Tailored Design of Electrochemically Degradable Anthraquinone Functionality toward Organic Cathodes

Area of Science:

• Materials Science
• Electrochemistry
• Organic Chemistry

Background:

• Organic cathode materials are crucial for rechargeable batteries.
• Understanding redox properties of non-carbon functionalities in 9,10-anthraquinone is limited.
• Halogenated nitrogen-based functionalities in anthraquinones can lead to structural instability.

Purpose of the Study:

• Investigate the potential of anthraquinones with halogenated nitrogen-based functionalities.
• Understand the cause of Li-triggered structural collapse during battery discharge.
• Propose solutions to mitigate structural decomposition and enhance performance.

Main Methods:

• Computational investigation of anthraquinone derivatives with varied functionalities (NX2, BX2, NH2, BH2).
• Analysis of Lewis acid-base interactions and electronic properties.
• Correlation of redox properties with electron affinity, solvation energy, and electronegativity.

Main Results:

• Li-triggered structural collapse is due to N-Li-X interactions, overpowering N-X bond repulsion.
• Replacing N/X with electron-deficient atoms (B, H) prevents decomposition by relieving N-X bond repulsion.
• BH2 substitution shows the most significant improvement in theoretical battery performance.
• Redox properties correlate better with electron affinity and solvation energy than electronegativity.
• Solvation energy is critical for determining electrochemical redox potential and cathodic deactivation.
• BH2-substituted anthraquinones exhibit enhanced Li storage due to sustained negative solvation energy.

Conclusions:

• Substitution with electron-deficient atoms like Boron and Hydrogen effectively stabilizes anthraquinone structures.
• The BH2 functional group offers the most promising pathway for high-performance organic cathode materials.
• Electron affinity and solvation energy are key descriptors for tuning redox properties and stability in organic batteries.