Tim Grewe, GM’s director of battery cell engineering and electrification strategy, held a virtual media conference today about the company’s EV battery strategy. It was a wide-ranging info session explaining the General Motors approach to chemistry, cell, and module design, and how EV batteries will be manufactured in high volume. “Categorically, we think that the pouch cell is the winner,” said Grewe.
As discussed during GM’s EV Day in March, the company is also changing from nickel-manganese-cobalt chemistry to an NCMA mix. The A stands for aluminum, the key to reducing the cobalt by 70%. While developed with LC Chem, its partner, the chemistry is proprietary for GM. Tesla is also reportedly making that switch to NCMA (with LG Chem’s help) for use in the made-in-China Model 3.
Today, Grewe said:
“This is a giant leap forward on the road to low-cost batteries, and actually keeping the performance and keeping the range. We’ve reduced the cobalt content in these batteries to 70% compared to what’s in our Bolt EV today.”
Perhaps the new information is that GM is ensuring a long life for the battery by “aluminum doping to the cathode structure.”
Thinking about volume
Simplification, modularity, and streamlining production is paramount to producing the cells at high speed and volumes. The company is working on faster formation times. Grewe believes that the size and shape of the pouch cell is critical.
“One cell is used across all of our applications, all of our vehicles ensure that we can take the benefits of manufacturing scale and quality. So you can kind of think of it as 100-amp hours, which is a big number. It’s about the same as 20 small cylindrical cells that you may be familiar with.”
“Instead of rolling those electrodes up and putting them individual cans, we lay them flat. And with that flatness, we then very securely weld them with robust joints, to have a long, single pouch.”
This enables GM to stack strategically stack the pouches for the application. They might be stacked vertically for a high-riding pickup and or arranged horizontally in a low sports car.
Grewe said this modular, stackable approach also enables the best packaging for vehicle footwells. According to Grewe, the footwell of one of its EVs alone can accommodate 22 kilowatt-hours of energy storage using a horizontal stacking technique.
The Ohio battery plant is the size of 30 football fields. Despite the size, Grewe was challenged about GM’s 30-gigawatt-hour capacity in Lordstown. The math would suggest that producing 1 million EVs would only enable an average output for 30kWh packs.
Grewe said the plant could increase its capacity, even double the output, through such measures as expanding the site and accelerating the line speeds.
He confirmed that only pouch cells will be produced in Ohio, while prismatics will be made in China for the company’s EVs sold in that market.
Other themes that he covered included:
- Progress on so-called breakthroughs. Grewe said, “I’m sure our true breakthrough innovations will be here sooner than anyone expected.” Grewe rattled off a list of developments, including next-generation electrolytes to produce a million-mile battery, solid lithium metal anodes, zero-cobalt chemistries, and better separators.
- Easy maintenance. Cells with different chemistries and modules of different sizes, and even future battery components, will be interchangeable in a pack. A wireless communication system in the pack will allow dealerships to mix and match, upgrading a single problematic module rather than replacing the entire pack.
Grewe responded to a question about how much consideration GM made for the ability to recycle or reuse cells from its EVs. He answered, again, by championing the pouch-cell design.
“The beauty of the pouch cell is you have a plus side and a minus side, and you have two tabs that are connected or welded together with the electrodes.”
“There’s 20 plus and minuses stacked together in that pouch. And so it was a fundamental strategy to say, well, how can you disassemble that and not have the cathode and the anode mixed together where you have to do some chemical process to separate those?”
“You can disassemble this pouch cell very easily. You take the two tabs, and you pull apart. And your cathode is in your right hand, and your anode is in your left hand. And now you enabled low-cost recycling.”