In mid-to-late February, a piece of news caused a stir in the new energy vehicle industry - Tesla is working with CATL to develop "cobalt-free batteries", which may be used in domestic models ?3 models. It directly caused several listed companies with cobalt-related businesses to fall directly to the limit, but for consumers, they may not understand the profound meaning behind this news.
So, what exactly is a "cobalt-free battery"? Does it really matter?
What is a cobalt-free battery?
Here is a brief introduction to science. The power batteries used in pure electric vehicles are divided into several categories according to different cathode materials. The two most mainstream technical lines in the market are "ternary lithium batteries" and "iron phosphate". Lithium battery. The separators, electrolytes and negative electrode materials of these two batteries are basically the same. The only difference is the positive electrode material.
From a broad perspective, batteries that contain cobalt in their cathode materials can be called "cobalt-containing batteries", and batteries that do not contain cobalt in their cathode materials can be called "cobalt-free batteries." Battery".
From a narrow perspective, "ternary lithium" refers to a polymer containing three metal elements: nickel (Ni), cobalt (Co), manganese (Mn) or aluminum (Al). Among them, the C in "NCM" and "NCA" represents cobalt element, so they all belong to "cobalt-containing batteries"; and the positive electrode of lithium iron phosphate battery is an olivine structure LiFePO4 material, so we usually think of "cobalt-free batteries" 』It is lithium iron phosphate.
Why use cobalt-free batteries?
Going further, why did Tesla suddenly switch to "cobalt-free batteries"?
In fact, Tesla has been working to reduce the use of cobalt over the years. In 2009, Tesla used lithium cobalt oxide batteries in the Roadster. In 2012, the amount of cobalt used in Model S was 11 kilograms per vehicle. In 2018, on Model 3, the amount of cobalt used was 4.5 kg/car. Until now. In 2020, Tesla plans to make cobalt-free batteries. The use of cobalt is gradually decreasing, and the ultimate goal is still due to "cost".
We all know that the core component of electric vehicles is the three-electric system. Among the three-electric system, the cost of the battery is the highest, accounting for 35%-40% of the cost of the entire vehicle; among the ternary lithium batteries, the cost of cobalt materials is the highest, accounting for 30%-40% of the cost of the entire battery pack. %. In lithium iron phosphate batteries, the cathode material only accounts for about 13%-15% of the battery cost.
At the 100-person meeting on electric vehicles held in the world some time ago, Ouyang Minggao, an academician of the Chinese Academy of Sciences, mentioned that the current cost of power batteries for new energy vehicles is between 0.6 and 1.0 yuan/Wh, with the lower limit It is a relatively cheaper lithium iron phosphate battery, and the upper limit is the higher cost ternary lithium battery. By replacing cobalt-free batteries, Tesla can continue to reduce costs and increase volume.
Using "cobalt-free batteries" not only reduces prices, but also stabilizes prices and supply. Because cobalt is typically a byproduct of copper or nickel mining, it is susceptible to fluctuations in demand and prices for these metals.
In addition, what is easily overlooked is that Tesla and CATL are actually getting rid of the shackles of core suppliers by adopting new battery technologies. Before this, we all knew that Tesla and Panasonic had established a very close cooperative relationship. However, when the Model 3 production capacity was ramping up, Panasonic's battery supply speed was criticized many times by Musk, and there were many "scandals." . In other words, when there is only one most critical core supplier, it is a huge risk for Tesla's production and manufacturing.
Increasing suppliers, developing new technical lines, and putting eggs in different baskets is a smarter solution in business competition. Just as the author was writing this, new news came out that Tesla is preparing to produce its own batteries, which also supports this speculation.
Interestingly, when the outside world speculated that Tesla would jointly develop a new generation of lithium iron phosphate batteries with CATL, "Tesla Shanghai Gigafactory" replied to netizens on Douyin saying : "Please pay attention to Tesla's battery launch in April. Cobalt-free does not mean it must be lithium iron phosphate." The comment was subsequently officially deleted. This makes us more curious about the cooperation between the two.
However, whether it is the route of using cobalt-free lithium iron phosphate batteries, or using NCM811 high-nickel batteries to advance to NCMA (nickel cobalt manganese aluminum) quaternary batteries, and gradually process them in the process route of other cladding elements instead of cobalt. This is a good thing, because:
For Tesla, cooperation with domestic power battery giant CATL can further reduce costs, improve efficiency, and increase battery supply channels. It can also ensure that the Shanghai factory is not restricted by battery bottlenecks, killing two birds with one stone.
As far as the new energy vehicle market is concerned, the cooperation between Tesla and CATL may further reduce the manufacturing costs of domestic Teslas, thereby continuing to explore the price space of domestic Teslas, and further Activate the domestic 250,000-class electric vehicle market.
BYD and Tesla thought of working together
Coincidentally, one month before Tesla's announcement, BYD also announced the launch of a new "cobalt-free battery" - super phosphoric acid Lithium-iron batteries are also officially called "blade batteries".
What is a blade battery?
The so-called blade battery refers to the "long battery solution" (mainly refers to the square aluminum shell), a battery that increases the length of the battery (flat Longer design), arranged together in an array, inserted into the battery pack like a "blade" to improve the battery pack integration efficiency. It does not refer to a specific size of battery cell, but can be made into batteries of different sizes based on different needs. The general principle is as follows:
By using blade batteries, the energy of BYD's lithium iron phosphate battery The density can reach 180Wh/kg, which is about 9% higher than before, while the volumetric energy density can be increased by 50%. At the same time, by changing the internal mechanism and other technologies, the unit cost can be reduced by 30%. According to BYD officials, the battery life of the new Blade can reach more than one million kilometers.
BYD officially announced that the "Han" will be the world's first model equipped with a "blade battery" and is expected to be launched in June this year.
What are the advantages of iron batteries?
The special thing about the blade battery is not only the new battery arrangement structure, but also the important point is that it is a lithium iron phosphate battery. This is also a decision that goes against the trend in the market where ternary lithium battery solutions have become popular.
BYD chose it because of its several advantages.
First of all, the P-O bond in the lithium iron phosphate crystal is stable and difficult to decompose. Even if it encounters high temperature or overcharge, it will not collapse and generate heat or form strong oxidizing substances like cobalt batteries. Therefore, Lithium iron phosphate batteries inherently have better thermal stability and are less likely to spontaneously ignite even if they are damaged by collision.
Ternary lithium with worse thermal stability frequently spontaneously ignites
Secondly, lithium iron phosphate also has better durability. The battery will only be discharged after the number of complete charge and discharge cycles is greater than 3,500 times. It will attenuate to 80% of the original value. Secondly, because it does not contain precious metals (nickel and cobalt metal elements), the production cost is lower, and the production process is more environmentally friendly.
The above advantages are not available in ternary lithium batteries.
Iron batteries have these advantages. Why have they not been used on a large scale before?
Let’s look at sales. In 2019, my country's power battery production and sales totaled 85.4GWh and 75.6GWh respectively. Among them, the cumulative production of ternary batteries was 55.1GWh, accounting for 64.6% of the total production, and the cumulative sales were 53.0GWh, accounting for 70.0% of the total sales. The cumulative production of lithium iron phosphate batteries was 27.7GWh, accounting for 32.4% of the total production, and the cumulative sales were 20.6GWh, accounting for 27.2% of the total sales.
Judging from this ratio, the market performance of ternary lithium batteries is obviously stronger than that of lithium iron phosphate. The main reason for this phenomenon is that iron batteries still have many shortcomings that have not been solved.
First, the low temperature performance is poor. The lower temperature limit of lithium iron phosphate battery is -20℃, and the discharge performance is poor in low temperature environment. The capacity retention rate at 0℃ is about 60~70%, at -10℃ it is 40~55%, and at -20℃ It is 20~40%. In contrast, ternary lithium batteries have a lower low temperature limit of -30°C and good low-temperature discharge performance. Under the same low-temperature conditions as lithium iron phosphate batteries, the mileage is attenuated by less than 15% in winter. Therefore, compared with ternary lithium battery packs, lithium iron phosphate is more dependent on the driving environment and battery temperature control system of electric vehicles.
The second is low energy density.
Due to chemical characteristics, the voltage platform of lithium iron phosphate batteries is low. The energy density of ordinary lithium iron phosphate batteries is about 140Wh/kg. Even BYD's super lithium iron phosphate battery has an energy density of only 180Wh/kg, which is still far behind the energy density of ternary lithium batteries of more than 200Wh/kg.
There is another point that is easier for everyone to overlook - the subsidy factor. The previous ternary lithium battery received more subsidies because of its higher energy density. Naturally, everyone took the easier path. However, after the subsidies fell across the board in 2019, the gap between the two became smaller and smaller. This is also the case for iron phosphate. One of the important reasons why lithium batteries have returned to people's attention. ?
How to overcome the energy density problem?
It is easier for everyone to understand the low-temperature performance and policy reasons. Here we focus on the energy density of iron batteries. This is the focus of CATL and BYD: BYD handed over the "blade battery" structure, while CATL handed over "CTP technology".
Characteristics of BYD's blade battery
Judging from the patent disclosed by BYD, the blade battery is made by elongating the length of the battery core and making it thinner, making it into an ultra-long battery of 430mm or even 2500mm. The battery core has pole lugs at both ends. Compared with traditional prismatic batteries, it has a "flat" and "long" shape, and directly eliminates the battery module link.
When the total volume of the battery pack is the same, the existing battery PACK structure has additional components such as side plates, end plates, fasteners, beams, and longitudinal beams of each module; while using BYD's battery pack has a new structure. Excluding the battery management system, distribution box and other components, the space utilization rate in the pack is about 62%. Affected by different battery cell layouts, the space utilization rate within the bag is 55% to 65%, and can even reach 80% if necessary.
Due to the reduction in parts, the weight is reduced, so the energy density per unit mass can also be increased, and the vehicle's cruising range can also be improved. Using the new structure of the battery PACK, the charge capacity is increased by approximately 20%-30%, and the cruising range can also be increased by 20%-30%.
Characteristics of CATL's CTP
Compared with BYD's blade batteries, CATL is not so radical in technology. It still retains the module concept, but the number of modules It has been reduced, or each module has become larger.
According to CATL’s patent, a large module is divided into small spaces by several plastic heat sinks. Square-shell batteries can be inserted into these small spaces just like computer hard drives. .
The side of each battery cell is also affixed with a thermally conductive silicone gasket, and the heat dissipation plate in the width direction of the battery core has a heat dissipation channel, which can be directly connected to the external cooling pipeline.
According to data from CATL, this can reduce the number of parts by about 40%, which come from the connection harnesses between modules, side panels, bottom panels, etc. In addition, while the battery volume remains unchanged, the volume utilization rate of the battery pack using CTP technology has also increased by 15%-20%.
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CATL’s CTP technology and BYD’s blade battery technology have greatly improved the energy density of lithium iron phosphate batteries. The boards are being replenished, and in the post-subsidy era, we may soon see the return of iron batteries.
In fact, no matter what technical line Tesla and CATL finally decide to use, the choice they make and BYD will have a huge impact on the existing ternary lithium battery market. By then, the cost of models will be reduced, and consumers will be able to buy the same excellent products for less money.
This article comes from the author of Autohome Chejiahao and does not represent the views and positions of Autohome.