Bio‐Inspired Polyanionic Electrolytes for Highly Stable Zinc‐Ion Batteries

Abstract For zinc‐ion batteries (ZIBs), the non‐uniform Zn plating/stripping results in a high polarization and low Coulombic efficiency (CE), hindering the large‐scale application of ZIBs. Here, inspired by biomass seaweed plants, an anionic polyelectrolyte alginate acid (SA) was used to initiate the in situ formation of the high‐performance solid electrolyte interphase (SEI) layer on the Zn anode. Attribute to the anionic groups of −COO − , the affinity of Zn 2+ ions to alginate acid induces a well‐aligned accelerating channel for uniform plating. This SEI regulates the desolvation structure of Zn 2+ and facilitates the formation of compact Zn (002) crystal planes. Even under high depth of discharge conditions (DOD), the SA‐coated Zn anode still maintains a stable Zn stripping/plating behavior with a low potential difference (0.114 V). According to the classical nucleation theory, the nucleation energy for SA‐coated Zn is 97 % less than that of bare Zn, resulting in a faster nucleation rate. The Zn||Cu cell assembled with the SA‐coated electrode exhibits an outstanding average CE of 99.8 % over 1,400 cycles. The design is successfully demonstrated in pouch cells, where the SA‐coated Zn exhibits capacity retention of 96.9 % compared to 59.1 % for bare Zn anode, even under the high cathode mass loading (>10 mg/cm 2 ).