Study On The Reaction Mechanism And Material Synthesis Of O3 - OO - MnO3 4 4 System In Microwave Field

Because of the high efficiency and non-polluting, Lithium-ion batteries, which have been widely used, have drawn great attention to research field and industry. This paper focuses on the reaction mechanism and materials synthesis of Li2O- Mn₃O₄-NiO system in microwave field, which can offer a help to the preparation of Li-ion batteries with good performance indicators. This paper firstly outlines the principles, applications and protection of microwave technology, and briefly overviews the theories of solid-diffusion and solid-phase reaction. It also summarizes the research progress of Na_0.44MnO₂ material. The diffusion couples were synthesized by SPS with high purity nanoscale Mn₃O₄, NiO and Li2CO3 powders as raw materials. We systematically studied the diffusion and phase-transformation laws of Mn₃O₄-NiO systems by varying the dwell time. By contrast with resistance heating, the advantages of microwave heating were highlighted. In addition, the synthesis of Na_0.44Mn02 whiskers had been finished, and its growth mechanism had been analyzed and interpreted.For Mn₃O₄-NiO diffusion couples, the diffusion interfaces was characterized by SEM, EDS and XRD technologies. The results are shown as follows:Almost no element diffusion was found in samples with no microwave incubation, and the couples still maintain the original phase structure; With the prolonged dwell time, element Ni noticeably diffuses into the MmO4 side in the Mn₃O₄-NiO diffusion couples, while Mn can hardly enter into the NiO side. Besides, the spinel NiMn2O4 occurs at the interface and acts a physical barrier for further diffusion of Mn. In contrast to resistance heating, microwave heating can induce a stronger diffusion of Ni. Besides, in the LiMn₂O₄-Li_0.4Ni_1.6O₂ diffusion couples, element Mn noticeably diffuses into the Li0.4Ni1.6O₂ side and the diffusion rate never slows down even with the dwell time up to 48 h. The monoclinic Li1.88（MnxNi1-x）1.12O3 with 0<x<1 appears at the interface. All these indirectly reflect that most of the diffusion regions may form a solid solution, but reaction diffusion occurs in the area near the interface since the solubility limit is exceeded.In the preparation of Na_0.44MnO₂ whiskers, all the whiskers were detected only on the Mn₃O₄ side. The results of SEM and TEM shows that crystallinity of the whiskers is pretty fine and their length-diameter ratio are also large; In contrast to resistance heating, the uniformity, length-diameter ratio and growth speed of the whiskers heated by microwave are totally better than the former one. Besides, the growth type of Na_0.44Mn02 whiskers belongs to vapor-solid growth mechanism; when temperature is at some lower value, gaseous molecules will be directly agglomerated on the bulge of Mn₃O₄ surface, and then begin to nucleate and grow without the participation of a catalyst.