Binder-free chemical synthesis of ZnFe₂O₄ thin films for asymmetric supercapacitor with improved performance

In this work, a simple, cost-effective, binder-free, and wet chemical successive ionic layer adsorption and reaction (SILAR) method is developed for the growth of ZnFe₂O₄ thin films on stainless steel substrate. The thin films were characterized using X-ray diffraction, scanning electron microscope, BET surface area analyzer, X-ray photoelectron spectroscopy, and electrochemical analyzer. The synthesized ZnFe₂O₄ thin films show excellent electrochemical properties by delivering maximum specific capacitance of 615 F g⁻¹ at 3 mA cm⁻² current density. The porous ZnFe₂O₄ thin film (SS/ZnFe₂O₄) is used as a negative electrode in combination with Mn₃O₄ (Mn₃O₄/SS, SILAR, positive electrode) for the fabrication of asymmetric supercapacitor device (SS/ZnFe₂O₄//Mn₃O₄/SS). The device shows maximum specific capacitance of 81 F g⁻¹ and delivers a maximum energy density of 28 Wh kg⁻¹ at 7.97 kW kg⁻¹ power density with comparable cycle stability showing 74 % capacitance retention over 3000 cycles. [Figure not available: see fulltext.]