Modulating Molecular Microheterogeneity within Electrolytes Controls Macroscopic Battery Performance

Area of Science:

• Electrochemistry
• Materials Science
• Physical Chemistry

Background:

• Aqueous batteries are limited by narrow electrochemical windows and high reactivity.
• Understanding and controlling water molecule reactivity in electrolytes is crucial but challenging.

Purpose of the Study:

• To investigate how ether molecules influence the microstructure of aqueous solutions.
• To establish correlations between electrolyte microstructure and the reactivity of water molecules.
• To enhance the electrochemical stability and performance of aqueous electrolytes.

Main Methods:

• Employed six ether molecules with varying structures and solvation powers.
• Analyzed microstructural parameters like solvation power difference, Li+ coordination number, and water cluster size.
• Investigated electrolyte performance in LiMn2O4||Li4Ti5O12 full cells and a 1 Ah aqueous pouch cell.

Main Results:

• A positive solvation power difference between ether and water promotes microheterogeneity, reducing Li+ coordination number and water cluster size.
• Small, isolated water clusters suppress long-range water diffusion, enhancing electrochemical stability.
• Diethyl ether optimized electrolyte microstructure, enabling fast Li+ diffusion and an expanded electrochemical window.
• Full cells achieved 97.5% capacity retention over 200 cycles; pouch cells delivered 80.93 Wh kg-1 energy density.

Conclusions:

• Microstructural tuning via ether molecules is effective for stabilizing aqueous electrolytes.
• Controlling water cluster size and Li+ coordination is key to improving battery performance.
• This approach offers a pathway for designing high-performance aqueous batteries for energy storage.