Constructing Quasi‐Single Ion Conductors by a β‐Cyclodextrin Polymer to Stabilize Zn Anode

Abstract Aqueous Zn‐ion batteries (AZIBs) are promising for the next‐generation large‐scale energy storage. However, the Zn anode remains facing challenges. Here, we report a cyclodextrin polymer (P‐CD) to construct quasi‐single ion conductor for coating and protecting Zn anodes. The P‐CD coating layer inhibited the corrosion of Zn anode and prevented the side reaction of metal anodes. More important is that the cyclodextrin units enabled the trapping of anions through host–guest interactions and hydrogen bonds, forming a quasi‐single ion conductor that elevated the Zn ion transference number (from 0.31 to 0.68), suppressed the formation of space charge regions and hence stabilized the plating/striping of Zn ions. As a result, the Zn//Zn symmetric cells coated with P‐CD achieved a 70.6 times improvement in cycle life at high current densities of 10 mA cm −2 with 10 mAh cm −2 . Importantly, the Zn//K 1.1 V 3 O 8 (KVO) full‐cells with high mass loading of cathode materials and low N/P ratio of 1.46 reached the capacity retention of 94.5 % after 1000 cycles at 10 A g −1 ; while the cell without coating failed only after 230 cycles. These results provide novel perspective into the control of solid‐electrolyte interfaces for stabilizing Zn anode and offer a practical strategy to improve AZIBs.