Morphological and Electrochemical Properties of ZnMn2 O4 Nanopowders and Their Aggregated Microspheres Prepared by Simple Spray Drying Process

Abstract

Phase-pure ZnMn2 O4 nanopowders and their aggregated microsphere powders for use as anode material in lithium-ion batteries were obtained by a simple spray drying process using zinc and manganese salts as precursors, followed by citric acid post-annealing at different temperatures. X-ray diffraction (XRD) analysis indicated that phase-pure ZnMn2 O4 powders were obtained even at a low post-annealing temperature of 400◦ C. The post-annealed powders were transformed into nanopowders by simple milling process, using agate mortar. The mean particle sizes of the ZnMn2 O4 powders post-treated at 600 and 800◦ C were found to be 43 and 85 nm, respectively, as determined by TEM observation. To provide practical utilization, the nanopowders were transformed into aggregated microspheres consisting of ZnMn2 O4 nanoparticles by a second spray drying process. Based on the systematic analysis, the optimum post-annealing temperature required to obtain ZnMn2 O4 nanopowders with high capacity and good cycle performance was found to be 800◦ C. Moreover, aggregated ZnMn2 O4 microsphere showed improved cycle stability. The discharge capacities of the aggregated microsphere consisting of ZnMn2 O4 nanoparticles post-treated at 800◦ C were 1235, 821, and 687 mA h g−1 for the 1st, 2nd, and 100th cycles at a high current density of 2.0 A g−1, respectively. The capacity retention measured after the second cycle was 84%. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.