Ultrathin 2D Ni/Co Hydroxide Heterostructures for High Energy Density Flexible Microsupercapacitor

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Assembling 2D ultrathin nanosheets into vertical heterostructures enhances energy storage by improving active sites, ion diffusion, and conductivity.
• Transition-metal hydroxides face challenges like random assembly, complex synthesis, instability, and poor interfacial contact, hindering their energy storage potential.

Purpose of the Study:

• To synthesize large-area, ultrathin, 2D Nickel/Cobalt hydroxide vertical heterostructures with nickel as the top layer.
• To overcome the limitations of traditional transition-metal hydroxides in energy storage applications.
• To investigate the synergistic effects and electrochemical performance of these novel heterostructures.

Main Methods:

• Wet chemical synthesis of 2D Nickel/Cobalt hydroxide vertical heterostructures.
• Electrochemical characterization including charge storage, capacity, and cycling stability tests.
• Density functional theory (DFT) simulations to understand interfacial interactions and electronic properties.

Main Results:

• Achieved 32% higher areal charge storage compared to Co/Ni hydroxide vertical heterostructures, 57% higher than Ni(OH)2, and 330% higher than Co(OH)2.
• Demonstrated high volumetric capacity (710 mAh cm-3) and energy density (285 mAh cm-3) in symmetric devices due to synergistic interactions.
• Flexible microsupercapacitors retained 75% capacitance after 15,000 cycles and showed stability under bending up to 135°.

Conclusions:

• The synthesized Nickel/Cobalt hydroxide vertical heterostructures offer superior electrochemical performance for energy storage.
• Synergistic interactions and optimized interfacial contact in these 2D heterostructures are key to enhanced energy density and stability.
• This study provides a valuable framework for designing advanced 2D heterostructures for next-generation energy storage materials.