Published on September 22nd, 2020 |
by Kyle Field
September 22nd, 2020 by Kyle Field
Tesla didn’t hold back at Battery Day, announcing a new tabless 4680 cell form factor, among many other things. The new form factor eliminates the tabs, increases energy density, maintains similar thermal characteristics of smaller cells, improves the power-to-weight ratio, streamlines manufacturing, and lowers cost.
Said another way, the new Tesla 4680 cell is the equivalent of bringing a potato gun to a french fry fight. Let’s walk through each of the improvements the new form factor brings to the table.
Scale Is Necessary
Tesla was content buying cells with its proprietary chemistry from its suppliers, but saw issues on the horizon. Tesla aims to grow consistently at a rate of 40–50% per year, and to do that, it is going to need more and more batteries. Tesla’s battery forecasts showed a gap between the production limits of its battery cell suppliers and Tesla’s internal demand for its automotive and energy storage businesses.
To solve this, Tesla’s teams have been hard at work buying and designing new technical solutions to drive further improvements in the battery cell format. Perhaps more importantly, Tesla leveraged its know-how in the battery cell manufacturing space along with its world-leading manufacturing equipment competency to rethink the entire process from start to finish.
We intend to increase, not reduce battery cell purchases from Panasonic, LG & CATL (possibly other partners too). However, even with our cell suppliers going at maximum speed, we still foresee significant shortages in 2022 & beyond unless we also take action ourselves.
— Elon Musk (@elonmusk) September 21, 2020
Step Change Improvement In Cell Manufacturing
As it sought greater efficiencies in automotive manufacturing, Tesla quickly pushed beyond merely designing and building products, going into the design of the machine that builds the machine. Manufacturing is hard, but Tesla’s commitment led it beyond the product to designing products that were easier to manufacturer. We first saw this with the Model 3, and work has continued with every iteration.
When the time came to design the new battery, Tesla looked all the way up the chain, to the starting point. Doing this is a reflection of Musk’s obsession with first principles thinking. He tries to start every design, every discussion with what is truly the lowest common denominator — the simplest truth anchoring our products to the minerals they are comprised of. When those have been defined and refined over and over again, it is then possible to build an optimized design.
In the battery world, we saw Tesla establishing new ground truths with the acquisition of the battery and supercapacitor pioneers at Maxwell Technologies and Hibar Systems. Tesla learned its way through the construction of its first Gigafactory in Sparks, Nevada, acquiring the manufacturing equipment experts at Grohmann Automation. Grohmann quickly became the primary developer for the battery cell production lines at Tesla’s Gigafactory 1, adding increasingly advanced production lines from Grohmann to the factory as more cell production capacity was needed.
Improving each of the primary silos comprising a battery was helpful and led to greater efficiencies at Gigafactory 1, but Tesla saw a greater vision. Full integration. At Tesla’s Battery Day event today, Drew Baglino unpacked the vision now being realized at Tesla.
“The vertical integration with the machine design teams at Grohmann, Highbar, and others allows us to really accomplish that because we don’t have any of these edge conditions between one piece of equipment and another,” Baglino said. “We can design the entire machine to be one machine and remove all these unnecessary steps.”
Tesla’s relentless pursuit of vertical integration comes from a desire to eliminate inefficiencies and improve the sustainability of the product. A byproduct of Tesla’s vertical integration is a much needed improvement in cost, driving the cost of Tesla’s products down over time.
The tabless architecture of the new 4680 cells also has a direct impact in improving manufacturability. Not only does the tabless design eliminate the need for a tab; it eliminates the need for the production lines to pause to add the tabs. The new tabless cells eliminate this bump in the road, enabling a manufacturing line that is less prone to manufacturing defects as it hums along, rolling up and spitting out massive 4680 cells.
“This is not just a concept or a rendering,” Baglino said. “We are starting to ramp up manufacturing of these cells at our pilot 10 GWh production facility just around the corner.” Tesla’s project Roadrunner established a pilot line for the manufacturing of the 4680 cells, and according to CEO Elon Musk, they see a clear path to ramping up the pilot line processes to gigawatt-hour and even terawatt-hour scale.
“It will take awhile to get to the 10 GWh [annualized] production capacity,” Musk said. The company expects to have the kinks in the new production lines ironed out in the next 12 months. At that point, it will be time to drive scale. “Actual production plants will be on the order of 200 GWh or more over time.”
Long term, it is not the new cell dimensions, chemistry, or configuration of its vehicles that Tesla holds as a core competency. Rather, manufacturing is the key. “Eventually, every car company will have long range electric cars,” an impassioned Musk said. “Eventually every company will have autonomy. But not every company will be great at manufacturing. Tesla will absolutely, head and shoulders, be above everyone else in manufacturing. That is our goal.”
One of the results of these efforts is a new 4680 tabless cylindrical battery cell format that brings a host of performance, manufacturing, and cost benefits to the table. As the name implies, the new jumbo cells are 46 mm in diameter and 80 mm in height. The larger jelly roll packs more active battery material into the casing for a 5× improvement in energy storage and a 6× increase in power. Scaling up to the pack, the new form factor alone delivers a 16% increase in range.
The new tabless 4680 cells are fundamentally superior to cells with tabs in just about every way. Even though they are larger, eliminating the tab actually makes it easier for electrons to get around inside the cell than in the current 2170 cells. “You actually have a shorter path length in a large tabless cell than you have in a smaller cell with tabs,” Musk said.
Improved Chemistry — aka, Silicon Is Awesome
The new cells are not the result of a single change to the size of the cells. Much like the numerous rewrites of Tesla’s autopilot over the years, the 4680 cells represent a fundamental rewrite of the history of battery cells at Tesla.
Silicon is used in Tesla’s batteries today, but its physical properties make it a bit of a challenging element to use at higher volumes. “The challenge with silicon is that it expands 4X when charged with lithium,” Baglino said. Silicon is the most abundant element in the earth’s crust after oxygen, making it a lower cost, easy to acquire commodity. In fact, sand is just silicon dioxide.
To work around silicon’s rough edges, Tesla perhaps unsurprisingly started with raw silicon. Right off the bat, that lowers the cost of the silicon and simply built a new chemistry to complement it. “Stabilize the surface with an elastic ion-conducting polymer coating that’s applied through a very scalable approach,” Baglino said.
That’s far simpler than current processes and allows for a higher percentage of silicon to be used in the cells. The result is a cheaper cell that also boasts higher capacity. “We can increase the range of our vehicles an additional 20%,” Baglino said. The icing on the cake is that the cells are also cheaper. “That’s another 5% [cost] reduction at the battery pack level.”
If it sounds like the ultimate win-win, you’re exactly right. That’s one of the many reasons Tesla’s Elon Musk has been bubbling over with excitement about the otherwise tech heavy Battery Day for the last few months.
Reimagining Cathode Production
According to Tesla, today’s cathode production processes are based on legacy chemistries and processes developed in silos. Tesla being Tesla, a new blank sheet of paper plan was drafted to optimize each step to minimize waste and cost from ore to cathode.
The simplified pictogram of an extremely complicated global supply chain spanning from the processing of raw ore to the delivery of the finished cathode is far less convoluted. Not only is it more streamlined, it is far cheaper and results in less waste.
Tesla’s new high nickel cathodes completely eliminate the need for cobalt. Chemically speaking, cobalt is a fantastic anchor for a cathode, but it comes with some serious caveats. Right off the bat, cobalt is toxic. The fewer toxic materials humans have to mine, process, and use, the better.
It is also extremely challenging to secure a source of cobalt that is sustainable as the vast majority of cobalt production in the world comes from a single country — the Democratic Republic of the Congo. The country’s leadership has not been the most stable and injecting hundreds of millions of dollars into an already corrupt system doesn’t help matters. With electric vehicles and consumer products putting even more strain onto an already challenged system, prices have become destabilized.
Ethics can sometimes slip by the wayside, with some human rights groups coining the term conflict cobalt. Roll all those factors together and cobalt, while beneficial in the battery cell, is anything but beneficial to a company looking to scale battery production up to 3 terawatt-hours per year by 2030.
Ditching cobalt in favor of a high nickel cathode also improves the cost of a cathode by 15% on a cost per kilowatt-hour basis. That’s massive. Designing and manufacturing cathodes from the ground up also gives Tesla a great head start at building its own internal battery recycling systems.
All told, Tesla’s work on cathodes resulted in a process that slashes the processing cost of a cathode by a staggering 76%. This is all done with far less equipment, translating to a 66% savings in capital expenditures for cathode production. As the icing on the cake, the new process uses far less water than traditional processing. In fact, the new process results in zero waste water.
Tesla is rolling all of these improvements into a new cathode production facility in North America. It will be located to minimize non value add travel for raw materials and intermediate products in the region.
Improved Thermal Characteristics
The improvement that does a lot of the heavy lifting to enable using a larger form factor is the tabless design. Eliminating the tabs reduces the internal resistance within the cell caused by the extra component. Internal resistance translates to more heat generation, a more complex manufacturing process, and higher cost.
Tesla’s new 4680 cell eliminates the internal tab, instead, integrating the function of the tab into the jelly roll itself, resulting in a clean, uniform look to the end of the cell. “We basically took the existing foils, laser powdered them, and enabled dozens of connections into the active material through this shingled spiral,” Tesla SVP Drew Baglino said.
Eliminating the tab on each cell, “Removes the thermal problem from the equation and allows us to go to the absolute lowest cost form factor and the simplest manufacturing process,” Baglino said.
Focusing on the thermal benefits of the tabless design of Tesla’s new 4680 cell, the new design enables the larger diameter cells to achieve thermal characteristics similar to that of a smaller cell. Said another way, they stay as cool as smaller cells, enabling Tesla to cram more power into the same physical volume.
Larger tabbed cells have historically struggled to shed heat at faster charging speeds. Tesla’s new cell disrupts the trend, charging nearly as fast as smaller cell, while bringing all the benefits of a larger cell to the table. Tesla was able to take the best of both worlds, completely disrupting the small but growing world of automotive battery cell production.
I Hear You, But So What?
That’s a lot of technical content for something most humans don’t ever think about. Battery cells are massively complex and Tesla’s latest rewrite of the fundamental building block going into its electric vehicles and energy storage might be challenging to digest. Let’s put a bow in it.
All told, Tesla’s new 4680 battery cell represents a paradigm shift in automotive energy storage. The new cells are far cheaper and can store far more power per unit of volume. They have been redesigned a as structural elements of the vehicle, resulting in a cheaper, more rigid vehicle.
Tesla rolled out hundreds if not thousands of small improvements today that bring step change improvements to the fundamental building block of Tesla’s business — the battery cell.
- 14% improvement in cost/kWh coming from the change in cell form factor
- 18% improvement in cost/kWh as a result of the 10X manufacturing footprint reduction and 10X manufacturing energy consumption reduction. The new dry manufacturing process enables pressing the active battery powder material directly into a film. The new manufacturing process is based on Maxwell Technologies’ proprietary “proof of concept” process. Process is not at production scale yet, but there is a “clear path” to large scale production.
- 5% improvement in cost/kWh coming from the increase utilization of silicon in the battery cells as detailed above.
- 12% improvement in
- 7% improvement in battery pack cost per kWh as a result of Tesla’s new integrated vehicle design. Tesla redesigned its vehicles using new front and rear castings that integrate with the battery pack. To accomplish this, Tesla developed a completely new alloy to enable casting of some of the largest components in the automotive space. These bolt directly into a new “structural battery”, eliminating the need for redundant, parallel elements in Teslas.
All told, Tesla’s redesign of the battery, cathode, and vehicle frame translate to an improvement of 56% in Tesla’s cost per kWh. That’s a game changer for Tesla and will enable a completely new generation of low cost electric vehicles and it all starts with the humble battery cell. Tesla has made significant progress in rethinking the battery cell and is well along the way to rolling them into production but all told, it will take the company 18 months for most of these changes to get to production.
All images capture from Tesla’s Battery Day stream.
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