This week, Colorado company Solid Power announced that it will partner with BMW to develop solid-state battery technology that could bring increased driving range, longer battery life, and better temperature tolerance to electric cars. The German automaker will invest an undisclosed amount in Solid Power, intending “to advance its technology in order to achieve performance levels required for high-performance electric vehicles.”
Although there’s a lot of buzz about solid-state batteries of late—and Toyota might have added to that in recent months—don’t expect BMW to bring the technology to production any time soon. Klaus Fröhlich, the BMW board member in charge of development and R&D activities, said that he doesn’t expect solid-state tech in a production vehicle from the company until at least 2025—partly because the temperature requirements remain too limited.
Mass-market deployment won’t be until at least 2030, Fröhlich anticipates, in part because lithium-ion batteries keep getting better. Energy density is increasing 30 percent every two or three years, he told C/D, while costs fall significantly.
Different EVs, Same Building Blocks
BMW is keeping that solid-state technology in its R&D departments for now, because its focus for the next decade is to produce electrified vehicles at a far more rapid rate. It has taken BMW more than four years since the first deliveries of its i3 electric car to reach just 200,000 cumulative global sales of electrified models. While half those cars were built in the past year, BMW will need to do much more if it is to achieve its goal of offering 25 fully electric or plug-in hybrid models worldwide, including versions of nearly all of its models, by 2025.
A fully electric Mini is on the way next year, and an all-electric version of the BMW X3 comes in 2020; BMW also keeps dropping hints about more models for its green/urban-focused BMW i sub-brand. But BMW’s electrification push accelerates in 2021, when it will release the fifth generation of its electric drivetrain and battery technology.
“[BMW] has to define its format for the next 15 years.”
— BMW Group R&D boss Klaus Fröhlich
Conceived for far higher production volumes—and to be scalable to work with all of BMW’s models, including battery-electric vehicles and plug-in hybrids—this new modular electrification kit incorporates the motor, drive gearing, and power electronics as a single, integrated core component. It draws power from a battery module that isn’t bound to any one model or purpose.
What Goes in Modules
Battery packs remain the most expensive of the major components in electric cars. BMW has put a tremendous engineering effort into developing proprietary battery modules that can be packaged into liquid-cooled battery packs of varying size and shape depending on the vehicle. “With the modules, you control the life cycle, the aging of each cell—so you can reduce cost or increase function,” he explained.
“What’s important is that I always use the same module,” Fröhlich explained. “I have a high module for SUVs, and I have a low module for sedans or perhaps sports cars.” The automaker, he said, worked especially hard on the lower-profile battery pack.
Regardless of the shape, the modular strategy better accommodates the nearly continuous improvement of lithium-ion cells. “Every two years, when I have an update on the cell chemistry, I could roll it out, within some months, to the whole portfolio,” Fröhlich said.
BMW has already been trying this on a smaller scale with its i3 and i8. A Gen 4 battery will soon be deployed to the refreshed i8 roadster and i8 coupe, less than 12 months after the i3, which reaps those same chemistry changes, hits the market. Looking ahead to Gen 5 and the full modular approach, BMW points to the Vision Dynamics concept, revealed this fall at the Frankfurt auto show as well as at the Los Angeles auto show. It’s an all-electric sports sedan with a 370-mile driving range that goes from zero to 60 mph in less than four seconds and offers a top speed of more than 125 mph.
Actually making battery cells, modules, and packs in much higher volumes is another hurdle. “I have to define my format for the next 15 years. Because the architectures, and all the factories—the gigafactories—they can’t move,” said Fröhlich.
BMW isn’t going to get directly involved in the battery-cell business. Instead, it has established a $240 million Battery Cell Competence Center next to its R&D center in Munich, where the aim is to build prototype cells, modules, and battery packs and lay out how they’ll be assembled for vehicles. According to Fröhlich, BMW is looking for an approach that’s a bit like the Apple manufacturing ecosystem. “The battery is not produced by Apple, but all the manufacturing details are defined by Apple,” he said, dodging a question about Chinese supply for North America. “So that’s what we intend to do, because manufacturing has such an impact on function, quality, and cost.”
As for the cell format, BMW is hoping for a good automotive-duty prismatic cell—the rectangular sort used in some personal electronics—because packaging is compact and more easily protected from intrusion. But it also could embrace pouch style batteries—the form used in the Chevrolet Bolt EV and Kia Soul EV, for instance—if the next-generation version becomes the prevalent one. The one battery format BMW simply won’t use is the cylindrical one—as Tesla embraces for all of its models—because cooling and packaging become more challenging. “The active material is only a third [by volume], and we have prismatic at more than 40 percent,” Fröhlich explained. “So if you want the same energy density you have to have an aggressive chemistry, with all the risks.”
Battery aside, BMW is looking to innovate in other ways. For instance, the new modular electric powertrain that arrives in 2021 will include a high-efficiency current-excited motor that, unlike permanent-magnet designs, isn’t dependent on rare-earth elements.
Charging remains a wildcard. BMW will start with a 400-volt architecture in 2021 with the modular platform (and likely 150-kW fast charging, which could return about 200 miles of range in a half hour); but switching to 800 volts (to keep up with the upcoming Porsche Mission E) isn’t a big deal, Fröhlich said.