Suspension Electrolyte for Protecting Aqueous Zinc Batteries From Calendar Aging

ABSTRACT Aqueous zinc batteries (AZBs) offer safety and cost‐effectiveness for large‐scale energy storage, yet their development is hindered by calendar aging originating from spontaneous Zn corrosion in aqueous electrolytes. This issue is especially critical for grid batteries, which remain idle for extended periods. Here, we present a strategy of suspension electrolyte to improve the calendar performance of AZBs by dispersing only 3 wt.% of Al 2 O 3 nanoparticles into a conventional ZnSO 4 electrolyte. Under a calendar‐aging protocol, Zn||Cu cells with Al 2 O 3 suspension electrolyte achieve a threefold enhancement in calendar lifespan and significantly improve Coulombic efficiency from 91.7% to 97.1%. We demonstrate that the Al 2 O 3 suspension electrolyte forms a protective interfacial layer at the Zn anode that serves as a physical barrier while absorbing water, H + , and OH − ions to mitigate water reactivity and buffer pH fluctuations, thereby effectively suppressing parasitic corrosion. Furthermore, Zn||MnO 2 full cells with Al 2 O 3 suspension electrolyte exhibit higher specific capacities across all rates and retain over 100 mAh g −1 at 1 A g −1 for 1500 cycles. These findings highlight suspension electrolyte as a low‐cost and effective approach to advancing AZBs for long‐duration large‐scale energy storage.