Toyota’s New Electric Motor Cuts Need for Costly (and Overwhelmingly China-Sourced) Rare-Earth Metal ""

By | February 27, 2018

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Automakers are making nearly continuous improvements to vehicle engines and structures by alloying their steels with an evolving list of special ingredients such as manganese, titanium, chromium, and nickel. But for electric cars, the essential recipe for making the physics work in electric motors and batteries can seem more than a little daunting.

One of the key ingredients in e-motors is neodymium, one of the most critical elements in the rare-earth magnets needed to create the permanent-magnet electric motors that are most common in today’s electric cars. Toyota is aiming to cut reliance on neodymium as it pushes ahead in developing a global electric vehicle.

True to their name, permanent-magnet motors—such as those in the Prius Prime and most EVs and hybrids—incorporate magnets mounted directly on or within the rotor (the rotating component of the motor), while electric current is applied to the windings of the stator (the stationary portion of the motor). Magnets that produce the power needed for EVs are rare-earth magnets, a type that’s lighter and can produce a stronger field (and thus more torque) than old-style ferrite magnets.

Toyota Prius Prime

Toyota Prius Prime

There are other motor designs, such as the AC induction motors that Tesla favors in its Model S and Model X or the current-excited motors being designed by some automakers for next-generation EVs (Audi is walking that path for its upcoming e-tron and e-tron Quattro). But production ease and efficiency keep automakers coming back to the permanent-magnet design—even Tesla, in its Model 3.

Toyota has found a way to cut the amount of neodymium in electric-motor magnets by 20 percent, with the potential to reduce it as much as 50 percent, while keeping the heat-resistant traits that make the metal a must-have. The automaker has completely reworked the grain surface of the magnets and gone to a two-layer structure that places concentrated neodymium on the surface but a diluted form of the element in the core, alloying it inside with cerium and lanthanum in a 3-to-1 ratio. The automaker notes that both of those new ingredients are abundant and relatively low in cost.

Performance of the new magnet (in terms of coercivity) is slightly better at the top of its operating-temperature spread—above about 270 degrees Fahrenheit—which is right where and when peak performance in an electric vehicle would be needed. Toyota plans to introduce a motor design incorporating the new magnets in electric power-steering systems in the next few years and in drive motors for electric vehicles within the next 10 years.

Toyota motors

Not in Shortage, But in Short Supply

“There are concerns that shortages will develop as electrified vehicles, including hybrid and battery-electric vehicles, become increasingly popular in the future,” Toyota wrote in a release. “Despite this, little effort has been made to address neodymium use.”

It’s indeed in short supply and is one of the 14 metals that a 2012 paper identified as being required at 1 percent or more of the total 2010 world supply, per year, between 2020 and 2030. The ramp-up in demand for neodymium and those other elements, which include cadmium, dysprosium, gallium, and vanadium, among others, is largely driven by projected growth in the green-energy sector, which needs those rare-earth magnets for motors and generators.

The term “rare earth” is almost a misnomer; while most rare-earth elements are plentiful in the earth, they tend to be difficult to extract from other minerals. Currently, most neodymium comes from China, where this past year the country’s government cracked down on illegal mines, sending prices of the element skyrocketing. If nothing is done to reduce the industry’s reliance on specific elements, we could just be trading one dependency—oil—for another.



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