As electric vehicle (EV) battery manufacturers seek to scale production while improving efficiency and sustainability, attention has turned to dry electrode processing. One significant advantage: it’s a solvent-free alternative to conventional slurry-based methods.
Karl Littau, Chief Technology Officer with Sakuu, an equipment and technology provider to the EV battery industry. (All images courtesy of Sakuu)
By eliminating toxic solvents, this approach reduces environmental impact while cutting energy use by eliminating the need for large-scale drying ovens. It also simplifies manufacturing and opens the door to new material combinations optimized for EV battery performance.
We recently spoke with Karl Littau, Chief Technology Officer at Sakuu, a San Jose-based company developing commercial-scale printing equipment and technologies for the battery industry. With a unique background in chemical and materials science applications, Littau offers insight into how dry processing impacts electrode structure, scalability, and compatibility with high-performance EV battery chemistries.
In this Q&A, he breaks down the fundamentals of dry electrode fabrication, discusses process control at scale, and explains why the transition could support faster charging, lower impedance, and more consistent EV battery performance.
Here’s what Littau shared…
Can you please explain the dry electrode process, including the key considerations for EV batteries?
Of course! Electrodes are where the energy is stored in batteries. In lithium-ion batteries, they’re made of thick films of graphite (for the anode) and metal oxide particles (for the cathode). Adhesive binders are used to hold them together and stick them to the copper and aluminum foils that carry the electricity into and out of the battery.
In most manufacturing (not just for batteries), thick films of particles are typically coated from a slurry, which is a mixture of particles and a solvent. But this can cause problems. The coatings must be dried, but the drying process cannot occur too quickly, or the electrodes will crack. Additionally, the solvents used are often toxic and must be recovered from the air, typically through the use of cryogenic traps.
The dry electrode process uses the same materials as the wet, except it eliminates the solvent. The electrodes are produced directly from dry powders on metal foils as a loose powder. Heat and pressure are then applied to bind the particles together.
The difference between the wet and dry processes is similar to the difference between ink-based printing and laser printing.
Innovations in dry-process battery manufacturing allow for the production of ultra-thin battery cells at scale. Here, the thickness of a single battery cell is favorably compared to a credit card.
When printing with inks, the prints must be carefully dried and can’t be too thick. In laser printing, the toners are deposited directly onto the paper. A fuser uses heat and pressure to bind the toners together and to the paper. Dry electrode printing is quite similar.
How does dry coating affect electrode thickness uniformity compared to slurry-based methods?
Both dry and wet coating can achieve excellent uniformity. In wet processing, the electrode slurries are uniformly coated from an extruder, which is held at a precise distance from the substrate (the metal foil current collector).
In dry printing, powders are printed onto substrates using controlled dispensing and precision rollers, which evenly distribute the powders before fusing.
What are the most significant challenges in achieving uniform active material distribution and porosity in dry-processed electrodes?
Dry processing solves several problems, including uneven drying and binder distribution in the electrodes. It also reduces the energy consumed because it doesn’t require high-temperature drying ovens.
Moreover, because the dry powders already contain all the binders and other additives necessary to form a thin film on the surface of each particle, the finished electrodes are naturally highly porous, with wide, straight pores, rather than the nano-sized, tortuous pores typically seen in wet cast electrodes.
How do dry-coated electrodes perform in terms of energy density and rate capability?
Dry-coated electrodes have an energy and power density equivalent to, or better than, those of wet-cast electrodes. This is due to their ability to achieve higher compaction ratios while maintaining low tortuosity in the pores.
For EV applications where thermal management is critical, how does dry processing affect heat generation or dissipation within the cell?
There is less heat generated during charge and discharge because the dry-processed electrodes have lower impedance.
Today’s dry-process electrode manufacturing equipment takes advantage of existing industry expertise in powder-based printing, enabling the rethinking of the entire manufacturing flow to achieve high-volume battery production.
From a materials standpoint, how does dry processing affect the cathode microstructure and ion transport over long driving cycles?
Due to the wide, open pores in the cathode resulting from dry processing, ion transport remains high throughout the electrodes over the cell’s lifetime. The behavior of the cathode active materials themselves remains unchanged and exhibits only minor changes over thousands of cycles.
Are there limitations in current dry electrode technologies when it comes to high-nickel chemistries or silicon-dominant anodes commonly used in EV batteries?
High-nickel cathode active materials are 100% compatible with dry electrode processing. In fact, all cathode materials used commercially in lithium-ion batteries have been shown to work very well in dry deposition.
Silicon-dominant anodes require significant formulation development, regardless of whether wet or dry processing is used. Dry-processed silicon anodes are completely possible with suitable binders developed specifically for this application.
How does the dry electrode process influence cell-to-cell consistency and yield at EV pack scale?
Cell-to-cell consistency is a strong function of uniformity and control during electrode fabrication. It’s possible to control dry powders with great precision. Precise thickness control can be achievable because dry processing separates the steps of deposition and compaction.
What are the implications of dry-coated electrodes on fast-charging performance in EVs?
As mentioned above, dry-coated electrodes already show higher ionic conductivity. Further improvements in the printing process can also help improve the rate performance of the cells made with dry processing.
That said, much of the limitation to faster charging is in the electrode materials themselves. Fortunately, improvements in cathode and anode chemistry will also aid as the technology matures.
What testing protocols are most useful to assess the long-term durability of dry electrodes under EV-relevant charge/discharge conditions?
The tests are essentially identical to those already used in today’s cells — reliability cycling with real-world, relevant cycling profiles.
The latest equipment for dry printing electrodes has a significantly smaller footprint than traditional wet manufacturing setups.
What materials (e.g., conductive polymers, hybrid binders, or nanostructured carbons) are being explored to improve dry electrode performance and processability at scale?
I think one of the most exciting advantages of dry processing is that materials can be used where no suitable solvent system currently exists. Many battery manufacturers are looking forward to exploring how to use inexpensive binders and other materials in battery electrodes, which the lack of suitable solvents for mass production has previously prevented them from using.
What are the biggest process control challenges in scaling dry electrode manufacturing for EV battery lines while maintaining consistency and performance?
The biggest challenge is that dry electrode manufacturing requires excellent formulation of the dry powder materials and precise control of the deposition process. Process controls that work well for liquid inks, and slurries are simply not suitable for dry powders. The materials are less cohesive and are governed more by frictional forces than by viscosity, exhibiting fluid-like behavior. Unlike fluids, powders will support shear stress and are compressible.
Fortunately, engineers in adjacent industries, such as document printing, have literally decades of experience with this kind of control. This means that today’s battery manufacturing equipment is having great success in leveraging its expertise in powder-based printing. The outcome? I’m happy to say it’s high-volume, production-capable equipment that offers excellent performance.
Filed Under: Batteries, FAQs