Enhancing long-term cycling and interfacial stability of PEO/LLZO quasi solid-state batteries through atomic layer deposition Al₂O₃ coatings

Polyethylene oxide (PEO)-based electrolytes exhibit great compatibility with lithium-metal anodes. However, complex cleavage reactions occur with cathode electrode at high voltages, and constructing artificial interfacial layers has emerged as an effective strategy. In this work, we employed atomic layer deposition (ALD) to build a nanometer-scale amorphous Al₂O₃ interlayer between the LiNi₀.₆Co₀.₂Mn₀.₂O₂ (NCM622) cathode and the PEO/Li 7 La 3 Zr 2 O 12 (LLZO) composite electrolyte, which enhanced the cycling stability of the cells at 4.3 V. With an optimized interfacial thickness, the capacity retention improved from 44.8% to 97.3% after 100 cycles and remained 86.5% after 200 cycles, accompanied by enhanced rate capability. The artificial interlayer suppressed parasitic reactions by blocking direct contact between the active material and polymer electrolyte, thereby alleviating interfacial polarization during cycling.