Ultra-Thin Hybrid Ion Exchange Interlayer for High Performance Aqueous Zn Metal Batteries

The application of aqueous zinc metal batteries (AZMBs) is limited by the poor cycling stability and undesired dendritic growth of Zn anodes. Herein, a Zn anode with an ultra-thin sulfonated poly(ether ether ketone) (SPEEK) and fluorinated carbon dots (FCDs) hybrid interlayer is developed to enhance AZMBs performance. The SPEEK/FCD interlayer possesses excellent stability and is found to play multiple functions, including effectively regulating electrolyte solvation structure by ion-exchange groups, promoting ion transport through the ion-exchange channels of the hybrid SPEEK/FCD interlayer, inducing the in situ formation of a stable ZnF₂-rich solid electrolyte interphase (SEI), and accommodating volume fluctuations during Zn plating/stripping cycles. As a result, at 1 mA cm^-2 and 1 mAh cm^-2, Zn||Zn symmetric cells with the optimized SPEEK/FCD Zn electrode exhibit an ultralong lifespan of over 5500 h, much better than that of the bare Zn electrode (119 h). In addition, at 1 A g^-1 after 1000 cycles, the Zn||V₂O₅ full cell with the optimized electrode retains 89.8% of its initial capacity, compared to 40.3% for the bare Zn electrode. These superior performances indicate the optimized Zn electrode is promising for next-generation AZMBs. Also, the simple and scalable method offers a valuable reference for improving the performance of other aqueous batteries and beyond.