acid etching for 60 min could deliver the excellent areal and gravimetric specific capacitance of 1385 mF cm−2 and 294.7 F g−1 at the current density of 1 mA cm−2, outstanding rate performance and superb cycling stability. Furthermore, the assembled FSC delivered a high energy density of 19.8 μWh cm−2 (4.03 Wh kg−1) at a power density of 50.1 μW cm−2 (10.2 W kg−1) and good flexibility under different bending conditions. This work provides a facile and efficient route to prepare high-performance carbon fiber based electrode materials in large scale for flexible all-solid-state energy storage devices. [ABSTRACT FROM AUTHOR]

Freestanding electrodes fabricated with hierarchical core-shell micro-/nano-structured materials synthesized from redox-type metal oxides show enormous potential for portable electronic devices. In this, a novel and facile strategy for the preparation of petaloid and origami-lantern shaped MnO 2 /Co 2 CH@C hierarchical porous core-shell nanorod arrays is proposed. The fabricated electrode based on MnO 2 /Co 2 CH@C hybrid composite exhibits superior capability of 2022 mF cm−2 under high current density of 5 mA cm−2, which can be explained by the well-oriented petal-like and origami-lantern shaped nanosheets as well as the 3D core-shell porous hierarchical structure. Additionally, a solid-state asymmetric supercapacitor equipment is assembled on basis of the synthesized hierarchical MnO 2 /Co 2 CH@C hybrid, exhibiting an energy density of 15 Wh kg−1 at the power density of 255 W kg−1. Notably, the multifunctional instrument can be operated by the assembled device for 8 min, while monitoring time, temperature and air humidity in a portable outdoor environment. Moreover, a blue indicator can also be operated for 9 min long, evidencing their potential commercial applications. Overall, this work demonstrates the promising potential of the synthesized novel origami-lantern shaped and highly oriented hierarchical composites for electrochemical energy storage applications. Petaloid and origami-lantern shaped MnO 2 /Co 2 CH@C hierarchical core-shell nanorod arrays are synthesized and employed for portable asymmetric supercapacitor. [Display omitted] • Petaloid and origami-lantern shaped MnO 2 /Co 2 CH@C hybrid is synthesized. • The fabricated MnO 2 /Co 2 CH@C electrode exhibits great electrochemical properties. • Multifunctional instrument and LED indicator can be powered for 8 min. • The instrument can monitor time, temperature and air humidity in outdoors. [ABSTRACT FROM AUTHOR]

Recently, elemental doping has proven to be an efficient method to improve the electrochemical performance of nanomaterials. In this work, we successfully synthesized Ni 1-x Co x MoO 4 with tunable morphologies through Co-doping by a facile chemical co-precipitation method, among which Ni 0.85 Co 0.15 MoO 4 displays an excellent specific capacitance (1301 F g−1 at 1 A g−1), which is higher than NiMoO 4 electrode (1050.4 F g−1 at 1 A g−1) and Ni 0.7 Co 0.3 MoO 4 electrode (755.2 F g−1 at 1 A g−1). In addition, Ni 0.85 Co 0.15 MoO 4 electrode shows excellent cycling stability with 86% retention of its original capacitance after 3000 cycles. Additionally, an asymmetric supercapacitor (ASC) device can be fabricated using Ni 0.85 Co 0.15 MoO 4 /nickel foam (Ni 0.85 Co 0.15 MoO 4 /NF) as positive electrode and active carbon/nickel foam (AC/NF) as negative electrode. The as-fabricated ASC achieves a high energy density of 37.26 Wh kg−1 at the power density of 400 W kg−1, highlighting its potential application for the efficient energy storage devices. Image 1 • This work proposed a facile chemical co-precipitation method for the synthesis of Ni 1-x CoxMoO 4 with tunable morphologies. • Different morphologies of Ni 1-x Co x MoO 4 were obtained by adjusting the Co doping ratio. • The Ni 0.85 Co 0.15 MoO 4 electrode exhibits excellent specific capacitance of 1301 F g−1 at 1 A g−1. [ABSTRACT FROM AUTHOR]