GM’s Ultium Battery System Future-Proofed
Although its new Ultium batteries have yet to be deployed, GM engineers already are designing the system for future technology advances.
Although its new Ultium lithium-ion battery technology won’t be in production electric vehicles (EVs) until 2021, GM engineers said in a recent media update that they have designed Ultium to quickly and efficiently integrate ongoing technology advances, some of which are well down the path to production-vehicle applications. Ultium is ready to accept new cell-chemistry changes or upgrades, including cathode and anode innovations.
With battery technology changing steadily, engineers working on the Ultium system had an eye to maintaining flexibility to incorporate advances into existing designs, said Tim Grewe, GM’s director of global electrification and battery systems. Grewe spoke with media in a conference call shortly after the company announced it had started to prepare the site near its former assembly plant in Lordstown, Ohio, that will build the first Ultium batteries with partner LG Chem. The new battery-cell manufacturing joint-venture operation is called Ultium Cells LLC.
Reducing cobalt, reducing cost
Today’s GM-LG Chem batteries, such as those used in GM’s only current EV, the Chevrolet Bolt, use familiar nickel-manganese-cobalt (NMC) cathode chemistry. But Grewe reiterated that the Ultium battery chemistry will be enhanced to nickel-manganese-cobalt-aluminum (NMCA), with the aluminum content displacing as much as 70% of the required cobalt.
“We’re also securing the supply of raw materials,” Grewe said, explaining that GM and LG Chem are “scouring the global value chain” to maintain reliable and cost-effective access to the raw materials vital to battery production. Cobalt’s strategic sourcing and mining practices are under increasing global scrutiny. Grewe noted that GM also is “keeping an eye towards sourcing as much as possible in North America,” although the U.S., with just 23,000 metric tons in reserves, is considered a minor source, according to the U.S. Geologic Survey.
He said Ultium’s significant reduction in cobalt content is a chief aspect in reducing cost to or less than the long-targeted $100 per kWh of battery energy density; a study by Bloomberg NEF pegged 2019 battery cost at more than $150 per kWh. And GM’s follow-on step is the so-called “zero cobalt-zero-nickel” anode, which aims to entirely eliminate cobalt – and further reduce reliance on a supply chain for precious metals.
Modular and flexible
The industry is far from consensus regarding battery-cell form factors – many automakers, including EV specialist Tesla, currently prefer cylindrical-shaped cells. Ultium is designed around a pouch form. Each cell initially will have about 100 amp-hours of capacity, or roughly the same amount as 20 cylindrical cells. At the same energy capacity, weight is 25% less than the batteries in today’s Chevy Bolt.
Grewe said GM believes the pouch to be the ideal format because it allows tight stacking in modules that can be horizontally or vertically oriented. Horizontal layouts, he said, are ideal for vehicles with lower roof heights and lower ground clearance, while vertically stacked cells are good for pickup trucks and SUVs with higher ground clearance and taller profiles. He said the option to place the flat cells in either orientation can help to get the most battery in a given vehicle architecture. Using horizontally arranged cells in a rear-seat footwell, for example, can package an extra 22 kW of battery capacity.
Solid lithium-metal development
Although consumers have yet to indicate much concern about battery longevity, Grewe said that battery cells with 1 million miles of service are “in our sights.” He also mentioned a new solid lithium-metal anode design that is projected to offer almost twice the energy density available from current battery cells. The Ultium system is designed to incorporate such technology “as soon as it’s ready,” Grewe vowed.
For now, however, he said reducing the content of expensive metals at the cell level remains today’s cost-reduction focus and that GM wants to reduce battery cost to the point at which “customers don’t have to pay a penalty” for buying and EV instead of an internal-combustion vehicle. “My job is to get there as fast as we can,” he asserted.
As previously announced, GM plans to launch 20 new EVs globally by 2023 – with battery capacities ranging from 50 kWh to 200 kWh. Grewe said the size of the Ultium cell was optimized to suit the coming family of EVs, while the new Ultium Cells factory production lines and footprint could be expanded, if necessary, if the company approaches its goal of selling 1 million EVs annually in the U.S. and China by 2025.