In-situ Characterization of the Thermal Degradation of LiNi0.8Co0.15Al0.05O2 Cathode Materials for Lithium Ion Batteries: Insights from Combined Synchrotron XRD, XAS and Environmental Microscopy Studies

Title
In-situ Characterization of the Thermal Degradation of LiNi0.8Co0.15Al0.05O2 Cathode Materials for Lithium Ion Batteries: Insights from Combined Synchrotron XRD, XAS and Environmental Microscopy Studies
Authors
박성민남경완장원영Xiqian YuEnyuan Hu황수연김광범정경윤Xiao Qing YangEric A. Stach
Keywords
in-situ characterization; cathode; thermal degradation; synchrotron; environmental microscopy
Issue Date
2013-04
Publisher
2013 MRS Spring Meeting
Abstract
Li-ion batteries have seen widespread application as secondary batteries in numerous applications in consumer electronics, and have attracted recent attention for various forms of electric vehicles. One particularly attractive material for the cathode is the Ni-rich system of LiNi0.8Co0.15Al0.05O2. These materials are being explored as a replacement to LiCoO2, as they offer several performance improvements, including higher energy density and lower cost. However, these materials have demonstrated a significant increase in impedance and capacity fade during ageing, or upon cycling at elevated temperatures. Additionally, when in highly delithiated states, the reduction of Ni ions during thermal cycling releases oxygen from the crystal structure, which can lead to both thermal runaway and violent reactions with the flammable electrolyte. We have utilized a variety of in-situ characterization methods to understand the mechanisms associated with the thermal degradation of LiNi0.8Co0.15Al0.05O2 materials, as a function of their delithiation / charge state. By combining time-resolved synchrotron x-ray diffraction and mass spectrometry, we directly show that these materials undergo a specific sequence of phase transformations - from layered to disordered spinel to rock salt - as a function of temperature, and directly correlate these phase transformations with the evolution of oxygen from the microstructure. In-situ observations in an environmental transmission electron microscope confirm these global average measurements on the nanoscale, and allow us to kinetically track the evolution of oxygen from the surfaces of the nanoparticles into their bulk. In-situ spectroscopic results - from XAS and EELS - allow correlation between electronic structure changes and the resulting phase transformations. Finally by performing these same thermal treatments in-situ to the TEM and in the presence of excess oxygen
URI
http://pubs.kist.re.kr/handle/201004/45061
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KIST Publication > Conference Paper
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