Jordan Geisigee of The Limiting Factor analyzes a recently published Tesla patent application providing insights into Tesla's cathode material production process, particularly for LFP (Lithium Iron Phosphate) cathode material. This process, developed over five years since Battery Day, aims to produce cathode powder – highly ordered, high-purity crystals that store lithium ions – at a lower cost than tariffed LFP material from China. This could enable Tesla to produce some of the lowest-cost LFP battery cells globally.
The video focuses on the process for making the cathode powder itself, distinguishing it from the dry coating process used to adhere the powder to battery cell foils. Geisigee credits Battery Bulletin and Joe Tegmeyer for their contributions to the analysis.
Traditionally, cathode production involves a complex process starting at a chemical plant, where metal is mixed with sulfuric acid to create metal sulfates. These sulfates are then transported to the cathode plant and mixed with water and carbonates in a continuously stirred tank reactor (CSTR) to form metal carbonate particles. These particles are separated, washed, filtered, dried, ground, and classified by size. Finally, they're mixed with lithium-containing powder, heated, and crystallized. This traditional method has drawbacks: it requires a separate chemical plant, generates heavy metal wastewater, and is capital-intensive due to the multiple reaction steps and equipment required.
Tesla's proposed process aims to solve these problems. The patent application is extensive, featuring wet and dry production paths and numerous process options. By analyzing the work history of the inventors (Bastion Ewald, Ulongleo, and Anthony Michael Thurston) and the equipment installed at Giga Austin's cathode factory (tracked by Joe Tegmeyer), including SACME compacting equipment and Clia SAGR kilns, Geisigee believes Tesla is most likely employing a spray granulation process detailed in Figure 8 of the patent application.
This process starts by adding all raw cathode materials into a mixing tank (801) to create a homogenous slurry of particulate matter, including metals, compounds supplying active ions like lithium and sodium, and materials like carbon doping for LFP cathodes. This single-step mixing eliminates the need for metal sulfates and allows for greater flexibility in sourcing materials. The slurry is then held in Tank 802 before being fed to a granulator (803), which is likely a spray granulator. Here, the slurry is sprayed while being heated, evaporating water and causing the individual particles to combine into larger, agglomerated secondary particles.
Next, at step 807, the particles undergo classification to ensure they are of the correct size for optimal battery performance. Undersized or oversized particles are then recycled back into the process via two potential pathways: either being milled into primary particles and returned to the granulator, or being returned to the initial mixing tank (801/802) to be recombined into the slurry feed. The spray granulation process eliminates the need for separate washing, filtering, and drying steps. This process also allows for the water that's off-gassed to be run through a condenser and reused.
Particles of the correct size are then sent to a furnace or kiln for calcination – heating and crystallizing in a nitrogen (for LFP) or oxygen (for high-nickel NMC) atmosphere. While the patent shows a rotary furnace, Tesla installed a Sagar roller hearth kiln at Austin, suggesting either the Sagar kiln is for test batches or the primary production method. Finally, presses or compactors are potentially used to pack the material into crucibles before the furnace or to de-agglomerate the cathode powder after the kiln, though Geisigee leans towards the latter.
Key innovations from the patent are the "one-pot process," combining all raw materials in one step, and the recirculation pathway for waste material recycling. These features are crucial for achieving the environmental and cost benefits Tesla touted at Battery Day.
While Tesla's process may have provided a significant 76% cost reduction five years ago, current LFP production in China also employs spray drying processes. However, it is not clear the Chinese process allows for waste recycling of solids, and it utilizes less efficient Sagar kilns. While Tesla may retain some advantages, Chinese manufacturers are catching up. However, this is not a major concern because even if Chinese cathode powder production reaches Tesla's cost level, Tesla will benefit from avoiding tariffs and transportation costs.
The conclusion is that Tesla's process allows control over its supply chain, ensures cost-effectiveness, and potentially gives a stronger bargaining position when dealing with companies like Nano 1, should there be any patent overlap. The subsequent video will explore the broader implications of this patent for the LFP4680 battery, speculated to be used in the CyberCab.