A STUDY OF TRANSITIONAL METAL MIGRATION IN NICKEL-RICH LAYERED METAL OXIDE CATHODE

• Main Author: Waraney Moesa Komalig, Ravanny
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/64187
• Institution: Institut Teknologi Bandung

Thermal instability and capacity retention have been the two most concerning problems encountered within the nickel-rich nickel-cobalt-manganese (NCM/LiNixCoyMnzO2, x > y, x > z, x + y + z = 1) layered-metal oxide (LMO) cathode for the Li-ion battery. Experimental observation finds formation of oxygen vacancy and spontaneous phase transition of the cathode structure under prolonged delithiation - the two turn out to occur alongside each other under certain environmental conditions. In this final thesis, a density functional theory (DFT) based study is done to determine how the occurrence of oxygen vacancy affect the nano-scale initiator of recurring phase transition: transitional metal migration from the layered-metal oxide slab toward the active Li+ ion site in between the slab. The analysis is done at 55% lithiation, which one predicts to correspond to the maximum conventional range for a discharged cell. Under delithiated state, the oxidation capability of transitional metal begin to diminish, allowing oxygen oxidation in exchange and thus causing the formation of oxygen vacancy. Oxygen that are only bonded to Ni have the lowest formation energy and a predicted formation temperature as low as 397 K. Energetic comparison shows that nearby vacancy also destabilizes the nearby residing transitional metal in the slab, thus allowing atomic dislocation. The presence of vacancy suppress this barrier of dislocation which consequently increase the kinetic rate of atomic migration. Further thermodynamics calculation is also done to predict the vacancy formation and atomic migration phenomena in a certain range of temperatur and pressure.