Tailoring electrochemically active sites in carbon fiber by edge oxygen functionalized strategy for high performance yarn energy storage

The fabrication of oxygen (O) functionalized carbon materials with fast charge transfer kinetics remains challenging because of the unavoidable loss of electrical conductivity caused by the disruption of sp² conjugated system. Herein, a novel edge-functionalized strategy is developed to enhance the electrical conductivity via an acid catalysis process. This process can tailor the O-species configuration for engineering edge-O active sites, and meanwhile re-establish a π-π conjugated system on the plane of carbon skeleton. Such a design endows the edge-O functionalized carbon fiber (EOCF) with abundant active sites and good electrical conductivity. Yarn energy storages have great potential in future wearable electronics. The main demand is how to develop the yarn electrode of high electrochemical performance by using economically viable materials and scalable fabrication strategies. By combining a scalable knitting process, with the low-cost electroactive EOCF, we prepare a yarn electrode which delivers extremely high capacitance of 511 mF cm⁻¹ (0.2 mA cm⁻¹) exceeding that of all yarn electrodes known, and can operate at good rate (239 mF cm⁻¹ at 20 mA cm⁻¹) with excellent mechanical properties. This work has universal significance in producing high-performance O-functionalized carbon materials for various energy storages.