Efficient Shuttling of Li ⁺ by an Amide at the COF/PEO Interface in a Composite Solid Polymer Electrolyte

Covalent organic frameworks (COFs)/poly(ethylene oxide) (PEO) solid electrolytes offer bright application prospects in all-solid-state lithium–metal batteries (ASSLBs), while they struggle with low ionic conductivity due to poor interfacial Li+ transport kinetics. This work employs acetamide (EA) as a shuttle to transfer Li+ at COF/PEO interfaces via the synergistic EA-PEO, EA-COF, and EA-Li+ interactions, thereby constructing continuous channels for fast Li+ transport. The resulting EA-modified COF/PEO solid electrolyte delivers an ionic conductivity of 1.01 × 10–4 S·cm–1 at 30 °C. In addition, the synergistic interactions induced by EA promote the dissociation of lithium salt, leading to a LiF- and Li3N-rich solid electrolyte interface (SEI) layer and thus enhanced interfacial stability. As a result, the LiFePO4-based ASSLB assembled with the PEO/LiTFSI-COF/EA solid electrolyte demonstrates exceptional cycling stability with 70.34% capacity retention over 1200 cycles at 1 C and 60 °C. Our work provides a powerful strategy to facilitate interfacial ion transport and reinforce long-term stability in solid polymer electrolytes.