Study of Thermal Decomposition of Li1-x(Ni1/3Mn1/3Co1/3)0.9O2 Using In-Situ High-Energy X-Ray Diffraction

Safety has been a major technological concern hindering the deployment of lithium-ion batteries for automobile applications. We investigated the decomposition mechanism of delithiated cathode materials at thermal abuse conditions using Li1.1[Ni1/3Mn1/3Co1/3]0.9O2 as a model cathode material. An in-situ high-energy X-ray diffraction technique was established as an alternative to conventional thermal analysis techniques like differential scanning calorimetry and accelerating rate calorimetry. The X-ray diffraction data revealed that the thermal decomposition pathway of delithiated Li1-x[Ni1/3Mn1/3Co1/3]0.9O2 strongly depended on the exposed chemical environment, like solvents and lithium salts. A phase transformation of dry delithiated Li1-x[Ni1/3Mn1/3Co1/3]0.9O2 was observed at about 278 degrees C, and its onset temperature was reduced to about 197 degrees C with the presence of the electrolyte. It is suggested that the reduction in thermal stability is possibly related to proton intercalation into the delithiated material.