COMPUTATIONAL INSIGHTS TO THE LAYERED TO SPINEL TRANSFORMATION IN Ni-RICH NCMs

Ni-rich Li-based layered Ni, Co, and Mn materials (NCMs) based electrode materials have emerged in recent years as an alternative to LiCoO₂, which has been commercialized by several companies for EV applications. Despite of the considerable research on Li/NaNi_xCo_yMn_zO₂ systems, the molecular level understanding of the effect of dopants on the electronic structure, voltages, and ion diffusion is very limited. However, the above information is essential for the design of new and efficient positive electrode materials. For example atomistic resolution parameters, such as the diffusion of sodium or lithium ions within the layers, are responsible for the power of the battery. The electronic structure, on the other hand, dictates the electric conductivity. It is clear therefore, that the real design of modern energy storage devices can benefit from atomistic resolution strategies, such as ab-initio modeling.

Many studies suggest improved performance of doped NCM based cathode materials. However the mechanism of enhanced performance still remains unclear. We present the computational study of the role of Zr-doped LiNi_0.6Co_0.2Mn_0.2O₂ (NCM-622) as a positive electrode material. In particular we reveal that Ni⁺² ion migration can initiate layer-to-spinel transformation. We also demonstrate the role of Zr⁺⁴ atoms of limiting the layered to spinel transformation of NCM-622 by investigating the electronic structure, and possible cation migration pathways.