Optimizing Energy Storage Performance: In situ Synthesized Manganese Oxide (Mn₃O₄) Nanoparticle-Based Symmetric Supercapacitor on a Paper Substrate

In this study, a redox reaction is employed to synthesize manganese oxide (Mn₃O₄) nanoparticles using potassium permanganate as a precursor in the presence of diethyl amine. The structural characterization reveals the formation of the tetragonal phase of Mn₃O₄ nanoparticles with a space group of I41/amd. A free-standing Mn₃O₄-based paper electrode is fabricated and its electrochemical performances are investigated. The electrode exhibits a maximum specific capacitance value of ~353 F g⁻¹ and an areal capacitance of ~530 mF cm⁻² at a current density of 0.2 A g⁻¹. A symmetric supercapacitor-based device is also designed using Mn₃O₄ nanoparticles as an active material in a gel electrolyte configuration. The Mn₃O₄ device achieves specific and areal capacity values of ~208 mAh g⁻¹ and 260 mA cm⁻², respectively, at a current density of 0.3 A g⁻¹. The device delivers maximum energy and power density values of ~104 Wh kg⁻¹ and ~220 W kg⁻¹, respectively, with ~92 % specific capacity retention at 0.3 A g⁻¹ after 5000 cycles. The above results suggest that the Mn₃O₄-based device has the potential for energy storage applications.