A free-standing Ni–Mn–S@NiCo2S4 core–shell heterostructure on carbon cloth for high-energy flexible supercapacitors

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Transition metal sulfides are a promising category of battery-type electrode materials for supercapacitors, but their sluggish reaction kinetics and inferior cycling stability have hindered their practical applications. Heterostructures composed of two types of transition metal sulfides can achieve excellent electrochemical performances through providing increased number of redox-active sites and facilitated ion/electron pathways, leading to improved surface reaction kinetics. Herein, a free-standing Ni–Mn–S@NiCo2S4core–shell heterostructure has been rationally synthesized on flexible carbon cloth through a two-step electrodeposition method. Benefiting from its unique nanosheet morphology and structure as well as the synergistic effect of different components, Ni–Mn–S@NiCo2S4 hybrid nanosheet achieves a high specific capacity of 939.0 C g−1 at a current density of 1 A g−1, outstanding rate capability (69.2 % capacity retention at 20 A g−1) and a long cycle life with with only 9.7 % loss after 5000 cycles at 5 A g−1. In addition, the fabricated Ni–Mn–S@NiCo2S4//porous carbon hybrid supercapacitor device delivers a high energy density of 59.1 Wh kg−1 at a power density of 344.8 W kg−1 and excellent cycling stability, demonstrating a promising potential in high-performance hybrid supercapacitors.