Truxenone‐Based Covalent Organic Framework/Carbon Nanotube Composite for High‐Performance Low‐Temperature Sodium‐Ion Batteries

Abstract

Abstract Low‐temperature rechargeable batteries face great challenges due to the sluggish reaction kinetics. Redox covalent organic frameworks (COFs) with porous structures provide a viable solution to accelerate the ionic diffusion and reaction kinetics at low temperatures. However, the applications of COFs in low‐temperature batteries are still at their infancy stage. Here, a composite electrode containing truxenone‐based COF and a small amount of CNTs is reported for low‐temperature sodium‐ion batteries. The truxenone‐based COF possesses high ratio of active centers and enables high theoretical capacity; while the CNTs guarantee the accessibility of the active sites, the charge transfer efficiency, and the fast reaction kinetics. As a result, the composite electrode shows a high reversible capacity of 365 mAh g −1 at 0.05 A g −1 (295 mAh g −1 after subtracting carbon contribution). Notably, it offers excellent low‐temperature performance that maintains a high discharge capacity of 263.8 mAh g −1 (203 mAh g −1 after subtracting carbon contribution) at 0 °C, which represents 74% of the capacity at room temperature. Even under extreme weather of −30 °C, the capacity maintains 156.8 mAh g −1 (119 mAh g −1 after subtracting carbon contribution) after 100 cycles, with a capacity retention rate of 97%. This work illustrates the synergistic effect of the fast ionic diffusion of truxenone‐based COF and the excellent charge transfer of the CNTs, offering a feasible way to realize low‐temperature sodium‐ion batteries.