Engineering d–p Orbital Hybridization in a Single‐Atom‐Based Solid‐State Electrolyte for Lithium‐Metal Batteries

Regulating lithium salt dissociation kinetics by enhancing the interaction between inorganic fillers and lithium salts is vital for enhancing the ionic conductivity in solid‐state composite polymer electrolytes (CPEs). However, the influence of fillers’ external electronic environments on lithium salt dissociation dynamics remains unclear. Here, we design single‐atom sites in metal‐organic framework fillers for poly(ethylene oxide) (PEO)‐based CPEs, boosting lithium salt dissociation through an electrocatalytic strategy. This strategy enhances lithium‐ion conductivity by tuning the coupling strength between the d and p orbitals of the fillers, as captured by a newly identified descriptor (λ) via high‐throughput density functional theory (DFT) calculations and machine learning. The optimal single atom (Ti) sites are incorporated into a ZIF‐8 matrix for PEO‐based CPEs, achieving an ionic conductivity exceeding 10⁻³ S cm⁻¹ at 30 °C. Additionally, the electrolyte forms a robust solid electrolyte interphase and is compatible with LiCoO₂, LiNi₀.₉Co₀.₀₅Mn₀.₀₅O₂, and sulfur cathodes. Consequently, the solid‐state lithium metal battery with the electrolyte demonstrates excellent cycling stability, maintaining performance over 5000 cycles at 10 C with LiFePO₄ cathodes and stable operation at ‐30 °C. These findings highlight the transformative potential of engineering d‐p orbital hybridization by incorporating single‐atom sites into inorganic fillers for designing highly ion‐conductive CPEs.