Ion-Specific Templating in Deep Eutectic Solvent Directs Carbon Architectures for High-Performance Potassium-Ion...

Area of Science:

• Materials Science
• Electrochemistry
• Green Chemistry

Background:

• Developing high-performance carbon anodes from sustainable biomass for potassium-ion batteries (KIBs) is challenging due to difficulties in controlling pore structure and defects.
• Current methods often rely on empirical approaches, lacking a predictable design principle.

Purpose of the Study:

• To establish a design principle for converting biomass into advanced carbon materials for KIBs.
• To demonstrate the role of metal ions in deep eutectic solvents (DES) in governing carbonization pathways.

Main Methods:

• Utilized choline chloride-urea-MCl2 (M = Ca, Mg, Zn) DES systems to investigate the effect of metal ions on biomass carbonization.
• Analyzed the structural properties (interlayer spacing, defect density, nitrogen configuration) of the resulting carbon materials.
• Evaluated the electrochemical performance of the carbon anodes in KIBs, focusing on capacity, rate capability, and cycling stability.

Main Results:

• Identified Ca2+ as the key ion that directs the formation of nitrogen-doped carbon with an ideal structure for K+ storage.
• Achieved expanded interlayer spacing (0.376 nm), optimized defect density, and a favorable pyrrolic-N configuration using Ca2+.
• The Ca2+-regulated carbon anode exhibited a high reversible capacity (320 mAh g-1), excellent rate capability (212 mAh g-1 at 1 A g-1), and long-term stability (89% retention over 2000 cycles).

Conclusions:

• The identity of the metal ion in DES plays a crucial role in controlling biomass carbonization for KIB applications.
• This work provides a universal principle for the predictive design of biomass-derived carbons for efficient potassium-ion storage.
• Deep eutectic solvents can be programmed as reaction media for advanced material synthesis.