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Solid-state lithium batteries have attracted great attention owing to their potential advantages in safety and energy density. Among various solid electrolytes, solid polymer electrolyte is promising due to its good viscoelasticity, lightweight, and low-cost processing. However, key issues of solid polymer electrolyte include poor ionic conductivity and low Li+ transference number, which limit its practical application. Herein, a new-type of ultraviolet cross-linked composite solid electrolyte (C–CSE), composed of ZIF-based ionic conductor (named ZIL) and polymer, is designed with enhanced ion transport. The ZIL is composed of ZIF-8 and ionic liquid, which can provide C–CSE with fast ion transport paths. Moreover, the proper pore size of ZIF-8 can restrict the migration of embedded ionic liquid and thus construct a solid–liquid transport interface between polymer chains and ZIF-8, which could achieve fast ion transport. In addition, ultraviolet irradiation can decrease the crystallization of C–CSE and thus increase the amorphous region. Consequently, the C–CSE show excellent electrochemical performance including high ionic conductivity of 0.426 mS cm–1 at 30 °C, high Li+ transference number of 0.67, and good Li|Li compatibility cycle over 1040 h. Experimental and computational results indicate that diffusion energy barrier of Li+ through ZIF-8 is smaller than that of polymer chains, which reveals a new Li+ transport mechanism between polymer chains and ZIL, from “chain–chain–chain” to “chain-ZIL-chain”. This work demonstrates rational design of ion transport paths at the interface of solid electrolyte could facilitate the development of solid-state lithium batteries as a promising novel strategy.

A structural unit showing a specific function can serve as a functional unit, ranging from atom/molecule system to microscale object. [3] Self-assembly refers to the fact that functional units spontaneously form well-ordered structures, which is ubiquitous in nature, like high-strength nacre, highly anisotropic and strong muscles, self-cleaning lotus effect. [4][5][6][7] The secret of these unique properties is the well-ordered structures formed by self-assembly process. Inspired by this, self-assembled artificial materials with revolutionary performances hold great promise in the field of energy storage and conversion. [8][9][10] In this regard, the incorporated ionic conductors in composite polymer electrolytes can be considered as functional units, which have been used to improve electrochemical properties, structural stability, and mechanical robustness. [11][12][13] Conventionally, the most incorporated ionic conductors are ceramic particles, such as perovskite-type Li 0.33 La 0.557 TiO 3 (LLTO), [14] garnet-type Li 7 La 3 Zr 2 O 12 (LLZO), [15] NASICON-type Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP), Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 (LAGP). [16] Recently, MOF impregnated with ionic liquid (IL) or liquid electrolyte has been served as a novel ionic conductor due to its internal massive pores, which can provide wellordered ion pathways. [17][18][19][20] And some MOF materials are used as fillers for solid polymer electrolytes to enhance the ionic conductivity. [21] However, these discrete particles in polymer electrolytes usually lead to insufficient ionic conductivity improvement because of the isolated and discontinuous lithium ions channels. [22,23] Based on this, 1D ionic conductors with high aspect ratio have been designed and fabricated for extended ions pathways, such as nanowires, [24] nanofibers, [25] and nanotubes. [26] Unfortunately, the ionic conductivity enhancement is still limited, because the obtained composites are fabricated by incorporating above powders into polymer electrolytes, in which these incorporated powders are prone to aggregate and precipitate along with solvent volatilization in the film-forming process, leading to heavy barriers for continuous ion conduction. [27][28][29] In addition, the randomly distributed powders in polymer electrolytes fail to provide strong support for lithium dendrite suppression.In order to overcome the issues of randomly distributed powders, some researchers pay attention to the spatial arrangement of incorporated ceramics in composite polymer 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 ac...

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