The Real Reason Tesla Developed The 4680 Battery..

Today, let's talk about the Tesla 4680 battery cell. This is a technology that we mention often, I know, but we're usually just glancing over it while we try to make a point about a larger subject. And that's not great, because the 4680 is a really complex and nuanced invention that often gets misunderstood or not explained properly, which I know we've been guilty of and other folks on YouTube have definitely been guilty of, big time. Is it really a game changer? Well, yes, but the reason goes a bit deeper than just endlessly repeating all of the information from last year's battery day slideshow. So here is our best effort to explain the real reasons why Tesla's 4680 battery is such a significant invention and how it stacks up against the rest of the battery industry. Let's get going. So the real story of the 4680 begins with its form factor. This is a size and shape of battery that no one else has tried to make before. In case you're not familiar, the 46 refers to 46 millimeters in diameter and 80 refers to a length of 80 millimeters. That's 1.8 inches diameter and 3.15 inches in length for our American homies who don't do metric. It's a chunky battery, even bigger than those old D cell batteries that we use to cram into big-ass flashlights and boom boxes and stuff. Those are 33 millimeters or 1.3 inches in diameter. It should also be pointed out that most electric cars do not use cylindrical battery cells. Tesla was always a bit different with this approach. For the first Roadster, the they used a 1865 cell, probably because at the time they were the cheapest and most readily available battery that would suit their needs. Anyone can just buy these things off the shelf and the 1865 batteries with nickel, cobalt, and aluminum chemistry have incredible energy density. Tesla continues to use this cell form factor, but with a customized and refined chemistry. They still use 1865s for their top-tier Model S and Model X vehicles, including the Plaid Edition that is currently the fastest accelerating production car in the world. For the Model 3 and Model Y, Tesla developed a new battery cell with Panasonic, the 2170, just a little bit bigger version of what they were already working with. Those are amazing batteries. They've powered the vast majority of Tesla vehicles made from 2018 onwards and have allowed Tesla to ramp up their production capacity from tens of thousands per year to 1 million cars per year. Using the larger battery cells in smaller packs on the Model 3 and Y allows for higher volume. The 2170 has since been adopted by high-end EV startups Rivian and Lucid as their battery of choice, though those companies only build like one car a day, so they can hardly be looked at as competition right now. Still, the majority of other electric cars on the road don't use cylindrical cells. They use a prismatic or large pouch design, which is a rectangle shape. In many ways, the rectangular cell is better for electric cars. You can store more energy density in a cell, but the rectangular ones have always been capable of a higher power output. Those are two terms that we should try and lock down. Energy is best thought of like the storage capacity of a battery, how much it can hold within the cell, and the power is the output, how fast that energy can get out of the cell and into the thing that is being powered, and those factors have a lot to do with what is inside the battery. Inside a cylindrical cell is something called the jellyroll. That makes it sound like something squishy, but the jellyroll is just thin, solid strips of metal layered on top of each other and rolled up very tightly. The outside sheet is a cathode, the inside sheet is an anode, and there is a layer of liquid electrolyte and graphite in between. We'll get to the electrolyte in a bit, but for now, we'll just focus on the cathode and anode. In a regular cylindrical cell like the 2170, there is a tab attached to one end of the cathode and a second tab attached to the opposite end of the anode. These are your positive and negative terminals. The cathode is the positive terminal. This is your conductive material, usually nickel and cobalt with either aluminum or manganese and coated with lithium. The anode is the negative terminal, and this is going to be a sheet of copper. These layers of metal are very thin and surprisingly long. If you were to unroll a 2170 cell, the cathode would be around 800 millimeters long or 31 inches, about the length of your arm. The thinner these layers are, the more surface area is present and the more energy storage capacity there will be. The downside with these long rolls, however, is that the electrons will have to traverse that whole 800 millimeters between the two tabs, and that reduces your power output. So the 2170 versus the 1865. The smaller 1865 cells have less surface area for energy capacity, but because they have a shorter distance between the tabs, they can get the power out of the cell faster, and that is very likely the reason that Tesla still use them for the top tier vehicle platforms like Model S Plaid with its earth shattering acceleration. The rectangular pouch design battery that you'd find in other electric cars or inside your cell phone or digital camera and all other kinds of devices, those have higher power output because instead of having the anode and the cathode all rolled up, they use multiple layers all laminated on top of each other. And that means a short trip for the electrons between the tabs, which can now have both positive and negative on the same end of the battery. So knowing all of that, we can loop back to the 4680 and start to figure out just how it manages to come up with five times the energy and six times the power of a 2170 cell. The 4680 has five times more energy capacity simply because it has roughly five times more size. Nothing really revolutionary there. If Tesla had said five times more energy density, then yes, that would be a groundbreaking development. But all they've done is make the jelly roll much longer inside that fighter battery, and therefore there is more surface area on the roll, and therefore it will store more energy. This is a common confusion, and I hope that sorts it out. I've definitely screwed that up in the past just from not taking the time to understand what these words mean. What is groundbreaking here is the power of the 4680 that's increased by six times over the 2170. Even though we just said that a longer jelly roll actually makes it harder to get the electrons out of the cell because they have to travel so far over the physical surface between the tabs. So how could Tesla possibly get six times more power out of a five times larger cell? They solved the problem by going tabless. Inside the 4680, the electrons don't have to travel the length of the jelly roll. They only have to travel the length of the cell itself, which is just 80 millimeters. But how does that work? The secret is the copper shingle design that we see in the renderings of the cell interior, that mesmerizing swirl of copper. There can be a bit of an optical illusion going on here. It kind of looks like a tunnel, but this is the flat end of the battery. If you remove the cover from the negative terminal of the 4680, this is what you would see. What they've done is made thousands of tiny cuts into that copper sheet to actually make thousands of little tabs on the anode. And they're all folded in towards the center, making contact between each roll of the copper. So now the electrons do not have to travel around and around in a spiral shape. They have a constant bridge across the diameter of the negative terminal. So the longest distance that they ever travel is down the length of the cell to the positive terminal. This is how Tesla created the five times reduction in the electrical path. Okay, that got a bit dense with information there. Hopefully everyone is still following along. I tried to explain this as simply as possible while still being accurate enough. There's obviously a ton of complex science ---- going on inside a battery that would never fit into a relatively short video. So bear with me. Now, much has been made of how the 4680 admits no competition for other batteries. And that's a very catchy title for a video. But again, it's an oversimplification of a very complex idea. We're going to try and bring just the right amount of simplification to the table here. So with the 4680 versus the 2170, the biggest advantage to the new cell is manufacturing efficiency. They're making one big cell instead of five smaller ones. And from what we understand, Tesla can now make one 4680 faster than they can make a 2170 due to advantages like not having to stop and weld in the little tabs anymore. That's a big win when we remember that battery cell supply is the single biggest bottleneck in electric car production. The semiconductor shortage will pass, but lithium ion batteries will continue to be a challenge for EV makers. Tesla will be making more cells faster and getting five times more out of each single cell that they make. When it comes down to the product level, the actual car and consumer experience, the 4680 cell itself doesn't make much of a difference. A bit more power and 16% more range, nice to have, but not nearly enough of a difference to make anyone think this is a huge game changer in all caps. The win to the car buyer comes when the 4680 is integrated with the structural battery pack. That's the part that actually changes everything. Also in all caps, Tesla has taken the design concept of an airplane wing that serves both as a fuel tank and a part of the structure, and they've applied that to a battery pack. It's the battery and the frame at the same time. The 2170 cell has to go into a module and the modules go into a pack and the pack goes into the frame. The 4680 goes from cell to pack and the pack becomes the center frame. Then front and rear giga castings get bolted on and you have an entire vehicle underbody in three big chunks. This new design is less complex, more efficient, and lighter weight. Tesla claims a 10% reduction in mass and 370 fewer parts and that in itself offers a 14% increase in vehicle range. Now we've got 16% plus 14% and now the 4680 equipped Tesla has gained 30% more total range over the same vehicle with 2170s. It also makes the car stronger, more stable, and safer in a collision, but your average car buyer isn't going to pay attention to that. They're just going to see 100 miles more range and that's what's going to get them stoked on a new Tesla. Then there are solid state batteries. This is another one where people tend to get confused. There is a common opinion that the 4680 is so amazing that solid state batteries are pointless. That's not the case. The idea of a solid state battery in electric cars would unlock a ton of potential. Lighter weight, greater efficiency, faster charging times, and greatly increased safety. It has a lot of promise to be the next big thing in battery design. So remember we talked about the anode and the cathode inside the battery cell? Well the thing that separates those layers is an electrolyte. In a lithium ion battery this is a liquid electrolyte solution that allows only the lithium ions to pass through from positive to the negative terminals. But like any other liquid this electrolyte layer is sensitive to temperature variations. You might have seen a battery that has swollen up in the middle or maybe even leaked out some of the electrolyte fluid. That is bad. If the electrolyte evaporates or leaks out there can be a short circuit between the anode and cathode that can lead to a fire or an explosion. If that starts happening under the floor of your vehicle then you are about to have a very bad day. So in short moving to a solid electrolyte would make life a lot less dangerous in an electric car. But it also means that the batteries can be made much smaller and more energy dense at the time which we know is impossible to do with lithium ion chemistry. And we also get the benefit of faster charging and higher power levels without ever having to worry about degrading or evaporating that liquid separator. It's great. The only problem is the solid state batteries are proving to be very hard to manufacture. People have been trying to solve this problem for over 40 years now. Duracell started working to crack the solid state battery formula in 1978 and even today we're still coming up short figuring out how to manufacture this design. Even with Toyota, Volkswagen, and General Motors all betting on solid state as the revolution that allows them to level up their electric vehicle platforms we are not there yet. The best estimates seem to say maybe in a year or so we might have a working prototype for solid state but then how long after that before mass manufacturing becomes possible. Tesla has spent over a year just working out the kinks in their own battery cell production line and that's why Tesla is winning with the 4680 because they are actually manufacturing this battery cell right now. Elon Musk is smart enough not to pin his hopes on a technology that might come to market someday in the future. Tesla is making the best battery that they can with what they have available at the moment. If something better comes about in the future then Tesla can pivot but in the meantime they are rocketing ahead while most other automakers are standing still and that's what makes them such a fun company to talk about. Hopefully you've had just as good of a time listening and more than anything we hope that you've learned something today or at the very least come away with a more solid understanding when it comes to EV batteries. As always let us know what you think in the comment section below. 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