Dual-ion Co-storage in a donor–acceptor covalent organic framework for high-performance low-temperature sodium-organic batteries

Abstract

The development of covalent organic framework (COF) cathodes for low-temperature sodium-ion batteries (SIBs) remains challenging due to sluggish reaction kinetics at low temperatures. Herein, we demonstrate a donor–acceptor (D–A) covalent organic framework constructed from p-type triphenylamine and n-type naphthalimide units as a robust cathode for low-temperature SIBs. The stable naphthalimide-based building blocks endow the constructed D–A framework with faster charge transport capability and enhanced redox kinetics, achieving a capacity of 135 mAh g⁻¹ at 0.1 A g⁻¹ and an impressive capacity retention of 80% after 2000 cycles at 1 A g⁻¹. Remarkably, it maintains high capacities of 108 mAh g⁻¹ at 0 °C and 85 mAh g⁻¹ at −20 °C, with a capacity retention rate of 91% after 300 cycles at −20 °C. The dual-ion co-storage mechanism of Na⁺ and PF₆⁻ has been elucidated through in situ spectroscopic characterization and theoretical calculations. This work provides a feasible molecular design strategy towards stable and high-performance porous organic cathodes for low-temperature SIBs.