Solvation engineering decouples bulk and interfacial chemistry for robust potassium-ion batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• High-performance potassium-ion batteries face challenges due to conflicting bulk and interfacial electrolyte properties, especially under harsh conditions.
• Existing electrolytes struggle to balance safety (non-flammability) with optimal electrochemical performance.

Purpose of the Study:

• To decouple conflicting electrolyte properties in potassium-ion batteries by engineering solvation structures.
• To achieve non-flammable, stable, and fast-cycling potassium-ion batteries through tailored electrolyte design.

Main Methods:

• Incorporated 2,2,2-trifluoroethyl trifluoromethanesulfonate into a trimethyl phosphate-based electrolyte.
• Engineered a dynamic, weakly bound anion-K+ solvation structure regulated by anion-solvent interactions.
• Investigated interface stabilization, desolvation barriers, and K+ transference number.

Main Results:

• Achieved highly reversible potassium plating/stripping (98.9% Coulombic efficiency in K||Cu cells).
• Demonstrated 85% capacity retention over 1600 cycles with a graphite electrode.
• Showcased stable, fast-cycling performance across a wide temperature range (-20 to +45°C) in various cell configurations.

Conclusions:

• The solvation structure engineering strategy effectively breaks the trade-off between bulk and interfacial electrolyte properties.
• This approach enables non-flammable, stable, and high-performance potassium-ion batteries.
• Precise tuning of microscopic solvation structures via anion-solvent interactions offers a viable path for electrolyte optimization.