Electrolyte‐Enabled Suppression of Static Corrosion for Long‐Cycle Calendar Life in Lithium Metal Batteries

The calendar life of lithium (Li) metal batteries is commonly evaluated through cycling performance, implicitly assuming that storage‐induced degradation follows the same interfacial processes. However, this work reveals that Li metal undergoes continuous non‐Faradaic interfacial corrosion under open‐circuit conditions, defining a distinct degradation pathway governing calendar aging, distinct from cycling‐induced failure. To quantify this process, we introduce a kinetically defined descriptor based on the degradation rate constant (λ), enabling direct evaluation of time‐dependent capacity loss during storage. This framework treats calendar aging as a corrosion‐driven kinetic process rather than an extrapolation of cycling behavior. We further show that static corrosion can be actively regulated via electrolyte design. Based on the degradation rate constants derived from capacity decay fitting, the LiNO 3 ‐15C5‐CsBr electrolyte projects a 2.7‐fold extension in storage lifetime at 100% SOC and a 3.4‐fold extension at 0% SOC versus the baseline electrolyte. Mechanistically, Cs + ‐mediated electrostatic shielding, Br − ‐induced interfacial polishing, and NO 3 − ‐derived inorganic passivation cooperatively stabilize the Li interface, suppress corrosion kinetics, and reduce irreversible Li loss, leading to a marked decrease in λ. These findings establish static corrosion as a distinct degradation mode in Li metal batteries and provide a quantitative framework for evaluating and regulating calendar aging beyond cycling metrics.