Thermal stability of charged LiNi0.5Co0.2Mn0.3O2 cathode for Li-ion batteries investigated by synchrotron based in situ X-ray diffraction

Abstract

Structural changes for LiNi0.5Co0.2Mn0.3O2 cathode material of lithium-ion battery with and without electrolyte during heating from 25 to 600°C are investigated using synchrotron based in situ X-ray diffraction. LiNi0.5Co0.2Mn0.3O2 without electrolyte first converts from a layered structure to disordered LiM2O4-type spinel and M3O4-type spinel phase as the temperature increases, then two different types of disordered spinel phases are co-existed up to 600°C and no further decomposition to MO-type rock salt phase is presented at all. The electrolyte accelerates the thermal decomposition of the charged cathode materials. The presence of the electrolyte alters the paths of the structural changes and lowers the onset temperatures of the thermal decomposition reactions. In the case of LiNi0.5Co0.2Mn0.3O2 with electrolyte, more dramatic structural changes are observed compared with LiNi0.5Co0.2Mn0.3O2 without electrolyte and MO-type rock salt phase and metallic phase are presented at the end of the heating.