Controlled synthesis of a high-performance α-NiS/Ni3S4 hybrid by a binary synergy of sulfur sources for supercapacitor

Nickel sulfide possesses ultra-high theoretical energy storage capacity. Though it is easily obtained, it is very difficult to exert its intrinsic strong capacity. In this work, a new strategy based on a binary synergy of sulfur sources is introduced. By regulating the molar ratio of two sulfur sources, a high-performance α-NiS/Ni3S4 binary hybrid is successfully synthesized. Interestingly, it is found that changing the molar ratio of two sulfur sources in hydrothermal process can efficiently regulate the components of product but cannot visibly affect its morphology. The electrochemical results indicate that this strategy is highly effective for improving the performance of nickel sulfide. As a result, a highest specific capacity of 214.9 mAh g−1 at 2 A g−1 was reached. In addition, the fabricated S3//rGO hybrid supercapacitor displays a highest energy density of 41.9 Wh kg−1 at a power density of 799.0 kW kg−1. Moreover, the device delivers an excellent cycle stability with 103% capacity retention rate after 10,000 cycles. These findings open a new avenue for the controlled synthesis of high-performance nickel sulfides or other metal sulfides.