Unveiling Competitive Coordination in Aqueous Lithium-Ion Electrolytes through Solvent Descriptor Engineering.

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Aqueous electrolytes for high-voltage lithium-ion batteries face limitations due to narrow electrochemical windows and unstable hydrogen evolution reactions (HER).
• These issues stem from the electrolyte's solvation structure, influenced by interactions between anions, water, and cosolvents coordinated with lithium ions (Li+).

Purpose of the Study:

• To develop a direct solvent descriptor for designing advanced electrolytes.
• To facilitate specific Li+-anion coordination within the solvation sheath to enhance battery performance.

Main Methods:

• Utilized a synergistic approach involving dielectric constant and dipole moment to engineer electrolyte solvation.
• Modified cation competitive coordination to reduce water's role in the primary solvation shell and promote stable interfacial chemistry.

Main Results:

• Achieved a wide electrochemical stability window of 4.55 V and suppressed HER.
• Demonstrated a stable 2.5 V LiMn2O4-Li4Ti5O12 full battery with high discharge capacity (138.4 mAh g-1) and excellent cycle life (99% Coulombic efficiency over 1000 cycles at 3 C).

Conclusions:

• Solvation structure modification via cation competitive coordination is a viable strategy for developing stable, high-energy-density aqueous batteries.
• The proposed descriptor enables rational design of electrolytes for advanced energy storage applications.