A robust conductive covalent organic framework for ultra-stable potassium storage

Abstract

Redox-active covalent organic frameworks (COFs) have garnered significant attention in the field of K-ion batteries (KIBs), but their applications are mainly hampered by their low electronic conductivity and insufficient cyclability owing to the large size of K-ions. Herein, we report a Ni-bis(dithiolene) and tetrathiafulvalene-based COF (Ni-TTF) with promising electronic conductivity and exceptional stability for high-performance KIB anodes. The redox-active units of Ni-bis(dithiolene) and tetrathiafulvalene (TTF) provide accessible sites for K-ion storage. The one-dimensional tunnel structure and good conductivity of Ni-TTF enabled fast charge (K⁺/e⁻) transfer. The reticular network structure maintained its stability in organic electrolyte and ensured a resilient electrode to sustain repeated K-ion intercalation/deintercalation. As a result, Ni-TTF delivered a high reversible capacity of 223 mA h g⁻¹ over more than 800 cycles at a current density of 1C (0.3 A g⁻¹). Moreover, Ni-TTF achieved ultrastable cyclability, without discernible capacity fading after 2500 cycles at 2C, ranking it among the best organic anode materials for KIBs. This contribution opened a new avenue in the design of robust COFs with promising redox activity and improved conductivity for ultrastable K-ion storage.