More Juicy Details About The Tesla / Maxwell Battery

Maxwell's new solvent-free process may suggest a larger format cylindrical cell is in the works.

The Reason Tesla Spent $218 Million On Maxwell Technologies

George Bower

By: George Bower

Jun 19, 2019 at 8:09am ET

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On Monday we published an article about the advantage of Maxwell’s new solvent-free manufacturing process. That new process should result in as much as 16X the production rate and an immediate 300 Wh/kg energy density because of a thicker electrode coating using today’s NCA chemistry. Thanks to commenters Doggydogworld and Martin Lacey for pointing us toward further research.

Additional Maxwell / Tesla Coverage:

Tesla's Maxwell Acquisition May Mean Improved Batteries That Cost Less

The Reason Tesla Spent $218 Million On Maxwell Technologies

Here’s what we found:

Maxwell had a joint project with A123 and the DOE to develop a dry electrode manufacturing process back in 2011 (Ref 1). This is the same process that Tesla and Maxwell are currently working on.

-Project start date: 2011

-Maxwell was promoting a thick coating with high production rates even back then (approx. 200 um thickness)

Maxwell's new solvent-free electrode manufacturing process has primarily been used on prismatic (A123) and pouch cells. Our research indicates a new larger format cylindrical cell may in the works to make this process compatible with cylindrical format batteries.

“Such thick electrodes are not suited for cylindrical or prismatic hard case cell formats where small winding radii in the order of 1 mm are applied in the center of the jelly roll. This would obviously form cracks and delaminate the active mass layer from the copper or aluminum substrates. However, we tested and wounded the electrodes on roll cores with 3” inner diameter which are a standard in industrial electrode fabrication with electrode rolls of 1000 m and more length. We did not observe cracks or delamination proving sufﬁcient ﬂexibility and adhesion.”-Ref 2

This may indicate that Tesla has an even larger format cell in the works to use with Maxwell’s new solvent-free manufacturing process. As pointed out in the Argonne report (Ref 3) larger format cells result in lower costs. So, we have multiple ways Maxwell’s new process can reduce costs: Lower cost simply due to the solvent-free electrode manufacturing process, lower cost because of a (potentially) larger format battery cell and higher energy density due to the thicker electrode. These higher energy cells have lower power, so Tesla would presumably increase the battery kWh’s to make up for it. Thus, the 400-mile range Model S.

In addition, the fact that Maxwell has been working on this since 2011 leads us to believe that Maxwell's new cells will be ready sooner rather than later.

Ref 1- “Dry process Electrode Fabrication” Michael Wixom, May 14, 2012, Project ID:ES134

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Ref 2-“Thick Electrodes for High Energy Lithium Ion Batteries”, Article (PDF Available) in Journal of The Electrochemical Society 162(7):A1196-A1201 · March 2015

Ref 3- “Modeling the Cost of Lithium Ion batteries for Electric Drive Vehicles” Argonne, ANL 11/32

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