Resolving Oxidative and Corrosive Calendar‐Aging via Electrolyte Engineering for Stable Lithium Metal Batteries

Abstract Localized high‐concentration electrolytes (LHCEs) improve the cycle life of lithium metal batteries (LMBs), but can potentially induce severe corrosion during rest periods, which ultimately impairs their calendar life. The corrosive effect of LHCEs on LMBs has hitherto been largely confined to lithium (Li) metal corrosion, without comprehensively considering the degradation of the cathode over time. Here, a systematic investigation of the underlying mechanism for the calendar aging of LMBs with conventional 1,2‐dimethoxyethane (DME)‐based LHCEs reveals that the surface degradation of a nickel‐rich layered cathode, driven by the oxidative decomposition of free DME, promotes transition‐metal dissolution, which in turn triggers cathode‐anode crosstalk that further accelerates degradation of the Li metal. To overcome this drawback of full cells, a weakly solvating 1,2‐dimethoxypropane (DMP)‐based LHCE, which concurrently suppresses Li metal corrosion and solvent‐driven cathode degradation, is introduced. As a result, the DMP‐based LHCE achieves 81% capacity retention over 220 cycles with a 12 h rest period during every cycle. These findings highlight the critical role of cathode‐side degradation in limiting the calendar life of LMBs and suggest a rational LHCE design strategy for simultaneously extending the operational and storage durability of these batteries.