Monitoring the Formation of Nickel-Poor and Nickel-Rich Oxide Cathode Materials for Lithium-Ion Batteries with Synchrotron Radiation

The syntheses of Ni-poor (NCM111, LiNi_1/3Co_1/3Mn_1/3O₂) and Ni-rich (NCM811 LiNi_0.8Co_0.1Mn_0.1O₂) lithium transition-metal oxides (space group R3̅m) from hydroxide precursors (Ni_1/3Co_1/3Mn_1/3(OH)₂, Ni_0.8Co_0.1Mn_0.1(OH)₂) are investigated using in situ synchrotron powder diffraction and near-edge X-ray absorption fine structure spectroscopy. The development of the layered structure of these two cathode materials proceeds via two utterly different reaction mechanisms. While the synthesis of NCM811 involves a rock salt-type intermediate phase, NCM111 reveals a layered structure throughout the entire synthesis. Moreover, the necessity and the impact of a preannealing step and a high-temperature holding step are discussed.