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

In this study, we explored a high-throughput automated chromatography strategy for fast screening high-performance fluorinated block copolymers as electrolyte additives for ultrastable Zn-ion batteries. The proposed polymer, synthesized through controlled reversible addition-fragmentation chain-transfer (RAFT) polymerization, features a hydrophilic oligo(ethylene glycol) methyl ether acrylate (OEGA) block to provide water solubility, and a fluorophilic perfluoropolyether (PFPE) segment as the fluorine source. Our investigations reveal that the balance between OEGA and fluorine plays a key role in modulating interactions between Zn²⁺ and the fluorinated polymer additives. The degree of polymerization (DP) of OEGA affects both the coordination environment of Zn²⁺ and water and the exposure of the hydrophobic fluorinated core. Meanwhile, the fluorinated segment facilitates the formation of a protective ZnF₂-rich layer, contributing to the stabilization of the solid electrolyte interphase (SEI). Benefiting from this synergistic effect, the polymer additive significantly improves battery performance, achieving stable cycling for 3800 h in symmetric Zn|Zn cells with a Coulombic efficiency (CE) of over 99.6% in Zn|Cu cells. Notably, the Zn|NVO full cell demonstrates excellent capacity retention, maintaining 98.4% of its initial capacity after 5000 cycles at 5 A g^-1, with a per-cycle capacity decay as low as 0.00032%. In addition, the Zn|NVO pouch cell delivers stable cycling with a capacity retention of 92% after 700 cycles. This work highlights the important role of composition balance in developing fluorinated polymer additives, puts forward valuable molecular design guidelines for functional additives for practical energy storage applications.