Synergistic Regulation of Li─O Binding and Anion Anchoring by Lewis Acidic Perovskites for Ultra‐Stable PEO‐Based All‐Solid‐State Batteries

ABSTRACT Poly(ethylene oxide) (PEO)‐based solid polymer electrolytes are promising candidates for all‑solid‑state lithium metal batteries, yet they are hampered by excessive Li + ‐coordination that inherently restricts ionic conductivity and electrochemical stability. Herein, defect‐rich layered perovskite Pr 2‐ x Sr x NiO 4 nanofillers are introduced via a Sr‐doping strategy to decouple these limitations. Mechanistically, the engineered oxygen vacancies and Ni 3+ Lewis acid sites function as dual regulators that anchor TFSI – anions to foster a stable inorganic‐rich SEI, while concurrently weakening the Li–O binding to expedite Li + transport kinetics. Consequently, the optimized electrolyte achieves a superior ionic conductivity of 5.17 × 10 −4 S cm −1 at 60 °C, an elevated Li + transference number of 0.56 at 25°C, and a broadened electrochemical stability window extending up to 4.9 V. Benefiting from these enhancements, the Li||Li symmetric cell demonstrates ultra‐stable cycling for over 4000 h (0.1 mA cm −2 ). In full cells, the electrolyte enables the LiFePO 4 cathode to deliver an initial discharge specific capacity of 151.6 mAh g −1 with robust retention over 500 cycles at 1 C, while also ensuring superior rate and cycling performance with the high‐voltage Ni 0.8 Co 0.1 Mn 0.1 O 2 cathode. Ultimately, this study validates defect engineering as a potent strategy to unlock high‐performance PEO‐based all‐solid‐state batteries.