Ultrasound-assisted electrodeposition of NiCo2O4-Bi2O3/CNTs on 3D-printed conductive scaffolds for high-energy flexible supercapacitors

Energy storage materials face critical challenges in terms of performance and fabrication scalability, highlighting the need for efficient processing methods and improved electrochemical properties. To address these challenges, this study employed a drop-casting technique to fabricate Bi 2 O 3 /CNT composite films on 3D-printed substrates, followed by the electrodeposition of NiCo 2 O 4 using various deposition methods. The study systematically compared Constant Potential Electrodeposition (CPE), Pulse Electrodeposition (PE), and Disordered Ultrasonic Deposition (DUD) to evaluate their effects on electrode performance. The ultrasonic field employed in the DUD method generated microstreaming and cavitation effects, promoting the nucleation and uniform dispersion of NiCo 2 O 4 and effectively reducing Bi 2 O 3 agglomeration on the CNT substrate. SEM and TEM analyses demonstrated that the DUD method facilitated a more uniform distribution of Bi 2 O 3 -NiCo 2 O 4 nanoparticles on the CNT surface, resulting in a larger surface area and improved electron conductivity compared to CPE and PE methods. XPS analysis confirmed the successful incorporation of Bi and Ni elements along with their respective oxidation states, while DFT calculations supported the enhanced electrochemical activity of the electrodes fabricated via the DUD method. Electrochemical evaluations further revealed that the DUD-fabricated electrodes exhibited a high specific capacitance of 2762.3F·g −1 , significantly outperforming those prepared using CPE and PE techniques. Moreover, the DUD-fabricated electrodes demonstrated excellent cycling stability, retaining 90.5 % of their initial capacitance after 15,000 cycles at 10 A·g −1 , with a coulombic efficiency of 93.3 %. The electrochemical performance of the Bi 2 O 3 -NiCo 2 O 4 /CNT//AC asymmetric supercapacitor (ASC) was also evaluated. The ASC showed a high energy density of 109.7 Wh·kg −1 at a power density of 450 W·kg −1 and maintained 92.3 % of its original capacitance after 15,000 cycles at 1 A·g −1 , highlighting its excellent long-term stability.