Rare Earth Elements (REEs) are a group of 17 metallic elements that includes the 15 lanthanides, plus scandium and yttrium. While not actually rare in the Earth’s crust, they are seldom found in high concentrations, making their mining and separation challenging. These elements possess unique magnetic, phosphorescent, and electrochemical properties that make them indispensable for modern high-technology applications. Electric vehicles (EVs) rely heavily on these metals for power density and efficiency. The specialized functions of REEs allow manufacturers to produce lighter, smaller, and more powerful components.
The Necessity of Rare Earths in EV Motors
The primary function of the electric motor in an EV is to deliver high torque and efficiency within a compact, lightweight package. To meet these demands, the vast majority of electric vehicles use Permanent Magnet Synchronous Motors (PMSMs). These motors utilize permanent magnets to create a constant, powerful magnetic field, which is significantly more efficient than older motor types.
Traditional magnets, such as those made from ferrite or alnico, are not powerful enough for vehicle traction applications. Rare earth magnets, particularly those based on the neodymium-iron-boron (NdFeB) formula, are the strongest permanent magnets available, generating magnetic fields of 1.6 Tesla or more. This superior magnetic strength allows engineers to miniaturize the motor while maximizing output and improving the vehicle’s driving range. Their effectiveness relies on high coercivity (the ability to resist demagnetization) and high remanence (the residual magnetic field strength).
Specific Elements Driving Motor Performance
The performance of an EV motor’s magnet is directly tied to the specific rare earth elements used in its construction. The foundation of nearly all high-performance EV motors is the pairing of the light rare earth elements, neodymium (Nd) and praseodymium (Pr). Neodymium is the primary component responsible for the magnet’s immense strength and high torque generation. Praseodymium is often alloyed with neodymium (NdPr mixture), contributing to magnetic field strength and improving corrosion resistance.
The resulting magnet, known as neodymium-iron-boron (NdFeB), offers exceptional magnetic power, but its performance degrades at high temperatures. Since EV motors generate considerable heat during sustained operation, thermal stability is a major concern. This is where the heavy rare earth elements, dysprosium and terbium, become necessary.
Dysprosium (Dy) is added to the alloy to enhance thermal stability, helping the magnet maintain its magnetic properties even when temperatures rise above 180°C. Terbium (Tb) serves a similar purpose, improving the magnet’s coercivity at elevated temperatures. Although only small amounts of dysprosium and terbium are required (often just 1–2% of the alloy), they are indispensable for preventing the permanent magnet from demagnetizing under the demanding conditions of an EV drivetrain.
Secondary Applications in Electric Vehicles
The use of rare earth elements in electric vehicles extends beyond the main traction motor to various other systems that enhance functionality and control. Many smaller motors throughout the vehicle, such as those used for power steering, braking systems, and seat adjustments, also rely on compact, high-efficiency rare earth magnets. These accessory motors benefit from the same high power-to-weight ratio that makes them effective for the primary drivetrain.
Rare earth elements are also incorporated into the advanced power electronics and sensor systems necessary for vehicle operation. Elements like lanthanum and cerium are sometimes used in specialized capacitors and components within the vehicle’s electrical architecture. These materials help manage the flow of high voltage and data, which is important for the sophisticated Battery Management System (BMS) that monitors and regulates the battery pack.
While rare earths are the core of EV motors, they are generally not a primary active material in the cathode or anode of the Lithium-ion battery. Energy storage relies on other materials, such as lithium, cobalt, manganese, and nickel. The application of rare earth elements is primarily focused on the conversion of electrical energy into mechanical movement and the precise electronic control of that process.