Computational Insights to the Layered-to-Spinel Structural Transformation in Ni-Rich Lithiated Transition Metals Oxide Materials (LiNi x Co y Mn z O 2 )

Abstract

Ni-rich lithiated transition metal oxides of layered structure (R-3m space group) LiNi x Co y Mn z O 2 (NCMs, x>0.5) represent a family of promising materials for positive electrodes of advanced lithium-ion batteries (LIB). These materials demonstrate reversible capacities around 160 – 190 mAh/g in the potential range of 2.8 – 4.3 V. Despite of the considerable research on improvement of these materials’ performance by lattice doping with cations, the molecular level of understanding 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 LIB. For example, atomistic resolution parameters, such as the diffusion of lithium ions within the layers, are responsible for the power of the battery. The electronic structure, on the other hand, dictates the electro-conductivity. Although many studies suggest improved performance of doped NCM cathode materials, the mechanism of the enhanced behavior still remains unclear. In this work, we present the computational study using ab-initio modeling of the role of Zr-doping on the electrochemical performance and structure of LiNi 0.6 Co 0.2 Mn 0.2 O 2  (NCM-622) electrode material. We show that how doping influences on the Li + /Ni 2+ mixing, charge distribution among transition metals, and lattice constants. In particular, we reveal that Ni +2  ions migration upon Li-deintercalation (charge) can initiate layered-to-spinel structural transformation. We also demonstrate the role of Zr +4  cations on limiting this transformation by investigating the electronic structure and possible Ni +2  migration pathways and mechanisms. In this presentation, the role of other multivalent dopant cations on the structural stability of NCM will be discussed.