Inorganic Oxide‐Based “Hydrophobic–Hydrophilic–Hydrophobic” Separators Systems for Long‐Life Zinc‐Ion Batteries

Abstract Hydrogen reduction reaction (HER) and corrosion limit the long‐life cycle of zinc‐ion batteries. However, hydrophilic separators are unable to prevent direct contact between water and electrodes, and hydrophobic separators have difficulty in transporting electrolytes. In this work, an inorganic oxide‐based “hydrophobic–hydrophilic–hydrophobic” self‐assembled separator system is proposed. The hydrophobic layer consists of a porous structure, which can isolate a large amount of free water to avoid HER and corrosion reactions, and can transport electrolyte by binding water. The middle hydrophilic layer acts as a storage layer consisting of the GF separator, storing large amounts of electrolyte for proper circulation. By using this structure separator, Zn||Zn symmetric cell achieve 2200 h stable cycle life at 5 mA cm −2 and 1mAh cm −2 and still shows a long life of 1800 h at 10 mA cm −2 and 1mAh cm −2 . The assembled Zn||VO 2 full cell displays high specific capacity and excellent long‐term durability of 60.4% capacity retention after 1000 cycles at 2C. The assembled Zn||VO 2 pouch full cell displays high specific capacity of 172.5mAh g −1 after 40 cycles at 0.5C. Changing the inorganic oxide materials, the hydrophobic–hydrophilic–hydrophobic structure of the separators still has excellent performance. This work provides a new idea for the engineering of water‐based battery separators.