PEO-based solid-state electrolyte modified by cationic covalent organic frameworks enabling high-performance all-solid-state Li metal and graphite anode batteries

Abstract

Covalent organic frameworks (COFs) with regular and ordered channels have been proved that they could offer extra space to accommodate ions and fast conduction pathways for ion motion. However, the ion conductivities of their own are not high because of most of them have no enough active segmental motion of polymer chains for ion transport. Polyethylene oxide (PEO) is the most typical and efficient solid-state polymer material for Li+ migration by the segmental motion of molecular chains. Herein, we propose a simple and effective strategy of introducing a small quantity of cationic COF additive EB-COF-TFSI into the PEO of low glass transition temperature to obtain high-performance solid-state electrolyte (SSEs) and Li batteries. The cationic COF structure not only provides fast pathway for Li+ but also these cations on it accelerate Li salt dissociation and Li+ conduction. As a result, the cycling time of Li symmetrical cells increases to triplication at a same test condition; the corresponding all-solid-state LFP and NMC//Li metal cells are stimulated to release higher specific capacities, exhibit an enhanced cycling stability and better rate capability. It is surprising that all-solid-state LFP//graphite cells show excellent charging and discharging performance no matter on longtime cycling or rate performance test which are both much better than that of Li metal cells and provide a great strategy for building commercial all-solid-state Li battery based the current structure of it.