Part 4: A ‘Drop-in’ Advanced Battery Production Process
The third post in this series focused on a specific near-term (2025) objective of the National Blueprint for Lithium Batteries, 2021–2030, “Promote the development of novel cell designs that reduce processing time, enable faster cell assembly, and decrease formation costs.” It describes how the Enovix 3D cell is the most significant battery architecture advancement in the last 30 years, in large part because it is well suited to accommodate silicon as the only active lithium cycling material in the anode. But as Harrold Rust, Enovix CEO and co-founder has stated, “Breakthroughs in core technology development and cell design only matter if they can be produced cost-effectively and at scale.”
That brings us to the second specific near-term (2025) objective of the Blueprint, “Dedicate resources to expedite the scale-up and commercialization of novel technologies and manufacturing techniques.” Dr. George Crabtree, Director, Joint Center for Energy Storage Research (JCESR), Argonne National Laboratory, says that for the U.S. to achieve a competitive or even a leading position in Li-ion battery manufacturing, the advanced battery technology, “should be capable of being ‘dropped in’ to the current Li-ion battery manufacturing process.”
A Standard Li-ion Battery Production Process
The graphic below illustrates the three-stage process used to produce most Li-ion cells today. Sony Corporation developed and commercialized the first Li-ion battery in 1991. They adapted magnetic recording tape production equipment — used to produce audio cassettes — to mix chemical slurries, coat them onto metal foil current collectors, calender the surface, and slit the coated metal foil into electrode sheets. Electrodes (anodes and cathodes) and separators are wound into a standard ‘jelly-roll’ cell assembly. Cells are then packaged in a polymer pouch, charged for first-cycle formation, and tested to assure quality.
A ‘Drop-in’ Advanced Battery Production Process
We’ve applied an innovative, low-cost approach that can ‘drop-in’ to an existing standard Li-ion battery manufacturing line and increase megawatt hour (MWh) capacity by about 30% relative to a conventional Li-ion battery production line at the same volume. Enovix has designed tools, produced by precision equipment companies, which incorporate proprietary processes to achieve precise laser patterning and high-speed roll-to-stack cell assembly.
The graphic below illustrates our changes to the standard three-stage production process. The first change is replacing graphite with silicon in our anode material. Other than a change in materials, our electrode fabrication process is identical to standard fabrication processes. The major ‘drop-in’ change is replacement of standard wound cell assembly with our proprietary roll-to-stack cell assembly, which consists of precise laser patterning and high-speed stacking. The final change is our inline pre-lithiation process that occurs after initial charge formation. First cycle formation efficiency of a graphite anode is about 90–95%. First cycle formation efficiency of a silicon anode is only about 50–60%. Our pre-lithiation process compensates for the low first cycle formation efficiency of the silicon anode. For a more dynamic view, watch our ‘drop-in’ cell assembly production process video.
The Blueprint states that, “In addition to the economic imperative for a competitive EV and advanced battery sector, the Defense Department (DoD) requires reliable, secure, and advanced energy storage technologies to support critical missions carried out by joint forces, contingency bases, and at military installations.” The next and final post in this series will address our contract to demonstrate advanced 3D Silicon™ Li-ion batteries for the U.S. Army.