High-performance layered NiCo2S4@rGO/rGO film electrode for flexible electrochemical energy storage

The rapid development of portable and wearable electronic devices requires novel energy storage devices. Flexible, high-performance electrode materials are critical for meeting the demands yet remain challenging. Here, a rationally designed flexible NiCo 2 S 4 @rGO/rGO film constructed with NiCo 2 S 4 @rGO frameworks is successfully prepared through a step-wise process (hydrothermal, freeze-drying, vacuum filtration, and then sulfurization/reduction). The NiCo 2 S 4 @rGO/rGO film as flexible electrode shows typical battery-type faradaic redox features and exhibits a high specific capacitance of 1100.0 F g −1 at 1 A g −1 , a good rate performance of 89.1% capacity retention at 10 A g −1 coupled with long cycling stability of 90.2% after 5000 cycles. The good electrochemical performance is mainly attributed to the loose layered structure and strong interaction between NiCo 2 S 4 and rGO nanosheets , which enhance the diffusion of electrolyte ions/electrons and decreases intrinsic resistance and contact resistance. A flexible hybrid supercapacitor assembled using the NiCo 2 S 4 @rGO/rGO film as cathode and the rGO film as anode shows a high energy density of 30.0 Wh kg −1 at a power density of 857.6 W kg −1 at an extended operating voltage of 1.8 V. The method can also be readily adapted for loading other bimetallic sulfides on rGO films, indicative of its feasibility and flexibility to prepare rGO-based hybrid film for high-performance flexible electrochemical energy storage .