Mitigating lithium (Li) corrosion during both storage and cycling is crucial for the performance of lithium-metal polymer batteries (LMPBs), as these systems undergo repeated storage and operation. Despite this, research has predominantly focused on enhancing cycling, often neglecting storage stability. Here, we demonstrate that a polymer electrolyte containing LiTFSI/LiBF4 and FEC (D-LiBF4 FEC) significantly improves both corrosion resistance and cycling stability. The D-LiBF4 FEC electrolyte forms a dense, LiF-rich solid-electrolyte interphase (SEI) during storage, effectively reducing polymer decomposition and enhancing long-term performance in repeated cycling-storage conditions. In contrast, conventional LiTFSI/LiBOB and LiTFSI/LiDFOB systems fail to maintain prolonged cycling life after storage, as their organic-rich SEIs exacerbate Li corrosion. Our multi-faceted analysis―including depth-profiling X-ray photoelectron spectroscopy, electron micrography, and electrochemical studies―highlights the critical role of a high LiF-to-organic ratio in the SEI. We further propose a representative cycling-storage protocol, under which our LMPBs demonstrated over 1,500 hours of operation at 0.3 mA cm？2 and achieved an extended lifespan of 10,000 hours for continuous cycling at 0.1 mA cm？2 at room temperature. These findings underscore the importance of addressing Li corrosion during storage periods and provide key strategies for designing polymer electrolytes to improve Li-metal electrode performance. ⓒ 2025