Electrochemical capacitive performance of thermally evaporated Al-doped CuI thin films

In this paper, we studied the electrochemical capacitive performance of thermally evaporated copper iodide thin film doped with different quantities of Al (3, 5, 7, and 9 mol%). The morphological structure, crystalline nature, and surface composition of the deposited films with different dopant levels were confirmed using X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and field-emission scanning electron microscopy (FE-SEM). The electrochemical performance was evaluated based on cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) measurements, and electrochemical impedance spectroscopy (EIS) in a Na2SO4 electrolyte. The XRD results confirm that the film is crystalline and has a face-centered cubic structure. The SEM images revealed trihedral-tipped structures with irregular nanocubes. The presence of the trihedral-tipped structures is more obvious in the Al-doped CuI films than in the bare film. We report a progressive increase in the specific capacitance values as the aluminum content increases, from 91.5 F g(-1) for the pure CuI film to 108.3, 126.2, 142.8, and 131.1 F g(-1) for the films with aluminum content of 3, 5, 7, and 9 mol%, respectively at a scan rate of 2 mV s(-1). The optimized CuI-Al electrode with 7 mol% aluminum content showed remarkable long-term cycling stability with 89.1% capacitance retention after 2000 charge/discharge cycles. Such a high performance for the CuI-7Al film as a supercapacitor can be ascribed to the aluminum doping, which increases the electrochemically active area compared to the bare CuI film and is critical for electron exchange at the electrode/electrolyte interface. Therefore, we introduce CuI-Al as a viable option for supercapacitor applications because of its low-cost production, excellent electrochemical performance, and cycling stability.

Automated summary

This paper investigates the electrochemical capacitive performance of thermally evaporated copper iodide thin film doped with different quantities of Al. The results show that aluminum doping increases specific capacitance values, with the CuI-Al electrode containing 7 mol% aluminum exhibiting remarkable long-term cycling stability. The optimized CuI-Al film is proposed as a viable option for supercapacitor applications due to its low-cost production, excellent electrochemical performance, and cycling stability.