Construction of Stable Li₂O-Rich Solid Electrolyte Interphase for Practical PEO-Based Li-Metal Batteries

Polyethylene oxide (PEO)-based solid polymer electrolytes (SPE) have garnered recognition as highly promising candidates for advanced lithium-metal batteries. However, the practical application of PEO-based SPE is hindered by its low critical current density (CCD) resulting from undesired dendrite growth. In this study, a PEO-based SPE that exhibits an ultra-high CCD (4 mA cm(-2)) is presented and enhanced lithium ionic conductivity through the incorporation of small amounts of P2S5 (PS). The crystalline Li2O-rich and P/S-containing solid electrolyte interphase (SEI) is revealed by cryo-electron microscope (cryo-EM) and Time of flight secondary ion mass spectrometry (TOF-SIMS), which inhibits dendrite growth and adverse reactions between SPE and reductive lithium, thus offering a spherical growth behavior for dendrite-free lithium metal anode. Consequently, utilizing the PS-integrated SPE, a Li-Li symmetric cell demonstrates reduced resistance during operation, enabling stable cycles exceeding 200 hours at 0.5 mA cm(-2) and 0.5 mAh cm(-2), a stringent test condition for PEO-based electrolytes. Moreover, a Li/SPE/LiFePO4 (LFP) pouch cell exhibits 80% capacity retention after 100 cycles with 50 mu m Li and 30 mu m PEO electrolyte, showcasing its potential for practical applications.