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Next-Gen EVs Need Battery and Powertrain Innovations

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To view the full presentation and all other session that took place during the 2023 Advanced Automotive Forum, register here to watch on demand through June 2.

At the recent Advanced Automotive Technology Forum 2023, from EE Times, industry experts discussed some of the battery and powertrain innovations needed for the next generation of electric vehicles (EVs), and challenges the industry faces to implement them.

An all-electric vehicle. (Source: U.S. Department of Energy)

EVs have been around for well over a decade. But while their adoption is growing, it will take some time before they capture a sizeable share of the market. For example, out of approximately 80.6 million new cars sold globally last year, less than 10% (7.8 million) were electric, according to a slide presented by Patrick Le Fèvre, chief marketing and communications officer at Powerbox.

Meanwhile, sales of cars are increasing and the number of vehicles on the road is growing, too. If today there are around 1.6 billion vehicles worldwide, by 2035 that number will grow to nearly two billion, according to the slide from Powerbox. In the EU, 2035 will be the year when sales of new cars with internal combustion engines (ICEs) will be banned. So, by that time, most automakers will have introduced top-to-bottom EV lineups.

There are many vehicles in the world and their number is growing. (Source: Powerbox)

There are many reasons why the adoption rate of EVs is relatively slow, and perhaps the best way to speed it up is to make EVs more attractive in general. There are several ways to do so, but many innovations are required.

For example, batteries and power electronics are among the major challenges. Specifically, as EVs require up to 20× more power compared with traditional automobiles, they present a considerable challenge for power experts in terms of building energy-efficient power conversion solutions, powertrain development and battery technology.

Converters and inverters need work

Today, most hybrid/plug-in hybrid electric vehicles (HEV/PHEV), as well as EVs, use converters and DC-AC invertors that comprise of silicon-based insulated gate bipolar transistors (IGBTs). These components are, in many cases, not compact and are not very efficient, yet they are cheap as they have been around for decades, according to a slide demonstrated by Pietro Scalia, director of automotive traction solutions at Onsemi.

For now, IGBTs may be good enough for most mass market applications. But the HEV/PHEV market will decrease as car manufacturers focus on battery-powered EVs (or BEVs), so higher-performance converters and inverters will get more widespread as EVs tend to feature higher performance traction motors.

Furthermore, while sedans and crossover EVs will remain the most popular types of vehicles with the highest market shares, SUVs, trucks and sports cars will see increased demand after 2025, which will rise demand for >250kW electric drives, according to Onsemi’s slide. This will increase demand for higher performance, higher efficiency, and smaller converters and invertors.

EV, HEV, and PHEV market trends and power class segmentation. (Source: Onsemi)

Building compact and efficient power-conversion solutions requires using wide-bandgap (WBG) semiconductor materials, such as gallium nitride (GaN) and silicon carbide (SiC). When compared with silicon, they offer higher power density (high electron mobility and breakdown voltage allows to build smaller and lighter PSUs), high efficiency (less power loss and lower temperatures, which lead to reduced cooling requirements and lower costs), fast switching speeds (leads to improved power conversion efficiency and reduced electromagnetic interference), and wide temperature ranges (higher reliability and durability).

While both GaN and SiC offer tangible advantages in power conversion applications, they are not interchangeable in all use cases, and the choice between the two depends on the specific requirements. For example, GaN has a higher electron mobility and can achieve higher power densities, which makes it more suitable for in-vehicle applications and chargers.

Actually, usage of GaN for in-car electronics like LiDAR, infotainment and headlights has been increasing and will keep increasing in the future. Furthermore, some traction motors now also use GaN converters, said Alex Lidow, CEO and co-founder of EPC, a supplier of GaN-based devices.

“Today, if you have a LiDAR system on a car, whether it be autonomous or just a level two or level three, that has GaN devices in it,” he said. “We have been on headlights with GaN for almost 10 years, infotainment systems, wireless charging, other than for the car, but wireless charging inside the car, and all sorts of advanced things like augmented reality heads up displays. These are all homes for GaN. As sure as the sun comes up in the morning, [GaN] will replace silicon, and everything that is in the 48-V range. We will see whether or not it moves to the traction [motors], and the onboard charging in the future, as well.”

Uses of GaN in cards. (Source: EPC)

On the other hand, SiC can handle higher voltages and offer better thermal performance, making it a suitable choice for high-power and high-temperature applications, such as traction inverters in EVs. Also, SiC technology is more mature and is sometimes cheaper to implement. Some SiC-based inverters may be cheaper than IGBT-based inverters.

“Finding the sweet spot of the performance versus the cost of the material [is important], I had a sweet spot at 250kW, where I can easily demonstrate that SiC is cheaper than IGBT in terms of area given the delta cost, calculating the extra need the you have to put in place for dissipating, you can have a much cheaper solution with silicon carbide,” Onsemi’s Scalia said.

It goes without saying that with higher efficiency comes miniaturization and weight loss on components levels, which in turn allows us to build more comfortable cars with longer range or make cheaper cars with sufficient range for everyday needs. Cost-efficient SiC MOSFETs along with innovative packaging opens doors to lower-cost EVs with decent motors.

“One part of our strategy at Qorvo [is addressing the] explosion of lower powered cars that are going to come,” said Anup Bhalla, chief engineer of power devices at Qorvo.

There is a persistent need in “getting the cost out of the solution for the people who want to build EV traction inverters and to make the [EV] technology more accessible,” he added.

Finding the right balance between an inverter or converter cost, efficiency, and reliability is a challenge that makers of SiC and GaN components, as well as EVs, must address whenever they build a new car, converter or inverter.

“When we tackle an inverter design with a customer, there is a lot of back and forth how they can extract the maximum benefit [as there are] regular tensions between efficiency they want to get the cost they are willing to pay,” Bhalla said. “This cost is always tied in with the reliability impact of trying to go too cheap. This system has to in the end be very reliable. And everybody has their own take on how they need to build the inverter to define their own advantage.”

SiC components for EVs and other uses. (Source: Qorvo)

Bhalla demonstrated a compact dual side cooled 150kW (12ohm/1200V) inventor comprising of three SiC MOSFETs in a top cool discrete package, as well as another invertor solution featuring top-cooled SiC MOSFETs that could be used for such applications.

“People will need to put traction inverters designed differently, maybe designed right around the motor, needing different form-factors,” he said. “Then they need different kinds of packaging solutions. The great thing is that these devices have become so efficient, that we can consider putting them into a top-cooled package getting a moderate amount of heat out and then build a traction inverter out of it.”

Onsemi’s slide claimed that usage of its EliteSiC Powertrain extends range by 8 to 12% due to higher efficiency compared with IGBT-based solutions. Furthermore, for high performance inverters, SiC is preferrable for many reasons, so its adoption is set to grow.

800-V bus and 48-V systems can help

Smaller, lighter and more efficient GaN and SiC converters and inverters are not the only means to make EVs simpler, cheaper, more spacious and more comfortable. Using an 800-V bus instead of a 400-V bus in EVs brings numerous benefits, including faster charging, increased range because of reduced weight of electrical components, and higher power output resulting in better performance.

Moreover, an 800-V power bus can enable more efficient energy recovery during regenerative braking. This is why sales of 800-V components are poised to grow at a compound annual growth rate (CAGR) of 63% versus 16% for 400 V, according to Scalia. Such a high CAGR certainly brings many opportunities for appropriate companies.

“Having spent over 34 years in automotive, the one thing I know is that the vehicle is not big enough for everything that needs to be put in it,” said Greg Green, director of automotive marketing at Vicor. “So, efficient use of space is very critical to our OEM customers. Being able to [convert] 2.5 kW of power from 400-V or 800-V [bus] down to 12 V ‘in the palm of your hand’ is important to them as they manage how to pull the full vehicle together.”

EV’s power delivery network and Vicor’s bus converters. (Source: Vicor)

Speaking of 12-V systems in vehicles, as cars in general gain electronics, the need for more advanced 48-V systems is growing as traditional 12-V systems get overloaded with everything electric that we want and need in cars nowadays. From cables to inverters, everything is getting too clumsy, big, hot and expensive.

“As cars are gaining electronics, whether they be for electric vehicles or just you know, ICE vehicles, the electronics [are] getting bigger and bigger, so they are moving to 48-V systems,” EPC’s Lidow said.

For modern cars with 48-V systems, GaN and SiC invertors and converters make a lot of sense, Lidow added. Due to GaN’s faster switching, it allows us to build higher frequency (e.g., 200Hz, 500Hz), smaller, lighter and more efficient systems. In fact, some GaN-based converters are 50% smaller, 40% more energy efficient (i.e., much cooler), and 10 to 15% cheaper than their silicon MOSFET-based counterparts to a large degree because these converters no longer need water cooling. Meanwhile, SiC can offer similar advantages.

“We are seeing the automotive 48-V systems at 500kHz and higher and as you go to higher frequencies, everything shrinks and of course, size and weight is very important,” Lidow said. “We have, for example, one program where the GaN-based converter for a 4kW electronic system is half the size of the [similar] silicon MOSFET-based system. And it was done by going to higher frequency, which meant fewer phases, which meant smaller inductors that had less resistance.”

Implementing an 800-V bus in an EV is costlier than a 400-V bus due to increased component costs as cables, connectors and inverters designed to handle higher voltages and currents are more expensive; additional safety measures to protect against high-voltage hazards; higher R&D investments in both battery and system architectures; and lower production volumes resulting in higher per-unit costs compared to components for 400-V bus. But the benefits of an 800-V bus are tangible, so its adoption will increase, and components costs will likely go down, according to Vicor’s expectations.

“The thing with BEVs is that there is a premium on efficiency, because every electron you are not using for propulsion is taking away from the range,” Green said. “So, it is important that all of the infotainment, all of the autonomous systems, the overall power conversion systems be as efficient as possible. Because there is only so many electrons in the battery.”

Apart from costlier components, there is another obstacle for automakers’ adoption of an 800-V power bus, which is compatible with 400-V charging stations. For companies like Qorvo and Vicor that specialize in GaN and SiC solutions, this represents an opportunity as they not only need to build those power conversion solutions, but they must maximize their reliability and manage their thermals.

“Even if you have an 800-V battery, you probably have 400-V loads that need to operate while the vehicle is being charged,” Green said. “So, we see OEMs that break their 800-V battery into essentially two 400-V batteries, so that while they’re charging, they can run 400-V loads while they charge one half the battery and then flip back over.… We can convert 150kW of power from 800 V to 400 V and vice versa in about 5.5 liters of space. This helps the OEMs in terms of managing the space inside the vehicle …. But even if you are 99% efficient at 150kW, that is still a lot of heat that has to be dealt with. So, paying attention to the thermal management and being able to make sure they can power the chilling systems if they charge the batteries is very important to them as well.”

Batteries center stage

Battery technology remains a crucial factor for EVs. Billions are spent on battery research in different countries as light and capacious batteries are required to extend the range of EVs, whereas their safety, cost and ease of utilization are important factors in making EVs mainstream.

“Battery manufacturers would like to have higher power density, low weight,” Powerbox’s Le Fèvre said. “Everybody tried to save weight in the core, but it is even more complicated than what we see with moving from traditional silicon to wide bandgap. Batteries do not have so much room to play. And then the time to market is extremely long.”

A BYD EV battery. (Source: BYD)

There is also increasing government pressure concerning battery lifetimes and the complete supply chain from raw materials to end-of-life, according to Le Fèvre. For example, Europe and the U.S. are pushing their digital product passport initiatives aimed to track batteries through their lifecycle starting from rare earth metals and all the way down to scrapyard using an RFID or barcode.

“We also have a lot of pressure from the government about the lifetime of the battery and the company’s complete supply chain from the raw material to the end-of-life,” Le Fèvre said. “There is an ongoing process both in the U.S. and Europe, which is called the digital product passport [that will equip] the battery with a barcode or RFID, [making it] possible for different state administrations and recyclers to [see the] complete chain.”

But, in addition to battery performance, reliability and costs, a steady supply chain is important. That is another challenge for the industry as it involves geopolitics.

BYD EV concept. (Source: BYD)

Most EV batteries in use today are lithium-ion (Li-ion) batteries. While Australia is the world’s largest producer of lithium, followed by Chile and Argentina, China is the world’s largest maker of Li-ion batteries, accounting for over 80% of global production.

Japan-based Panasonic and South Korea-based LG Chem are also among major suppliers, but as adoption of EVs increases, the role of China in the supply chain will rise, too.

Just like how European automakers and governments want automotive chip suppliers to localize their manufacturing, it looks like they might eventually want to also localize battery production. Yet, it is not easy because of the ongoing Russia-Ukraine war and ongoing tensions between the U.S. and China.

“What we are seeing here in Europe due to these unfortunate situations in Ukraine and Russia, is a lot of our discussion about how we can secure the supply chains and how can we secure that we have manufacturing in Europe?” Le Fèvre said. “I guess the U.S. has exactly the same concern and in Japan it is important to localize manufacturing to secure supply chains. Here in Sweden, we have a company, Northvolt, that is expanding manufacturing, [and is] going to sign an agreement with the Polish company.”

Students crucial to future EV development

A lot of new EV technologies have been developed in recent years, but many more have yet to be developed, so new people are extremely important for the EV industry. Therefore, the field presents numerous opportunities for students. Today, power designs in general, as well as GaN and SiC technologies, converge various disciplines, such as magnetics, fluid dynamics, thermal management and digital electronics, according to Lidow.

Tesla Model S. (Source: Tesla)

This multidisciplinary approach offers students an opportunity to develop comprehensive skills, enabling them to excel in WBG materials, device design, packaging challenges, thermodynamics, fluid dynamics and electronics.

“I need to resonate on the multidisciplinarity right here—we have engineers, which have to touch definitely thermodynamics, fluid dynamics, packaging, and in the end, of course, electronics together,” Scalia said.

For obvious reasons, developing strong fundamental engineering problem-solving skills is crucial for success in this rapidly evolving field.

“It is important to have a good technical base, but be flexible, because you really do not know where the road is going,” Green said. “But if you are well skilled and the basic engineering problem solving skills, you will do well.”

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