Turning Air Exposure into an Advantage for Lithium Metal Anodes

Lithium metal anodes (LMAs) are central to next-generation high-energy batteries, but extreme air sensitivity hinders their commercialization. Expanding the allowable air-exposure window would let LMAs use existing Li-ion battery manufacturing infrastructure. Here we show that a two-step protocol of prolonged dry pretreatment followed by brief controlled air exposure engineers a mechanically robust surface reaction layer (SRL) on Li metal. Insufficient pretreatment yields a poorly adherent SRL that delaminates on air exposure, whereas optimal pretreatment yields a composite oxide/hydroxide/carbonate SRL that accommodates growth-induced compressive stress (20–290 MPa) by wrinkling rather than delaminating. This wrinkled, adherent SRL promotes uniform Li deposition and improved electrochemical stability: full cells built with the optimally processed anode maintain stable cycling performance up to 1,300 cycles with higher sustained capacity than cells using as-received Li. These findings establish the chemo-mechanical principles governing SRL evolution during air exposure and provide practical guidelines for handling LMAs under realistic atmospheric conditions.