Interface Engineering of Biomass‐Derived Carbon used as Ultrahigh‐Energy‐Density and Practical Mass‐Loading Supercapacitor Electrodes

Abstract The development of flexible electrodes with high mass loading and efficient electron/ion transport is of great significance but still remains the challenge of innovating suitable electrode structures for high energy density application. Herein, for the first time, lignosulfonate‐derived N/S‐co‐doped graphene‐like carbon is in situ formed within an interface engineered cellulose textile through a sacrificial template method. Both experimental and theoretical calculations disclose that the formed pomegranate‐like structure with continuous conductive pathways and porous characteristics allows sufficient ion/electron transport throughout the entire structures. As a result, the obtained flexible electrode delivers a remarkable integrated capacitance of 6534 mF cm −2 (335.1 F g −1 ) and a superior stability at an industrially applicable mass loading of 19.5 mg cm −2 . A pseudocapacitive cathode with ultrahigh capacitance of 7000 mF cm −2 can also be obtained based on the same electrode structure engineering. The as‐assembled asymmetric supercapacitor achieves a high areal capacitance of 3625 mF cm −2 , and a maximum energy density of 1.06 mWh cm −2 , outperforms most of other reported high‐loading supercapacitors. This synthesis method and structural engineering strategy can provide materials design concepts and a wide range of applications in the fields of energy storage beyond supercapacitors.