Amphiphilic Fluorinated Block Copolymer Additives for Ultrastable Aqueous Zn-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Developing stable and high-performance zinc-ion batteries is crucial for next-generation energy storage.
• Electrolyte additives play a key role in stabilizing the solid electrolyte interphase (SEI) and improving battery longevity.
• Fluorinated polymers offer unique properties for enhancing electrolyte performance due to their chemical stability and tunable characteristics.

Purpose of the Study:

• To explore high-throughput screening of fluorinated block copolymers as electrolyte additives for ultrastable zinc-ion batteries.
• To investigate the role of polymer composition, specifically the balance between hydrophilic and fluorophilic segments, in modulating battery performance.
• To establish molecular design guidelines for effective functional additives in energy storage applications.

Main Methods:

• Synthesis of fluorinated block copolymers using controlled reversible addition-fragmentation chain-transfer (RAFT) polymerization.
• Incorporation of hydrophilic oligo(ethylene glycol) methyl ether acrylate (OEGA) and fluorophilic perfluoropolyether (PFPE) blocks.
• High-throughput automated chromatography for fast screening of polymer additives.
• Electrochemical testing of zinc-ion batteries (symmetric Zn|Zn, Zn|Cu, and Zn|NVO cells) to evaluate performance metrics like Coulombic efficiency and capacity retention.

Main Results:

• The balance between OEGA and fluorine content in the polymer additives critically influences Zn²⁺ interactions and SEI formation.
• Fluorinated segments promote the formation of a protective ZnF₂-rich SEI layer, enhancing interfacial stability.
• Polymer additives enable stable cycling for 3800 hours in symmetric Zn|Zn cells (CE > 99.6%) and achieve excellent capacity retention (98.4% after 5000 cycles) in Zn|NVO full cells.

Conclusions:

• Compositional balance in fluorinated block copolymers is vital for designing effective electrolyte additives for zinc-ion batteries.
• The developed polymer additives significantly enhance battery cycle life, Coulombic efficiency, and capacity retention.
• This study provides valuable molecular design principles for advanced functional additives in practical energy storage systems.