Preparation And Performance Of Layered LiMnO₂as Cathode Material For Lithium-ion Battery

Orthorhombic LiMnO2is one of the most promising cathode materials forlithium ion battery due to its high theoretical discharge capacity, low cost andenvironmental friendliness. The electrochemical performance of о-LiMnO2isclosely related to the preparation method and its morphology. Because hydrothermalmethod can effectively control the crystallinity, morphology and size distribution ofthe prepared material, the о-LiMnO2with various morphology are synthesized byhydrothermal method with γ-MnOOH nanorods, α-Mn2O3nanorods, Mn2O3-air andMn2O3-N2as precursor seperately. The structure, morphology and electrochemicalperformance of the materials are investigated by X-ray diffraction, scanning electronmicroscopy, transition electron microscopy and charge/discharge test.The γ-MnOOH nanorods are synthesized by hydrothermal method usingKMnO4and CTAB as raw materials. The optimal γ-MnOOH nanorods are:preparated at180℃for12h with the molar ratio of KMnO4/CTAB3:1, and theheating rate is5℃·min-1. The diameters and lengths of the γ-MnOOH nanorods areabout200-500nm and5-10μm in sequence. The о-LiMnO2nanorods aresynthesized by hydrothermal method using γ-MnOOH nanorods and LiOH·H2O.The initial discharge capacity of o-LiMnO2nanorods is167.1mAh·g-1at0.1Cbetween2.0and4.5V, and its maximum capacity is194.4mAh·g-1. The capacityretention is about78.8%after30cycles. After calcined at high temperature, themorphology of o-LiMnO2becomes particles from nanorods, which makes itselectrochemical performance worse.The o-LiMnO2-air and o-LiMnO2-N2particles are synthesized separately withMn2O3-air and Mn2O3-N2precursor which are prepared by calcining MnO2under airand nitrogen atmosphere in sequence, and the o-LiMnO2-air exhibits betterelectrochemical performance than the o-LiMnO2-N2. The α-Mn2O3nanorodsobtained by calcining γ-MnOOH nanorods under high temperature are used tosynthesize o-LiMnO2-α nanoparticles, whose electrochemical performanc is poor.So the morphology of the precursor has an important influence on the morphology of o-LiMnO2, and as a sequence the electrochemical performance of o-LiMnO2isalso influenced.