Trace amounts of fluorinated surfactant additives enable high performance zinc-ion batteries

Aqueous zinc-ion batteries are promising alternatives to lithium-ion batteries for grid-scale energy storage. However, the practical application of AZIBs is challenged by side reactions and unsatisfactory performance. Electrolyte additives are reported that can inhibit side reactions on the Zn anode and enlarge the working potential window of aqueous electrolytes. Here we propose that trace amounts of perfluorooctanoic acid (PFOA) can facilitate long-term reversible Zn deposition in AZIBs due to perfluorinated n-octyl chains ordered orientation adsorbing on the electrode surface. Benefitting from its intrinsic surfactant properties, PFOA additives can reduce the surface tension of electrolytes and improve the wettability of electrolytes on the electrode. Symmetric Zn cells survived up to 2200 hours owing to the self-adjusting absorption layer. The molecular dynamics results show that the as-formed electronegative adsorption layer acts as a zincophilic layer to regulate the ions in the electrolyte. With adding PFOA, the electrochemical stability window of aqueous electrolyte enlarged to 2.1 V. Owing to the ultra-low additive usage amount, this strategy provides a facile and low-cost method to tackle common issues in AZIBs.