Facile synthesis of self-supported amorphous cobalt-nickel tungstate thin films for high performance asymmetric supercapacitor: role of Co and Ni variation

Pseudocapacitors and redox capacitors are among the most promising candidates for high specific energy and power delivery owing to their rapid charge-discharge capability and excellent cyclic stability. In this work, high-performance, self-supported nickel cobalt tungstate electrodes are fabricated via a facile successive ionic layer adsorption and reaction (SILAR) method with varying nickel-cobalt ratios. The optimized nanospherical Ni 0.25 Co 0.75 WO 4 electrode achieves a remarkable specific capacity of 785.72 C g −1 at 1.1 A g −1 , nearly three times higher than that of pristine nickel tungstate and cobalt tungstate. Moreover, Ni 0.25 Co 0.75 WO 4 exhibits excellent cycling stability, retaining 77% of its initial capacity even after 5,000 cycles at 4.1 A g −1 . When assembled into a hybrid supercapacitor (HSC) with reduced graphene oxide (rGO) as the negative electrode, the device operates at 1.6 V and delivers a high specific energy of 50.41 Wh kg −1 at a specific power of 1.74 kW kg −1 . These findings demonstrate that nickel cobalt tungstate is a promising electrode material for high-performance supercapacitors and highlight a cost-effective synthesis approach with outstanding charge storage capability.