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 degrees 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 degrees 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 degrees 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 degrees C. image