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 LiNi0.8Co0.15Al0.05O2 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.
Highlights
Lithium-ion batteries are experiencing the large applications in mobile electronic devices and electric vehicles worldwide
O TM ions especially the rate capability, than that of NCA-735 which contains the lowest antisite defects, we perform the calculations from the perspective of activation barrier which strongly affects the diffusion of lithium ions in electrode materials
When a lithium ion migrates to the nearest lithium vacancy, it has to pass through the adjacent tetrahedron sites, in which the neighboring transition metal ion hinders the Li+ diffusion because of the strong electrostatic repulsion (Figure 5(b))
Summary
Lithium-ion batteries are experiencing the large applications in mobile electronic devices and electric vehicles worldwide. High-energy density and high-power density are the two most important factors in a commercial lithium-ion battery. For the cathode materials, compared to the widely used LiFePO4, LiMn2O4, and LiNi1/3Co1/3Mn1/3O2 [1,2,3,4], the layered nickel-rich materials with higher capacity (170200 mAh g-1) and appropriate working voltage (~3.75 V), such as LiNi0.6Co0.2Mn0.2O2, LiNi0.8Co0.1Mn0.1O2 (NCM811), and LiNi0.8Co0.15Al0.05O2 (NCA) [5,6,7,8], have attracted more and more attention. One of the challenging problems of layered nickel-rich cathode materials is the Li+/Ni2+ antisite defects which result from their similar ionic radii (Li+: 0.072 nm, Ni2+: 0.069 nm) [9, 10]. The cosubstitution of Co and Mn or Al for
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