By Allison Proffitt
January 21, 2021 | Celina Mikolajczak, VP of Engineering and Battery Technology at Panasonic Energy of North America (PENA), updated the Advanced Automotive Battery Conference attendees yesterday on the Gigafactory located outside Reno, Nevada—a shared space between PENA and Tesla. PENA occupies 2/3 of the floorspace and the whole facility is at about 30% of its planned size. PENA has achieved its target of 35 GWh/year of cell production, Mikolajczak said, and added that in August 2020, the company shipped its 3 billionth cell.
The Gigafactory consists of 8 coating lines, 32 die heads, 46 press machines, 13 top cap production lines, and 7 formation lines. The Gigafactory can fill more than 19,000 formation trays per day. PENA is also in the process of adding its 14th cell assembly line, Mikolajczak said, to increase factory capacity by 10%.
“These kinds of economies of scale are substantial,” Mikolajczak pointed out. “They allow us to really bring price reductions to our customers. And this is really what the roadmap is to a lower cost cell overall.”
The cells at PENA are all designed by Panasonic—beginning with development in Japan of new materials, new supply chains, and new cell designs—but are customized to customer requirements. “Really for electric vehicles, to really optimize the performance of that vehicle, you need a customized cell that really was designed for the operation of the vehicle,” Mikolajczak said. The engineering team at PENA, then, leads the final cell and equipment design validation.
Panasonic is currently converting production lines to produce a new cell model with 5% increased energy density and excellent fast charge, Mikolajczak said. Cobalt reduction is another innovation priority; Mikolajczak said, ultimately, Panasonic is aiming for cobalt-free design. She said PENA expects energy density to improve 20% within five years.
Form Factor Considerations
Mikolajczak revealed a bit of PENA’s thinking about emerging form factors. Currently Panasonic produced cylindrical cells in 18650 and 2170 form factors. “We are studying the 4680 format,” Mikolajczak said. “I get a lot of questions about this format. We are definitely studying it, and like any form factor, this cell—if we choose to produce it—will have its merits and demerits compared to other form factors.”
While pack architects consider many different issues impacted by form factor, Mikolajczak highlighted pack design for propagation resistance and long-term reliability among two notable criteria for which a smaller cell may be advantageous.
Cell size impacts pack propagation resistance, she pointed out. Smaller cells generate less heat individually when undergoing thermal runaway. “If you start with a smaller cell, with a smaller quanta of energy in it, it can be a bit easier to design pack that is propagation resistant,” Mikolajczak said. She also pointed out that smaller packs require less engineering and maybe less expensive materials to achieve propagation resistance.
For cells in a parallel series, when one cell fails due to high impedance, current flow is divided among the remaining healthy cells in the series. “If you’ve got a very big parallel count—a lot of cells—that current redistribution is probably not such a big difference and not such a strain on the health of the remaining cells,” Mikolajczak explained. “But if you have only a few cells in parallel and you lose one of them due to some kind of high impedance fault, you redistribute current among a much smaller number of cells.” While this may not be a problem under normal charging conditions, fast charging such a pack could accelerate degradation. “Again, a pack designer that is looking at a smaller pack with maybe smaller series elements might choose to use smaller cells to increase the reliability of that pack in the long term,” she concluded.
Sustainability at PENA
Finally, Mikolajczak highlighted PENA’s sustainability efforts—a big part of Panasonic’s innovation roadmap, she said. PENA has always recycled its typical factory valuable waste, but is now committed to taking recycling “a step further,” she said.
PENA has begun a partnership with Redwood Materials in Carson City, Nevada. Redwood Materials is a recycling venture of Tesla co-founder JB Straubel. The company’s mission states: “We at Redwood are planning ahead to address the problems and opportunities coming when millions of EV’s batteries need an end of life solution and when the electronics piled up in your drawers at home find a new life… We know it is not too early to plan for “un-manufacturing” the many Gigawatt-hours of batteries being built today.”
Redwood Materials will handle PENA’s recycling of factory valuable waste as well as help develop processes to recycle hazardous materials that would incur fees for disposal and develop process that return Li-ion battery materials from all sources—both PENA’s scrap as well consumer electronics—to the raw materials supply chain. “We’re particularly excited about the prospect of returning copper, cobalt, nickel, and lithium into the supply chain for ourselves,” Mikolajczak said. “This is really great for sustainability, and it’s also really great for reducing cell BOM [bill-of-materials] costs as we contemplate increasing prices of many commodity materials that are needed for the production of Li-ion cells.”
The Advanced Automotive Battery Conference is running live Jan 19-21, and archives will be available afterward for registered attendees. Learn more at https://www.advancedautobat.com/europe.