Sodium Ion Capacitor Using Pseudocapacitive Layered Ferric Vanadate Nanosheets Cathode.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Sodium ion capacitors (SICs) offer a low-cost energy storage solution with high energy and power densities.
• Traditional SICs often use electric double-layer capacitive cathodes, which limit overall capacity.
• There is a need for advanced cathode materials to overcome capacity limitations in SICs.

Purpose of the Study:

• To develop high-performance non-aqueous sodium ion capacitors (SICs) with enhanced energy and power densities.
• To investigate the potential of pseudocapacitive layered ferric vanadate (Fe-V-O) as a cathode material for SICs.
• To elucidate the sodium storage mechanisms in both the cathode and anode materials.

Main Methods:

• Synthesis of layered ferric vanadate (Fe-V-O) nanosheets for use as a cathode.
• Assembly of non-aqueous SICs utilizing Fe-V-O cathodes and hard carbon (HC) anodes.
• Electrochemical characterization, including rate capability and cycling stability tests.
• Kinetics analysis and ex situ characterizations to understand the sodium storage mechanism.

Main Results:

• The Fe-V-O nanosheets cathode exhibited excellent rate capability and cycling stability.
• Pseudocapacitive sodium storage in Fe-V-O was confirmed, with over 83% of capacity from capacitive contribution.
• The hard carbon anode demonstrated a capacitive-adsorption mechanism and superior rate capability.
• The assembled HC//Fe-V-O SIC achieved a maximum energy density of 194 Wh kg⁻¹ and a power density of 3,942 W kg⁻¹.

Conclusions:

• Pseudocapacitive cathodes, specifically Fe-V-O, are highly effective for enhancing both energy and power densities in sodium ion capacitors.
• The synergistic combination of Fe-V-O cathodes and HC anodes leads to high-performance SICs.
• This study demonstrates a promising strategy for developing next-generation sodium-based energy storage devices.