One-pot construction of 3-D graphene nanosheets/Ni3S2 nanoparticles composite for high-performance supercapacitors

One-Step Cooperative Growth of High Reaction Kinetics Composite Homogeneous Core-Shell Heterostructure

Reaction kinetics can be improved by the enhanced electrical contact between different components growing symbiotically. But so far, due to the necessity for material synthesis conditions match, the component structures of cooperative growth are similar, and the materials are of the same type. The collaborative growth of high-reaction kinetics composite homogeneous core-shell heterostructure between various materials is innovatively proposed with different structures in one step. The NiCo-LDH and PPy successfully symbiotically grow on activated carbon fiber fabric in one step. The open channel structure of the NiCo-LDH nanosheets is preserved while PPy effectively wrapped around the NiCo-LDH. The well-defined nanostructure with abundant active sites and convenient ion diffusion paths is favorable for electrolyte entry into the entire nanoarrays. In addition, owing to the enhanced electronic interaction between different components through XPS analysis, the NiCo-LDH@PPy electrode shows outstanding reaction kinetics and structural stability. The as-synthesized NiCo-LDH@PPy exhibited excellent super-capacitive storage capabilities, robust capacitive activity, and good rate survival. Furthermore, an asymmetric supercapacitor (ASC) device made of NiCo-LDH@PPy and activated carbon (AC) is able to maintain a long cycle life while achieving high power and energy densities.

Recent Progress of Hollow Carbon Nanocages: General Design Fundamentals and Diversified Electrochemical Applications

Hollow carbon nanocages (HCNCs) consisting of sp2  carbon shells featured by a hollow interior cavity with defective microchannels (or customized mesopores) across the carbon shells, high specific surface area, and tunable electronic structure, are quilt different from the other nanocarbons such as carbon nanotubes and graphene. These structural and morphological characteristics make HCNCs a new platform for advanced electrochemical energy storage and conversion. This review focuses on the controllable preparation, structural regulation, and modification of HCNCs, as well as their electrochemical functions and applications as energy storage materials and electrocatalytic conversion materials. The metal single atoms-functionalized structures and electrochemical properties of HCNCs are summarized systematically and deeply. The research challenges and trends are also envisaged for deepening and extending the study and application of this hollow carbon material. The development of multifunctional carbon-based composite nanocages provides a new idea and method for improving the energy density, power density, and volume performance of electrochemical energy storage and conversion devices.

Synthesis of NiCo2S4@NiMoO4 Nanosheets with Excellent Electrochemical Performance for Supercapacitor

Currently, the research of energy storage devices mainly focuses on enhancing their electrochemical performance. Core-shell structured NiCo2S4@NiMoO4 is thought to be one of the most promising electrode materials for supercapacitors due to its high specific capacitance and excellent cycle performance. In this work, we report NiCo2S4@NiMoO4 nanosheets on Ni foam by a two-step fabricated method. The as-obtained product has a high capacitance of 1035 F g−1 at 1 A g−1. The as-assembled supercapacitor has a high energy density of 32.4 W h kg−1 at a power density of 3230 W kg−1 and a superior cycle performance, with 70.1% capacitance retention. The electrode materials reported here might exhibit potential applications in future energy storage devices.

An Amorphous-Crystalline Nanosheet Arrays Structure for Ultrahigh Electrochemical Performance Supercapattery

Hybrid supercapacitors (HSCs), also called supercapattery, which can substitute for low power density batteries have attracted extensive interest. However, when HSCs comes to commercial applications, there is still space for improvement in energy density. It seems that designing of electrode with high capacity is an effective measure. Herein, amorphous-crystalline MoO₃ -Ni₃ S₂ /NF-0.5 nanosheet arrays are developed as battery-type electrodes. Specifically, the sheet-like structure of crystalline Ni₃ S₂ can achieve rich structural nanocrystallization, improving the redox reaction efficiency. Meanwhile, the disordered structure and irregular surface of the amorphous MoO₃ are conducive to maximize the contact between the electrode and electrolyte, slowing down the volume change caused by the continuous charge-discharge process. As a result, it displays an ultrahigh areal specific capacity of 8.52 C cm^-2 at 5 mA cm^-2 , and superior lifespan up to 7500 cycles with 90.0% retention. Further, when assembled into HSCs, the specific capacity reaches 1.47 C cm^-2 , corresponding to an energy density of 4.18 mWh cm^-2 at a power density of 0.34 mW cm^-2 . Totally, the design of the unique structure displays a valuable measure for rational development of high energy density hybrid energy storage devices that are not limited to supercapacitors.

One-pot synthesis of N,S-doped pearl chain tube-loaded Ni3S2 composite materials for high-performance lithium-air batteries

To improve the high reversibility of lithium-air batteries, an air electrode needs to have excellent electrochemical performance and spatial structure. Ni3S2 nanoparticles are loaded onto an N,S-doped pearl chain tube (N,S-PCT) by a method called quasi-chemical vapor deposition (Q-CVD). Additionally, N and S are doped during the synthesis process, thereby forming an ideal pipe rack-like structure. The large amount of space in the tube rack can provide sufficient storage to act as a buffer for the discharge products, and the interconnected tubes can effectively promote the dispersion of O2 and electrolyte. The addition of Ni3S2 nanoparticles effectively reduces the charge transfer resistance, thereby increasing the electron mobility of the cathode. Ni3S2@N,S-PCT cathodes effectively improve the cycling and high-rate performance of lithium-air batteries, demonstrating an ultrahigh discharge capacity of 16 733.7 mA h g-1 at a current density of 400 mA g-1 and an ultrahigh discharge capacity of 5088.1 mA h g-1 at a current density of 1000 mA g-1. When the cut-off capacity is 1000 mA h g-1, the battery with the Ni3S2@N,S-PCT-800 electrode can achieve cycling stability for 148 cycles. This research provides a new solution for the design of lithium-air batteries with high electrocatalytic performance.

Dual-functional NiCo2S4 polyhedral architecture with superior electrochemical performance for supercapacitors and lithium-ion batteries

Dual-functional NiCo₂S₄ polyhedral architectures with outstanding electrochemical performance for supercapacitors and lithium-ion batteries (LIBs) have been rationally designed and successfully synthesized by a hydrothermal method. The as-synthesized NiCo₂S₄ electrode for supercapacitor exhibits an outstanding specific capacitance of 1298Fg^-1 at 1Ag^-1 and an excellent rate capability of ~80.4% at 20Ag^-1. Besides, capacitance retention of 90.44% is realized after 8000 cycles. In addition, the NiCo₂S₄ as anode in LIBs delivers high initial charge/discharge capacities of 807.6 and 972.8mAhg^-1 at 0.5C as well as good rate capability. In view of these points, this work provides a feasible pathway for assembling electrodes and devices with excellent electrochemical properties in the next generation energy storage applications.

The construction of a 2D MoS2-based binder-free electrode with a honeycomb structure for enhanced electrochemical performance

MoS₂ is in situ grown on Ni foam while maintaining a 2D morphology and a MoS₂/Ni₃S₂/NF electrode is obtained with a 3D honeycomb microstructure.

Ni(OH)2 Nanoflakes Supported on 3D Ni3 Se2 Nanowire Array as Highly Efficient Electrodes for Asymmetric Supercapacitor and Ni/MH Battery

Porous Ni(OH)₂ nanoflakes are directly grown on the surface of nickel foam supported Ni₃ Se₂ nanowire arrays using an in situ growth procedure to form 3D Ni₃ Se₂ @Ni(OH)₂ hybrid material. Owing to good conductivity of Ni₃ Se₂ , high specific capacitance of Ni(OH)₂ and its unique architecture, the obtained Ni₃ Se₂ @Ni(OH)₂ exhibits a high specific capacitance of 1689 µAh cm^-2 (281.5 mAh g^-1 ) at a discharge current of 3 mA cm^-2 and a superior rate capability. Both the high energy density of 59.47 Wh kg^-1 at a power density of 100.54 W kg^-1 and remarkable cycling stability with only a 16.4% capacity loss after 10 000 cycles are demonstrated in an asymmetric supercapacitor cell comprising Ni₃ Se₂ @Ni(OH)₂ as a positive electrode and activated carbon as a negative electrode. Furthermore, the cell achieved a high energy density of 50.9 Wh L^-1 at a power density of 83.62 W L^-1 in combination with an extraordinary coulombic efficiency of 97% and an energy efficiency of 88.36% at 5 mA cm^-2 when activated carbon is replaced by metal hydride from a commercial NiMH battery. Excellent electrochemical performance indicates that Ni₃ Se₂ @Ni(OH)₂ composite can become a promising electrode material for energy storage applications.

Biotemplate derived three dimensional nitrogen doped graphene@MnO2 as bifunctional material for supercapacitor and oxygen reduction reaction catalyst

Natural diatomite with abundant pores was used as a biotemplate for the massive production of three-dimensional (3D) porous graphene by chemical vapor deposition method. Subsequent template removal and nitrogen doping treatment yield nitrogen doped 3D graphene with preserved shape and complex internal features of the diatomite. After further deposition with MnO₂ nanosheets, the N-doped 3D graphene@MnO₂ (N-G@MnO₂) hybrid exhibited excellent supercapacitor and good oxygen reduction reaction (ORR) performance. Accordingly, the porous N-G@MnO₂ electrode exhibited a high specific capacitance (411.5 F g^-1) and a good cycling performance (88.3% capacitance retention after 4000 charge/discharge cycling test). When tested in a two-electrode configuration, N-G@MnO₂ achieved a wide potential window up to 1.8 V with a high energy density of 46.1 Wh kg^-1. Furthermore, the as-prepared N-G@MnO₂ showed good performance in oxygen reduction reaction, which is comparable to those of commercially available Pt/C electrode. The enhanced capacitive and electrocatalytic properties and stability is due to the synergistic interactions between the porous 3D graphene and MnO₂ nanosheets. The results indicate that the 3D N-G@MnO₂ could be useful for supercapacitor and ORR catalyst.

In situ self-assembly of Ni3S2/MnS/CuS/reduced graphene composite on nickel foam for high power supercapacitors

Transition metal sulfides (TMS), as promising electroactive materials for asymmetric supercapacitors, have been limited due to their relatively poor conductivity and cycle stability. Here ternary Ni₃S₂/MnS/CuS composites were assembled in situ on nickel foam (NF) using a hydrothermal method via electrostatic adsorption of Ni⁺, Mn²⁺ and Cu²⁺ ions on a reduced graphene (rGO) nanosheet template. The chemical structure was characterized by various analytic methods. Ni₃S₂/MnS/CuS has spherical morphology assembled from closely packed nanosheets, while Ni₃S₂/MnS/CuS@rGO has a three-dimensional porous spherical structure with much lower diameter because rGO nanosheets can play the role of a template to induce the growth of Ni₃S₂/MnS/CuS. At a current density of 1 A g⁻¹, the specific capacitance was obtained to be 1028 F g⁻¹ for Ni₃S₂/MnS/CuS, 628.6 F g⁻¹ for Ni₃S₂/MnS@rGO, and 2042 F g⁻¹ for Ni₃S₂/MnS/CuS@rGO, respectively. Charge transfer resistance (R_ct) of Ni₃S₂/MnS/CuS@rGO (0.001 Ω) was much lower than that of Ni₃S₂/MnS@rGO by 0.02 Ω, and lower than that of Ni₃S₂/MnS/CuS by 0.017 Ω. After 5000 cycles, the Ni₃S₂–MnS–CuS@RGO electrode maintains 78.3% of the initial capacity at 20 A g⁻¹. An asymmetric supercapacitor was subsequently assembled using Ni₃S₂/MnS/CuS@rGO as the positive electrode and rGO as the negative electrode. The specific capacitance of asymmetric batteries was maintained at 90.8% of the initial state after 5000 GCD.

Transition metal sulfides (TMS), as promising electroactive materials for asymmetric supercapacitors, have been limited due to their relatively poor conductivity and cycle stability.

Dual carbon-modified nickel sulfide composites toward high-performance electrodes for supercapacitors

Dual carbon-modified nickel sulfide composites have been facilely prepared and they deliver excellent energy storage performance for supercapacitors.