Synergistic Regulation of Ion‐Transport Networks via Polar Segment–MOF Coupling for Long‐Cycling Solid‐State Li–CO 2 Batteries

ABSTRACT Li–CO 2 batteries are promising due to their high theoretical energy density and CO 2 utilization, but practical applications are limited by sluggish Li + transport, severe polarization, and unstable liquid electrolytes. Herein, we develop a novel composite solid electrolyte (CSE) by integrating polar‐segment engineering with metal–organic framework (MOF) modification. The oxygen‐containing groups of poly(allyl acetoacetate) (PAAA) provide abundant coordination sites for rapid Li + transport, while amino‐functionalized UiO‐66‐NH 2 immobilizes TFSI − anions and promotes lithium‐salt dissociation. Density functional theory (DFT) calculations and molecular dynamics (MD) simulations reveal strengthened Li + coordination, weakened Li + –TFSI − association, and more continuous Li + diffusion pathways. Benefiting from the optimized ion‐conduction network and improved Li/electrolyte interface, the CSE exhibits a high ionic conductivity (6.64 × 10 −4 S cm −1 at 30 °C), an enhanced Li + transference number (0.46), and oxidative stability up to 4.96 V vs. Li + /Li. Consequently, the assembled solid‐state Li–CO 2 battery delivers a high discharge capacity of 28908 mAh g −1 at 200 mA g −1 and exceptional cycling stability over 3600 h. Separately, the PAU‐based Li–air battery under ambient‐air conditions exhibits stable cycling for 500 h. This work provides an effective strategy for interfacial and ion‐transport engineering toward high‐performance solid‐state Li–CO 2 batteries.