A Four-Electron-Transfer Robust Small-Molecule Organic Anode for Low-Strain Potassium Storage

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Potassium-ion batteries (PIBs) are attractive for grid-scale energy storage due to potassium's abundance.
• Developing high-capacity, stable anodes for PIBs is crucial for their practical application, especially for accommodating large K⁺ ions.

Purpose of the Study:

• To introduce 2,2 -bipyridine-4,4 -dicarboxylic acid (BDA), a small-molecule organic compound, as a high-performance anode material for PIBs.
• To investigate the electrochemical properties and storage mechanism of BDA in PIBs.

Main Methods:

• Electrochemical testing (galvanostatic cycling) to evaluate capacity and cycling stability.
• In situ/ex situ characterizations and theoretical calculations to elucidate the K⁺ storage mechanism.

Main Results:

• BDA demonstrates a high reversible capacity (398 mAh g^-1 at 100 mA g^-1) and excellent cycling stability (retaining 186 mAh g^-1 after 1000 cycles at 1000 mA g^-1).
• The K⁺ storage mechanism involves initial irreversible deprotonation/potassiation forming K₂BDA, followed by reversible storage dominated by carbonyl and imine sites with minimal volume change.
• An all-organic PIB utilizing a BDA anode achieved a high energy density of 174 Wh kg^-1.

Conclusions:

• BDA is a viable small-molecule organic anode for high-performance PIBs, addressing the limitations of current anode materials.
• The study provides insights into the mechanism of organic anodes in PIBs, paving the way for future material design.