Influence of the microstructure and its stability on the electrochemical properties of EMD produced from a range of precursors

• Published in: Journal of solid state electrochemistry 2013-12, Vol.17 (12), p.3191-3198
• Main Authors: Biswal, A., Tripathy, B. C., Sanjay, K., Meyrick, D., Subbaiah, T., Minakshi, M.
• Format: Article
• Language: English
• Subjects: Analytical Chemistry; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Condensed Matter Physics; Electrochemistry; Energy Storage; Original Paper; Physical Chemistry
• ISSN: 1432-8488; 1433-0768
• DOI: 10.1007/s10008-013-2231-z

The influence of the microstructure and the stable crystal structure on the electrochemical properties of the electrolytic manganese dioxide (EMD) produced from manganese cake (EMD MC ), low-grade manganese ore (EMD LMO ), and synthetic manganese sulfate solutions (EMD SMS ) is reported. X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetry/differential thermal analysis, field emission scanning electron microscopy (FESEM), and chemical analyses were used to determine the structural and chemical characteristics of the EMD samples. The charge–discharge profile was studied in 9 M KOH using a galvanostatic charge–discharge unit. All the samples were found to contain predominantly γ-phase MnO 2 , which is electrochemically active for energy storage applications. FESEM images show that preparation method significantly influences surface morphology, shape, and size of the EMD particles. In almost all cases, nanoparticles were obtained, with spindle-shaped nanoparticles for EMD MC , platy nanoparticles in the case of EMD LMO , and anisotropic growth of tetra-branched star-like nanoparticles of EMD SMS . These nanoparticles arrange themselves in a near net-like fashion, resulting in porosity of the flakes of EMD during electrochemical deposition. Thermal studies showed loss of structural water and formation of lower manganese oxides. The EMD MC showed superior discharge capacity of ~280 mAh g −1 as compared to EMD LMO (275 mAh g −1 ) and EMD SMS (245 mAh g −1 ).