Anionic covalent organic framework electrolyte with tailored ion channels for high-areal-capacity solid-state lithium metal battery

Covalent organic frameworks (COFs) are an emerging class for solid-state electrolytes due to their ordered and customizable ion transport nanochannels. Although high ionic conductivity (σLi+) and Li+ transference number (tLi+) are achieved, the high-areal-capacity solid-state lithium metal battery (LMB) still encountered challenges, which is mainly determined by homogeneous Li+ flux through channels and interfaces. Herein, we design a COF coupling anionic skeletons with branched ion-conductive chains (COF-S) as tailored fast ion-transport channels to achieve high-areal-capacity solid-state LMB. Then the dispersed COF-S-based electrolyte is further obtained by incorporating ethoxylated trimethylolpropane triacrylate (ETPTA) and LiFSI (ETPTA-COF-S) via in situ light solidification. In this way, the abundant SO3− groups promote Li+ adsorption and facilitate axial transport via 1D channels, thus enabling high σLi+ of 1.29 mS cm−1 and tLi+ of 0.83. The branched chains can tailor ion channels to suppress large-size anions transport, disperse and uniform Li+ flux, thus leading to high average Coulombic efficiency (CE) up to 98.43 % for 100 cycles (∼800 h) at 0.5 mA cm−2 under the high areal capacity of 2 mAh cm−2. When paired with 2 mAh cm−2 LiFePO4 (LFP) cathode and thin Li anode of 20 µm Li∥ETPTA-COF-S∥LFP exhibits superior cyclic stability for 80 cycles.