Morphology-engineered NiCo ₂ O ₄ with tagetes-like architecture for high-performance supercapacitors: linking material design to device fabrication

Abstract The rapidly growing demand for portable electronics and electric transportation has placed significant pressure on existing energy storage technology. To meet these challenges, there is a critical need to develop advanced supercapacitor materials. This study presents a detailed investigation of NiCo 2 O 4 , linking material design with device fabrication to assess its electrochemical performance. A simple one-step hydrothermal route was employed, where precise control of urea concentration yielded an optimized (NICO-3) with superior electrochemical performance. Structural and morphological characterization confirmed the formation of a stable cubic spinel structure. Electrochemical studies (2-electrode system) in a symmetric NiCo 2 O 4 //NiCo 2 O 4 configuration revealed a high specific capacitance of 532 F g −1 at 2 A g −1 , along with an energy density of 32 Wh kg −1 and a power density of 3000 W kg −1 . The device exhibited excellent cycling stability, retaining 90.3% of its initial capacitance after 4000 charge–discharge cycles. To demonstrate practical applicability, a symmetric device was fabricated that powers a 27-LED array for 10 min. Finally, a coin-cell prototype was integrated at lab scale that successfully lit seven LEDs for 10 min.