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Solvothermal Synthesis of Octahedral LiMn1.5Ni0.5O4 Particles for Li-ion Batteries
Oral Presentation
Authors
School of Metallurgy & Materials Engineering, Iran University of Science and Technology (IUST), Narmak, Tehran, Iran
Abstract
Lithium-ion batteries (LIB) is widely used in portable electronic device, such as mobile phone and cameras due to high energy density, high working voltage and long cycle life. The electrochemical properties of LIBs depend on the materials characteristics of cathode materials. Among various cathode materials, LiMn1.5Ni0.5O4 (LMNO) with spinel structure has a three dimensional channel for the migration of lithium ions, leading to the high working voltage (~ 4.7 vs. Li/Li+), good theoretical capacity (148 mAh g-1), and high energy density (650 Whkg-1). The electrochemical performance of LMNO powders are influenced by factors such as particle size, morphology, crystallinity, crystallographic structure, and purity, mainly adjustable through control over the synthesis method. Different methods have been used to prepare the LMNO powders such as solid state reaction, sol gel, co-precipitation, solution combustion, hydrothermal/solvothermal, etc. Among them, hydrothermal/solvothermal process is a suitable method to obtain highly crystalline powders with homogeneous particle size distribution. The particle size and morphology can also be controlled by a choice of solvents, and reaction conditions in hydrothermal/solvothermal process. In this study, LMNO powders have been synthesized by solvothermal method using oxalic acid as precipitant agent. Furthermore, the various amounts of citric acid was added to tune the structure, morphology, specific surface areas, and electrochemical properties which are characterized by X-ray diffractometry, simultaneous thermal analysis, N2 adsorption-desorption, scanning electron microscopy, and galvanic charge/discharge test. The single phase LMNO powders are obtained by calcination at 800 °C for 2 h. With the increase of citric acid contents, the particle size increases from 0.3 to 1.2 m. Due to the reduction conditions during calcination process, the amounts of Mn3+ are increased with the amount of citric acid, leading to the capacity fading at high cycle numbers. The synthesized LMNO powders without citric acid showed the best electrochemical properties with a discharge capacity of 81 mAh g-1 and capacity retention of 95% following 30 cycles at a current rate of 0.1C.
Keywords