Structure-Property Correlations in Aqueous Binary Na⁺/K⁺-CH₃COO^- Highly Concentrated Electrolytes

Area of Science:

• Electrochemistry
• Materials Science
• Physical Chemistry

Background:

• Aqueous electrolytes are crucial for electrochemical applications like energy storage.
• Highly concentrated acetate salt solutions, particularly potassium acetate (CH3COOK), enable water-in-salt electrolytes.
• These electrolytes enhance cathodic stability and are compatible with alkali-ion battery materials.

Purpose of the Study:

• To investigate the physicochemical and electrochemical properties of concentrated aqueous binary solutions of CH3COOK and CH3COONa.
• To identify an optimal electrolyte composition for rechargeable alkaline-ion batteries.
• To understand the fundamental interactions and phase behavior within these concentrated solutions.

Main Methods:

• Preparation and characterization of aqueous binary acetate salt solutions.
• Measurement of conductivity and electrochemical stability window.
• Raman spectroscopy for analyzing interaction networks and phase evolution.
• Crystallization kinetics studies.

Main Results:

• A solution of 20 mol kg-1 CH3COOK + 7 mol kg-1 CH3COONa exhibited the best balance of properties.
• This optimal solution showed a conductivity of 21.2 mS cm-1 at 25 °C.
• An electrochemical stability window of up to 3 V was observed under specific conditions.

Conclusions:

• Concentrated acetate salt solutions are viable electrolytes for electrochemical applications.
• The investigated CH3COOK/CH3COONa system demonstrates potential for rechargeable alkaline-ion batteries.
• Further understanding of solution behavior via spectroscopy aids in optimizing electrolyte design.