C. K. Lin, Y. Piao, Y. C. Kan, J. Bareno, I. Bloom, Y. Ren, K. Amine and Z. H. Chen (2014) Probing Thermally Induced Decomposition of Delithiated Li1.2-xNi0.15Mn0.55Co0.1O2 by in Situ High-Energy X-ray Diffraction. Journal/Acs Applied Materials &, Interfaces 6 12692-12697. [In English]
Web link: http://dx.doi.org/10.1021/am502689f
Keywords: ,safety, thermal stability, cathode, X-ray diffraction, lithium-ion, battery, LITHIUM-ION BATTERIES, STRUCTURAL-CHANGES, CATHODE MATERIALS, STABILITY, OXIDE, SAFETY, XRD

Abstract: Safety of lithium-ion batteries has been a major barrier to large-scale applications. For better understanding the failure mechanism of battery materials under thermal abuse, the decomposition of a delithiated high energy cathode material, Li1.2-xNi0.15Mn0.66Co0.1O2, in the stainless-steel high pressure capsules was investigated by in situ high energy X-ray diffraction. The data revealed that the thermally induced decomposition of the delithiated transition metal (TM) oxide was strongly influenced by the presence of electrolyte components. When there was no electrolyte, the layered structure for the delithiated TM oxide was changed to a disordered Li1-xM2O4-type spinel, which started at ca. 266 degrees C. The disordered Li1-xM2O4-type spinel was decomposed to a disordered M3O4-type spinel phase, which started at ca. 327 degrees C. In the presence of organic solvent, the layered structure was decomposed to a disordered M3O4-type spinel phase, and the onset temperature of the decomposition was ca. 216 degrees C. When the LiPF6 salt was also present, the onset temperature of the decomposition was changed to ca. 249 degrees C with the formation of MnF2 phase. The results suggest that a proper optimization of the electrolyte component, that is, the organic solvent and the lithium salt, can alter the decomposition pathway of delithiated cathodes, leading to improved safety of lithium-ion batteries.