Synthesis of porous Mn-based spinel microspheres with enhanced lithium storage properties

Abstract

Mn-based spinel materials MgMn2O4 with porous structure were synthesized by reverse coprecipitation method at annealing temperature of 700–900 °C. The as-synthesized samples were compared with those prepared by solid-state reaction method. The phase, micro-morphology and cation distribution of spinel materials were studied by using X-ray powder diffraction, scanning electron microscope, transmission electron microscope and X-ray photoelectron spectroscopy. The results show that the MgMn2O4 samples obtained by reverse coprecipitation method are porous microspheres, and the particle size of the samples grows with the increase of annealing temperature. The material annealed at 700 °C has the most regular morphology, and the microspheres with a diameter of about 2 µm are assembled from uniform nanoparticles (50–60 nm). X-ray photoelectron spectroscopy analysis show that all samples are mixed spinel, Mn exists in multivalent state, Mn2+ ions occupy tetrahedral sites and Mn3+ / Mn4+ ions occupy octahedral sites of spinel structure. The effects of synthesis conditions on the inversion degree (ν) of MgMn2O4 spinel were discussed. As the anode material of Li-ion batteries, the sample annealed at 700 °C shows the best electrochemical performance, and the lithium storage capacity in the first cycle is 1037.8 mAhg−1. The enhanced lithium storage properties of the anode material are due to its regular porous microsphere structure, which is conductive to contact between the electrode materials and electrolyte and improves the migration of lithium ions. In addition, the relationship between cation distribution in spinel structure and electrochemical properties was also discussed.