Fabrication of Scalable Covalent Organic Framework Membrane‐based Electrolytes for Solid‐State Lithium Metal Batteries

The conventional covalent organic framework (COF)‐based electrolytes with tailored ionic conducting behaviors are typically fabricated in the powder morphology, requiring further compaction procedures to operate as solid electrolyte tablets, which hinders the large‐scale manufacturing of COF materials. In this study, we present a feasible electrospinning strategy to prepare scalable, self‐supporting COF membranes (COMs) that feature a rigid COF skeleton bonded with flexible, lithiophilic polyethylene glycol (PEG) chains, forming an ion conduction network for Li+ transport. The resulting PEG‐COM electrolytes exhibit enhanced dendrite inhibition and high ionic conductivity of 0.153 mS cm−1 at 30 °C. The improved Li+ conduction in PEG‐COM electrolytes stems from the loose ion pairing in the structure and the production of higher free Li+ content, as confirmed by solid‐state 7Li NMR experiments. These changes in the local microenvironment of Li+ facilitate its directional movement within the COM pores. Consequently, solid‐state symmetrical Li|Li, Li|LFP, and pouch cells demonstrate excellent electrochemical performance at 60 °C. This strategy offers a universal approach for constructing scalable COM‐based electrolytes, thereby broadening the practical applications of COFs in solid‐state lithium metal batteries. A large free‐standing PEG‐COF membrane (COM) has been fabricated to serve as a polymer electrolyte for solid‐state lithium metal batteries. By adjusting the lengths of PEG chains within the framework, a satisfactory ion conductivity of 0.153 mS cm−1 at 30 °C was achieved. Benefiting from the collaborative effect of guest‐promoted transport, the Li|Li, Li|LFP, and pouch cell assemblies with PEG‐COM polymer electrolytes demonstrated excellent electrochemical performance at 60 °C.