Oxidation Of Manganese Lithium-ion Battery Cathode Materials For Preparation And Battery Performance

Over the past decades, MnO2, as a well-known transition-metal oxide, is one of the most attractive inorganic materials because of their wide applications in many chemical processes such as the ion exchange, biosensor, catalysis, and energy storage in lithium secondary battery and supercapacitor. In comparison with other transition metal oxides used in lithium secondary battery and supercapacitor, manganese oxides have unique advantages such as low toxic, good capacity, and inexpensive cost. Up to now, many manganese oxides with unique nanostructure and morphology have been investigated, and they are expected to play an important role in applications for the cathode materials of lithium-ion secondary batteries. In this paper, we have contrallablly synthesizedβ-MnO2 with unique morphology by a facile hydrothermal route and spinel lithium manganese oxides by using a simple solid-state reaction, respectively. The structure and morphology of the as-materials have been characterized by XRD, SEM, TEM, and their electrochemical property has also been studied.This paper mainly consists of three sections, reviewer, experiments and conclusion. Introduction part (Chapter I) reviews the mechanism and features of lithium ion secondary batteries, the development trend of the positive electrode materials for lithium secondary battery, the crystal structure and the synthesis menthods of manganese oxides. And this research purpose is also indicated.In chapter II,β-MnO2 with semi-tubular morphology has been synthesized in a mixed solution of KMnO4 and MnCl2 by a facile hydrothermal method without using any surfactants and templates, and the effect of reaction conditions on the morphology and crystalline of the obtained product has also investigated. KMnO4 and MnCl2-4H2O are used as raw materials, the optimism fabrication parameters ofβ-MnO2 with semi-tubular morphologies are systematically studied on the basis of the hydrothermal reaction temperature, the molar content of raw material and the HNO3 solution concentration. The structure and the electrochemical performance ofβ-MnO2 with semi-tubular morphology have been characterized by XRD, SEM, TEM, cyclic voltammetry method and the discharge/charge tests. The research results indicate thatβ-MnO2 with semi-tubular morphology can be easily obtained by hydrothermally treating KMnO4 and MnCl2 in an acid solution, and the acid solution concentration, hydrothermal reaction temperature and molar content of raw material have some influence on the morphology and crystalline of the final products. The electrochemical performance ofβ-MnO2 with semi-tubular morphology shows that the as-preparedβ-MnO2 electrode exhibits high discharge capacity and better cycle performance, it is expected for a potential application in lithium-ion second battery.In Chapter III, Theβ-MnO2 with semi-tubular morphology that is obtained in chapter II and different lithium sources such as LiOH-H2O, CH3COOLi-2H2O, Li2CO3 are used as raws, spinel-type lithium manganese oxides are prepared by a simple solid-state reaction. The structure and the electrochemical performance of the obtained LiMn2O4 are systematically investigated by XRD, SEM, TEM, cyclic voltammetry method and the discharge/charge tests. The experimental research results indicate that the differert lithium sources in the reaction system influence the morphologies and the electrochemical properties of the obtained materials, but hardly influence the phase structure of the obtained materials. When CH3COOLi-2H2O is used as raw, the obtained LiMn2O4 shows good electrochemical property and maintains the semi-tubular morphology of theβ-MnO2 precursor, while the similar results can not obtained by using LiOH·H2O and Li2CO3 as lithium sources. In addition, the electrochemical properties of the obtained materials have been researched.In Chapter IV, the research conclusions are obtained on the basis of the chaperⅡand chapter III.