In Situ Polymerization Permeated Three‐Dimensional Li+‐Percolated Porous Oxide Ceramic Framework Boosting All Solid‐State Lithium Metal Battery

Abstract Solid‐state lithium battery promises highly safe electrochemical energy storage. Conductivity of solid electrolyte and compatibility of electrolyte/electrode interface are two keys to dominate the electrochemical performance of all solid‐state battery. By in situ polymerizing poly(ethylene glycol) methyl ether acrylate within self‐supported three‐dimensional porous Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 framework, the as‐assembled solid‐state battery employing 4.5 V LiNi 0.8 Mn 0.1 Co 0.1 O 2 cathode and Li metal anode demonstrates a high Coulombic efficiency exceeding 99% at room temperature. Solid‐state nuclear magnetic resonance results reveal that Li + migrates fast along the continuous Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 phase and Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 /polymer interfacial phase to generate a fantastic conductivity of 2.0 × 10 −4 S cm −1 at room temperature, which is 56 times higher than that of pristine poly(ethylene glycol) methyl ether acrylate. Meanwhile, the in situ polymerized poly(ethylene glycol) methyl ether acrylate can not only integrate the loose interfacial contact but also protect Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 from being reduced by lithium metal. As a consequence of the compatible solid‐solid contact, the interfacial resistance decreases significantly by a factor of 40 times, resolving the notorious interfacial issue effectively. The integrated strategy proposed by this work can thereby guide both the preparation of highly conductive solid electrolyte and compatible interface design to boost practical high energy density all solid‐state lithium metal battery.