Crown-ether-programmed covalent organic framework nanochannels enable quasi-single-ion conductivity for solid-state lithium metal batteries

Solid-state lithium (Li) metal batteries are hindered by sluggish Li+ transport and anion-driven interfacial instabilities in polymer electrolytes. Herein, we develop a quasi-single-ion-conducting polymer electrolyte by embedding a crown ether-functionalized covalent organic framework (COF) into a fluorinated polymer matrix. Imine (C = N) linkages in the COF and polar fluorinated polymer domains cooperatively immobilize TFSI− via electrostatic adsorption and pore-defined confinement, while the imine sites and crown-ether oxygens dynamically decouple Li+ from its counter-anion and provide exchangeable coordination nodes for rapid interlayer migration along ordered COF channels. As a result, the electrolyte delivers a high ionic conductivity of 1.15 × 10−3 S cm−1 with a high Li+ transference number of 0.91, establishing a continuous Li+-preferential transport network that homogenizes ion flux, promotes the formation of thin and compact interphases, and stabilizes Li anodes and high-voltage cathodes. This crown ether-COF design establishes a broadly applicable design paradigm for decoupling ion transport and interfacial chemistry, paving the way toward next-generation long-lifetime Li metal batteries.