Phase inversion assisted scalable covalent organic frameworks based porous high processable solid-state electrolytes for lithium metal batteries

Solid-state electrolytes (SSEs) with properties of high ionic conductivity, large electrochemical windows and outstanding mechanical strength are essential for high energy density and safety solid-state lithium metal batteries (LMBs). Covalent organic frameworks (COFs) is a kind of well-defined crystalline porous frameworks, considered as ideal materials for transporting ions. Whereas, COFs based solid-state electrolytes are generally fabricated via powder pressing process, resulting to fragile nature. Herein, we carry a kind of sp 2 carbon bond linked nitrile substituted COFs (COFs-CN) to fabricate the solid-state electrolytes CPPSSEs via facile phase inversion process and in-situ polymerization in which polymer poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) as matrix and 1M polyvinylene carbonate@lithium bis(trifluoromethanesulfonyl)-imide (LiTFSI) (1M PVC@LiTFSI) as polymer electrolytes. Electrolyte CPPSSEs exhibit excellent electrochemical properties with a high ionic conductivity up to 4.5 × 10 −4  S cm −1 , 0.2 eV activation energy, as well as high Li + transference number of 0.75, and enlarged electrochemical windows of 4.85 V at 25 °C. Additionally, the mechanical strength of CPPSSEs is also outstanding with tensile stress 1.22 MPa and tensile strain 92 %. For the symmetric cells Li/CPPSSEs/Li, CPPSSEs has excellent compatibility with lithium metal electrode for over 200 h at the current densities of 0.05, 0.1 mA cm −2 . Finally, LiFeO 4 (LFP), CPPSSEs and lithium anodes are used to assemble cells LFP||Li, which can work stably with high specific capacity. The COFs-CN based CPPSSEs via phase inversion and in-situ polymerization could be a kind of highly promising outstanding SSEs for solid-state LMBs.