Hydrophilic “bridge” tannins for stabilizing the metal selenides onto activated carbon for binder-free and ultralong-life asymmetric supercapacitors

Abstract

Coupling electroactive species with carbon substrates to synthetize composite electrodes holds great promise for obtaining excellent supercapacitors. However, the poor bonding between the carbon supports and the electroactive species is still a bottle-neck to be addressed. Herein, we report a rational design and fabrication of NiCo₂Se₄ supported on tannin-doped activated carbon by employing tannin as the structure coupling bridge between the two components, which effectively tunes the electronic structural states and results in strong coupling effects with NiCo₂Se₄. Benefiting from the structural characteristics, the as-obtained N-doped activated carbon–tannin–NiCo₂Se₄ (NAC–TA–NCS) composites, especially, the NAC–TA–NCS 10 : 1 hybrids (the mass ratio of NAC–TA–NCS to tannin is 10 : 1) deliver the best electrochemical properties. The NAC–TA–NCS 10 : 1 electrode shows the highest specific capacitance value (1262 F g⁻¹ at 0.5 A g⁻¹, 1060 F g⁻¹ even at 30 A g⁻¹), excellent rate property, and outstanding cycling stability (95.095% of the initial value after 10 000 cycles at 5 A g⁻¹). Meanwhile, the as-obtained NAC–TA–NCS 10 : 1//AC could achieve a high energy density of 78.19 W h kg⁻¹ at the power density of 0.859 kW kg⁻¹ at 50 A g⁻¹ as well as the outstanding cycling stability with 97.35% of the initial value after 10 000 cycles. The work exhibits that the NAC–TA–NCS hybrids are promising electrode materials for energy storage. The hydrophilic strategy could be extended to assemble other kinds of active species on different supports, and holds potential for achieving effective and robust electrode materials for energy-related devices.