High‐Performance Garnet‐Type Solid‐State Lithium Metal Batteries Enabled by Scalable Elastic and Li⁺‐Conducting Interlayer

Abstract Promoting the interfacial Li⁺ transport and suppressing detrimental lithium dendrites are the main challenges for developing practical solid‐state lithium metal batteries. In this respect, interface rationalizing to synergize the enhancement of ion transport and suppression of lithium dendrites is of paramount significance. Herein, a novel strategy is demonstrated to address those issues by a designed multifunctional composite interlayer. The photocrosslinkable polymer is introduced in a scalable elastic skeleton, which promotes the migration and diffusion of Li⁺. Moreover, adding perfluoropolyether in the interlayer benefits to regulating the formation of LiF‐rich interface, sufficiently suppress the growth of lithium dendrites. Benefitting from the elasticity, high Li⁺ conductivity and the lithium dendrites suppression capability, the interlayer can significantly improve the interfacial performance of the solid electrolyte/lithium interface, thus leading to the greatly enhanced electrochemical performance of solid‐state lithium metal batteries. A high critical current density of 3.6 mA cm⁻² and a long cycling life at 1.0 mA cm⁻² for >400 h are achieved for the symmetric cells. Besides, when used in a pouch‐type full cell coupled with LiNi_0.6Co_0.2Mn_0.2O₂ cathode, a high charged capacity of 3.25 mAh cm⁻² can be maintained through 20 cycles, demonstrating its great potentials for practical application.