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Text｜Han Yongchang

Editor: Li Qin

Apple's 10-year long race to build a car ended in failure, causing global sympathy. Tesla, the world's largest car company by market value, also has a similar "Titan" project, which is the 4680 large cylindrical battery.

According to 36Kr, Tesla has invested $3 billion in the project over five years since 2019, a "rarely large-scale project in the company", but it has not yet been mass-produced. As the core component of electric vehicles, Tesla hopes to lead the industry through the research and development and application of 4680 batteries. But obviously, this wish has not been realized.

In Musk's drastic layoff plan, the 4680 battery project naturally became the hardest hit area, "from 1,600 people to only 1,000 people left." There were even rumors in the industry that Tesla wanted to abandon this technology, and the storm was brewing.

But unlike the script of Apple Car, Tesla's 4680 large cylindrical battery has ushered in a turning point.

Several engineers close to Tesla told 36Kr that the latest task of Tesla's battery team is to mass-produce the fully dry 4680 large cylindrical battery by the end of the year. "There are already cells being installed in vehicles for testing. We will start mass production in the United States, followed by European factories."

Battery costs have become the biggest obstacle to profitability for electric car companies. Tesla's 4680 battery is naturally seen as an opportunity for car companies to control their own lifeline. Following Tesla, domestic and foreign battery manufacturers are actively making plans. At its peak, NIO planned a production capacity of 40GWh.

But today, most companies have already given up. A person from a battery factory said, "Overseas car companies will come to exchange ideas, but domestic car companies are not interested at all."

The continued price war in the auto market has dampened the industry's enthusiasm, and the market is no longer willing to pay for new technologies. Amid the depression, Tesla's quiet breakthrough seems to be a source of hope.

Tesla's dry electrode technology can not only be used in 4680, but is also the ultimate production method for future solid-state batteries.

This technology can shorten the entire production line by about 100 meters, which is close to the length of a football field. Industry insiders told 36Kr that the positive and negative electrodes are all manufactured using the dry method, which can save 2-3 cents per watt-hour of battery cell price.

What does this mean? The lowest price for a square lithium iron phosphate battery cell is currently 0.32 yuan per watt-hour, of which the BOM cost, manufacturing cost, and labor cost total 0.28-0.3 yuan. The savings from Tesla are already the profits of most second-tier battery manufacturers.

China is the country with the most complete power battery industry chain and the richest technology in the world. However, Chinese battery companies are struggling to reduce costs at the moment, and no one has noticed that Tesla is already one step ahead of Chinese companies in the field of large cylindrical batteries.

This step may take several years to cross.

"Tesla has found the "silver bullet" by overcoming the dry electrode"

In 2019, Tesla announced that it would acquire the US startup Maxwell, which owns a core patented technology - dry electrodes, for a 55% premium of US$218 million.

Musk saw the great potential of this technology and used it to manufacture the electrodes of 4680 batteries.

The traditional wet process requires mixing the powdered materials of the positive and negative electrodes with toxic solvents, preparing a slurry, and applying it to the corresponding foil. It is then baked in an oven up to 100 meters long to remove moisture before the electrode is finally formed.

Tesla uses a dry process that mixes the positive and negative electrode powders with a special binder and presses them directly onto the foil. This way, no water is involved in the entire process, eliminating the drying step.

Tesla estimates that compared with the wet method, the dry electrode process can reduce costs by more than 18% and equipment investment by 41%. Some equipment manufacturers also told 36Kr that if both positive and negative electrodes are manufactured using the dry method, the price of the battery cell per watt-hour can be saved by 2-3 cents.

The first key step in manufacturing dry electrodes is to mix the powder materials of the positive or negative electrode. The mixed powder needs to be completely uniform, which is where the difficulty lies.

An engineer close to Tesla told 36Kr that if you make a bucket of powder, the results of the first and last scoops are completely different. The results of the powder after two hours or eight hours are also different. If the mixture is not even, the electrode is almost unusable.

The more difficult step is rolling. The traditional rolling process uses rollers to compact the dried electrode sheets, which can ensure the performance of the battery cell.

Tesla used graphite material for the negative electrode, which is soft and easier to press, and quickly achieved mass production. However, the positive electrode is made of very hard metals such as nickel and cobalt, which is equivalent to pressing fine gravel into a smooth mirror surface. The difficulty is self-evident. The dry positive electrode is also the biggest hurdle in the mass production of 4680.

The aforementioned engineer said that the equipment would be damaged if the positive electrode was not pressed carefully. "It takes 45 days to repair the equipment each time, so the progress of mass production is delayed indefinitely."

Musk's initial goal for the 4680 was to start mass production in 2021 and reach a production capacity of 100GWh in 2022. Obviously, this goal was too optimistic.Fortunately, after the efforts of the engineering team, the dry-process positive electrode technology has achieved a breakthrough by the end of 2022.

An engineer told 36Kr that the dry-process positive electrode had already produced an electrode roll (a large roll of electrode), but various problems would arise when winding it into a battery cell, such as easy breakage due to too fast speed.

Throughout 2023, Tesla was obsessed with solving all problems in the manufacture of pole pieces to make the pole rolls more perfect. But "this is an almost impossible problem to solve."

It was not until April this year that Drew Baglino, Tesla's senior vice president in charge of three electric systems, announced his resignation. Baglino was the main person in charge of 4680. After his resignation, the dry process route also underwent adjustments.

"We will still use the pole coil produced at the end of 2022 and optimize the winding process, which will make it easier to solve the problem." said an engineer.

He said that one of the problems Tesla faced before was that the thickness of the electrodes was different, which caused the foil and the electrodes to be out of the same plane when rolled. "It's like you take four pieces of paper of different thicknesses and roll them together, which can easily cause problems."

But this is not a complicated process. Existing wet process technologies also face such problems. "Suppliers have solutions, but the cost is relatively high."

The shift in technology is the key to Tesla's confidence in making the all-dry process 4680. "The task by the end of the year is to mass produce the dry process 4680. Now the cells are being installed in vehicles for quality testing." An engineer close to Tesla told 36Kr.

Of course, there is more than one technical route for 4680, and battery companies are also developing corresponding products.

"The domestic large cylinder dilemma: internal process obstacles and external semi-solid extrusion"

Tesla, known for its innovation, has still found it difficult to master the dry electrode process and can only use graphite as the negative electrode. Chinese, Japanese and Korean power battery companies have directly adopted a roundabout tactic, that is, all use mature wet technology and combine it with silicon-carbon negative electrodes to achieve mass production.

Both routes have their own advantages and disadvantages. Theoretically, Tesla's dry technology eliminates the oven stage and has more advantages in manufacturing costs, but using only graphite as the negative electrode, the improvement in energy density is very limited.

Although the manufacturing cost of mature wet process technology remains the same, it has higher energy density and better performance. The price is that the expansion problem of silicon negative electrode is difficult to solve. According to 36Kr, many domestic battery manufacturers are currently stuck in this link.

Of course, adjustments to the manufacturing process of large cylindrical batteries also bring more uncertainties.

Compared with the traditional cylindrical battery production line, the large cylindrical process requires higher coating precision. "Previously, the coating was for a single pole, and the entire surface was coated, and the two sides were aligned, but the large cylinder is a full pole, with many sides, and they all need to be aligned when coating." An engineer told 36Kr.

Full Tab Technology

This puts a lot of pressure on the equipment. The coating accuracy requirement of 4680 is a deviation of ±0.1mm, but most domestic equipment can only achieve ±0.5mm at present.

Of course, this problem is not unsolvable. "Japanese coating equipment dares to guarantee a deviation requirement of 0.1mm when signing the contract, but the price is 3-4 times that of domestic equipment," said the engineer.

This is just a coating problem. The full-tab problem is also not unanimous. Whether it is full-tab molding or collector plate welding, the methods adopted by battery companies are different.

To give a simple example, when the tab is formed, whether the flattening or cutting and folding process is adopted, small debris or burrs may be generated. If they enter the battery cell, there will be a risk of thermal runaway.

Battery manufacturing is like the barrel principle, and the shortest board determines the manufacturing yield and efficiency. Each of these problems must be properly solved before large cylindrical batteries can be successfully mass-produced.

However, due to the ongoing price war, the mass production of large cylindrical batteries has been repeatedly postponed. At the same time, semi-solid batteries with higher energy density have also begun to move towards mass production, grabbing orders from car companies.

Pure electric vehicles have always pursued energy density. Weilai's 150-degree semi-solid-state battery pack has been tested on the road live, with a range of more than 1,000 kilometers. This year, Zhiji L6 released the Light Year Edition equipped with a semi-solid-state battery, which is expected to be delivered within the year.

According to statistics from the Power Battery Industry Innovation Alliance, in the first half of this year, 2154.7MWh of semi-solid-state batteries have been installed in vehicles, which are enough to power more than 14,000 NIO ET7s.

Semi-solid batteries benefit from high energy density and have accelerated the pace of mass production. Not to be outdone, large cylindrical batteries have also joined the fast-charging camp. Battery companies such as EVE Energy, Sinovation, and Zhengli New Energy have successively released large cylindrical products that support 4-6C rates.

Semi-solid batteries and large cylindrical batteries are both new battery technologies close to mass production. There are different opinions in the industry on the attitudes towards the two.

One opinion is that after semi-solid-state batteries are mass-produced, large cylindrical batteries will be powerless to fight back. Semi-solid-state batteries have almost absolute advantages in terms of energy density and future development (all-solid-state), and the only problem is the high cost.

Another opinion is that the large cylinder has more advantages than the semi-solid state. Based on safety considerations, the large cylinder is a steel shell, while the semi-solid state is a soft package. Whether the high-nickel ternary battery in the form of a soft package can pass the new national standard of "no fire and no explosion" thermal runaway test is still a question.

But whether it is large cylindrical or semi-solid, the mass production time has been postponed in the automotive industry's ongoing cost-cutting war.

"Mass production of large cylinders requires Tesla to go all out"

In the battery industry, practicality has become the biggest advantage, and breakthroughs in new technologies are no longer as attractive as the low prices of mature technologies.

Large cylindrical batteries are also unable to reverse the trend. Automakers and battery companies that were once enthusiastic about this technology have all begun to stop, with the exception of Tesla.

"Tesla will start mass production of large cylindrical batteries using the full dry process in the United States by the end of the year, and its European factories will begin using them shortly thereafter," a person familiar with the matter told 36Kr.

Tesla has always been an early adopter of new technologies. Whether it is the use of integrated die-casting or the installation of end-to-end large models on vehicles, Tesla was the first to make breakthroughs, and many car companies followed suit. Such examples are not uncommon.

If Tesla successfully mass-produces large cylindrical batteries and uses them on a large scale by the end of the year, this cycle can be repeated.

Large-scale cost reductions in the manufacturing industry are achieved through process improvements. Tesla's dry electrode technology and the production speed of large cylinders have hit this key point.

The production speed of cylindrical batteries has now reached 300PPM (300 cells per minute). If large cylindrical batteries are calculated at this speed, the production efficiency can be almost 4-5 times that of square batteries.

Coupled with the reduction in investment in equipment and production materials brought about by dry technology, large cylindrical batteries may be limited by yield and efficiency in the short term, but the cost reduction brought about in the long run will be very considerable.

The significance of large cylinders to car companies lies more in the standardization of battery specifications. If batteries become standard products for procurement, prices will drop and car companies will have greater control over battery suppliers.

Of course, the PACK design of large cylindrical batteries is a difficult point. "Few domestic car companies have this technical capability." A battery industry engineer told 36Kr.

"The difficulty of packaging large cylinders is that there are too many welding points, but it is not a completely unsolvable problem. We can just invest money to do it. It's just that car companies don't have the money now."

The battery industry is also very nervous about this technology, especially CATL. As the global leader in batteries, CATL's production lines are almost all square battery production lines. If large cylindrical batteries are adopted by most car companies, CATL will need to change its production strategy, which is extremely costly.

Someone close to CATL told 36Kr, "Ning Wang does not seem to support large cylinders on the surface, but he has invested more money than anyone else in private."

He analyzed to 36Kr that CATL has an internal production line for large cylindrical batteries with an efficiency of about 150PPM. Based on the production line cost and the scrapped battery cells produced, the investment is conservatively estimated to be several hundred million yuan.

Tesla is attracted by the production efficiency of cylindrical batteries. The winding form of cylindrical cells is theoretically the same as the production method of toilet paper rolls. Currently, CATL's winding speed is 100 meters per minute, which is already the top level in the battery industry, while the winding speed of paper rolls can easily reach 1,000 meters per minute.

There is still huge room for improvement in the battery production process. This is one of the reasons why Musk is stubborn in developing 4680. He wants to change the traditional way of battery manufacturing, just like changing traditional car manufacturing.

According to Musk's original expectations, the 4680 battery can reduce battery manufacturing costs by about 20%, equipment investment costs by 35% and factory floor space by 70%.

This battery solution is the basis for Tesla's next round of large-scale expansion, using cheaper batteries to make cheaper cars, thereby earning more profits, and then investing in research and development and capacity expansion. This cycle will achieve Musk's grand vision: to accelerate the arrival of the electric car era and accelerate the world's transition to sustainable energy.

The large cylindrical battery provides the manufacturing basis for this vision, and it seems to be on the eve of the final leap.