Small-Dipole-Molecule-Containing Electrolytes for High-Voltage Aqueous Rechargeable Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• High-voltage aqueous rechargeable batteries offer safety and high specific energy but are limited by low-cost electrolytes with narrow electrochemical stability windows (ESW).
• Electrolyte decomposition in aqueous systems is primarily driven by the hydrogen bond network of water molecules within solvation sheaths.

Purpose of the Study:

• To develop low-cost aqueous electrolytes with enhanced safety and a wide ESW for aqueous lithium-, sodium-, and zinc-ion batteries.
• To investigate the mechanism of ESW expansion using small dipole molecules.

Main Methods:

• Synthesis of aqueous electrolytes incorporating small dipole molecules: glycerol (Gly), erythritol (Et), and acrylamide (AM).
• Utilized ab initio molecular dynamics (MD) simulations to analyze solvation-sheath structures and water molecule interactions.
• Fabricated and tested aqueous ion batteries using the developed electrolytes.

Main Results:

• Achieved an ESW exceeding 2.5 V in aqueous electrolytes containing Gly, Et, and AM.
• MD simulations confirmed that dipole molecules disrupt water's hydrogen bond network and deplete water from charge carrier solvation sheaths, widening the ESW.
• A lithium-ion battery using a Gly-containing electrolyte demonstrated a 2.45 V output and maintained 119.6 mAh g^-1 after 400 cycles.

Conclusions:

• Small dipole molecules effectively expand the ESW of aqueous electrolytes by modifying the hydrogen bond network and solvation structure.
• This strategy enables the development of safe, high-voltage, and low-cost aqueous electrolytes for advanced energy storage systems.
• The findings offer a new pathway for designing superior electrolytes for aqueous rechargeable batteries.