Solution-Processable Covalent Organic Framework Electrolytes for All-Solid-State Li–Organic Batteries

Solid electrolytes (SEs) are milestones in the technology roadmaps for safe and high energy density batteries. The design of organic SEs is challenged by the need to have dynamic structural fluidity for ion motion. The presence of well-ordered one-dimensional (1D) channels and stability against phase transition in covalent organic frameworks (COFs) render them potential candidates for low-temperature SEs. Herein, we demonstrate two milestones using hydrazone COF as an SE: it achieves an ion conductivity of 10–5 S cm–1 at −40 °C with a Li+ transference number of 0.92 and also prevents the dissolution of small organic molecular electrode in all-solid-state batteries. Using 1,4-benzoquinone as the cathode, a lithium battery using hydrazone COF as a SE runs for 500 cycles at a steady current density of 500 mA g–1 at 20 °C. Considering that hydrazone COF is readily amenable to large-scale production and facile post-synthetic modification, its use in an all-solid-state battery is highly promising.