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

Effects of chemical composition and vacant oxygen defects on the performance of Ni(OH)2–Ni0.85Se heterostructure nanowires as supercapacitor electrodes

The research focus of supercapacitors is the composition and structural design of electrode materials.

Hierarchical core-shell nickel hydroxide@nitrogen-doped hollow carbon spheres composite for high-performance hybrid supercapacitor

Designing electrode materials with high performance and maximum utilization is of great desire for supercapacitors, which highly depend on the intrinsic electrochemical properties and the optimal frameworks of the electrode materials. The hierarchical core-shell structure with various types of pores can make the most of the electrode material due to the easy access of electrolyte into the interior electrode and large exposure of electrode into the electrolyte. In this work, nickel hydroxide@nitrogen-doped hollow carbon spheres (Ni(OH)₂@NHCSs) electrode material with a hierarchical core-shell structure was obtained using a hard template and the following chemical-precipitation method. Ni(OH)₂@NHCSs electrode displays an excellent specific capacity of 214.8 mA h g^-1 (that is 1546.6 F g^-1), higher than the Ni(OH)₂ counterpart (108.9 mA h g^-1, that is 784.1 F g^-1) at 1 A g^-1 in 2 M KOH electrolyte. The assembled Ni(OH)₂@NHCSs||NHCSs hybrid supercapacitor (HSC) delivers an energy density of 37.5 W h kg^-1 at 800.0 W kg^-1 and an outstanding stability with 79.2% of retention rate for 10,000 cycles at a current density of 8 A g^-1. The Ni(OH)₂@NHCSs electrode exhibits excellent electrochemical performance primarily contributed by its unique hierarchical core-shell structure, high specific surface area and enhanced electrical conductivity.

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.

Template-Free Preparation of α-Ni(OH)2 Nanosphere as High-Performance Electrode Material for Advanced Supercapacitor

Although it is one of the promising candidates for pseudocapacitance materials, Ni(OH)₂ is confronted with poor specific capacitance and inferior cycling stability. The design and construction of three-dimensional (3D) nanosphere structures turns out to be a valid strategy to combat these disadvantages and has attracted tremendous attention. In this paper, a 3D α-Ni(OH)₂ nanosphere is prepared via a facile and template-free dynamic refluxing approach. Significantly, the α-Ni(OH)₂ nanosphere possesses a high specific surface area (119.4 m²/g) and an abundant porous structure. In addition, the as-obtained α-Ni(OH)₂ electrodes are investigated by electrochemical measurements, which exhibit a high specific capacitance of 1243 F/g at 1 A/g in 6 M KOH electrolyte and an acceptable capacitive retention of 40.0% after 1500 charge/discharge cycles at 10 A/g, which can be attributed to the sphere’s unique nanostructure. Furthermore, the as-assembled Ni(OH)₂-36//AC asymmetric supercapacitor (ASC) yields a remarkable energy density of 26.50 Wh/kg, with a power density of 0.82 kW/kg. Notably, two ASCs in series can light a 2.5 V red lamp sustainably for more than 60 min, as well as power an LED band with a rated power of 25 W. Hence, this 3D α-Ni(OH)₂ nanosphere may raise great potential applications for next-generation energy storage devices.

1D-on-1D core-shell cobalt iron selenide @ cobalt nickel carbonate hydroxide hybrid nanowire arrays as advanced battery-type supercapacitor electrode

Sluggish kinetics and poor structural stability are two main obstacles hampering the exploration of transition metal selenides (TMSs) for supercapacitor. Developing a reasonable core-shell heterostructure with unique morphology is an effective approach to resolve these issues. Herein, a core-shell cobalt iron selenide (CoFe₂Se₄) @ cobalt nickel carbonate hydroxide (CoNi-CH) heterostructure is directly fabricated on carbon cloth via an electrodeposition method followed by a hydrothermal reaction. In this well-defined heterostructure, one-dimensional (1D) CoFe₂Se₄ nanowires function as the cores and CoNi-CH nanowires as the shells, which combines the merits of highly conductive CoFe₂Se₄ for rapid electron transfer and highly electroactive CoNi-CH for multiple redox reactions. Further, the intimate interaction between CoNi-CH and CoFe₂Se₄ realizes large surface area with hierarchical network and generates rich heterointerfaces with modified the electronic structure. By virtue of its facile 1D-on-1D nanoarchitecture and synergistic effect, the CoFe₂Se₄@CoNi-CH electrode delivers a increased specific capacity of 218.6 mAh g^-1 at 1 A^-1 and enhanced rate capability (65.5% at 20 A g^-1) compared with pure CoFe₂Se₄ and CoNi-CH. Besides, a hybrid supercapacitor is established by coupling CoFe₂Se₄@CoNi-CH cathode and porous carbon anode, which enjoys a maximum energy density of 67.3 Wh kg^-1 at 765.9 W kg^-1 and prominent durability with 85.4% of capacity retention over 20,000 cycles.