Fast ion conduction assisted by covalent organic frameworks in poly(ethylene oxide)-based composite electrolyte enabling high-energy and strong-stability all-solid-state lithium metal batteries

The synthesized covalent organic frameworks (COFs) have greatly numerous interior spaces and ordered organic skeletons and channels. On the one hand, their special structures spread all over the poly(ethylene oxide) (PEO) matrix could enhance the mechanical strength of solid-state electrolytes, help improve physical stability against moisture and chemical/electrochemical stability against Li metal. On the other hand, they not only have the property of inorganic nanoparticles to decrease the PEO crystalline region but also provide fast ion transport pathways for PEO-based electrolyte. In this work, merely 3wt.% synthesized COF CPs-BT powder can greatly improve the electrochemical performance of solid-state PEO-based electrolytes. The COF-related electrolytes show an ionic conductivity up to 1.5 × 10−4 S cm−1 at 40 °C. And the corresponding LiFePO4/Li metal cells exhibit incomparable cycling stability among reported solid-state PEO-based composite electrolytes, even though having undergone the multiple high-rate tests and 350 times cycling charge and discharge, they can discharge 155 mAh g−1 capacity with almost 100% coulombic efficiency. It should be noted that this electrolyte has no any liquid solution and the electrochemical performance improvement is mainly ascribed to the COF additive CPs-BT.