High-Performance Flexible Solid-State Asymmetric Supercapacitors Based on Bimetallic Transition Metal Phosphide...

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Transition metal phosphides (TMPs) are promising electrode materials for supercapacitors due to high capacity and conductivity.
• Developing advanced TMPs with enhanced electrochemical performance is crucial for energy storage applications.

Purpose of the Study:

• To synthesize bimetallic cobalt-nickel phosphide (CoNiP) ultrafine nanocrystals supported on carbon nanofibers (CNFs).
• To investigate CoNiP/CNF as a positive electrode material for asymmetric supercapacitors.
• To explore the impact of the Co:Ni ratio on supercapacitor performance.

Main Methods:

• Synthesis of bimetallic CoNiP ultrafine nanocrystals on CNFs.
• Electrochemical characterization of CoNiP/CNF as a supercapacitor electrode.
• Fabrication of a flexible solid-state asymmetric supercapacitor.
• Density functional theory (DFT) calculations to understand capacitance enhancement.

Main Results:

• Optimal Co:Ni ratio in CoNiP/CNF yielded an exceptional specific capacitance of 3514 F g⁻¹ and capacity of 1405.6 C g⁻¹ at 5 A g⁻¹.
• DFT calculations revealed that enriched density of states near the Fermi level contributes to enhanced capacitance.
• The fabricated flexible solid-state supercapacitor demonstrated a specific capacitance of 118.7 F g⁻¹ at 20 mV s⁻¹, an energy density of 32.2 Wh kg⁻¹, and excellent cycling stability.

Conclusions:

• Bimetallic CoNiP/CNF exhibits superior electrochemical performance compared to monometallic counterparts, setting a new benchmark for TMP-based supercapacitor electrodes.
• The developed flexible solid-state supercapacitor shows significant promise for practical applications in flexible electronic devices.
• The synergistic effect between cobalt, nickel, and carbon nanofibers is key to achieving high energy storage performance.