Hierarchically Self‐Assembled MOF Network Enables Continuous Ion Transport and High Mechanical Strength

Abstract Composite solid electrolytes have attracted significant interest because they overcome the defects of single‐component solid electrolytes. However, the discontinuous ion transport and weak mechanical support caused by randomly distributed powders lead to inferior ionic conductivity and poor mechanical strength. Herein, a hierarchically self‐assembled metal‐organic framework (MOF) network is designed to provide continuous ion transport and mechanical support for composite polymer electrolytes. This unique structure is achieved by constructing well‐ordered MOF nanocrystals along 1D polyimide fibers to provide continuous linear pathways for lithium ions at the micrometer scale, and the 1D MOF fibers are interconnected to form a monolithic 3D network for continuous Li + transport in the bulk of composite electrolytes. Meanwhile, sub‐nano pores and Lewis acid sites in MOF nanocrystals can selectively confine the movement of larger anions as ion sieves to promote Li + transport. In addition, the strong banding between MOF and polyimide, coupled with the robustness of the polyimide skeleton, endows the MOF network with high mechanical strength and flexibility. Accordingly, the resultant composite electrolyte delivers a high ionic conductivity and desired mechanical strength. This work shows that rational spatial arrangement of incorporated powders from disorder to order by a self‐assembly strategy can yield novel properties for composite solid electrolytes and solid‐state lithium batteries.