Nanostructured Mn-Doped Ni–Co Hydroxide Microspheres for Fast-Kinetics Supercapacitors

Abstract

Transition-metal double hydroxides offer many benefits, including abundant nanostructures, low cost, easy preparation, diverse compositions, and adjustable physicochemical properties, which have a wide range of applications and are highly promising for the development of high-performance electrode materials. Herein, hydrangea-like manganese-doped nickel−cobalt double hydroxide (NiCoDH-Mn) nanostructures were prepared through a fast one-step microwave hydrothermal method within a few minutes. A thorough analysis was conducted on how the nanostructure, crystal structure, and electrochemical properties of the samples were affected by the amount of the Mn doping content. Density functional theory (DFT) calculations demonstrated that the introduction of Mn doping can generate impurity levels around the Fermi level of NiCoDH, enhancing its electrical conductivity. At a current density of 1 A g −1 , the optimized NiCoDH-Mn has a remarkable specific capacity of 107.4 mA h g −1 . Even when the current density increases by 15 times, it can still maintain a high specific capacity of 66.3 mA h g −1 . After undergoing 1500 cycles with a current density of 5 A g −1 , the electrode's capacity remains 128%. The hybrid supercapacitor consisting of the NiCoDH-Mn cathode and mango seed-derived activated carbon anode has an impressive energy density of 47.9 W h kg −1 and a power density of 850 W kg −1 . Moreover, it boasts an impressive capacitance retention rate of 87.5%, even after 5000 cycles. We offer a highly effective and speedy approach to creating highperformance transition-metal hydroxides that are ideal for energy storage systems.

Layered double hydroxide-based electrode materials derived from metal–organic frameworks: synthesis and applications in supercapacitors

“…Manganese (Mn) is particularly notable for its high conductivity, rich oxidation states, high theoretical capacity, and abundance, facilitating its wide application in enhancing the electrochemical performance of binary LDHs. 38 We reported the synthesis of Ni–Co–Mn LDH hollow nanocages by etching bimetallic CoMn-ZIF with nickel nitrate. The resulting Ni–Co–Mn LDH exhibited significantly better performance in specific capacitance and rate performance compared to the binary Ni–Co LDH.…”

Rapid Microwave Hydrothermal Synthesis of NiCoMo Sulfide Nanosheet Arrays for Hybrid Supercapacitors

“…Developing and synthesizing novel materials for electrodes with enhanced electrochemical efficiency is a direct and practical approach to enhance the storage of energy for these devices. The specific surface area of transition metal compounds is critically linked to their pseudocapacitive performance. , Pseudocapacitance pertains to a particular form of energy storage mechanism that involves Faradaic reactions, wherein electrolyte ions engage in redox reactions at or adjacent to the surface of the electrode. Exposing a considerable amount of reactive sites for the electrolyte ions through a greater specific surface area results in an enhancement of the pseudocapacitance.…”