Ni3S2 nanorods and three-dimensional reduced graphene oxide electrodes-based high-performance all-solid-state flexible asymmetric supercapacitors

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Exploring efficient all-solid-state flexible supercapacitors is particularly attractive to face the rapid growing demand of powers for flexible and wearable energy storage devices. Herein, we report a novel strategy to prepare high-performance all-solid-state flexible asymmetric supercapacitors based on nanostructured Ni3S2 nanorods as positive electrode and three-dimensional reduced graphene oxide (3DrGO) as negative electrode. Due to the tunable morphological structures and novel electronic properties of heazlewoodite phase Ni3S2 and interconnected porous 3DrGO, the synthesized electrode materials exhibit high specific capacitances, excellent rate performance and cycling stability. Furthermore, combining capacitive and faradaic energy storage mechanisms, the constructed asymmetric supercapacitor can work complementarily in separate operating voltage, thus leading to substantially enhanced energy and power densities. Remarkably, the optimized device is able to be cycled reversibly in the voltage range of 0–2.2 V, but still delivers high energy density (70.58 W h kg−1), high power density (33.0 kW kg−1 at 52.44 W h kg−1), and excellent cycling stability (with 90.4% specific capacitance retained even after 5000 cycles). Moreover, the device exhibits good flexibility without performance degradation. Significantly, the conception of the combining capacitive and faradaic energy storage mechanisms in this work undoubtedly enables new perspective in exploring high-performance energy storage systems.