Small-Molecule Organic Cathodes with Carbon Coating for Highly Efficient Potassium-ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Small-molecule organic cathodes are promising for potassium-ion batteries (PIBs) due to their high capacity.
• However, dissolution of these organic cathodes in electrolytes limits their long-term stability and practical application in PIBs.

Purpose of the Study:

• To address the dissolution issue of small-molecule organic cathodes in PIBs.
• To develop a novel surface self-carbonization strategy to enhance the stability and electrochemical performance of organic cathodes.

Main Methods:

• Synthesized a new soluble small-molecule organic compound: [N,N'-bis(2-anthraquinone)]-1,4,5,8-naphthalenetetracarboxdiimide (NTCDI-DAQ).
• Applied surface self-carbonization by precisely controlling carbonization temperature and time to form a thin amorphous carbon protective layer on NTCDI-DAQ particles.
• Evaluated the electrochemical performance of the modified NTCDI-DAQ@C in PIBs using half and full cells.

Main Results:

• The surface self-carbonization effectively formed a controllable amorphous carbon layer, significantly increasing the insolubility of NTCDI-DAQ in liquid electrolytes.
• In half cells, NTCDI-DAQ@C exhibited superior capacity stability (84%) compared to bare NTCDI-DAQ (35%) over 30 cycles.
• In full cells with a KC8 anode, NTCDI-DAQ@C delivered a peak discharge capacity of 236 mAh g−1 and maintained 40% capacity over 3000 cycles at 1 A g−1, achieving a high energy density of 255 Wh kg−1.

Conclusions:

• The surface self-carbonization strategy is an effective method to improve the stability and electrochemical performance of soluble small-molecule organic cathodes in PIBs.
• The NTCDI-DAQ@C material demonstrates excellent cycling stability and high energy density, positioning it as a competitive candidate for advanced potassium-ion battery applications.