Flower-like Ni3Sn2@Ni3S2 with core-shell nanostructure as electrode material for supercapacitors with high rate and capacitance.

To enhance the specific capacitance as well as maintain satisfactory rate performance of nickel hydroxide and nickel sulfide, in this work, the ultra-fine nickel-tin nanoparticles with high conductivity are selected to synthesize Ni3Sn2@Ni(OH)2 and Ni3Sn2@Ni3S2 nanoflowers. Alloy as the core material improves the electrical conductivity of the composite, and the nanosheets prepared by electrochemical corrosion effectively avoid aggregation as well as increase the active sites of the electrode material. By adjusting the corrosion time, the Ni3Sn2@Ni(OH)2 with better morphology displays a high specific capacitance (1277.37C g-1 at 1 A g-1) and good rate performance (1028C g-1 at 20 A g-1). After sulfurization, the optimal Ni3Sn2@Ni3S2 perfectly retains the morphological characterizations of the precursor and exhibits ultra-high specific capacitance (1619.02C g-1 at 1 A g-1) as well as outstanding rate performance (1312C g-1 at 20 A g-1). The samples before and after vulcanization both have the excellent electrochemical properties, which is attributed to the rational design and construction of the alloy-based core-shell nanostructures. Besides, the all-solid-state hybrid supercapacitor (HSC) is assembled by Ni3Sn2@Ni3S2 as the positive electrode and activated carbon as the negative electrode, displaying outstanding energy density of 70.54 Wh kg-1 at 808.67 W kg-1 and excellent cycling stability (93.21 % after 10,000 cycles). This work provides a novel ingenuity for synthesizing high-performance supercapacitor electrodes.

Core-shell Ni1.5Sn@Ni(OH)2 nanoflowers as battery-type supercapacitor electrodes with high rate and capacitance.

Poor conductivity and aggregation of two-dimensional Ni(OH)2 nanosheets hinder their extensive applications in supercapacitors. In the current study, a core-shell nanoflower composite is successfully synthesized using a high conductivity Ni1.5Sn alloy and Ni(OH)2 nanosheets via a facile two-step hydrothermal reaction. The alloy material enhances the conductivity of the sample and promotes electron transport for Ni(OH)2. The as-prepared core-shell structure effectively restrains the clustering of nanosheets and improves the specific surface area of active materials. The optimized NS@NL-3 displays an outstanding specific capacitance (1002.2C g-1 at 1 A g-1) and satisfactory capacitance retention rate (80.63% at 20 A g-1) by adjusting the coating amount of Ni(OH)2 nanosheets, which is significantly higher compared with the performance of pure Ni(OH)2 (609.6C g-1 at 1 A g-1 and 55.64% at 20 A g-1). The all-solid-state hybrid supercapacitor (HSC) is fabricated with activated carbon (AC) as the negative electrode and NS@NL-3 as the positive electrode, which shows a high energy density of 57.4 Wh kg-1 at 803.6 W kg-1 as well as a superior cycling stability (88.45 % after 10,000 cycles). Experiment shows that 42 LEDs are effortlessly lit by two series-wound solid-state HSC devices, which indicates its high potential for practical applications.

WS2 nanosheets@ZIF-67-derived N-doped carbon composite as sodium ion battery anode with superior rate capability.

Devising novel composite electrodes with particular structural/electrochemical characteristics becomes an efficient strategy to advance the performance of rechargeable battery. Herein, considering the homogeneous transition metal sulfide with N-doped carbon derived from zeolitic imidazolate framework-67 (ZIF-67) and WS2 with large interlayer spacing, a laurel-leaf-like Co9S8/WS2@N-doped carbon bimetallic sulfide (Co9S8/WS2@NC) is engineered and prepared via a step-by-step method. As an electrode material for sodium ion batteries (SIBs), Co9S8/WS2@NC composite delivers high capacities of 480 and 405 mA h g-1 at 0.1 and 1.0 A g-1, respectively. As the current density increases from 0.1 to 5.0 A g-1, it provides specific capacity of 359 mA h g-1 with a capacity retention rate of 78.0%, which is higher than that of Co9S8@NC (63.5%) and WS2 (58.6%). The Co9S8/WS2@NC composite anode maintains a stable specific capacity (354 mA h g-1 at 2.0 A g-1). It also exhibits a high capacitive contribution ratio of 90.8% at 1.0 mV s-1. This study provides a new and reliable insight for designing bimetallic sulfide with two-dimensional nanostructure for energy storage.

Hierarchical Carbon Nanowire/Ni@MnO2 Nanocomposites for High-Performance Asymmetric Supercapacitors.

A 3D hierarchical carbon cloth/nitrogen-doped carbon nanowires/Ni@MnO2 (CC/N-CNWs/Ni@MnO2 ) nanocomposite electrode was rationally designed and prepared by electrodeposition. The N-CNWs derived from polypyrrole (PPy) nanowires on the carbon cloth have an open framework structure, which greatly increases the contact area between the electrode and electrolyte and provides short diffusion paths. The incorporation of the Ni layer between the N-CNWs and MnO2 is beneficial for significantly enhancing the electrical conductivity and boosting fast charge transfer as well as improving the charge-collection capacity. Thus, the as-prepared 3D hierarchical CC/N-CNWs/Ni@MnO2 electrode exhibits a higher specific capacitance of 571.4 F g-1 compared with those of CC/N-CNWs@MnO2 (311 F g-1 ), CC/Ni@MnO2 (196.6 F g-1 ), and CC@MnO2 (186.1 F g-1 ) at 1 A g-1 and remarkable rate capability (367.5 F g-1 at 10 A g-1 ). Moreover, asymmetric supercapacitors constructed with CC/N-CNWs/Ni@MnO2 as cathode material and activated carbon as anode material deliver an impressive energy density of 36.4 W h kg-1 at a power density of 900 W kg-1 and a good cycling life (72.8 % capacitance retention after 3500 cycles). This study paves a low-cost and simple way to design a hierarchical nanocomposite electrode with large surface area and superior electrical conductivity, which has wide application prospects in high-performance supercapacitors.

Ag nanosheets grown on Cu nanowire-based flexible films for sensitive non-enzymatic glucose sensors.

Cu nanowire (Cu NW) and Ag nanosheet (Ag NS) bimetallic nanocomposites were fabricated on a flexible polyethylene terephthalate (PET) slice for non-enzymatic glucose sensing via a facile two-step approach, vacuum filtration, and galvanic displacement. Low-cost Cu NW-based conductive films were employed as the conductive substrates to substitute the traditional glassy carbon electrodes or indium tin oxide electrodes. The highly stable Ag NSs grow directly on the surface of Cu NWs without additional binders. The AgNO3 concentration and displacement time were adjusted to control the consumption of Cu NWs and the growth of Ag nanostructures. With the large load of Ag and the great connection of Cu NWs, a high sensitivity of 2033 µA mM-1cm-2, a fast amperometric response of 2 s, a wide linear range of 0.0015-4.02 mM, and a satisfactory result in human serum analysis were obtained by this novel Ag NS/Cu NW/PET sensor. Especially the sensitivity of the sensor was over four-fold higher than that of pure Cu NWs/PET, benefiting from the synergistic effect of bimetals. Furthermore, the Ag NS/Cu NW/PET sensor demonstrated a stable amperometric signal against mechanical bending. The material holds promise to use to fabricate flexible electrochemical devices.