Engineering <i>d</i>‐<i>p</i> 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, LiNi_0.9Co_0.05Mn0.05O₂, 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.