An Ion-Channel-Restructured Zwitterionic Covalent Organic Framework Solid Electrolyte for All-Solid-State Lithium-Metal Batteries

Abstract

Organic solid electrolytes offer an effective route for safe andhigh-energy-density all-solid-state Li metal batteries. However, it remains achallenge to devise a new strategy to promote the dissociation of strong ionpairs and the transport of ionic components in organic solid electrolytes.Herein, a zwitterionic covalent organic framework (Zwitt-COF) withwell-defined chemical and pore structures is prepared as a solid electrolytecapable of accelerating the dissociation and transport of Li ions. TheZwitt-COF solid electrolyte exhibits a high room-temperature ionicconductivity of 1.65×10−4Scm−1with a wide electrochemical stabilitywindow. Besides, the Zwitt-COF solid electrolyte displays stable Liplating/stripping behavior via effective inhibition of the formation of Lidendrites and dead Li, leading to superior long-term cycle performance withretention of 99% discharge capacity and 98% Coulombic efficiency in anall-solid-state Li-metal battery. Theoretical simulations reveal that theincorporation of zwitterionic groups into COF can facilitate the dissociation ofstrong ion pairs and reconstruct the AA-stacking configuration by dissociativeadsorption of Li+ions on Zwitt-COF producing linear hexagonal ion channelsin the Zwitt-COF solid electrolyte. This strategy based on Zwitt-COF canprovide an alternative way to construct various solid-state Li batteries.