Doping Strategies in Ni-Rich NCM Cathode Materials for Next-Generation Li-Ion Batteries: A Systematic Computational Study

Abstract

Layered lithiated oxide cathode materials with mixed transition metals (TMs), such as Ni–Co–Mn (NCM), are the workhorses of Li-ion batteries in the current electric vehicle industry. Among NCM cathodes, Ni-rich (Ni >50% of all TMs) variants can provide high capacities of ∼220 mAh/g, but they suffer from faster capacity fading than their low Ni-content NCM counterparts. Minor doping (≤1%) of transition metal and other metal atoms is one of the advantageous strategies to suppress cathode degradation during cycling. Herein, we provide subnanoscale insights into the effects of dopants on Ni-rich NCM cathode materials for Li-ion batteries across different charge states and correlate our findings with experimental observations. In this study, we consider eight metal dopants with different oxidation states (Al 3+, Nd 3+, Y 3+, Ti 4+, Ta 5+, Nb 5+, W 6+, Mo 6+ ) for NCM cathodes containing 85% Ni–LiNi 0.85 Co 0.10 Mn 0.05 O 2, as a representative promising Ni-rich NCM material. We systematically study the effect of minor doping on structural characteristics, electronic structure, surface behavior, and electrochemical properties of NCM851005 cathodes using first-principles density functional theory calculations and force-field-based methods. Most dopants improve the structural stability of the bulk material and its surfaces by reducing the concentration of Ni 3+ ions and forming strong bonds with the host lattice oxygen, hence possibly preventing crack formation in NCM particles during cycling. The general findings regarding the role of dopants in Ni-rich layered NCM cathode materials presented in this work can guide the future design of high-energy density cathodes for advanced Li-ion batteries.

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