Single-pot hydrothermal synthesis of manganese phosphate microrods as a cathode material for highly stable flexible solid-state symmetric supercapacitors

Abstract Here, we report a binder-free synthesis of microrods-like manganese phosphate thin film over stainless steel substrate by a facile, single-pot hydrothermal method. The XRD analysis reveals that, the formation of manganese phosphate [Mn3(PO4)2] material of a monoclinic crystal structure. From SEM images observed microrods like morphology of manganese phosphate with an average width of ∼25 μm. The manganese phosphate electrode shows a better electrochemical performance with a specific capacitance of 145 F g−1 at 0.2 mA cm-2 current density in 1.0 M Na2SO4 electrolyte. Moreover, the flexible solid-state symmetric electrochemical energy storage device was assembled with PVA-Na2SO4 solid gel-electrolyte consists of manganese phosphate as anode and cathode electrode. The corresponding symmetric supercapacitor achieves a high energy density of 11.7 Wh kg−1 at a high power density of 1.41 kW kg−1 with an excellent specific capacitance of 37 F g−1 at 0.1 mA cm-2 current density. Manganese phosphate shows long-term electrochemical cyclic stability at a current density of 0.8 mA cm-2 for 9000 galvanostatic charge-discharge cycles with excellent capacitance retention (99 %). This excellent capacitive performance confirms that the manganese phosphate is promising material and fabricated flexible solid-state symmetric supercapacitor has high potential in the field of portable and bendable energy storage devices.