Mechanochemical Activation of Mn3O4: Implications for Lithium Intercalation

Abstract

Manganese oxide (Mn3O4) was subjected to mechanochemical activation (MCA) using a planetary ball mill to investigate the influence of milling parameters on lithium intercalation. After activation, Mn3O4 was lithiated in suspension with organolithium compounds. Structural changes, including LiMn3O4 formation, were analyzed by powder X ray diffraction (PXRD) with Rietveld refinement, supported by scanning electron microscope (SEM), transmission electron microscopy (TEM), physisorption isotherms, and inductively coupled plasma mass spectrometry (ICP-MS). Additional insights into lattice defects were obtained via Raman spectroscopy, electrochemical impedance spectroscopy, and in situ pressure and temperature monitoring during milling. No phase transformation occurred during MCA, though crystallite size decreased to 8.5(5) nm after 4 h at 400 rpm in a zirconia milling jar. Notably, a final crystallite size of 90(9) nm was reached after just 10 min at the same speed. MCA did not cause significant oxygen release from the structure. Short-duration MCA at sufficient speed enhanced lithium intercalation in Mn3O4, whereas prolonged milling or lower speeds hindered the process. These findings demonstrate that brief mechanochemical activation effectively improves lithium intercalation in transition metal oxides, offering a promising approach for tuning electrochemical properties.