Study of Thermal Decomposition of Li_(1-x)(Ni_(1/3)Mn_(1/3)Co_(1/3))_(0.9)O_2 Using In-Situ High-Energy X-Ray Diffraction

摘要

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 Li_(1.1)[Ni_(1/3)Mn_(1/3)Co_(1/3)]_(0.9)O_2 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 Li_(1.1)[Ni_(1/3)Mn_(1/3)Co_(1/3)]_(0.9)O_2 strongly depended on the exposed chemical environment, like solvents and lithium salts. A phase transformation of dry delithiated Li_(1.1)[Ni_(1/3)Mn_(1/3)Co_(1/3)]_(0.9)O_2 was observed at about 278 ℃, and its onset temperature was reduced to about 197℃ 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.