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A Brief Overview of Tesla’s Battery Day

Tesla’s Battery Day was a showcase for Elon Musk to show off his company’s latest battery improvements. Both the event and the annual stockholder meeting took place at the same time, on Tuesday, September 22, 2020, at 1:30 p.m. Pacific Time.

The Battery Day event focused on Tesla’s efforts to maximize efficiency, reduce cost and complexity, and achieve its mission of accelerating sustainable energy transitions. Tesla introduced its 5-step approaches in cutting battery prices and announced two new electric cars they developed.

The presentation started with two of Tesla’s goals in battery production: terawatt-hour scale of battery production and the production of more affordable cells. They announced that a 56% reduction in battery price per kilowatt-hour was realized, following their five areas of focus: cell design, cell manufacturing, anode materials, cathode materials, and cell vehicle integration.


1. Cell design

It has been three years since Tesla announced their previous battery model, the 2170 cell. This Battery Day, Tesla introduced its new cell, the 4680 cell, with a 46 mm diameter and a height of 80mm. These cells enabled easier manufacturing because it requires fewer components, and showed a five-time reduction in the electrical path, which shortened the distance traveled by electrons. Compared to the 2170 cell in 2017, the 4680 cell has five times more energy and six times more power; it increases the car’s maximum travel distance by 16%.


2. Cell factory

Tesla has been working on the manufacture of dry battery electrodes. The original process for producing dry reusable cells required a method of drying wet electrode powder. Tesla entirely removed the drying process and developed a technology that turns powder directly into film. The shortened procedure reduces footprint and energy used in production to a tenth of what were previously required, and high-speed continuous motion assembly, enabling Tesla to accomplish its goal to make one factory to have the same production output as two to three factories, with a 75% reduction in spending per gigawatt-hour and ten times smaller footprint per GWh. Tesla’s Gigafactory that produced 150GWh in 2018 will now produce 1TWh during the same time. Elon Musk claims that there is still a lot of work to do with the newly developed technology, however.


3. Anode

The anode material for Tesla’s future batteries will change from graphite to silicon. Silicon reduces the anode’s cost to $1.2 per KWh and increases vehicle drive range by 20%. Silicon stores nine times more lithium compared to graphite, but the problem is that its volume expands when reused frequently. Thus, Tesla announced they would be using raw silicon and stabilizing the surface with an elastic coating.


4. Cathode

Cathodes are like bookshelves, holding the lithium ions. If it doesn’t have a stable structure, the battery loses its cycle life and degrades quickly. Most lithium-ion batteries contain cobalt as their cathode material although it’s unstable and damaging to the environment. Elon Musk believes that nickel will solve the current issue. Nickel is cheap and has the highest energy density, but needs to be stabilized to be used as a cathode. Tesla aims to maximize nickel usage and remove cobalt from its cathode, resulting in a 15% reduction in cathode cost per kWh. Moreover, Tesla diversified its cathode materials to avoid being constrained by nickel availability. Depending on their products, a different cathode with different combinations of nickel and iron will be used. For example, mass sensitive vehicles like Tesla’s Cybertruck or the Semi will entirely be using nickel.

Tesla plans to mine the significantly untapped lithium in Nevada’s clay using table salt. Musk says that it’s an environmental-friendly approach for mining.


5. Cell vehicle integration

Tesla is developing technology for single piece casting, leading to a 40% reduction in rear underbody cost and 79 fewer parts per car. Since no heat training and coating procedure are required, it results in a significant decrease in complexity and production cost. This leads to an overall 7% reduction in cost. Tesla’s vehicles will be using a structural battery, which means that the battery pack will become the car's structure. This enables batteries to be packed more densely with no extra parts, leading to a dramatic reduction in cost. Since battery packs are closer to the center of the car, safety is also enhanced.

Overall, Tesla accomplished a 56% reduction in cost per kWh, a 54% increase in vehicle drive range, and a 69% reduction in spending per GWh. Elon Musk claimed that it would take around three years to fully realize their technology, showing the possibility of electric vehicle powertrains costing less than combustion engines.

Two new cars are introduced: the fully-autonomous $25,000 car and the Model S Plaid. No significant details were revealed about the $25,000 car during the presentation, however. The Model S Plaid takes less than two seconds to reach a speed of 60 miles per hour, travels a quarter-mile in less than nine seconds, and has a maximum range of 520 miles, outrunning the Lucid Air.

For more information, watch the full event video uploaded on Tesla’s YouTube channel: https://www.youtube.com/watch?v=l6T9xIeZTds


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