The Impact of Lithium Anode Interface on Capacity Fade in Polymer Electrolyte-Based Solid-State Batteries

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This study investigates the Li stripping/plating morphology and failure mechanisms in full cells consisting of a solid polymer electrolyte (SPE) with two commercial Li anodes, Li chip and Li foil. The primary identified failure mechanism in the SPE is capacity fade, regardless of Li manufacturer or polymer thickness. While the cathode's role in capacity fade is evident, the Li anode significantly influences cycling performance, with Li foil cells cycling 50% longer than Li chip cells, a statistical difference. Postmortem scanning electron microscopy and X-ray photoelectron microscopy results attribute the Li Chip's faster capacity fade to a loss of contact and continuous growth of the solid electrolyte interface (SEI). Conversely, Li foil maintains consistent contact with the solid polymer, displaying a thin and stable SEI. Additionally, failure mechanisms between a gel electrolyte in previous work and the dry solid polymer electrolyte is compared.