Elon Musk used Tesla’s much-anticipated Battery Day presentation not to disclose some super cell, but to outline an aggressive, comprehensive and radically innovative approach to battery design, manufacturing and vehicle integration that he projected will result in a 56% reduction in cost/kWh and a $25,000 electric vehicle in about three years.
The baseline precept for the presentation was the centrality and associated difficulty of manufacturing new technologies at a scale sufficient to make a tangible difference. Rapidly scaling global battery manufacturing capacity, Musk pointed out, is absolutely central to achieving large-scale electrification and climate goals.
Tesla has two battery-related goals, Musk said. The first is terawatt-scale battery production. “Tera is the new Giga.” Gigafactory Nevada currently has a capacity of about 0.15 TWh. The second goal is a more affordable battery cell.
What troubles me is that we don’t yet have a truly affordable car. The curve of the cost per kWh of batteries is not improving fast enough.—Elon Musk
Drew Baglino, Tesla’s Senior Vice President, Powertrain and Energy Engineering, said that the company has a plan to halve the cost per kWh based not on a single innovation, but across the entire chain from raw materials to vehicle integration. 55Musk and Baglino described five major battery manufacturing sub-areas in which Tesla is developing new technology:
- Cell design
- Cell factory
- Anode materials
- Cathode materials
- Cell-vehicle integration.
Tesla projects that its innovations in battery design, manufacturing and vehicle integration will result in a 56% reduction in cost/kWh as well as an increase in range.
Cell design. Musk and Baglino described a major design change for cylindrical cells: a move to a tabless battery with a “shingled spiral” replacing the traditional anode/separator/cathode jellyroll. The new tabless battery enables dozens of connection into the active materials and reduces the electrical path length from 250mm to 50mm.
With the new technology, comes an accompanying move to a larger format: 4680 (46 mm diameter, 80 mm long), compared to the current 2170 and 1865. The new cell gains 5x energy, +16% range, and 6x power just from form factor alone.
Baglino said that Tesla is starting to ramp up manufacturing of the new tabless cell at the company’s pilot 10 Gwh production facility in Fremont; it will take about a year to reach 10 GWh annualized rate.
Tesla attributes a 14% reduction in cost per kWh just to the cell form factor change.
Cell factory. Battery manufacturing comprises four main processes: creation of the electrodes (coating); winding; assembly; and formation (charging for the first time, verifying quality). Tesla is addressing every step in the process with an eye to making it better and more scalable.
The current wet coating process consists of mixing powders with solvents; coating and drying in an oven; solvent recovery; and compression to the final density. Tesla is moving to a dry coating process to eliminate the solvent step, supported in part by the acquisition of Maxwell Technologies, the ultracapacitor company.
[Dry coating] is very hard to do. The dry coating [Maxwell] had was sort of like a cold proof of concept. We have revved the machine four times. It’s not in the bag. There is still a lot of work to do. There are major issues in scaling this up, but it is close to working. It does work, but with not a high yield. There is a clear path to success but a ton of work to get there. We will probably be on machine rev 6 or 7 by the time we get to scaled production.—Elon Musk
Tesla is also working to redesign the assembly process itself using the bottling industry as inspiration, and focusing on speed and density of the production process itself (i.e., smaller factory footprint).
The aim of Tesla is to be the best in manufacturing of any company on earth.—Elon Musk
Tesla is taking a similar approach to formation, moving to charging thousands of cells at once. This will result in an 86% reduction in formation investment (which currently accounts for about 25% of the investment in assembly) and a 75% reduction in footprint.
Viewed another way, from a smaller footprint than Giga Nevada, Tesla could get many times the cell output.
Tesla plans to manufacture 100 GWh of cells in 2022, and 3 TWh by 2030. Tesla will continue to use its cell supplier partners. Tesla production will be supplemental to what it buys from the suppliers, reducing the weighted cost per cell. Long term, Tesla sees an incremental 18% reduction in the cost/kWh due to its projected assembly innovations.
Anode. Tesla is proposing a step-change in the capability and cost of silicon anode materials by moving to raw metallurgical silicon, thereby cutting out the expense of the other current highly engineered materials.
Tesla says that it will stabilize the surface of the silicon with elastic on a conductive polymer coating. The silicon material will deliver an anode cost reduction along with an increase in range.
Cathode. Tesla will take a three-tiered approach to the cathode materials in its batteries, Musk said: iron for cycle life, nickel-manganese for an intermediate solution, and a new high-nickel cathode material targeting very long range, the Cybertruck, and so on.
Beyond the metals themselves, the cathode process is a big target for Tesla. Tesla believes it can reduce investment by 66% and the process cost by 76%—and yield zero waste water—by directly consuming raw nickel metal powder, and simplifying the entire process. In other words, Tesla is proposing to eliminate intermediate nickel production.
Tesla will build a new cathode facility in North America, and co-locate lithium conversion at that site, using a new acid-free saline extraction process. Tesla said it has secured a terawatt-hour scale lithium resource in the US. Tesla will also use material from recycled batteries.
Tesla said its cathode innovations will contribute to a 12% reduction in the cost/kWh.
Cell-vehicle integration. Tesla is moving toward a process in which a single-cast front-end and single-cast back end will be joined to a structural battery pack fabricated in a direct-to-pack process—i.e., no intermediate assembly of cells into modules which are then integrated into a pack.
Tesla is already using single-piece casting from front and rear body components. To achieve that, it commissioned the largest casting machine ever made, and also developed a new high-strength aluminum alloy that is very castable.
The structural battery serves a dual purpose as energy device and as intergal structure, very similar to current aircraft design in which the fuel tanks are intergal to the wings.
Structural batteries improve mass and range, Musk said. Also, the construction technique allows cells to be packed more densely. Structural adhesives glue the cells to the top and bottom sheet; the steel shell case of the battery cells transfer sheer from the upper face sheet to the lower. Load is transferred into the pack in a smooth way so that there is no arbitrary point load. The result is even stiffer than a regular car, Musk said.
Longterm, any car not with this architecture will not be competitive.—Elon Musk
Such a design also enables massive simplification in the factory, with a 35% reduction in floorspace. Tesla calculates this is all worth another 7% reduction in $/kWh, bringing the total reduction to 56%.
It will take a year to 18 months to realize the advantages. Full realization is in three years or about. If we could do this instantly, we would. It bodes well for the future, with long-term scaling massively increased. Long term, we want to make about 20 million vehicles per year.
What does this mean for future products? EV powertrains that cost less than combustion engines. About three years from now, we can make a compelling $25,000 electric vehicle.—Elon Musk