Facile Synthesis of Zn-Co-S Nanostrip Cluster Arrays on Ni Foam for High-Performance Hybrid Supercapacitors

Synthesis of Ni3S2 and MOF-Derived Ni(OH)2 Composite Electrode Materials on Ni Foam for High-Performance Supercapacitors

Honeycomb-like Ni(OH)₂/Ni₃S₂/Ni foam (NF) was fabricated via a two-step hydrothermal process and subsequent alkalization. Ni₃S₂ with a honeycombed structure was in-situ synthesized on the NF surface by a hydrothermal process. MOF-derived Ni(OH)₂ nanosheets were then successfully grown on the Ni₃S₂/NF surface by a second hydrothermal process and alkaline treatment, and a large number of nanosheets were interconnected to form a typical honeycomb-like structure with a large specific surface area and porosity. As a binder-free electrode, the prepared honeycomb-like Ni(OH)₂/Ni₃S₂/NF exhibited a high specific capacitance (2207 F·g^-1 at 1 A·g^-1, 1929.7 F·g^-1 at 5 mV·s^-1) and a remarkable rate capability and cycling stability, with 62.3% of the initial value (1 A·g^-1) retained at 10 A·g^-1 and 90.4% of the initial value (first circle at 50 mV·s^-1) retained after 5000 cycles. A hybrid supercapacitor (HSC) was assembled with Ni(OH)₂/Ni₃S₂/NF as the positive electrode and activated carbon (AC) as the negative electrode and exhibited an outstanding energy density of 24.5 Wh·kg^-1 at the power density of 375 W·kg^-1. These encouraging results render the electrode a potential candidate for energy storage.

Hierarchically nanostructured Zn0.76C0.24S@Co(OH)2 for high-performance hybrid supercapacitor

It is a great challenge to achieve both high specific capacity and high energy density of supercapacitors by designing and constructing hybrid electrode materials through a simple but effective process. In this paper, we proposed a hierarchically nanostructured hybrid material combining Zn_0.76Co_0.24S (ZCS) nanoparticles and Co(OH)₂ (CH) nanosheets using a two-step hydrothermal synthesis strategy. Synergistic effects between ZCS nanoparticles and CH nanosheets result in efficient ion transports during the charge-discharge process, thus achieving a good electrochemical performance of the supercapacitor. The synthesized ZCS@CH hybrid exhibits a high specific capacity of 1152.0 C g^-1 at a current density of 0.5 A g^-1 in 2 M KOH electrolyte. Its capacity retention rate is maintained at ∼ 70.0% when the current density is changed from 1 A g^-1 to 10 A g^-1. A hybrid supercapacitor (HSC) assembled from ZCS@CH as the cathode and active carbon (AC) as the anode displays a capacitance of 155.7 F g^-1 at 0.5 A g^-1, with a remarkable cycling stability of 91.3% after 12,000cycles. Meanwhile, this HSC shows a high energy density of 62.5 Wh kg^-1 at a power density of 425.0 W kg^-1, proving that the developed ZCS@CH is a promising electrode material for energy storage applications.