Developing electric motors less dependable on rare earth magnets




In 1997, Toyota upset the status quo by launching the first generation Prius, complete with a hybrid powertrain that utilized rare-earth magnets.

Materials such as Neodymium Iron Boron (NdFeB) made great performance benefits possible, facilitating the creation of small yet powerful traction motors. However, by 2012 these materials had begun to increase in price, and the industry in turn looked for alternatives, with more availability and sustainability.

The question is, what other ready-to-market alternatives are there to continue producing powerful and reliable drivetrains?

According to electronicdesign.com, there are four main types of magnets: Ceramic (ferrite), AlNiCo, Samarium Cobalt (SmCo), and Neodymium (NdFeB). The latter is one of the most commonly used in motors for hybrid vehicles and electric vehicles. Neodymium magnets have higher remanence, along with much higher coercivity and energy production, but often a lower Curie temperature than the alternatives.

“Special neodymium magnet alloys that include terbium and dysprosium have been developed with higher Curie temperatures, allowing them to tolerate higher temperatures of up to 200°C. Because of the rare-earth magnet properties, no other magnet material can match their high strength performance. You cannot really replace rare-earth magnets,” says Da Vukovich, president of Alliance LLC, quoted in the article.

In addition to the four main types of magnets listed above, rare-earth magnets are divided in two: Light Rare Earth (LRE) and Heavy Rare Earth (HRE). “The global rare-earth reserves consist of approximately 85 percent LRE and 15 percent HRE. The latter are the ones providing magnets rated at high temperature that are suitable in many automotive applications,” as expressed by electronicdesign.com.

And the reality is that, in 2018, 93 percent of all the EVs produced in the world had a powertrain driven by permanent magnet motors made up of rare earths.

This supposed an increase of one percent with respect to the data of the previous year. This information, extracted from the data of the EV Motor Power and Motor Metals Tracker platform of Adamas Intelligence, shows that this technology continues to be the most used, due to its smaller size and greater efficiency.

Rare-earth magnet usage and history

A permanent magnet synchronous electric motor incorporates magnets composed of rare earths, such as dysprosium, gadolinium or neodymium. Thanks to them, drivetrains do not need external excitation, nor brushes, to generate the magnetic field in the rotor and spin it when exposed to the externally generated field in the stator, which makes them more compact and simple.

The flow density is a property of these magnets that is used for the generation of energy generated by the movement. Its main feature is that, after being magnetized, they retain their flow lines, similar to the batteries in which the electric charges move.

Permanent magnets became widespread industrially in the 1990s and are used today in most electric cars. This reality, which Adamas data shows, is due to its greater efficiency: Up to 15 percent in relation to asynchronous induction motors, reaching higher available power density, both gravimetrically (kW/kg) and volumetrically (kW/cm3).

The biggest problem with this type of electric motors is that they contain exotic materials, due to their scarcity and because their origin is limited to few countries. This makes them more expensive to manufacture.

However, from the OEM point of view, their greater efficiency allows another fundamental component, the battery, to be smaller, thus reducing costs.

Adamas adds that the demand for permanent magnet motors will continue to grow in the future. But this trend could be reversed by the increase in the supply and demand of electric vehicles, which is causing the cost of batteries per kWh to decrease faster than expected. This opens the door to the use of induction motors to avoid the use of scarce materials sourced from a limited number of suppliers.

As an example, Tesla has used this type of motor in its electric cars from the beginning. BMW, in its new fifth-generation electric motors, intends to abandon permanent magnet motors. After years of development, the firm has achieved a very compact system, capable of generating up to 250kW and, thanks to external excitation, also giving greater torque control, maximizing power and efficiency.

New electric motors with less dependence on rare earths

Since 2013, German research organization, Fraunhofer, has been assessing the availability of rare earths before the arrival of automobile electrification. The research has aimed at finding a new solution for a more efficient use of these materials.

The results have been presented recently and include a series of optimized production processes, guidelines for recycling and the use of new materials that replace rare earths.

The institute has been able to demonstrate that the current demand for these materials, especially dysprosium and neodymium, can be reduced by a fifth by applying the solutions described in the conclusions of its study.

For the investigation, two electric motors were used without external stimulation – that is, permanent magnets of dysprosium and neodymium to activate the magnetic field in the motor rotor and cause its rotation. This type of electric motor is the most used today by the automotive industry in its electric vehicles, since it gives rise to very compact and easy-to-manufacture motors by not needing electrical components for external rotor excitation. Their demand will increase dramatically as a consequence.

According to the spokesperson for the project, Professor Ralf B. Wehrspohn, the initial objective was to reduce the need for the use of rare earths by half of the two motors of the study. By combining different technical approaches, they were able to meet this goal and even exceed their expectations.

According to the researchers themselves, “The project is unique due to its breadth and depth.” The systematics used have included quantum computer simulations, with various types of magnetic materials, to the preparation of magnet prototypes in their almost definitive form for use in electric motors. The recycling of rare earths after the use phase was also studied.

The organization will now seek to collaborate with the industry to bring the results to the market.

The beginning of this investigation took place after the sudden increase in the price of these materials in 2013. China, which produces and uses 90 percent of world production, declared the suspension of exports, causing a crisis in the market. This situation revealed the dependence of the European markets on the Chinese industry, so the large German car consortiums rushed to find a viable alternative.

Toyota to reduce neodymium used in its new electric motors

Toyota is developing electric motors that include up to 50 percent less rare-earth metals, amid concerns over a shortage of supply as automakers compete to expand their electric vehicle lines.

The Japanese firm has created a new type of magnet for motors that can reduce the use of neodymium by half and at the same time eliminate other elements like terbium and dysprosium. Toyota will use lanthanum and cerium instead, which cost 20 times less than neodymium. The automaker already has agreements with its suppliers to manufacture the magnets.

One of the main suppliers of rare earths is China, but the actions of the authorities against illegal mining have affected the production of these metals. Toyota has big plans in the electricity sector, and it cannot risk relying on metals whose mass production is not guaranteed.

Toyota expects that the demand for neodymium will exceed the offer from 2025, at which time the company intends to offer an electrified version of each vehicle in its lineup. By 2030, the Japanese automaker intends to sell 5.5 million electrified vehicles, including plug-in, electric and fuel cell hybrids.

The production of lithium and cobalt, metals used in electric car batteries, also represents a concern for manufacturers. Tesla, for example, has been in talks with the government of Chile – one of the world's leading lithium producers – to build a lithium processing plant in the South American nation. On the other hand, Samsung SDI works in the development of cobalt-free batteries, metal whose production also generates controversy.

Compromised availability and lack of sustainability is prompting the industry to be less reliant on rare-earth magnets. As we have covered, work is well underway at producing viable, sustainable alternatives, with a supply that will remain flexible enough to accommodate even the most optimistic global electric vehicle sales forecasts.

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