Architecting GMs new EV batteries
The 2023 Cadillac Lyric will offer an Ultium battery with about 100-kW-h capacity, capable of more than 300 miles’ range per charge. DC fast charging capability will be standard. (Cadillac)

Architecting GM’s new EV batteries

Ultium strategy boss Andy Oury talks about the LG Chem collaboration, future energy densities and “multiple paths” to cobalt-free cathodes.

By 2023 General Motors promises to have 20 new electric vehicles of all shapes, sizes and market segments on sale. They’re underpinned by the company’s BEV3 flexible dedicated EV architecture, electric machines developed in-house, and a family of battery modules called Ultium. GM has ambitious plans for Ultium, as engineer Andy Oury (below), GM’s lead architect and strategy manager for high-voltage battery packs explained to Editor Lindsay Brooke.

Battery suppliers say energy densities of 500 W-h/kg are needed to deliver 400-500 miles of EV range. Is that GM’s thinking?
Prior to electric trucks entering the scene, the discussion was about watt-hours per liter – volumetric energy density, which is important. But in doing packs for trucks that are twice as ‘big’ electrically and carry a lot of mass, the watt-hours-per-kilogram metric really stands out now as being exceptionally important. We’re planning for multiple upgrades to the Ultium system throughout its life cycle and cells with extremely high specific energy are definitely in the scope.

GM still conducts battery core-chemistry R&D. Where are the demarcations between GM and your partner LG Chem in Ultium development?
If you’re looking for a ‘clean’ split, it would be at the perimeter of the cell. LG has the responsibility to engineer the cell internals and we have everything else. GM has responsibility for the pack design and Ultium architecture. The RASIC model for Ultium is most like Gen-1 and Gen-2 Volt and less like the Bolt EV. Once we settled on a good balance and made some decisions together, the cell supplier has responsibility to design the chemistry. But GM has what I call a ‘support and approval’ role there. We use our expertise in robust design to build Design of Experiments and help optimize the anode and cathode. And like any great automotive partnership, we listen to each other, push each other and we both bring innovations to the party.

What is the status of GM’s effort to redesign cathodes, with the aim to reduce or eliminate cobalt?
We have multiple options here, but we’re not yet ready to discuss development timelines. I will note that we’ve already gone to market, on a limited scale, with cobalt-free cathodes in the past. The challenge is to get reasonable energy density with zero-cobalt/zero-nickel cathodes going forward. There are multiple paths to get there.

Talk about ensuring the pickup truck duty cycles customers expect with electric propulsion.
Our electric trucks are a paradigm shift – more energy, higher-power charging, more mass and more cost. Making electric trucks that people love drives home the message that electric vehicles are here to stay. That will drive more volume for batteries and related components, encourage more R&D and investments. Every success we have in electric trucks will roll out across every EV we develop.

The packaging of our double-stacked battery and accommodating the mass is all about getting the ‘bones’ of the structure right. This is a clean-sheet approach to the vehicle architecture; it has some very efficient load paths and it’s got novel body construction that’s probably going to be its own SAE Paper at some point. How we connect the key load-bearing members in a very efficient way from one end of the chassis to the other was necessary for the electrification system that’s in it.

For thermal, the benefits of our scalable/modular approach become clear. Each of our battery modules includes its own highly efficient, low-cost cold plate. So, building a bigger battery gives greater cooling capability. The rest of the vehicle’s HVAC system has to scale to keep up as is typical among different classes of vehicle.

Where does the industry stand on a standardized cell form factor?
It would be great if there was a common form factor but it seems that the industry won’t arrive at a standardized [cell] form factor for perhaps the next 15 years. Fundamentally the calculus is that to have a ‘common’ cell it would need to be small, to fit a variety of vehicle shapes and sizes – and ‘small’ electrically, to fit a variety of electrical needs. The cost of all those small parts and connections adds up and that drives us and other OEMs toward larger-format cells. As soon as you go larger format it becomes harder to integrate into multiple platforms from different OEMs and drive proliferation in cell size and shape. Despite these challenges, we can still drive a lot of commonality across the industry where the balance of the cell cost is in the raw materials.

There is not enough transparency in the markets for battery raw materials. But as we purchase more and more volume of materials, the specifications will become more common, the market will become more transparent and that will drive more innovation. We see cell manufacturers already trying to drive OEMs toward what they call ‘platform’ chemistries where they can get economies of scale across multiple OEMs – even if those cells have unique physical construction. So, we’ll see multiple formats out there.

And companies have made significant R&D investments in these different formats. If GM wants to be the best OEM partner for cell suppliers, we have to honor those investments and the expertise they have for the balance of this decade. We don’t want to immediately obsolete people’s equipment. It’s important for us to have flexibility to let this play out. Now with Ultium, we can use a standard cell to cover all of our brands’ applications. When the standard cell is combined with our architecture, we get quality and cost benefits while meeting diverse customer needs.

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