Improved Performance of Ionic Liquid Supercapacitors by using Tetracyanoborate Anions

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Supercapacitors offer high power density but limited energy density compared to batteries.
• Developing electrolytes with wider electrochemical windows is crucial for enhancing supercapacitor energy density.
• Ionic liquids (ILs) are promising electrolytes due to their wide electrochemical stability.

Purpose of the Study:

• To investigate the potential of ILs containing tetracyanoborate ([B(CN)4]) anions as electrolytes for supercapacitors.
• To evaluate the electrochemical performance, including operating voltage and specific capacitance, of these novel IL electrolytes.

Main Methods:

• Synthesis and characterization of ILs featuring the [B(CN)4] anion.
• Fabrication and testing of two-electrode supercapacitor devices using the developed IL electrolytes.
• Electrochemical performance evaluation at various charge/discharge rates.

Main Results:

• ILs with [B(CN)4] anions exhibited a high maximum operating voltage of 3.7 V.
• Supercapacitors demonstrated high specific capacitances (e.g., 20 F/g at 15 A/g) even at high rates.
• The [B(CN)4]-based ILs outperformed commonly studied ILs in terms of energy storage and power delivery across all tested rates.

Conclusions:

• Ionic liquids containing the tetracyanoborate anion are effective electrolytes for high-performance supercapacitors.
• These electrolytes enable significantly higher operating voltages and improved energy and power densities.
• The study highlights a promising pathway for advancing supercapacitor technology for broader applications.