Facilitating Lithium-Ion Diffusion in Layered Cathode Materials by Introducing Li ⁺ /Ni ²⁺ Antisite Defects for High-Rate Li-Ion Batteries

Abstract

Li⁺/Ni²⁺ antisite defects mainly resulting from their similar ionic radii in the layered nickel-rich cathode materials belong to one of cation disordering scenarios. They are commonly considered harmful to the electrochemical properties, so a minimum degree of cation disordering is usually desired. However, this study indicates that LiNi_0.8Co_0.15Al_0.05O₂ as the key material for Tesla batteries possesses the highest rate capability when there is a minor degree (2.3%) of Li⁺/Ni²⁺ antisite defects existing in its layered structure. By combining a theoretical calculation, the improvement mechanism is attributed to two effects to decrease the activation barrier for lithium migration: (1) the anchoring of a low fraction of high-valence Ni²⁺ ions in the Li slab pushes uphill the nearest Li⁺ ions and (2) the same fraction of low-valence Li⁺ ions in the Ni slab weakens the repulsive interaction to the Li⁺ ions at the saddle point.