Fluorine Induced Oxygen Vacancy Created MnV LDH Nanoflower Cathode for Planar Hybrid Supercapacitors

In recent years, supercapacitors have attracted considerable attention for their progressive improvement in energy density, power output and cyclic stability. To meet the growing demands for high capacitance electrodes, divalent and trivalent cations alongside anionic substitution in metallic oxides were investigated for the development of high-performance electrodes. Rhombohedral nanoflowers of MnV LDH was synthesized by an in situ hydrothermal method with different Mn:V ratios (1:3, 1:1 and 3:1). Among these, the MnV LDH (3:1) molar ratio demonstrated superior pseudocapacitive performance due to the enhanced redox activity and improved active surface area. Furthermore, fluorine doping was implemented for producing oxygen vacancies, which improved the integrity of the structure, electrical conductivity, electrochemically active sites and ion transport properties of the MnV LDH (3:1) electrode. The resulting F-MnV LDH electrode exhibited a higher specific capacitance of 2872 F g–1 at 1 A g–1 current density and with 95% capacitance retention even after 10,000 continuous cycles. A flexible planar hybrid supercapacitor device was constructed using the F-MnV LDH cathode, activated carbon anode and quasi-solid state PVA-KOH gel electrolyte, which exhibited 66.5 Wh kg–1 energy density at 801 W kg–1 power density with excellent performance of only 17% capacitance decay after 10,000 continuous cycles. These results indicate the synergistic impact of optimized Mn:V ratio and fluorine-induced oxygen vacancies, confirming the F-MnV LDH electrode is a promising cathode material for next-generation energy storage systems.