Reactive negative electrodes like lithium (Li) suffer serious chemical and electrochemical corrosion by electrolytes, leading to deteriorated battery lifespan. This study quantitatively monitors Li corrosion and solid-electrolyte-interphase (SEI) progression using electrochemical tools and cryo-electron microscopy. A correlation between continuous Li corrosion and SEI dissolution is established. An anti-corrosion artificial passivation layer of low-solubility polymer and metal fluoride is designed, achieving prolonged operation of Li symmetric and Li||LiFePO4 cells with a 74% reduction in Li corrosion. This success extends to ampere-hour-scale pouch cells, demonstrating a strategy to improve Li metal battery durability by reducing Li loss.
