Ternary Nanohybrid of Ni3S2/CoMoS4/MnO2 on Nickel Foam for Aqueous and Solid-State High-Performance Supercapacitors

Research Progress in the Preparation of Transition Metal Sulfide Materials and Their Supercapacitor Performance

Transition metal sulfides are widely used in supercapacitor electrode materials and exhibit excellent performance because of their rich variety, low price, and high theoretical specific capacity. At present, the main methods to prepare transition metal sulfides include the hydrothermal method and the electrochemical method. In order to further improve their electrochemical performance, two aspects can be addressed. Firstly, by controllable synthesis of nanomaterials, porous structures and large surface areas can be achieved, thereby improving ion transport efficiency. Secondly, by combining transition metal sulfides with other energy storage materials, such as carbon materials and metal oxides, the synergy between different materials can be fully utilized. However, future research still needs to address some challenges. In order to guide further in-depth research, it is necessary to combine the current research-derived knowledge and propose a direction for future development of transition metal sulfide electrode materials.

NiCo2S4/MoS2 Nanocomposites for Long-Life High-Performance Hybrid Supercapacitors

Metal sulfides (MS) and mixed metal sulfides (MTMS) have been considered potential candidates over their metal oxide/mixed metal oxide counterparts in recent years. Herein, one MTMS, i.e., NiCo₂S₄, was combined with 2D MS MoS₂ through a single-step solvothermal process with different morphologies (sheet-like and rod-like) for supercapacitor applications. The resulting electrode exhibited excellent coulombic efficiency, high specific capacitance, superior energy density, and, most importantly, ultra-high cycling stability. In particular, the electrode delivered a capacitance of 2594 F g^-1 at 0.8 A g^-1 after 45,000 charge/discharge cycles with a remarkable stability of 192%. Moreover, the corresponding hybrid supercapacitor device displayed an impressive coulombic efficiency of 123% after 20,000 cycles and 118% after 45,000 cycles. In addition, the device also exhibited a decent energy density of 31.9 Wh kg^-1 and good cycling stability of 102% over 15,000 cycles.

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.