Inhibiting interfacial side reactions via constructing a hydrophilic separator toward durable and fast Zn storage

Aqueous Zn-ion batteries have garnered considerable attention ascribed to the cost-effectiveness, high safety and environmental sustainability. However, the cycling life is severely restricted primarily due to H₂O-induced side reactions. Herein, the interfacial side reactions are significantly restrained via fixing H₂O molecules within a smartly designed hydrophilic separator. Consequently, the durable and fast Zn storage performance is not only remarkably achieved, but the effects of hydrophilic separator on inhibiting interfacial side reactions are also comprehensively revealed. First, the interfacial H₂O molecules can be anchored in the designed hydrophilic separator through a hydrogen bonding between hydroxyl groups and H₂O molecules, effectively decreasing the moisture content at the electrode-electrolyte interfaces, thereby significantly inhibiting interfacial side reactions. Second, desolvation process of hydrated Zn ions is prominently enhanced when passing through the hydrophilic separator, in favor of boosting kinetics performances. As a result, the as-designed hydrophilic separator enables symmetric cells with a long lifespan (2000 h at 10 mA cm⁻²), as well as full cells with fast-charging (183.2 mAh g⁻¹ at 20 A g⁻¹) and stable-cycling capabilities (81.26 % retention after 5000 cycles). This study illustrates how hydroxyl groups inhibit interfacial side reactions and provides insights for developing other advanced separators in aqueous batteries.