NiFe-Layered Double Hydroxide Nanosheets on MoSe2 Nanospheres for Supercapacitor Energy Storage

In this study, MoSe2 and NiFe-LDHs were synthesized on a self-supported conductive nickel foam (NF) substrate via a one-step method. Specifically, MoSe2 was grown on the nickel foam via a one-step solvothermal method to form the MoSe2/NF precursor material. Subsequently, NiFe-LDHs were deposited on the MoSe2/NF substrate through a one-step hydrothermal method, resulting in the formation of the NiFe-LDHs/MoSe2/NF composite material. We found that although both NiFe-LDHs and MoSe2 monomers have certain disadvantages, such as a tendency to agglomerate and relatively poor electrical conductivity, their combination yields an interesting "two negatives make a positive" effect. The NiFe-LDHs/MoSe2/NF composite exhibits a high specific capacitance of 6790 mF cm(-2) at a current density of 2 mA cm(-2), which is significantly higher than that of NiFe-LDHs (1317.6 mF cm(-2)) and MoSe2 (1475.2 mF cm(-2)). Additionally, the composite demonstrates excellent cycling stability, with a capacitance retention of 99.87% after 4000 cycles. In contrast, NiFe-LDHs/NF retains only 54.01% of its capacitance after 2000 cycles, and MoSe2/NF retains only 48.15% after the same number of cycles. The asymmetric supercapacitors (ASCs) assembled from the NiFe-LDHs/MoSe2/NF composite and activated carbon (AC) show remarkable performance. These devices have a high potential window of 0-1.55 V and achieve an extremely high energy density of 0.5558 mWh cm(-2) at a power density of 1.55 mW cm(-2). Moreover, they exhibit an ultrahigh capacitance retention of 99.1% after 10,000 cycles, indicating excellent cycling stability. The Coulombic efficiency of the capacitor remains at a high value of approximately 99.8% throughout the cycling process. NiFe-LDHs/MoSe2/NF and similar materials can be designed for flexible supercapacitors integrated into clothing or skin patches to power sensors. In the context of medical device designs requiring energy storage components to rapidly release substantial energy, they may also play a critical role.