Design-driven multi-element doping for long-life High-Ni NCM cathodes: Criteria-guided dopant selection and one-pot element-specific intraparticle placement

Abstract

Despite their high energy density, Ni-rich layered NCM cathodes suffer from coupled degradation rooted in structural instability. Here, a criteria-guided Ti-Al-Mg co-doping strategy (complementary roles, radius compatibility, near-trivalent charge, abundance) is implemented via a one-pot solid-state route. Crucially, near-surface Mg enrichment is directly mapped, presumably associated with its larger ionic radius. Together with Ti/Al incorporation into bulk transition-metal (TM) slabs, this element-specific intraparticle placement of multi-dopants is coordinated—an inherently non-trivial task—via a one-pot calcination without multistep gradient engineering. This radius-mismatch-driven, one-pot placement constitutes a previously unreported route to couple interfacial stabilization (Mg at the surface) with bulk lattice reinforcement (Ti/Al in TM slabs). Leveraging the complementary contributions of the three dopants, this coordinated placement suppresses Li/Ni cation mixing, crack propagation, and impedance growth. In Li-metal half-cells, the resulting cathode (TAM-1) exhibits significantly enhanced cycling stability, retaining 94.5% capacity after 500 cycles at 1C, outperforming undoped Ni83 (30.0%). Operando optical microscopy directly visualizes suppressed crack initiation/propagation in TAM-1. Overall, this study establishes that both rational dopant selection (Ti/Al/Mg chosen by explicit criteria) and element-specific dopant placement (near-surface Mg; bulk TM-slab Ti/Al) are practical, generalizable levers for durable Ni-rich layered oxides—enabling bulk–interface co-reinforcement with standard solid-state processing.