Overlooked calendar issues of aqueous zinc metal batteries

Although the zinc metal plating and stripping chemistry offers a high specific capacity, this process suffers from poor reversibility, a crucial factor for long-term energy storage. Most studies so far have been focusing on cyclic aging but overlooked the impact of calendar aging on zinc metal behavior. In this perspective, we highlight the nearly cycle-independent and time-linear calendar aging mode of zinc metal anodes due to the lack of a protective solid-electrolyte interphase (SEI). This calendar aging could be the dominant factor in battery degradation throughout the entire life cycle. We advocate for a more critical evaluation of the battery lifespan and suggest strategies to circumvent calendar aging.