By Louis Fourie
CAPE TOWN – On September 22, during a Tesla Battery Event after its annual shareholder meeting, Elon Musk lifted the veil regarding the battery innovations at Tesla. And as always, the revelations were revolutionary.
Elon Musk has stated several times in the past how important sustainable energy was. At the Battery Day he emphasised again that the future of world depends on accelerated sustainable energy generation, storage of energy and electric vehicles.
Except for offering an improved storage product that would provide more energy, allow longer travel distances and is cheaper to manufacture, Musk has the overarching goal of more affordable electric Tesla vehicles of $25 000 (about R412 500). Therefore, more affordable battery cells are needed, since affordable battery cells mean affordable cars, which will increase sales and thus sustainability.
To manufacture an affordable battery cell, Tesla (typically) went back to the drawing board to rethink their current product and processes and came up with a multi-modal, creative engineering, and innovative approach not only with regard to the battery, but also the manufacturing processes. All aspects of the battery have been reconsidered in their overall goal to halve the cost per kW/h.
Tesla decided to rethink how cells are designed and produced. Five aspects were dramatically innovated:
Cell design
Tesla discovered that a change in form factor (diameter and length) from their 1 865 battery (18” diameter and 70” length) to the 2 170 battery (18” x 70”) delivered 50 percent more energy resulting in a lower dollar to kW/h cost. Since the curve of size versus cost/kW/h flattened they eventually decided on the optimum size of the new 4 680 battery (46” x 80”).
However, the challenge with bigger cylindrical cells of supercharging and higher costs had to be overcome. This was done through simplifying the manufacturing such as fewer shingles, fewer parts and five times reduction in the electrical path link.
A reduction in the electrical path link means the distance the electron travels is less leading to thermal benefits. Tesla also got rid of tabs and simplified the coding, while simultaneously increasing the energy by six times on the optimum form factor alone. More energy resulted in a range increase of the Tesla car of 16 percent.
Less tabs also influenced the production process and made it much faster, allowing Tesla to significantly ramp up production at their 10gW/h facility.
Just the innovations in cell form factor resulted in average 14 percent $/kW/h reduction.
Cell factory
Inspired by the mass production processes of the paper and bottling industry, Tesla decided to improve almost every process in the battery cell manufacturing.
Electrode process
Materials are coded on to the foils. Currently a wet coding process is used for the electrode. Tesla changed this to a dry process by skipping the solvent and solvent recovery. Although a very complex process, the dry coding allowed them a tenfold reduction in footprint and energy, as well as a massive reduction in investment.
These changes allow Tesla maximum velocity in this high-speed continuous motion assembly and enables them to achieve seven times line output. Since speed and density are achieved through vertical integration, the factory is also much smaller and consists of one machine. Tesla is, therefore, more competitive and can accomplish with one factory what others achieve with two, five or even 10 factories.
Formation
Formation is when the cell is charged for the first time, the electrochemistry is set, and the quality is verified. It represents 25 percent of the investment. Tesla was able to achieve a decrease of 86 percent in formation investment and a decrease of 75 percent in formation footprint, meaning more power with less space. The contribution to the total improvement is a decrease of 18 percent in $/kW/h.
Anode materials
Tesla has been able to reduce the $/kW/h for anode materials by 32 percent due to the use of silicon. Tesla uses silicon due to its abundant availability and because it stores nine times more lithium than graphite, the typical anode material.
In comparison with silicon structured in SIO Glass ($6.6/kW/h) or graphite ($10.2/kW/h), Tesla silicon only costs $1.2/kW/h.
This is achieved by taking the raw metallurgical silicon, stabilising the surface through elastic ion-conducting polymer coating, and integrating it in the robust network by highly elastic binder and electrode design. These innovations increased the distance by 20 percent at a much lower cost. The contribution to the total savings is a decrease of 5 percent in $/kW/h.
Cathode materials
Cathode material innovations resulted in a 37 percent reduction in $/kW/h. The metals used in the manufacturing determines the costs, for example, Cobalt costs $30/kW/h, Nickel $15/kW/h, and Iron only $5kW/h.
The metal determines the amount of lithium that can be accommodated, and if the cell can retain its structure without reducing the cycle life.
Cobalt is very stable, but expensive. Tesla, therefore, decided to maximise nickel and remove all cobalt, novel coatings and dopants. This allowed them a 15 percent reduction in cathode $/kW/h.
The traditional cathode process involved metal sulphate production (metal + sulphuric acid), raw materials input (metal sulphate plus more chemicals plus water), cathode production (a number of processes) leading to the final product (cathode plus wastewater plus by-products).
This process was greatly simplified by Tesla: raw materials input (metal plus water), cathode production (less processes), final product (cathode). This resulted in a 66 percent reduction in capex investment, a 76 percent reduction in process costs and zero wastewater. Directly consuming nickel powder simplified the metal refining and recycling. Through the co-location of lithium conversion and a sulphate-free process Tesla achieved a 33 percent reduction in lithium cost and a 100 percent electric facility collocated with the cathode plant.
Tesla even improved the lithium extraction from clay by making it an acid-free saline extraction.
Tesla also has a strong focus on recycling cells after their 15-year lifetime, since the recycled metals from a cell are far more desirable and cost-effective than from raw ore.
Cathode innovations contributed to the overall cost savings, a 12 percent reduction in $/kW/h.
Cell-vehicle integration
Tesla achieved a 49 percent $/kW/h reduction in cell-vehicle integration by using single piece casting for the front and rear body.
Tesla’s materials team developed its own new alloy containing giga-casting innovations, such as shot size, velocity, pressure, tonnage, and no heat treating or coating.
The battery now becomes part of the structure, similar to aircraft fuel tanks in the shape of wings. These structural batteries improved the mass (10 percent reduction) and range (14 percent increase) of the Tesla car by using 370 fewer parts.
Tesla further employed simplification on the factory level and not only on the product level, leading to a 55 percent reduction in investment per gW/h and a reduction in floorspace. The overall contribution of cell-vehicle integration to the manufacturing costs is a reduction of 7 percent in $/kW/h.
Conclusion
The number of innovations and comprehensiveness is typical of Tesla. They rarely leave a product or process untouched to lower production costs.
All these efforts resulted in a massive total cost reduction of 56 percent $/kW/h (14 percent cell design +18 percent cell factory +5 percent anode material +12 percent cathode material +7 percent cell vehicle integration).
Simultaneously they increased the range of the cars by 54 percent (16 percent cell design +20 percent anode material +4 percent cathode material +14 percent cell vehicle integration).
The investment per gW/h was reduced by 69 percent (7 percent cell design +34 percent cell factory +4 percent anode material +16 percent cathode material +8 percent cell vehicle integration).
All the above innovations and cost savings will eventually lead to more affordable vehicles and greater energy sustainability. This will put electric cars in the same price category as petrol-powered cars, thereby making them more accessible.
Tesla is already the industry leader with regard to range optimisation of lithium-ion batteries in electric cars, and now has dramatically improved on this at a lower cost and faster process.
There is no doubt that Tesla remains one of the most innovative companies, especially if the number of patents registered by them is followed.
Professor Louis C H Fourie is a futurist and technology strategist.
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