Pulsed laser deposited CoFe2O4 thin films as supercapacitor electrodes

Abstract

The influence of the substrate temperature on pulsed laser deposited (PLD) CoFe₂O₄ thin films for supercapacitor electrodes was thoroughly investigated. X-ray diffractometry and Raman spectroscopic analyses confirmed the formation of CoFe₂O₄ phase for films deposited at a substrate temperature of 450 °C. Topography and surface smoothness was measured using atomic force microscopy. We observed that the films deposited at room temperature showed improved electrochemical performance and supercapacitive properties compared to those of films deposited at 450 °C. Specific capacitances of about 777.4 F g⁻¹ and 258.5 F g⁻¹ were obtained for electrodes deposited at RT and 450 °C, respectively, at 0.5 mA cm⁻² current density. The CoFe₂O₄ films deposited at room temperature exhibited an excellent power density (3277 W kg⁻¹) and energy density (17 W h kg⁻¹). Using electrochemical impedance spectroscopy, the series resistance and charge transfer resistance were found to be 1.1 Ω and 1.5 Ω, respectively. The cyclic stability was increased up to 125% after 1500 cycles due to the increasing electroactive surface of CoFe₂O₄ along with the fast electron and ion transport at the surface.