Lignin-Based N-Carbon Dots Anchoring NiCo2S4/Graphene Hydrogel Exhibits Excellent Performance as Anodes for Hybrid Supercapacitor

A NiCo₂S₄/N-CDs/RGO ternary composite hydrogel was prepared via a one-step hydrothermal method, utilizing lignin-based nitrogen-doped carbon dots as a bridge connecting NiCo₂S₄ and graphene. The specific capacitance of NiCo₂S₄/N-CDs/RGO significantly outperforms that of the GH and NiCo₂S₄/RGO electrodes, achieving 1050 F g^-1. The 3D mesh porous hydrogel structure mitigates NiCo₂S₄ nanoparticle aggregation, providing a larger specific surface area for enhanced charge storage. The abundant functional groups of N-CDs interact with Ni (II) and Co (III) cations, favoring NiCo₂S₄ particle synthesis. Additionally, an assembled solid-state asymmetric supercapacitor employing NiCo₂S₄/N-CDs/RGO as the positive electrode exhibited excellent energy density (68.4 Wh kg^-1) and cycle stability (82% capacitance retention after 10,000 constant current charge-discharge cycles).