Flexible Hybrid Supercapacitor Constructed from Nickel–Cobalt Sulfide on Nickel-Based Flower-Like Carbon as Positive and Nitrogen-Rich Carbon as Negative Electrodes

Of prime importance for renewable energy development, supercapacitors have excellent merit in producing superior power densities and long-cycle stability. The well-matched electrochemical properties of electroactive materials and the great chemical and mechanical features of flexible substrates ensured their applicability to high-performance electronic devices. Nowadays, advanced nanocomposites benefit from boosting energy densities and durability alongside addressing unbalanced ion capture in asymmetric supercapacitors (ASCs). The unique carbon nanocomposites, particularly those modified with transition metal compounds, have emerged as promising candidates, exhibiting both capacitive and pseudocapacitive properties. Herein, Ni-based flower-like nitrogen-rich carbon (NCNi) was directly synthesized on a carbon felt (CF) substrate through an ecobenign hydrothermal treatment. Subsequently, hierarchical nickel–cobalt sulfide nanosheets (NiCoS) were chemically (C) and electrochemically (EC) decorated on NCNi, which were finally employed as binder-free positive electrodes. The NiCoS@NCNi@CF electrode materials exhibited perfect surface wettability, specific surface area, great structural stability from the core of the NCNis, and also a faster charge transfer mechanism from reversible redox reactions of NiCoS shells. To prepare an ASC device, the bare carbon skeleton of Ni removed-NC@CF was used as the negative electrode. The fabricated EC-NiCoS@NCNi@CF // NC@CF cell rendered not only a wide potential window of 1.6 V but also a reasonable energy and power density of 64.77 W h kg–1 and 420.13 W kg–1 at 0.5 A g–1. In addition, the assembled ASC exhibited remarkable cycle stability (92.9% of its initial capacity after 4000 cycles) and preserved its capacitive performance even if bent. Benefiting from remarkable charge storage capacity, the fabricated devices powered various light-emitting diodes (ranging from red to blue) as energy consumers for several minutes. The exceptional electrochemical performance, coupled with a well-suited asymmetric design, highlights the extraordinary potential of the fabricated devices for high-performance wearable electronics.