Ultrafast Microwave Synthesis of Nickel-Cobalt Sulfide/Graphene Hybrid Electrodes for High-Performance Asymmetrical Supercapacitors

Abstract

Nickel-cobalt sulfides (NCSs) with rich redox-active sites and remarkable theoretical capacitance have been regarded as promising electrode materials for supercapacitors. Various approaches have been developed for the synthesis of NCSs-based electrode materials. However, most of these methods require complex steps, high energy consumption, and time-consuming processes, which result in high cost, chemical contamination, and safety problems. Herein, we demonstrated a one-step ultrafast microwave approach for the successful preparation of NCS/graphene composite in 1 min. The prepared NCS/graphene composite can be used as a high-performance supercapacitor electrode with a high specific capacitance of 710 F g–1 at a current density of 0.5 A g–1 and a prominent cycling stability of 75% capacitance retention after 10 000 cycles. In addition, a high-performance asymmetric supercapacitor (ASC) was assembled using NCS/graphene composite as a positive electrode and activated carbon as a negative electrode. The fabricated ASC can deliver a high energy density of 30.29 Wh kg–1 at a power density of 400 W kg–1 and exhibit excellent cycling stability with a capacitance retention of 112% after 10 000 cycles. These impressive results demonstrated that microwave synthesis can be used as a highly efficient and ultrafast approach for the preparation of high-performance NCSs-based electrode materials.

Engineering of Transition Metal Sulfide Nanostructures as Efficient Electrodes for High-Performance Supercapacitors

“…The morphology and composition of TMEMs and the type of the electrolytes are the main factors that determine the SC’s performance . Unlike traditional TMEMs, binary transition metal sulfide (BTMS) electrodes (i.e., NiCo 2 S 4 , CoMoS 4 , CuCo 2 S 4 , MnCo 2 S 4 , and ZnCo 2 S 4 ) possess inherently higher storage capacity, higher electrical conductivity, quicker electron/ion diffusion, better redox properties, and better reversibility with long cycle life. − Additionally, they are endowed with unique physicochemical characteristics, thermal stability, several oxidation states, and richer Faradaic redox reaction properties that enhance the SC’s activity and durability significantly . Furthermore, BTMSs are easily prepared using various high-yielding methods from inexpensive and earth-abundant resources and could be easily combined with other materials or substrates to operate as electrodes for SCs.…”

Sophora-like Nickel–Cobalt Sulfide and Carbon Nanotube Composites in Carbonized Wood Slice Electrodes for All-Solid-State Supercapacitors

“…The unpleasant energy density is usually increased by combining carbon materials with pseudocapacitive materials, including conductive polymers and metal oxides or sulfides . For example, nickel–cobalt sulfide (NCS) has abundant redox reaction sites and high theoretical specific capacitance that help it enter the field of energy. − However, the inherent conductivity that NCS materials perform is not sufficient to achieve high-rate charge transfer, resulting in a sharp decline in capacitance and magnification performance, especially under fast charge/discharge rates. In addition, the structure of the electrode material is unstable in the scene of continuous charging and discharging. − In view of the above problems, the combination of NCS with a suitable structure and carbon-based materials, which have stable structural characteristics and high conductivity, may be an ideal strategy to obtain electrode materials with better comprehensive performance.…”

High-Performance MnO2 Nanowire/MoS2 Nanosheet Composite for a Symmetrical Solid-State Supercapacitor

“…It has been widely researched that a pseudocapacitor is an essential technological approach for superior electrochemical energy storage applications due to its excellent charge transfer reactions. − , Usually, transition metal oxides, such as MnO 2 , are promising for active substances in pseudocapacitors because of the striking cation exchange. The pseudocapacitors, such as the ruthenium oxide-based devices (RuO 2 ), have a large specific capacitance of 1580 F/g (at 1 mV/s).…”