Design of a multifunctional gradient double coating layer for a stable thin zinc anode with high depth of discharge

Abstract

Practical application of aqueous zinc-ion batteries (ZIBs) is challenging because of the uncontrolled dendrite growth and interfacial side reactions on zinc anodes. Here, we propose a multifunctional gradient double coating strategy comprising a hydrophilic gelatinized-starch film top layer (GF) and a conductive, zincophilic carbon bottom layer (C). This hierarchical design mitigates aqueous corrosion while optimizing the desolvation kinetics and Zn deposition. The hydrophilic layer regulates the solvation structures, whereas the conductive carbon matrix enhances ionic conductivity and promotes uniform Zn nucleation. Furthermore, the mechanically robust coating suppresses dendrite propagation and stabilizes the electrode interface. Thus, the modified Zn anode achieves exceptional cycling stability (3000 h at 1 mA cm⁻²/1 mA h cm⁻²) and deep cycling capability (200 h at 85% DOD_Zn). In a full cell with a vanadium-based-oxide cathode (V₂O₅), 60.4% of the capacity is retained after 1000 cycles. This strategy provides valuable insights into interfacial engineering for next-generation ZIBs.