Sol–gel synthesis of manganese oxide supercapacitor from manganese recycled from spent Zn–MnO2 batteries using organic acid as a leaching agent

Abstract

In this study, manganese recycled from cathodes of spent Zn–MnO2 batteries was used for the sol–gel synthesis of a manganese oxide pseudocapacitor with high specific capacitance. The recycled material is a mixture of α-MnO2, Mn3O4, and ZnMn2O4, according to X-ray diffraction, energy dispersive X-ray, Raman spectra, and chemical analysis. Manganese oxide has smaller particle size when synthesized at 700 °C for 3 h (M1) than when synthesized at 700 °C for 12 h (M2), as evidenced by scanning electron microscopy and transmission energy microscopy. The specific capacitances of M1 and M2 after 1000 cyclic voltammetry cycles at 50 mV s−1 are 350 F g−1 and 125 F g−1, respectively. After 500 galvanostatic cycles at 1.0 A g−1, M1 and M2 exhibit specific capacitances of 275 F g−1 and 150 F g−1, respectively. Electrochemical impedance spectra revealed that M1 has lower charge transfer resistance and diffusion resistance than M2.