Highly reversible zinc anode enabled by composite tailored polyimide separator

Zinc-ion batteries (ZIBs) are highly suitable for storing energy due to their exceptional safety and efficiency. However, uncontrolled Zn2+ deposition builds and quickly penetrates the separator. To surmount this obstacle, a fundamental coating of polyimide (PI) on commercial GF separator (PI@GF) is used enabling quick kinetics and minimal overpotential in 0.5 M Zn triflate TMP electrolyte. The separator has widespread imide –CO–N–CO– groups that interact strongly with Zn2+, therefore, it increases anode-electrolyte wettability and modifies Zn2+ solvation structure. The composite separator efficiently protected the Zn anode, for 6000 hours at 1 mA cm-2, compared to 110 hours with the standard GF separator even surviving till 6 mA cm-2 and more importantly, has excellent safety at high temperature (50 ⁰C) with ultra-large areal capacity of 10 mAh cm-2. Due to its exceptional characteristics, the PI@GF separator enhances the transference of Zn2+ ions from 0.45 to 0.53, by facilitating the guidance of zinc ion nucleation, growth, and deposition while maintaining 99.7% coulombic efficiency for 1000 hours. Undoubtedly, the energy barrier for Zn2+ transport across the PI@GF separator was decreased via simulation studies. This study reveals how functional separator design may influence Zn2+ deposition activity and provide a dendrite-free Zn anode.