A New Magnet for Electric Cars

The advent of electric cars is spawning innovations in almost every technology field including batteries, motors, wires, PCBs, electronics, and many more. Electric cars require powerful and efficient motors, and for that, magnets used in the motors must be stronger than usual.

Toyota Motor Corporation has developed a new magnet for electric motors, and they have reduced by 50% the use of critical rare-earth elements they were using so far. As the number of electric cars is set to increase rapidly in the future, Toyota is expecting this heat-resistant magnet, which uses less neodymium, will find increasing use in the electrified vehicles.

Neodymium, terbium, and dysprosium are rare-earth elements that industries popularly use when manufacturing strong magnets. Although the magnets made from these elements can operate in high-temperature conditions, they are expensive. Toyota has replaced a proportion of the neodymium in these magnets with lanthanum and cerium, as these are low-cost rare earth elements.

Manufacturers of magnets use neodymium as it provides their products with high heat resistance and coercivity—the ability to maintain magnetism at high temperatures. However, simply using less neodymium and using lanthanum and cerium instead would cause the motor to underperform. Therefore, Toyota had to adopt newer technologies to overcome the deterioration in motor performance. The result was a successful magnet with half the amount of neodymium, but equivalent levels of heat resistance and coercivity.

Toyota expects this new magnet to maintain a balance between the supply and demand of resources especially that of the valuable rare earth elements, while being useful in the expanding world of electric automobiles and robotics. Toyota is continuing in its efforts to enhance the performance further, and evaluate the use of the magnet in a greater number of products. They are also aiming to accelerate the development of technologies for mass-producing the magnets, so that different products can adopt them easily, including robots and vehicles.

Use of rare earth elements in magnets enables them to maintain magnetism even at high temperatures. For this, they require about 30% of the elements in the magnets to be of the rare earth types.

Adding neodymium in magnets makes them more powerful, but automotive applications require them to operate at high temperatures. Although adding terbium and dysprosium improves the high-temperature coercivity, it also makes the magnets more expensive. Toyota’s efforts at creating cheaper magnets with reduced use of neodymium have finally paid off.

Although at present, the production volumes of neodymium are adequate there are concerns that as the development of electrified vehicles picks up, the demand will outstrip supply. This is may become a bigger concern as electrified vehicles include hybrid electric as well as battery powered electric vehicles of all types are likely to become more popular in the future.

Toshiba uses three new technologies in their magnets to help maintain coercivity at high temperatures, even with reduced neodymium. For this, they had to refine the grains in the magnet, use two-layers of high-performance grain surfaces, and use an alloy with a specific ratio of lanthanum and cerium.