Faster Ion Switching NiCo 2 O 4 Nanoparticle Electrode-Based Supercapacitor Device with High Performances and Long Cycling Stability

Although nanostructured NiCo 2 O 4 is the most appealing and studied electrode material by far as it is cheap, nontoxic, and efficient for supercapacitor application, it still lacks suitable device application comprising a wide voltage window and high operating current density, high specific energy and power, and absolute stability. Here, we report a successful application of our NiCo 2 O 4 nanoparticles (NPs) in a highly efficient electrochemical supercapacitor device, which is brought to reality because of the NPs’ fast ion intercalation/extraction and fast reversible Faradaic surface reactions. The as-synthesized spinel NiCo 2 O 4 NPs are 65 nm in average diameter, have 59 m 2 /g of surface area, and 0.44 cm 3 /g of pore volume. Charge storage capability and reliability of the material as an active electrode have been demonstrated in terms of a conventional three-electrode method and in a coin-cell device. Specific capacity values of 150.56 to 41.66 mAh·g –1 (1084 to 300 Fg –1 in terms of capacitance) have been realized in the applied potential window (0.0–0.5 and 0.0–1.5 V) and in current densities of 2 to 10 Ag –1, which are >98% stable in any of these given conditions up to 20 000 measured charge–discharge cycles. The NiCo 2 O 4 NP electrode exhibits a maximum energy density of 10.42 Wh kg –1 and a power density of 3750 Wkg –1 at 10 Ag –1 and makes itself an efficient electrode material for superior supercapacitor devices. These high performances are corroborated to the ultrafast intercalation reaction of electrolyte ions with nickel cobaltate at the electrode surface.