「Core Tips」
The Tesla 4680 battery began mass production, and Musk did a lot of subtraction on this battery:
Eliminate the polar ears; abandon the "oven", skip the solvent, direct coating; the battery is integrated directly into the chassis.
Musk, who is supreme in the "principle of subtraction", what is his ultimate goal? What does he want to achieve with the 4680 battery?
Author | Gokuneng
Edited by | Li Xin
1. Texas Athletic Show: 4680 hangs like a sausage
On April 7, U.S. time, about 15,000 people watched the Tesla Cyber Rodeo, a celebration that opened at the Texas Gigafactory near Austin, USA.
At the event, many new gadgets were displayed, and the audience who paid attention to the power battery turned their attention to the 4680 battery.
Tesla hoisted the 4680 battery like a sausage, a group of 69 batteries in two rows, suspended in 12 columns, a total of 828 batteries, in the middle is a heat dissipation water cooling plate.
The 69 painted polar pieces, fixed at both ends and hanging down, reflect the manufacturing effect of the battery cell.
The 4680 battery structure, directly combined with the whole vehicle, the battery is surrounded by a stronger cast aluminum structured body, so integrated with the high-pressure cast aluminum lower housing.
The 4680 battery which is suspended
The 4680 battery cell was developed and produced in Flummont, produced in Austin, and the battery cell has begun mass production in April, and the production capacity can only be released in the second quarter of this year.
Tesla's new plant in Texas uses a linear assembly line, and all the processes are concentrated in a long, narrow plant.
In the era of cell to chassis (CTC), Tesla's entire factory was more efficient, and the battery factory was a piece of the puzzle.
Judging from the exposed Texas factory layout, more important than CTC, Tesla has completely reconstructed the traditional automobile manufacturing process.
Schematic diagram of the interior of the Texas plant
While traditional cars are stamped to welded to painted, and then assembled serial logic, the Texas plant is based on front-and-rear casting and CTC battery systems, and vehicle production becomes parallel and modular assembly.
This change not only brings about a reduction in production rhythm and cost, but also a revolution in the manufacturing logic of new energy vehicles: sub-module iteration, heterogeneous platform integration.
All links in the entire industry chain have been included in the scope of Musk's rethinking.
In front of Musk, tradition is just an object of change, just like the birth of the 4680 battery, everything is the embodiment of the "first principle", the embodiment of the "subtraction principle".
2, the scale effect has risen, but the brand has not yet risen
The name 4680 is a simplified version.
Power batteries are divided into three main categories from the shape: cylindrical, square and soft bags. Among them, the 4680, like the 18650 and 21700 batteries, is a cylindrical battery.
18650 and 21700, 18 (mm) and 21 (mm) represent the battery diameter, 65 (mm) and 70 (mm) represent height, and the last 0 represents the cylinder.
The 4680 is also named this way. 46 (mm) is the diameter of the battery, 80 (mm) is the high, 0 represents the cylinder, which is habitually omitted by industry insiders, so it is referred to as 4680.
Knowing this, you know that the 4680 is larger than the 18650 and 21700 heads.
A single 18650 battery cell has a volume of 16541 cubic millimeters; the volume of the 21700 is 24245 cubic millimeters, and the volume of the 4680 is 132960 cubic millimeters.
Thus, 4680 is equivalent to 8 18650 large, equivalent to 5.5 21700 large.
Wang Feng, chief engineer of Hangzhou Botan Science and Technology Engineering Co., Ltd., pointed out that 4680 has advantages in the volume energy density of cylindrical products, but it has no advantages compared with square batteries such as blades.
"A square can fill the box completely, but 4680 can't." Wang Feng told Super Source Force, "You take 4 round cups and squeeze them together, you look at the gap in the middle, you will understand." ”
Wang Feng told Super Source Force that 4680 has reached its limit, "I don't think Musk will expand its volume anymore, because there is no way to expand." ”
Although the cylindrical battery, the 4680 is a large one, but compared with the square battery, it is still small and has an advantage that is often overlooked.
Wang Feng used tiles as an example to illustrate the volume advantage of 4680.
"Like the floor tiles, compared to the small bricks, the big bricks are expensive and inconvenient. For example, 1 meter × 1 meter brick, it is very troublesome to paste, it is inconvenient to carry the sticker, and it is easy to damage in the middle, which will increase the cost. ”
Compared with batteries such as square blades, 4680 single batteries are only equivalent to a few percent of a blade battery, which is easy to install, cheap to replace, and the scrap rate will be reduced.
3, 4680 optimization: throw away the polar ear to become the infinity ear
The 4680 battery structure, first of all, reduces the polar ear.
The polar ear is the protruding part of the positive pole of the battery, which is the round point of the dry battery. This place is the place where the battery is most prone to overheating when charging and discharging. Heat cannot be controlled, and battery manufacturers cannot make large batteries. Because the larger the battery, once burned and exploded, the more powerful it is.
Since Ji Er is disobedient, throw it away.
That's what Musk told his battery program leader Drew Baglino.
The advantage of the 4680 is the use of electrodeless ear technology, or full polar ear technology.
Infinity Ear 4680
"What is the equivalent?" It's like there's a toll station in the middle of the highway, and now the toll booth has been dismantled, so that the vehicle is 8 lanes in both directions everywhere. Wang Feng said.
Electrodeless ear technology allows electrons to run shorter between the electrodes.
"In a blade battery, a meter long coat is wound around, and the distance the electron actually runs is longer. The electrons in the 4680 only run 80 mm. Wang Feng explained that 4680 is a breakthrough in technology, not a breakthrough in materials. And the polar ear can not be solved, forever exists, Tesla is to turn the polar ear into a large piece, called the full polar ear.
Without polar ears or full polar ears, how does the 4680 battery work?
The flow of electrons is like a group of people crossing a bridge, the polar ear is equivalent to a bridge, when everyone passes through a bridge, the bridge has to bear a huge load, the load can be understood as the heat generated by the resistance.
The infinity ear design is equivalent to tearing down the bridge, filling in the bottom of the bridge, and the crowd walking to the other side, no different from normal walking.
In layman's terms, it is from point-to-point transmission to face-to-face transmission, the electron conduction area becomes larger, the transmission efficiency becomes higher, the generation of pole ear overpotential is avoided, and heat accumulation is reduced.
The polar ear itself also has a resistance, and removing the polar ear is equivalent to solving a part of the heat source.
It is precisely because the heat generation of the 4680 battery is controllable, and it can improve the charging current and improve the charging efficiency, Tesla can let go of the big battery.
Overall, the advantages of the electrodeless ear are: the electron movement path is shortened by 5%-20%, the internal resistance is reduced by 5-20 times, the electronic offset and overpotential phenomenon are significantly reduced, and the battery life is improved. The contact area between the conductive coating and the battery housing reaches 100%, dispersing the heating area.
How the infinity posterior ear electrons work
However, this is also the difficulty of the 4680 mass production line.
"Just like two pieces of paper, you have to fold it back, and the negative electrode can't be short-circuited." Wang Feng pointed out that the bipolar ear becomes a non-polar ear, which is technically an innovative point, and it may be glued through a glue or welded. "Fold back round and round, to ensure the sealing of the battery, can not be short circuit, this is its process difficulty."
Wang Xin, an engineer at Jianghuai Automobile R&D Center, believes that the electrodeless ear of 4680 is indeed difficult to engage in, and the process level is higher. Domestic general battery manufacturers may not be able to take it down, including laser welding and other troubles.
4, 4680 process: abandon the oven to skip the solvent direct coating
Subtraction, much more than the polar ear.
Typically, manufacturing batteries requires starting with a large amount of electrode powder, mixing them with water or solvent to form a large amount of slurry, and then coating it on metal foil to form electrodes. Therefore, the electrodes must be dried in a huge oven and then the solvent removed.
Musk's battery project will be Drey Baglino directly announced: the company will abandon the oven, skip the solvent step ... Directly from dry mix to coating.
The above method of 4680 battery actually inherits the dry electrode technology.
Tesla is prepared for this.
Back in 2019, Tesla acquired Maxwell, the world's leading battery technology company, and used the dry electrode technology it developed for the 4680.
Tesla's 4680 battery is much like a dry battery.
Wang Feng, chief engineer of Hangzhou Botan Science and Technology Engineering Co., Ltd., believes that Tesla 4680 follows the idea of dry batteries and is pursuing standardization.
"Dry batteries have undergone more than 100 years of development and achieved battery standardization, and the difference is only in the coating materials." Wang Feng pointed out that the biggest advantage of 4680 is standardized production, because mass production can control the defect rate of finished products.
Therefore, whether it is to improve the capacity of the battery cell or to use the electrodeless ear technology, the original intention of the 4680 is still to solve the problem of large-scale production of batteries. Wang Feng told Super Source Force that the core problem of 4680 is that the process process is simple, and the goal is to produce and use it like the No. 5 dry battery.
The thickness of the electrode material of the 4680 is increased from 55 microns to 60 microns, which increases the activity of the electrodes, increases the energy density by 5%, and prolongs the cycle life of the battery.
Saves solvents and the 4680 costs less to make.
5, 4680 on the car: the battery is directly integrated on the chassis
The 4680 gets on the car, reducing the traditional battery pack link and integrating directly into the chassis.
The battery packs commonly used in electric vehicles are composed of multiple modules, and each module is composed of a single battery.
4680 battery module suspended
For example, the battery pack of Model3 consists of 2 large and 2 small total of four modules in series, 25 series battery modules in large modules, 23 series battery modules in small modules, each series battery module consists of 46 21700 single cells in parallel, and four groups total 4416 single cells.
The total weight of the entire battery system is about 474 kg, of which the battery weighs about 312 kg, the upper housing, battery manager and other accessories weigh a total of about 53 kg, and the lower housing, structural parts, cooling lines and cables weigh about 62 kg. The total area of the four battery modules is about 2.7 square meters, and the energy density is 170Wh/kg.
21700 battery pack on Model 3
The 4680 battery pack eliminates the module design and integrates the battery and chassis directly. This integrated technology is CTC (Cell to Chassis), which integrates the entire vehicle body.
Wang Feng pointed out that battery technology involves manufacturing process and cost, first deformed to modules, and then to moduleless technology (CTP, Cell to Pack).
CTC technology is similar to the CTP principle, which essentially reduces the components of the battery pack to improve the battery integration efficiency, reduce the weight of the battery pack, improve the energy density, and increase the cruising range.
Using the 4680 battery pack of CTC technology, the 960 (40X24) cells are directly arranged with an energy density of 215Wh/kg.
The area of the 4680 battery pack is about 2.57 square meters, which is 5% less than the area of the 21700 battery pack. The total weight of the entire battery system is about 438kg, the total weight of the cooling system and the battery is 348kg, and the battery manager, upper and lower housings and cables are optimized to weigh about 90kg. The 4680 battery pack weighs less than the Model 3 battery pack.
Compared with the two, the 4680 battery pack has a 15% increase in capacity, and it is easy to have a 100kwh battery capacity.
The 4680 CTC redefines the battery layout by integrating a triple-electric system that saves 370 parts, reduces body weight by 10 percent, and reduces battery costs by 7 percent per kilowatt-hour.
Tesla's earliest patented technology is no welding into groups, which is very similar to dry batteries, and it can be used with a card inside.
"To do Pack into groups, you also need technology, 4680 if a card is ready to use, or talk about a fart technology? What more bikes do you want? Wouldn't it be enough to tuck it in? Can blades do that? Can't do it. Wang Feng said.
The 4680 thus reduces the number of batteries used in a single vehicle.
The single battery used in one vehicle has been reduced from 4416 to 960. The direct benefit of this reduction is that the 4680 is better than the previous battery consistency.
In general, battery charging and discharging have a cut-off voltage, the battery pack to charge the cut-off voltage or discharge cut-off voltage to work, once there is a battery suddenly show full or suddenly no power state, the battery pack's battery management system will be adjusted, which is the consistency adjustment.
Is the 4416 cell consistency of the 21700 battery pack better tuned, or is the 960 cell of the 4680 battery better tuned? The answer is obvious.
6, Musk 4680 subtraction: the ultimate goal is to run to the standard and after-sales
After these subtractions were done, Musk called the 4680 a "structural battery."
Musk did so much subtraction, why on earth?
"He understands things more thoroughly: only standardization can be mass-produced, if the battery is broken, is it cheaper to replace the broken 4680 battery after the system detects it?" Wang Feng said that as soon as the blade battery cell is broken, it is necessary to replace a large one, and the cost of replacing the module is higher.
Wang Feng believes that in fact, all of Musk's subtractions are headed for the ultimate problem: for after-sales.
"What's the difference between steamed buns and bread?" It makes no difference, it's all about filling your stomach. Wang Feng said that the warranty period of Chinese vehicles is long, and the core problem of enterprises is: what you sell, you have to sell after.
"You can't say that after 8 years, this car will not be repaired if it is broken." Wang Feng pointed out that even if the battery factory no longer exists, because the product is standardized, the car manufacturer does not have to worry about after-sales maintenance.
Musk wants to be a worldwide standard product, and this standard product must be tested and recognized by the market for a long time.
A battery expert who did not want to be named told "Super Source Force" that the development of power batteries for more than 30 years, domestic companies had to do something different from others: at that time, in order to change oil to electricity, the car factory required battery factories to develop a variety of strange batteries, but this battery can not achieve the general purpose in a broad sense.
Wang Feng also believes that Tesla's choice of cylindrical batteries, at least 30 years of process technology support, is more mature, "not random innovation."
The key is that the mass production of batteries must achieve a certain yield rate.
The latest news is that Tesla's 4680 yield rate in Texas has reached 90%, and the yield rate at Austin factory has sometimes reached 93%.
A battery expert who did not want to be named told Chaoyuanli that the yield rate of cylindrical batteries reached 90%, which is relatively easy to achieve.
Why didn't Musk choose a solid-state battery as a breakthrough?
According to Wang Feng, in industrial products, especially in the automotive field, very mature plates are needed to try. Under normal circumstances, car companies will not try and make mistakes.
The latest Japanese intelligence shows that Japan's solid-state batteries already have the ability to mass-produce, but the process is more complex, and large-scale use in automobiles requires a process, which cannot be done in the short term.
"Japan's solid-state battery technology is basically stable, but who dares to put it on the car for large-scale use?" Wang Feng said, "As soon as a problem occurs, it will be recalled, how much does it cost?" Who can stand it? ”
Therefore, he believes that solid-state battery technology, with and mature, are two different things.
"Under such circumstances, the original material system of 4680 is more stable and less risky." Wang Feng pointed out, "Musk used the lowest cost to solve the most difficult problems. ”
7, five-step process method: Mars attaches the most importance to the reduction process
In fact, Musk has been doing subtraction.
When Musk once took people on a tour of his rocket factory, he repeatedly emphasized: reduce the process.
During a tour of the starship base, Musk said that while I was often asked what kind of rocket engine was designed, the basic design of the engine was done in the former Soviet era.
Next, Musk divides the manufacturing process into 5 stages:
The first is to define the main issues, the second is to cut the process, the third is to optimize, the fourth is to continuously increase the speed, and finally the automation to deal with mass production.
Musk says adding something that may be needed is not good. He stressed the importance of the cut process in No. 2.
According to Musk, when developing reusable rockets, many people suggested many functions, but most of the results were useless.
Musk said bluntly that if something is missing that is really needed, it can be added later, but if it is only added without modification, it means that the entire process has not been fully reduced, and there must be excess.
Tesla has existing failure cases in the principle of reduction.
Tesla has installed fiberglass liners on the upper part of the battery box of pure electric cars, and invested a lot of money to automate the process.
Musk has since asked technicians: Why is this padding needed?
The person in charge of battery safety answered: For the prevention of noise and vibration.
The person in charge of noise and vibration immediately replied: it is used to prevent fires.
Two departments, given different reasons.
Musk asked for testing and came to the conclusion that the padding was not needed.
This is not adhering to the principle of subtraction, resulting in too much waste.
Looking back at Tesla's 19-year history, Musk has been staying in for 18 years, and he has been using the following routine to advance the principle of subtraction:
1) Start by setting an impossible goal to leapfrog
2) Internal disagreements are constant, and various rumors of failure are frequent
3) The team worked hard
4) Approach the target
5) Achieve disruption
In electric vehicles, Musk still uses this routine.
It has set the goal of reducing battery costs by more than half and building a $25,000 electric car.
His team, following this path, is running towards the goal he has set.
8, when the technology encounters obstacles: Musk will also speak softly
The principle of subtraction is challenging, difficult, and often encounters obstacles.
For example, the coating process used by the 4680 is to apply the material directly to the metal foil.
Polar pieces that have been coated
The coating must be smooth and uniform. To do this, the coated foil is squeezed by huge rollers in a process known as "calendering".
Musk has said that the slurry passes through the drum and is flattened like pizza dough, but very hard.
Musk's metaphor is apt because calendering is a regular part of battery production, like rolling a pizza dough. But for the 4680, calendering didn't work at first.
When the electrode becomes larger and thicker, the cell area increases, the defect rate increases, and when the cathode is thicker, more pressure must be applied to make the metal particles flat and smooth.
The 4680 uses nickel-manganese cobalt or nickel-cobalt aluminum materials, and when the battery is calendered, it will face a battlefield of broken particles.
Faced with difficulties, Musk said that during the calendering process, the calender rollers were dented, and he and his team "did not anticipate this."
Baglino argues that this is not a scientific problem, it is an engineering problem. It's not a question of whether it's a question, it's a question of when.
In the face of difficulties, Musk is not 100% confident.
"We have a spare plan for a non-structural battery pack and a 2170," Musk said, leaving room for it, "and we don't want to overemphasize the dry cathode, maybe a 10 percent or 15 percent cost improvement or something like that." ”
Musk added: "10% is still not to be underestimated, especially the production of hundreds of GWh batteries per year. ”
The latest public information shows that Tesla's above problems may have been solved.
Data shows that Tesla has produced more than 1 million 4680 batteries. However, these quantities are far from enough to install the demand, because 1 million 4680 batteries loaded with Model Y can only roll off the production line of 1041 vehicles.
In addition to removing the output, the 4680 battery still needs to "put aside the advertisement to see the efficacy".
Wang Xin analyzed that the 4680 battery is not a subversive product. From the perspective of car companies, Tesla competes with other car companies and needs a competitive weapon. Secondly, Tesla's self-produced batteries play a leading role in the market, and other battery manufacturers do not want to be outdated in the technical route, do not want to be abandoned by Tesla, and choose to follow up on the bet.
Wang Xin believes that compared with the 4680 battery, Tesla's real selling point is its intelligence, and this idea for the entire industry will be subversive.
From the moment Musk stepped into the car-making field, he vowed to build "cool cars."
Build a cool car, the way is not smooth.
According to biographer Higgins, tesla cars, with their doors closed and windows broken, made terrible screams when they got on and off the car. Automotive data company JD Power also announced in 2106 that Tesla was the worst of the luxury brands and the worst in the industry as a whole.
Higgins asserted at the time that Musk himself was gambling and that "it was a century of bets."
But with the listing of Model3, ModelS, ModelY and so on, sales data is tilting towards Musk.
At least for now, Musk has won halfway.