Achieving stable potassium-ion batteries by regulating solvent-cation-anion interactions

Area of Science:

• Electrochemistry
• Materials Science
• Physical Chemistry

Background:

• Understanding electrolyte behavior is crucial for advanced battery technologies.
• Potassium-ion batteries (KIBs) and lithium-ion batteries (LIBs) utilize various electrolyte components.
• Solvation structures significantly impact interfacial reactions and battery performance.

Purpose of the Study:

• To investigate the unique solvation structure of potassium bis(fluorosulfonyl)imide (KFSI) in 1,2-diethoxyethane (DEE).
• To compare these interactions with other electrolyte systems involving lithium ions and different solvents.
• To elucidate the role of these interactions in solid-electrolyte interphase (SEI) formation and solvent co-intercalation.

Main Methods:

• Computational modeling of ion-solvent interactions.
• Analysis of solvation structures (e.g., K+, Li+, FSI-, DEE, DME).
• Comparison of KFSI/DEE with KFSI/DME, LiFSI/DEE, and LiFSI/DME electrolytes.

Main Results:

• The KFSI/DEE electrolyte exhibits unique DEE-K+-FSI- interactions distinct from DME-based or Li+-based systems.
• The FSI- anion plays a significant role in interfacial reactions, contributing to a stable SEI.
• Preferential desolvation of intact DEE molecules from the K+ solvation shell is observed, differing from FSI- desolvation.

Conclusions:

• The unique solvation structure in KFSI/DEE is responsible for enhanced SEI formation.
• This solvation behavior may explain solvent co-intercalation into graphite anodes observed in LiFSI/DEE and KFSI/DME electrolytes.
• Further research into specific ion-solvent interactions can optimize electrolyte design for high-performance batteries.