Tesla acquired Maxwell Technologies in 2019, a company claiming to have pioneered a dry coating method for manufacturing supercapacitors.
Tesla’s interest wasn’t in supercapacitors themselves, but rather in the dry coating process to potentially slash the cost of its planned 4680 battery cells.
Traditional electrode manufacturing for lithium-ion batteries involves mixing a powder containing active materials with solvents and chemicals to form a paste, which is applied to a carrier film and dried in energy-intensive, expensive ovens. Dry coating eliminates this need, along with the associated costs and factory space.
Musk’s Deadline and Potential Consequences
According to Chinese news source Late Post, Elon Musk is pushing for mass production of 4680 cells with dry-coated electrodes by the end of 2024 for use in customer vehicles.
Failure to achieve this could result in Tesla abandoning its 4680 cell development altogether. Currently, the 4680 cells in the Cybertruck are a hybrid, with dry-coated anodes and traditionally wet-coated cathodes sourced from suppliers like LG.
Cathode Coating: The Key Challenge
Producing cathodes with dry coating presents the most significant challenge, but also the greatest potential for cost reduction.
While hurdles remain in transferring the process to cathodes, a confidential source suggests mastering it could provide Tesla with a “significant boost.” However, the cell’s performance and cost haven’t yet met Tesla’s expectations.
Year-End Progress and Potential Abandonment
The Information reports that Musk has tasked the battery team with cutting costs and achieving a “pivotal innovation” by year’s end, likely referring to dry coating the cathode.
Three sources contributed to the report, with two indicating that Musk might abandon the cell if the issue isn’t resolved by then. This would only affect Tesla’s in-house production, not the use of 4680 cells from suppliers like Panasonic in Tesla vehicles, though the cost without dry coating remains uncertain.
The Promise of Dry Coating
At the time of the Maxwell Technologies acquisition, Dr. Maximilian Holland estimated Tesla’s cell costs at around $100/kWh. Maxwell’s dry battery electrode technology was projected to reduce production costs by 10-20%, potentially paying for the acquisition within a few years.
Further benefits included time savings, environmental advantages, and performance enhancements like a 300 Wh/kg energy density with a potential path to 500 Wh/kg.
Manganese Cathode Breakthroughs
There are reports of Tesla successfully developing high manganese content cathodes. These are cheaper than high nickel content materials but have historically suffered from poor cycle stability, rendering them unsuitable for electric vehicles.
A recent patent application for doped, manganese-rich cathode active materials could extend the lifespan of such cells. However, they’ve only achieved 94% of original capacity after 50 cycles, a step forward but still below the threshold for electric cars.
A February 2024 Nature journal research paper identifies lithium- and manganese-rich layered oxide materials (LMRO) as promising cathode materials for next-generation batteries due to their high energy density.
However, practical applications are hindered by challenges like low initial Coulombic efficiency, rapid capacity fading, and voltage decay, which Tesla engineers are working to overcome under Musk’s watchful eye.
Musk’s Optimism Amidst Challenges
In a Q&A session after the company’s annual meeting, Musk expressed optimism about the 4680 cell’s progress, citing its use in all Cybertrucks and highlighting Tesla’s innovative cathode and lithium refining processes.
He emphasized the stark contrast between Tesla’s clean and efficient refineries and those of the rest of the industry.
While speculation abounds regarding Tesla’s progress, concrete information is scarce. Dry coating of cathodes appears to be lagging behind expectations, potentially delaying the full realization of the 4680 battery cell’s benefits. Whether Tesla has a backup plan remains to be seen.