Agar‐Based Interface for Suppressing Parasitic Reactions toward High‐Performance Aqueous Zn‐Ion Batteries

Abstract With advantages including high capacity, intrinsic safety and low cost, aqueous zinc‐ion batteries (AZIBs) are ideal electrochemical energy storage devices for large‐scale and portable energy storage. However, the development of AZIBs suffers from tricky challenges, such as the notorious Zn dendrite growth and severe parasitic reactions. Herein, as a low‐cost and nontoxic biomass, agar is adopted to construct an interface layer on Zn foil to mitigate side reactions and induce uniform Zn deposition on Zn anodes. The interaction between Zn 2+ and polar functional groups of agar can regulate Zn 2+ distribution and promote Zn 2+ desolvation, thus simultaneously achieving homogenous Zn deposition and suppressed hydrogen evolution reaction. Meanwhile, SO 4 2− anions are blocked from contacting Zn surface due to electrostatic repulsion, greatly restraining corrosion and passivation. Consequently, Zn||A‐Cu asymmetric cell operates normally for 590 cycles with an average coulombic efficiency of 99.5 %, suggesting good reversibility of Zn plating/stripping. Notably, A‐Zn symmetric cell exhibits a long lifespan of 1100 h at 2 mA cm −2 . Furthermore, the A‐Zn||NVO full cell displays a superb capacity retention of 94.8 % after 3600 cycles at 5 A g −1 . This work offers a novel interface modification method for constructing stable and dendrite‐free anodes of AZIBs.