Battery for autonomous driving from CATL: Safe, fast, slow old

Contents

With the Shenxing Pro batteries, Chinese battery manufacturer CATL is launching batteries on the market that are designed to remain functional for a certain period of time even if individual cells overheat. This should give the driver or a self-driving car time to park the vehicle safely.

For Europe

“In Europe for Europe and in the future from Europe” is a new strategy for the Chinese battery manufacturer. CATL will produce batteries in Europe that are tailored to the needs of European drivers. They also want charging to be as fast as refueling and a high level of safety in the event of battery damage. A car that has to coast down the hard shoulder of the highway because the power supply fails is not a nice idea, nor is a battery fire—just like the analogous scenarios of sudden loss of drive or engine fire in conventional drives.

Trends beim Elektroantrieb

• Von Spitzenleistung bis Rekordzeit: So schnell laden Elektroautos Im Jahr 2025
• Elektroautos: Rabatte auf den Strompreis an der Wallbox automatisch nutzen
• Elektroautos: Preiswerte Modelle im Anflug
• Batterie im Elektroauto: Fortschritte bei der Ladeleistung und Zellchemie
• Schwerpunkt Batterie: Fallende Zellkosten für Elektroautos
• Batterie im Elektroauto: LFP - Die eiserne Enttäuschung
• Überzeugende deutsche Elektroautos auf der IAA – endlich geliefert!
• Antriebswende für alle: Das Endzeitszenario
• Wie weit Elektroautos auf der Langstrecke kommen: 21 Modelle im Vergleich

Shenxing Pro are LFP batteries (lithium iron phosphate), which surprisingly combine long range, service life, and safety with extremely fast charging. CATL is presenting two versions at the IAA in Munich: a fast-charging version with an energy content of around 110 kWh and one with the additional designations “Super Long Life” and “Long Range” and 122 kWh. CATL promises a calendar service life of twelve years or one million kilometers, with an aging rate of nine percent after 200,000 kilometers.

Charging at tank speed

The fast-charging batteries promise a charging speed of 12C. Theoretically, they can be fully charged in five minutes at a sufficiently powerful charging station. That would be charging at tank speed. In practice, however, even in the optimum temperature and SoC window, charging takes place with a falling power curve. CATL specifies ten minutes at 25 degrees for a charge from ten to 80 percent and 20 minutes at -20 degrees from 20(!) to 80 percent. Converted to the WLTP, that would be 478 km in ten minutes, and at -20 degrees, still an impressive 410 km in 20 minutes.

The super-fast charging variant of the Shenxing Pro achieves this with a peak charging power of more than 1.3 MW. Even with a charge level of 20 percent, the output is still 830 kW. The batteries are designed for European driving profiles and enable a suitable electric car to accelerate from 0 to 100 km/h in 2.5  seconds. However, the charging station must also be suitable—such giants would first have to be distributed over a large area in the infrastructure before the advantages of battery technology could be used in reality. Truck manufacturers are currently working with one-megawatt columns, only a few of which have been installed for trial operation along European highways.

Fast despite LFP cell chemistry

12C charging with LFP batteries, which are not known as fast power suckers, is the result of material and construction work. For the aforementioned winter resistance, LFP cell chemistry requires a lot of heating, but CATL also wants to have improved the anodes. CATL has rethought the cell as a basic unit: the anode is given a proportion of graphite with elastic buffer layers and an inorganic solid electrolyte layer, which should increase both the cycle stability and possible charging performance. According to the Chinese battery experts, more than 70 percent of the battery capacity should be retained after more than 10,000 charging cycles. The basis for a car life of several hundred thousand kilometers.

Thanks to its modified geometry, the Wave-Cell enables bonding and cooling on all six surfaces. It changes the structure of the battery: modules can be packed more densely, the cooling works more efficiently, and the cells last longer. This increases the packing volume efficiency to 76 percent and the rigidity by 25 percent. The structure is also designed to provide additional protection for the cooling channels.

Protection against thermal runaway

The battery manufacturer also promises a technology designed to improve safety. It is presenting a battery that should make it possible to drive off a road in a relaxed manner and park the vehicle in a safe place or even at the nearest garage—without the battery management system immediately cutting off the power in the event of a cell defect to prevent worse. According to the motto "no propagation," a fault in one cell should not be able to spread to the neighboring cells and thus the entire battery. This would lead to a self-accelerating overheating reaction and more heat than the battery can dissipate. The temperature would then rise faster and faster, and chemical decomposition would generate additional heat until a safety valve opens to relieve the pressure. Smoke and flames, and in extreme cases a battery fire, can be the result.

With Shenxing Pro batteries, on the other hand, a defect should not be able to spread to neighboring cells. The car should also remain drivable. To achieve this, the battery management system disconnects the affected cell(s), actively cools them, and keeps the rest of the pack in operation. Although the power is reduced, the drive, steering, brake booster, lights, and heating remain active in a controlled manner for over an hour, according to CATL. This gives the driver enough time to drive safely to the hard shoulder, to the next exit, or, at best, even to a workshop. The batteries also remain predictable for the breakdown service: the system remains electrically stable and is monitored instead of switching off in a chaotic manner or undergoing a thermal runaway.

Barriers against chemical decomposition

Multi-stage protective measures in the cell are designed to create a barrier against the dreaded thermal runaway that is almost impossible to overcome. These include a flame-retardant electrolyte, a non-flammable separator, and a nano-coated cathode. Other components include aerogel barriers, a fire-resistant coating, the actively cooled high-voltage rail, and, in particular, the monitoring of critical cell parameters such as insulation, temperature, voltage, and pressure. CATL did not say which customers will be the first to buy the new battery technology and when it will be possible to enter the market with these batteries. However, the fairly precise details on performance and the nature of the announcement suggest that products are already relatively advanced.

(dahe)