Sulfur-deficient Co 9 S 8 /Ni 3 S 2 nanoflakes anchored on N-doped graphene nanotubes as high-performance electrode materials for asymmetric supercapacitors

In this paper, Co9S8/Ni3S2 nanoflakes (NFs) with sulfur deficiencies were grown in-situ on N-doped graphene nanotubes (N-GNTs). They were successfully prepared through electrodeposition followed by hydrogenation treatment, which is able to act as a self-supported electrode for asymmetric supercapacitors (ASCs). Combining the defect-rich active materials with highly conductive skeletons, the hybrid electrode N-GNTs@sd-Co9S8/Ni3S2 NFs show ultrahigh specific capacity of ∼304 mA h g−1 and prominent rate capability (capacity retention ratio of ∼85% even at 100 A g−1), and deliver a long cycling lifespan of ∼1.9% capacitance loss after 10000 cycles. In addition, an ASC was constructed using the as-synthesized composite electrode as the positive electrode and active carbon (AC) as the negative electrode. The fabricated device shows a high energy density of ∼45.1 Wh kg−1 at ∼3.4 kW kg−1 and superior cycling stability. This work substantiates a smart strategy to fabricate novel composite electrode materials for next-generation supercapacitors by incorporating riched deficiencies into nanostructures.