1D Anionic Covalent Organic Frameworks With Directed Migration of Alkali Metal Ions for High Ionic Conductivity.

Rational construction of high-performance ionic conductors is a critical challenge in the field of energy storage. In this study, a series of 1D anionic titanium-based covalent organic frameworks (COFs) containing abundant alkali metal ion migration sites, namely, COF-M-R (M = Li, Na, K; R = H, Me, Et), is constructed. The integration of negative TiO ₆ ^2- sites on 1D anionic COFs allows alkali metal cations to migrate directly through the channels. Meanwhile, the π-π stacking of 1D chain-to-chain allows the distribution of ion-migration sites in 2D planes. In view of this, multidimensional ionic transport in COFs is realized to achieve high ionic conductivity. COF-M-Rs exhibit an increased ionic conductivity as the counterions change from Li ⁺ to Na ⁺ to K ⁺ . Notably, COF-Na-Et has an impressive ionic conductivity as high as 0.81 × 10 ^-3 S cm ^-1 . The different decorated groups (H, Me, and Et) on the skeleton influence the dissociation of the cation from the polyanion. This study offers deep insights into the design of COF-based solid-state electrolytes to achieve high ionic conductivity by increasing the ionic transport dimensions.
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