Quantitative corrosion framework for anti-corrosive passivation design to extend calendar life in lithium metal batteries

Reactive lithium metal renders it prone to corrosion, which severely limits calendar life and practicality in energy storage. Despite its importance, corrosion-induced degradation remains largely qualitative and lacks a clear mechanistic understanding. Here, we present a quantitatively integrated and experimentally validated framework that correlates lithium corrosion with interphase growth kinetics and interfacial morphological evolution. Guided by this model, a bi-layered anti-corrosive passivation layer composed of lithium polyacrylate embedded with lithium silver alloy-fluoride interphase is rationally designed. The outer polymer-rich layer resists swelling and blocks corrosion, while the underlying LiAg/LiF-rich interphase enhances interfacial transport kinetics. Operando X-ray microscopy reveals that calendar-aged lithium regions are particularly vulnerable to accelerated corrosion, which intensifies dendritic formation and is effectively suppressed by the passivation layer. Consequently, full-cells show a high-rate capacity of 133 mAh g^-1 at 10 C (6 min) and retain 74.6% capacity after 400 cycles at 0.5 C (120 min), with Coulombic efficiency above 99.9%. Under a four-hour rest protocol for calendar life evaluation, full-cells maintain 75.1% capacity after 200 cycles, and further pouch cell testing shows 85.5% capacity after 640 cycles. This study offers insights into corrosion dynamics and informs the design of passivation strategies for improving calendar life in lithium metal batteries.