Battery Innovator Award and Panasonic’s Cylindrical Cell Preferences

By Kyle Proffitt 

April 9, 2024 | Shoichiro Watanabe, CTO of Panasonic Energy, accepted the Shep Wolsky Battery Innovator Award last month at the 2024 International Battery Seminar. In his address, Watanabe championed the three-fold improvement in battery energy density seen over the last 30 years of development and expressed appreciation for the increased adoption of electric vehicles and Panasonic’s relationship with Tesla.

A Battery Innovation Career

Panasonic Energy is ramping up production, Watanabe said. He showed a graph of cumulative cylindrical battery manufacturing for EVs at Panasonic, beginning with 1865 cells (same as 18650) in 2010 entirely within Japan. They expanded in 2017 with the assembly of 2170 cells in the US, where three clearly delineated phases of increasing slope could be seen, corresponding to what Watanabe described as “hell production”, getting better but fighting through COVID, and finally getting things worked out. This all added up to 15 billion cumulative cells in 3 million EVs by the end of 2023. Currently, Watanabe says, they average output of 5.6 million cells and consume 160 tons of cathode material per day.

“Battery production is always a bottleneck to expanding EV production,” Watanabe said. In line with this, he reported 50 GWh of total generated batteries (40 US, 10 Japan) in 2022 and Panasonic’s vision for expanding to 200 GWh by 2030.

Panasonic plans to stick with the cylindrical cell. “It’s the same shape. It’s a very simple answer,” Watanabe says. A gigafactory requires a huge investment to get up and running, and sticking with this reliable design has allowed Panasonic to improve yield every 2-3 years. “This is totally different than semiconductors or liquid crystal industries,” Watanabe said, referring to fields where technology allows for major advances over shorter periods of time. Additionally, Watanabe says cylindrical cells have the highest energy density, an efficient shape for development, and provide production advantages.

Watanabe highlighted cylindrical cell safety. He said Panasonic has numerous ideas for introducing new technologies and new chemistry, but the difficulty comes in balancing factors such as capacity with safety. However, he said that the smaller cell and uniform shape makes this balancing act easier. He pointed to the iron can encasing their cylindrical cells and said it is very important for its melting point above 1500 degrees Celsius, which prevents the propagation of a thermal runaway event from one cell to another.

He also championed the reliability of the design, mentioning the included side cooling and the associated advantages in the area of fast charging. With Panasonic having over 100 years’ experience in producing dry batteries, Watanabe says this cylindrical design allows greater productivity. “We can provide dry batteries faster than machine guns,” he jokingly reported.

Managing Environmental Impact

Panasonic is making efforts to have a positive environmental impact, but Watanabe says that only 14% of the carbon footprint can be attributed to battery manufacture at the factory. The remaining emissions all originate in the supply chain from mining to material delivery and are essentially built in to purchased materials. However, Panasonic has set a goal of reducing the company’s total carbon footprint 50% by 2030, including taking steps to address inefficiencies in the supply chain and working with more local partners. One step includes developing relationships with a number of sites in the US and Canada for acquiring natural graphite, copper foil, and cathode materials, reducing the distance these materials must travel.

Watanabe showed drone footage of a new Gigafactory under construction in De Soto, Kansas, about 200 acres in size, which reportedly plans to produce 30 GWh annually. Using lessons learned in their Nevada factory over the previous 5 years, Watanabe said Panasonic has over 500 specific line items for improved production in the Kansas factory, which he believes will translate to 20% or greater improvements in productivity.

Watanabe also reported two new cells that Panasonic is working on with energy densities of 800 Wh/L or more. These involve collaborations with Sila and Nexeon for silicon anode improvements and additional undisclosed cathode and process improvements. Finally, Watanabe said that Panasonic is always striving toward higher capacity and lighter materials and working on new designs and processes. He demonstrated this with a lithium metal anode cylindrical battery that normally experiences jelly roll deformation from the volume changes. However, after certain design optimization steps were applied, no deformation occurred.