Low cost flexible 3-D aligned and cross-linked efficient ZnFe₂O₄ nano-flakes electrode on stainless steel mesh for asymmetric supercapacitors

A simple and economic approach for growth of 3-D aligned and cross-linked ZnFe₂O₄ nano-flakes on a flexible stainless steel mesh (FSSM) substrate (300 mesh) using a rotational chemical bath deposition technique for fabricating efficient asymmetric supercapacitors is reported. The prepared ZnFe₂O₄ nano-flake thin film (ZnFe₂O₄/FSSM-300) as an anode in combination with Ni(OH)₂/FSSM-300 as a cathode was used as an asymmetric supercapacitor. Furthermore, ZnFe₂O₄ nano-flakes were also grown on FSSM with a different mesh and designated as ZnFe₂O₄/FSSM-200, ZnFe₂O₄/FSSM-250 and ZnFe₂O₄/FSSM-300 for investigating the effect of mesh size on the morphology formation and their electrochemical performance. Amongst the samples, ZnFe₂O₄/FSSM-300 exhibited excellent supercapacitive properties, such as a higher specific capacitance (1625 F g^-1 at 1 mA cm^-2) and excellent cycle stability (8000 cycles, 97% retention), which was marginally higher than ZnFe₂O₄/FSSM-250 (545 F g^-1 at 1 mA cm^-2, 70% retention), ZnFe₂O₄/FSSM-200 (241 F g^-1 at 1 mA cm^-2, 56% retention) and other earlier reported ferrites. In addition, the fabricated asymmetric pseudocapacitor device delivered better performance with high specific capacitance (118 F g^-1 at 5 mA cm^-2), excellent cycle stability (8000 cycles, 83% capacitance retention) and high energy density (42 W h kg^-1) even at higher power density (5 kW kg^-1).