In-situ X-ray 회절법을 이용한 과충전 및 과방전 상태의 LiMn2O4-LiNi1/3Co1/3Mn1/3O2 양극 합성체에 관한 연구

Abstract

Recently, the lithium ion batteries have been investigated intensively and widely used in energy devices and storage systems. For the lithium ion battery applications, LiMn2O4 spinel have been investigated as one of the promising material for conventional cathode due to its low cost, low toxicity, fast kinetics and remarkable safety properties. The new layered LiNi1/3Co1/3Mn1/3O2 cathode material is another good candidate due to its low cost, high specific capacity, and good thermal stability properties. There are many reports about thermal properties of LiMn2O4 and LiNi1/3Co1/3Mn1/3O2 cathode material using various techniques such as differential scanning calorimetry (DSC), thermogravimetry/differential thermal analysis (TG/DTA), accelerated rate calorimetry (ARC), and micro-calorimetry. However, not much information on the structural changes of over-charged or over-discharged LiMn2O4 and LiNi1/3Co1/3Mn1/3O2 cathode has been reported. In the case of LiNi1/3Co1/3Mn1/3O2 cathode materials, at over-charged states (highly delithiated), the reduction of Ni4+ releases oxygen that can accelerate severe thermal runaway by reacting with the electrolyte before leading to catastrophic failure of the battery. In this paper, the results of the structural change studies of the over-charged or over-discharged LiMn2O4 – LiNi1/3Co1/3Mn1/3O2 composite cathode during cycling using in situ synchrotron based XRD technique are reported. These results provide valuable guidance for the structural change behavior and different contributions of each individual component. Additionally, helpful information in redesigning and optimizing the LiMn2O4 and LiNi1/3Co1/3Mn1/3O2 composite cathode will be provided for Li-ion battery research.