CATL already has a factory in Germany, along with a $5 billion battery factory under construction in Indonesia, and plans a similar investment in the US. Its own investments in lithium and cobalt mines help protect the company from commodity price fluctuations. But one of the key factors for CATL’s global expansion will be cell-on-chassis technology, where the battery, chassis and underbody of an EV are integrated as one, completely eliminating the need for a separate battery pack in the vehicle.
Redistributing most of the batteries will also free up space in a car’s design for a more spacious interior, as designers will no longer need to raise an EV’s floor height to hide the cells underneath in a large plate. Freed from these previous limitations, since cells can make up the entire chassis, manufacturers will be able to squeeze more cells into each EV, thereby increasing range.
CATL estimates that production vehicles of this design will achieve a range of 1,000 kilometers (621 miles) per charge—a 40 percent increase over conventional battery technology.
The Body Shop
At Tesla’s 2020 Battery Day, the company shared information about some key advancements. While Tesla’s new 4680 battery dominated the headlines, CEO Elon Musk and senior vice president Drew Baglino described how Tesla’s car manufacturing was changing through the use of large-scale castings to replace some smaller components. They also said that Tesla would start using cell technology in the body by 2023.
Using the analogy of an airplane wing – where now instead of having a wing with a fuel tank inside, tanks are shaped like wings – the pair said the battery cells would be integrated into the structure of a car. To do this, Tesla has developed a new adhesive. Normally, the adhesive in a battery pack holds the cells and packaging plates together and acts as a fire retardant. Tesla’s solution adds a strengthening function to the adhesive, making the entire battery carry the charge.
McTurk explains: “Integrating the cells into the chassis allows the cells and the chassis to become multi-functional. The cells become energy storage and structural support, while the chassis becomes structural support and protection for the cells. This effectively cancels the weight of the cell box, turning it from dead weight into something valuable to the vehicle structure.”
According to Tesla, this design, along with its casting, can allow vehicles to save 370 parts. This reduces body weight by 10 percent, lowers battery costs by 7 percent per kilowatt-hour, and improves the vehicle’s range.
While Tesla’s larger-volume 4680 battery appears to play an integral role in the company’s ability to transition to a cell-in-body design, CATL’s new Qilin battery boasts a 13 percent increase in capacity over the 4680, with a volume utilization efficiency of 72 percent and an energy density of up to 255 watt-hours per kilogram. It is set to become a key part of CATL’s third-generation cell-to-package solution and is likely to form the basis of the company’s cell-to-chassis offering.
A light cell
For those who think these new battery technologies are still a few years away, the cell-in-chassis is actually already here. Fast-growing but still relatively unknown Chinese electric vehicle startup Leapmotor claims to be the first company to bring to market a production car featuring cell-on-chassis technology. Leap’s C01 sedan should go on sale before the end of 2022. Using proprietary technology, which the company has offered to share for free, Leap says the C01 offers better handling (better weight distribution of cell models chassis may be responsible for this ), slightly longer ground clearance and improved crashworthiness.
Many EVs were previously built from internal combustion car platforms—and some still are—but the adoption of cell-to-chassis designs will make those older platforms hopelessly obsolete. According to Frost at Sprint Power, “commitment from the majority [manufacturers] towards an EV-only future with more integrated designs, such as cell-on-chassis, will lead to significant improvements in the overall design and performance of EVs.
While cell-to-chassis technology is clearly the next step with EVs, it’s not a panacea. Technologies such as solid-state batteries and sodium-based batteries are likely to be part of the puzzle. And cell-to-chassis adoption will undoubtedly bring new problems for the industry.
First, replacing defective cells will be much more difficult in a cell-to-chassis housing, since each cell will be an integral part of the car structure. Then there is the question of what happens when the car is scrap. Currently, the modules can find their way into many second-life applications, but McTurk believes the larger battery sizes in cell-in-pack and cell-in-chassis designs could limit them to grid storage applications.