A New Approach to Car Batteries Is About to Transform EVs

CATL already has a plant in Germany, along with a $5 billion battery plant under construction in Indonesia and plans for a similar investment in the US. Its own investments in both lithium and cobalt mining help shield the company from commodity price fluctuations. But one of the key factors for CATL’s global expansion will be cell-to-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 the batteries’ bulk will also free up space in a car’s design for a roomier interior, since designers will no longer need to raise the floor height of an EV to stash the cells underneath in a big slab. Freed from these previous constraints, as the 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 ranges of 1,000 kilometers (621 miles) per charge—a 40 percent increase over conventional battery tech.

Body Shop

At Tesla’s 2020 Battery Day, the company shared information about a few key advancements. While Tesla’s new 4680 battery dominated the headlines, CEO Elon Musk and senior vice president Drew Baglino outlined how production of Tesla cars was changing through the usage of large-scale die-cast parts to replace multiple smaller components. They also said that Tesla would start using cell-to-body technology by around 2023.

Using the analogy of an aircraft wing—where now instead of having a wing with a fuel tank inside, the tanks are wing-shaped—the duo said the battery cells would become integrated into a car’s structure. To do that, Tesla has developed a new glue. Normally the glue in a battery pack keeps the cells and pack plates together and acts as a fire retardant. Tesla’s solution adds a strengthening function for the adhesive, making the whole battery load-bearing.

McTurk explains: “Integrating cells into the chassis allows the cells and the chassis to become multi-purpose. The cells become energy-storing and structurally supporting, while the chassis becomes structurally supporting and cell-protecting. This effectively cancels out the weight of the cell casing, turning it from dead weight into something valuable to the structure of the vehicle.”

According to Tesla, this design, along with its die-casting, could allow vehicles to save 370 parts. This cuts body weight by 10 percent, lowers battery costs by 7 percent per kilowatt-hour, and improves vehicle range.

While Tesla’s 4680 battery with its larger volume seems to play an integral role in the company’s ability to move to a cell-to-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-pack solution and will likely form the basis of the company’s cell-to-chassis offering.

An Easy Cell

For those thinking these breakthrough battery technologies are still a few years off, cell-to-chassis is in fact already here. The rapidly growing but still relatively unknown Chinese EV startup Leapmotor claims to be the first company to bring a production car featuring cell-to-chassis technology to market. 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 superior handling (the better weight distribution of cell-to-chassis designs might account for this), slightly longer range, and improved collision safety.

Many EVs were previously created from the platforms of internal-combustion cars—and some still are—but the adoption of cell-to-chassis designs will make those older platforms hopelessly outclassed. According to Frost at Sprint Power, “the commitment by most [manufacturers] to an EV-only future in conjunction with more integrated designs, such as cell-to-chassis, will lead to significant improvements in the overall design and performance of EVs.”

While cell-to-chassis tech is undoubtedly the next step with EVs, it is not a panacea. Technologies like solid-state batteries and sodium-based batteries are likely to be parts of the puzzle. And cell-to-chassis adoption will undoubtedly introduce new problems for the industry.

For one thing, replacing faulty cells will be far more difficult in a cell-to-chassis housing, as each cell will be an integral part of the car’s structure. Then there is the question of what happens when the car is scrapped. Currently, modules can find their way into many second-life applications, but McTurk believes the larger battery sizes in cell-to-pack and cell-to-chassis designs may limit them to grid-storage applications.

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