Network-Anchored Nanocages Create Weakly Solvating Electrolytes for Subzero Aqueous Zinc Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Low-temperature operation of aqueous zinc batteries is hindered by electrolyte freezing and slow interfacial kinetics due to strong ion-solvent interactions.
• Developing electrolytes that function effectively in sub-zero conditions is crucial for expanding battery applications.

Purpose of the Study:

• To engineer a weakly solvating hydrogel electrolyte for stable low-temperature aqueous zinc battery performance.
• To investigate the role of steric effects and solvation structure on electrochemical properties at sub-zero temperatures.

Main Methods:

• Fabrication of a hydrogel electrolyte incorporating network-anchored fluorinated zirconium-based metal-organic polyhedra (MOPs).
• Electrochemical testing of Zn||Zn symmetric and Zn||MnHCF full cells at temperatures down to -40°C.
• Spectroscopic, electrochemical, and theoretical analyses to elucidate ion solvation and interfacial mechanisms.

Main Results:

• The developed electrolyte enables stable cycling of Zn||Zn symmetric cells for over 3700 hours at -40°C.
• Zn||MnHCF full cells exhibit a capacity of 65.8 mAh g⁻¹ at -20°C (82% retention after 350 cycles) and 24.6 mAh g⁻¹ at -40°C.
• Zr-based MOPs were shown to weaken Zn²⁺ solvation, accelerate charge transfer, and suppress parasitic reactions.

Conclusions:

• The steric-regulated, weakly solvating hydrogel electrolyte effectively addresses low-temperature limitations in aqueous zinc batteries.
• Metal-organic polyhedra provide a viable strategy for designing advanced electrolytes for extreme condition energy storage.
• This work presents a new design paradigm for low-temperature aqueous battery electrolytes.