Nanofibrous Covalent Organic Frameworks as the Cathode, Separator, and Anode for Batteries with High Energy Density and Ultrafast-Charging Performance

Abstract

To meet the demand for longer driving ranges and shorter charging times of power equipment in electric vehicles, engineering fast-charging batteries with exceptional capacity and extended lifespan is highly desired. In this work, we have developed a stable ultrafast-charging and high-energy-density all-nanofibrous covalent organic framework (COF) battery (ANCB) by designing a series of imine-based nanofibrous COFs for the cathode, separator, and anode by Schiff-base reactions. Hierarchical porous structures enabled by nanofibrous COFs were constructed for enhanced kinetics. Rational chemical structures have been designed for the cathode, separator, and anode materials, respectively. A nanofibrous COF (AA-COF) with bipolarization active sites and a wider layer spacing has been designed using a triphenylamine group for the cathode to achieve high voltage limits with fast mass transport. For the anode, a nanofibrous COF (TT-COF) with abundant polar groups, active sites, and homogenized Li⁺ flux based on imine, triazine, and benzene has been synthesized to ensure stable fast-charging performance. As for the separator, a COF-based electrospun polyacrylonitrile (PAN) composite nanofibrous separator (BB-COF/PAN) with hierarchical pores and high-temperature stability has been prepared to take up more electrolyte, promote mass transport, and enable as high-temperature operation as possible. The as-assembled ANCB delivers a high energy density of 517 Wh kg^–1, a high power density of 9771 W kg^–1 with only 56 s of ultrafast-charging time, and high-temperature operational potential, accompanied by a 0.56% capacity fading rate per cycle at 5 A g^–1 and 100 °C. This ANCB features an ultralong lifespan and distinguished ultrafast-charging performance, making it a promising candidate for powering equipment in electric vehicles.