If it were someone else, they could hold five press conferences for this.

Translation in English Markdown Text:

On September 22, Tesla held its first Battery Day at the Fremont factory in California. During the event, Elon Musk solemnly and proudly showcased the improvements Tesla has made in enhancing power batteries, and the audience went from being bored during the shareholder proposal to being thrilled by the end of the battery presentation. Although most of the content discussed was part of Tesla’s long-term plan, it was still enough to be inspiring.

Summary of Battery Day

Elon started the Battery Day by showing a PowerPoint slide which demonstrated the change of battery cost over time. It revealed that as the battery cost got lower, the rate of the cost decline gradually slowed down, similar to how the charging power diminishes if the battery is almost full.

Elon thinks that the cost reduction trend is not happening fast enough, so he began to lay the groundwork. In the latter part of the Battery Day’s event, Tesla introduced five innovations in power batteries that were unprecedented and shockingly impressive. The resulting outcome is as follows:

Despite the already low cost of power batteries, Tesla’s comprehensive measures led to a 56% overall cost reduction in power batteries, a 54% increase in mileage, and a 69% reduction in the cost of producing 1GWh battery.

The direct impact of this result is that the total cost of the EV powertrain with batteries can be lower than that of the IC powertrain. Based on this, Tesla will also launch a $25,000 entry-level product, expected to begin production in 3 years.

Returning to the core of Battery Day, the key to achieving these results is Tesla’s five major improvements, and let’s start with the most significant one.

Integrated Chassis: Unprecedented Vehicle Engineering Innovation

This time, Tesla made the battery pack the core of its chassis, and it is now integrated into the structure. The chassis and battery are fused together, serving as both the container for the battery cells and a structural component. Tesla also made the battery pack non-modular, with only battery cells and no intermediary modules, maximizing the use of pack space.# More Powerful is that Tesla has divided the chassis into three parts: front, middle and rear, with the battery only in the middle part. The front and rear of the car are cast from alloy as two huge monolithic structures.

Compared with traditional cars/electric cars, this chassis structure, which is composed of three large monolithic structures, greatly improves the strength, and Elon said that the convertible made by this structure will be even stronger than the current hardtop car.

The large monolithic structures at the front and rear of the car are made by the world’s largest casting equipment, and in the research and development stage, they faced a problem: there was no alloy material on the market that could meet this level of monolithic casting requirements. Therefore, Tesla developed an unprecedented alloy formula to meet the material requirements.

As a result, the overall battery cost was reduced by 7%, the overall endurance was increased by 14%, the overall weight was reduced by 10%, and the number of parts required to manufacture the chassis was reduced by 370.

Deformation and Change of Cores

Have you seen the cross-sectional image of the chassis above and found that the battery cells look different? Yes, this is another big core content of this Battery Day – the new cylindrical battery cell.

The new battery cell is called 4680 battery cell, with a diameter of 46mm and a length of 80mm. The appearance shows that the battery cell has become larger directly, just like the relationship between the 2170 and 1865. The larger monolithic structure also reduces the middleware of the overall battery part, which can lower the production cost and improve the endurance at the same time.

However, increasing the cylindrical volume will also increase the difficulty of heat dissipation, and safety also needs to be considered. Blindly increasing the size of the battery cell to a certain stage can even have a negative effect on the endurance. Tesla has discovered through research that when the diameter of the battery cell is 46mm, it is the best balance point between cost and endurance. This is also the source of the “46” size.

The great thing about the 4680 battery cell is not only its larger size, but also the internal structure that uses a pole-less electrode. After removing the poles (the bar-shaped objects on both sides of the battery in figure 1), the current collecting fluid of the battery cell is directly connected to the battery cell cover/shell, greatly increasing the contact area and reducing the internal resistance of the battery cell. This also reduces heat generation when the battery cell is charged. This solves the heat dissipation problem of large battery cells and increases their maximum output current. Ultimately, compared with the 2170 battery cell, the 4680 battery cell has a single cell capacity increased fivefold and a single cell output increased sixfold. This means that the output power density has improved by 20%. As a result, the overall battery cost has decreased by 14%, and the overall range has increased by 16%.

Cobalt-free Cathode

As previously rumored, Tesla has introduced a new cobalt-free chemical formula in the battery cell. Tesla has achieved a zero cobalt content on the cathode of the battery cell, and opted for a high-nickel formula instead. The main materials that can be used for the cathode are cobalt, nickel, and iron. Cobalt is the most expensive, with lower energy density than nickel. Nickel costs less than cobalt by over a third, has a slightly greater density and is a more optimal choice when considering both cost and energy density. Iron is the cheapest but has only about half the density of the former two. However, the active chemistry of nickel presents a great challenge for thermal management, which Tesla has addressed through the use of a new coating and appropriate additives applied to the high-nickel cathode, under the cobalt-free formula. The pole-less electrode design also contributes to the thermal management of the high-nickel battery.

However, aside from high-range products that use high-nickel batteries, Tesla still uses common cobalt-containing and iron batteries in other models.

Tesla’s engineers found that production costs accounted for 35% of the cost of the cathode. They further discovered that the production process was very cumbersome and time-consuming, including four major stages and various tricky sub-stages.

At this point, Tesla decided to streamline manufacturing processes.# Markdown Output

“Simple is hard”, thinking of “being lazy” takes effort. Tesla has done a lot of subtraction in this process, integrating as many separate manufacturing processes as possible into one, greatly reducing the time-consuming material transfer and loading and unloading processes in the manufacturing industry. The manufacturing process of positive electrode sulfate is complicated and produces a large amount of wastewater. Tesla skipped this step with a process that does not require sulfate saltification and a series of other optimizations. The final manufacturing optimization process only consists of 3 major steps and 4 minor steps, reducing the cost of the positive electrode production process by 76% and the factory construction cost by 66%.

As a result, the overall battery cost has been reduced by 15%, the overall range has increased by 4%, and the formula is cobalt-free.

Silicon-doped negative electrode

Do you remember the micrograph of the silicon-doped negative electrode in the battery daily cover image? The one that Elon wore on his T-shirt is also this. Elon said that in terms of performance, silicon is a very good choice as a battery negative electrode material because of its extremely high energy density. It can store lithium metal 9 times that of graphite negative electrode, and the content of silicon elements on Earth is also very high, second only to oxygen elements, and there is no need to worry about reserves.

However, using silicon as a negative electrode has a fatal flaw, its expansion can reach 4 times its own volume, and such expansion will cause damage to the negative electrode structure, and the corresponding problem is that the cycle number of the silicon negative electrode material is not good.

Multiple silicon negative electrode structures, including silicon nanowires, cannot solve this problem well, but since Tesla uses them, it must have solved the problem before adopting them. Elon said that in order to improve the negative impact of expansion, Tesla took two measures, first reducing the silicon content of the negative electrode by 20%, and second covering the silicon element of the negative electrode with elastic ion bonds to reduce expansion and increase the cycle life of silicon-doped negative electrode batteries.

The result: the cost of the battery is reduced by 5% (the negative electrode cost of $1.2/kWh), and there is a 20% increase in range.

Production, also amazing

The above parts are all “produced items”, and the manufacturing equipment, as one of Tesla’s products, also played an important role in this “battery leap forward.”

Looking at the manufacturing industry, Tesla found that the automation level of the printing industry and the bottled beverage industry is extremely prominent, and the efficiency is very high while the cost is very cheap. Inspired by this, Tesla decided to achieve integration in its own production. First, Tesla spent a lot of effort to eliminate the “electrolyte solvents preparation” process, and instead compressed the solid electrode powder directly into the roll of the battery. Elon said that this seemingly simple step is very challenging to implement technologically, but once it is achieved, it brings a 10 times space utilization rate and 1/10 energy consumption on this production line, and is now very close to mass production.

In the assembly process, Tesla created an uninterrupted assembly line, which Elon referred to as the highway of the manufacturing process. There are no traffic lights and everything moves along smoothly. What kind of improvement does this type of assembly line bring? One assembly line can achieve a production capacity of 20 GWh, which is seven times higher production efficiency than before.

The trick? “Design the entire machine as one machine.” Achieve a high level of integration at the factory level and remove all non-essential steps.

Elon stated that Tesla’s goal is to become the best manufacturing company in the world and in all industries. In the long term, the progress at the factory level is the most important for Tesla and is also a key element in achieving the road to renewable energy.

If that is not enough, Elon also added this sentence: “Our factory advantage is difficult to replicate.”

Result: The overall cost of electric batteries was reduced by 18%, and the construction cost of factories decreased by 34%.


With improvements in vehicle structure, battery cell structure, positive electrode improvement, negative electrode improvement, and factory improvement, Tesla achieved a significant breakthrough in cost reduction of 56% and increased driving range by 54%. Tesla significantly deviated from the industry’s cost curve, emphatically demonstrating Tesla’s ability to set its own trends in the electric vehicle industry.

First Principles Thinking

The content of today’s Battery Day made me think “Wow” for the first few minutes. It can be said that every aspect of Tesla’s five major battery improvement steps can expand into a large number of topics. However, I am extremely tired, mixed with memories of the conference, and I took a nap.

After waking up, I read through the content again, but this time with a few questions in mind:

Why did Tesla do this? How did they discover shortcomings in the above areas and solve them? Moreover, at a higher level, what does this mean for Tesla’s sustainable energy goals?

First of all, on a more intuitive and understandable level, I think that Tesla as a publicly traded company must pursue profits, and cost reduction should be a natural thing. However, the shock this time is that Tesla directly cut battery costs by 56%, which is quite remarkable given that they have already done well in cost control for the Model 3. It feels as though Tesla is competing with something.

Looking back at the conference, this picture gave me some clues.A colleague asked me a question a long time ago: “Do you know why Tesla started making electric cars with the Model S/X?”

My answer at the time was because Tesla wanted to position itself as a high-end brand.

“That’s only one aspect. The more important reason is that the price of power batteries at the time was only manageable for that level of car,” my colleague said. “Think about it, if the Model 3 had debuted five years earlier without any changes, Tesla wouldn’t be where it is today.”

In fact, looking back at those words, they can be translated as “at that time, the cost of electric cars was not advantageous compared to gasoline cars, and the lower the positioning of the car model, the more obvious the price disadvantage caused by the cost of power batteries.”

Alternatively, it can be translated into a conclusion: the lower Tesla’s brand goes into the low-end product line, the more competitive the cost of power batteries becomes.

Today, Tesla’s announcement of the production of a compact new car at a price of $25,000 in three years also indicates that Tesla can now make a model representing the bottom line of traditional high-end brands, the compact car, while ensuring profitability.

After the long preface of the five major stages and with a 56% reduction in battery costs, the statement “EV powertrain costs are lower than those of gasoline cars” seems like a summary.

Then there’s the second question: How did Tesla discover and solve the shortcomings at every level?

Let’s take a look at what Tesla has done this time:

On battery structure, increase the size of the battery cell, reduce the number of cells, and reduce the middle layer inside the cell;

On electrodes, reduce the use of rare metals and increase high-density elements;

In the factory, eliminate unnecessary processes on a large scale, integrate processes that cannot be reduced, and reduce production transfers and downtime;

On chassis structure, make the structure “integrated,” integrate the battery pack with the chassis, and use large-component units instead of many small parts for the body.

As you can see, from small to large, Tesla’s deductions are all about “eliminating intermediaries,” while its additions are all about integrating processes that cannot be removed.

Yes, the familiar “first principles.”

This Tesla-like feature has been mentioned by Elon many times, including Battery Day this time.

To sell cars cheaply, you must reduce transactional intermediaries, so Tesla goes direct; because raw materials for batteries are not expensive, optimizing manufacturing processes can keep battery costs sustainable close to raw material prices; too many parts will complicate assembly and reduce structural strength, so Tesla makes the car body into three units…

In the eyes of industry veterans, Tesla, who is dedicated to “first principles,” is sometimes unreasonable, and its simple ideas seem a bit naive and amateurish in the face of huge challenges. But every time Tesla completes the impossible, the “first principles” that drive its challenges always shine brightly.

“Simple is hard.”

Simple is not just simplicity, but the ultimate.

So what does this have to do with Tesla’s mission to “accelerate the world’s transition to sustainable energy”? Isn’t Tesla’s goal to make cars cheaper and more competitive?

Indeed, in other words, the ultimate goal is to sell more cars. To attract global consumers to buy more Teslas with cheaper and more ultimate product power.

And then? Tesla expects the “more” to be enough to transform the energy structure. When electric cars are sold enough, the production of power batteries will be larger, corresponding to the cost of power batteries will be cheaper, and then it will be possible to lower the cost of vehicles and sell more cars.

In this process, the threshold for battery cost is constantly being lowered, and the performance of the battery is constantly improving. One day, when the price of the battery is low enough that battery storage can easily be profitable, when the production capacity of the battery is far more than just cars, you can imagine a scene like this: electric cars are everywhere, and every household has energy storage stations. These energy storage points are flexible and form a new social energy system with the power grid, an energy system that can be operated by electricity alone.

And this scene can be traced back to today’s optimization of the structure of a battery cell.

After reading Tesla’s Battery Day, some people commented, “Is that it?” What I want to say is that yes, it is. Every step that Tesla takes is based on the optimization and improvement of basic science and process technology, and it has been practicing the first principle from the very beginning, promoting high performance at the same price for electric vehicles and fuel vehicles, and promoting the development of sustainable energy.

That’s it, Tesla has always been Tesla, and has never changed.

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This article is a translation by ChatGPT of a Chinese report from 42HOW. If you have any questions about it, please email bd@42how.com.