Rare-Earth Substitution as a Resource Strategy for EV Traction Motors: Design Compensation Trade-Offs and Break-Even Electricity Carbon Intensity

Rare-earth substitution in electric vehicle traction motors is increasingly discussed to reduce dependence on critical raw materials and mitigate environmental burdens associated with rare-earth production. However, such substitution is not a simple material replacement. The lower magnetic energy density of ferrite magnets requires geometric and structural design compensation, increasing bulk material throughput and potentially altering operational efficiency. The environmental outcome of rare-earth substitution depends on system-level trade-offs between manufacturing-stage material demand and use-phase electricity consumption. This study evaluates rare-earth substitution as a resource strategy through a cradle-to-grave life cycle assessment of two functionally equivalent EV traction motors based on different permanent magnet technologies: a mass-produced NdFeB-based motor and a rare-earth-free ferrite-based spoke-type motor designed to achieve comparable traction performance through geometric compensation. Manufacturing, use-phase, and end-of-life stages are modelled consistently, with electricity consumption derived from efficiency maps under the WLTC driving cycle. Results show that the ferrite-based motor exhibits higher manufacturing-related greenhouse gas emissions due to increased demand for electrical steel, copper, aluminum, and composite materials, while achieving lower lifetime electricity consumption. A break-even electricity carbon intensity of approximately 60 g CO₂-eq/kWh is identified. Above this threshold, the ferrite-based design delivers lower total life cycle climate impacts despite higher material demand; below it, the advantage diminishes as electricity systems approach low-carbon conditions. These findings establish quantitative boundary conditions linking material substitution decisions to electricity system characteristics and underscore the importance of evaluating critical material strategies within the broader context of energy system transformation.