Enhanced performance of multi-dimensional CoS nanoflake/NiO nanosheet architecture with synergetic effect for asymmetric supercapacitor

Core-Shell Structured Carbon Nanofiber-Based Electrodes for High-Performance Supercapacitors

The combination of multiple electrode materials and their reasonable structural design are conducive to the preparation of composite electrodes with excellent performance. In this study, based on carbon nanofibers grown with Ni(OH)₂ and NiO (CHO) prepared by electrospinning, hydrothermal growth, and low-temperature carbonization, five transition metal sulfides (MnS, CoS, FeS, CuS, and NiS) were hydrothermally grown on their surfaces, exhibiting that CHO/NiS had the optimal electrochemical properties. Subsequently, the effect of hydrothermal growth time on CHO/NiS revealed that the electrochemical performance of CHO/NiS-3h was optimal, with a specific capacitance of up to 1717 F g^-1 (1 A g^-1), due to its multistage core-shell structure. Moreover, the diffusion-controlled process of CHO/NiS-3h dominated its charge energy storage mechanism. Finally, the asymmetric supercapacitor assembled with CHO/NiS-3h as the positive electrode demonstrated an energy density of 27.76 Wh kg^-1 at a maximum power density of 4000 W kg^-1, and it still maintained a power density of 800 W kg^-1 at a maximum energy density of 37.97 Wh kg^-1, exhibiting the potential application of multistage core-shell composite materials in high-performance supercapacitors.

Tailoring the interfacial surfaces of tungsten and molybdenum tungsten disulfide electrodes for hybrid supercapacitors

The layered structures of tungsten disulfide (WS₂) and molybdenum tungsten disulfide (MoWS₂) are considered as the most promising electrode materials for energy storage devices. Herein, MS (magnetron sputtering) is required for the deposition of WS₂ and MoWS₂ on the surface of the current collector to attain an optimized layer thickness. The structural morphology and topological behavior of the sputtered material were examined via X-ray diffraction and atomic force microscopy. Three-electrode assembly was used to start the electrochemical investigations to identify the most optimal and effective sample among WS₂ and MoWS₂. CV (cyclic voltammetry), GCD (galvanostatic charging discharging), and EIS (electro-impedance spectroscopy) techniques were employed to analyze the samples. After preparing WS₂ with optimized thickness as the superior performing sample, a hybrid device was designed as WS₂//AC (activated carbon). With a remarkable cyclic stability of 97% after 3000 continuous cycles, the hybrid supercapacitor generated a maximum energy density (E_s) value of 42.5 W h kg^-1 and 4250 W kg^-1 of power density (P_s). Besides, the capacitive and diffusive contribution during the charge-discharge process and b-values were calculated by Dunn's model, which lay in the 0.5-1.0 range and the fabricated WS₂ hybrid device was found to have a hybrid nature. The outstanding outcomes of WS₂//AC make it suitable for future energy storage applications.

Hierarchical CuCo2O4@CoS-Cu/Co-MOF core-shell nanoflower derived from copper/cobalt bimetallic metal-organic frameworks for supercapacitors

Rational design of composite materials with unique core-shell nanoflower structures is an important strategy for improving the electrochemical properties of supercapacitors such as capacitance and cycle stability. Herein, a two-step electrodeposition technique is used to orderly synthesize CuCo₂O₄ and CoS on Ni foam coated with Cu/Co bimetal metal organic framework (Cu/Co-MOF) to fabricate a hierarchical core-shell nanoflower material (CuCo₂O₄@CoS-Cu/Co-MOF). This unique structure can increase the electrochemically active site of the composite, promoting the Faradaic redox reaction and enhancing its electrochemical properties. CuCo₂O₄@CoS-Cu/Co-MOF shows a prominent specific capacitance of 3150 F g^-1 at 1 A g^-1, marvelous rate performance of 81.82% (2577.3 F g^-1 at 30 A g^-1) and long cycle life (maintaining 96.74% after 10,000 cycles). What is more, the assembled CuCo₂O₄@CoS-Cu/Co-MOF//CNTs device has an energy density of 73.19 Wh kg^-1 when the power density is 849.94 W kg^-1. It has unexpected application prospects.