So, what is a "cobalt-free battery"? Is it really important?
What is a cobalt-free battery?
Here is a simple science popularization. The power batteries used in pure trams are divided into several categories according to the different cathode materials. At present, the two most mainstream technical circuits on the market are ternary lithium battery and lithium iron phosphate battery. The separator, electrolyte and negative electrode materials of these two batteries are basically the same, and the only difference is the positive electrode material.
Broadly speaking, a battery containing cobalt in the cathode material can be called a "cobalt-containing battery", and a battery without cobalt in the cathode material can be called a "cobalt-free battery".
In a narrow sense, "ternary lithium" refers to a polymer containing three metal elements: nickel (Ni), cobalt (Co), manganese (Mn) or aluminum (al), in which C in "NCM" and "NCA" represents cobalt, so they all belong to "cobalt-containing batteries"; The anode of lithium iron phosphate battery is LiFePO4 material with olivine structure, so we usually think that "cobalt-free battery" is lithium iron phosphate.
Why use cobalt-free batteries?
Furthermore, why did Tesla suddenly switch to cobalt-free batteries?
In fact, Tesla has been trying to reduce the use of cobalt for many years. In 2009, on Roadster, Tesla used lithium cobalt oxide batteries. 20 12, in modeling? On S, the consumption of cobalt is 1 1kg/ vehicle. 20 18, in modeling? 3. The dosage of cobalt is 4.5 kg/vehicle. So far. In 2020, Tesla intends to manufacture cobalt-free batteries. The use of cobalt is gradually decreasing, and the ultimate goal is because of "cost".
As we all know, the core component of electric vehicles is the three-electric system. Among the three power systems, the cost of battery is the highest, which can account for 35%-40% of the cost of the whole vehicle; Among ternary lithium batteries, cobalt has the highest cost, accounting for 30%-40% of the total battery cost. In lithium iron phosphate battery, the cathode material only accounts for about 13%- 15% of the battery cost.
At the previous committee of 100 for electric vehicles, Gao, an academician of Chinese Academy of Sciences, mentioned that the cost of power batteries for new energy vehicles at this stage is between 0.6~ 1.0 yuan /Wh, of which the lower limit is the relatively cheaper lithium iron phosphate battery and the upper limit is the higher-cost ternary lithium battery. By replacing the cobalt-free battery, Tesla can continue to reduce the cost and volume.
The use of "cobalt-free battery" includes not only the decline of price, but also the stability of price and supply. Because cobalt is usually a by-product of copper or nickel mining, it is easily affected by the demand and price fluctuation of these metals.
In addition, it is easy to be overlooked that Tesla and Contemporary Ampere Technology Co., Ltd. are actually getting rid of the shackles of core suppliers by adopting new battery technology. Before that, we all know that Tesla and Panasonic have established a very close cooperative relationship, but in Model? 3 When the production capacity climbed, Panasonic's battery supply speed was repeatedly vomited by Musk, resulting in many "scandals". In other words, when there is only one key core supplier, it is extremely risky for Tesla's manufacturing.
Increasing suppliers, developing new technical routes and putting eggs in different baskets are smarter plans in business competition. Just as the author put pen to paper, new news came out that Tesla was preparing to produce its own batteries, which also confirmed this speculation.
Interestingly, when it was speculated that Tesla and contemporary Amperex Technology and Limited would jointly develop a new generation of lithium iron phosphate batteries, Tesla Giga Shanghai replied to Tik Tok netizens, "Please pay attention to Tesla's battery conference in April, because there is no cobalt, it does not mean that it must be lithium ferrous phosphate", and then the comment was 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 battery or the route of using NCM8 1 1 high nickel battery to advance to NCMA (nickel-cobalt-manganese-aluminum) quaternary battery, other coating elements are gradually used to replace cobalt in the process. This is a good thing, because:
For Tesla, cooperation with the domestic power battery giant Contemporary Ampere Technology Co., Ltd. can not only further reduce costs, but also improve efficiency. At the same time, it can increase the battery supply channels and ensure that the Shanghai factory is not restricted by the battery bottleneck, which can kill two birds with one stone.
As far as the new energy vehicle market is concerned, the cooperation between Tesla and Contemporary Ampere Technology Co., Ltd. will further reduce the manufacturing cost of domestic Tesla, further explore the price space of domestic Tesla, and further activate the domestic 250,000-class electric vehicle market.
BYD and Tesla thought of it together.
Coincidentally, before Tesla announced 1 month, BYD also announced the launch of a brand-new "cobalt-free battery"-super lithium iron phosphate battery, which is also officially called "blade battery".
What is blade electricity?
The so-called blade battery refers to the "long cell scheme" (mainly refers to the square aluminum shell), which is a technology to improve the integration efficiency of the battery pack by increasing the length of the battery (flat length design), arranging them in an array and inserting them into the battery pack like a "blade". It doesn't refer to a battery with a specific size, but can be made into batteries with different sizes according to different requirements. The general principles are as follows:
The energy density of BYD's lithium iron phosphate battery can reach 180Wh/kg, which is about 9% higher than before, while the volume energy density can be increased by 50%. At the same time, the unit cost can be reduced by 30% by changing the internal mechanism and other technologies. According to BYD's official introduction, the life of the new blade battery can reach more than one million kilometers.
BYD officially announced that "Han" will be the world's first model equipped with "blade battery", which is expected to be launched in June this year.
What are the advantages of iron batteries?
The uniqueness of the blade battery lies not only in the brand-new battery arrangement structure, but also in the fact that it is a lithium iron phosphate battery. This is also a decision made under the market trend that ternary lithium battery scheme has become a common practice.
BYD chose it because of its several advantages.
Firstly, the P-O bond in LiFePO4 crystal is relatively stable and difficult to decompose. Even if it encounters high temperature or overcharge, it will not collapse and heat up or form strong oxidizing substances like cobalt batteries. Therefore, lithium iron phosphate battery has better natural thermal stability, and it is not easy to spontaneously ignite even if it collides and breaks.
Lithium ternary with poor thermal stability often spontaneously ignites.
Secondly, the durability of lithium ferrous phosphate is better, and the power will decay to 80% only after a complete charge-discharge cycle of more than 3500 times. Furthermore, because it does not contain precious metals (nickel and cobalt), the production cost is lower and the production links are more environmentally friendly.
All the above advantages are not available in ternary lithium batteries.
Iron batteries have these advantages, why haven't they been widely used before?
Let's look at sales. In 20 19, the cumulative production and sales of power batteries in China were 85.4GWh and 75.6GWh respectively, of which the cumulative production of ternary batteries was 55. 1GWh, accounting for 64.6% of the total production, and the cumulative sales volume was 53.0GWh, accounting for 70.0% of the total sales. The cumulative output of lithium iron phosphate battery is 27.7GWh, accounting for 32.4% of the total output, and the cumulative sales volume is 20.6GWh, accounting for 27.2% of the total sales volume.
Judging from this ratio, the market performance of ternary lithium batteries is obviously stronger than that of lithium ferrous phosphate. The main reason for this phenomenon is that there are still many shortcomings of iron batteries that have not been solved.
First, the low temperature performance is poor. The lower temperature limit of lithium iron phosphate battery is -20℃, and its discharge performance is poor in low temperature environment. The capacity retention rate is about 60 ~ 70%, 40 ~ 55% at-10℃ and 20 ~ 40% at -20℃. In contrast, ternary lithium batteries have good low-temperature discharge performance when the lower limit is -30℃. At the same low temperature as lithium iron phosphate battery, the mileage attenuation in winter is less than 15%. Therefore, compared with ternary lithium battery pack, lithium ferrous phosphate is more dependent on the on-board environment and battery temperature control system of electric vehicles.
Second, the energy density is low. Lithium iron phosphate battery has a low voltage platform due to its chemical characteristics, and the energy density of ordinary lithium iron phosphate battery is about 140Wh/kg. Even BYD's super lithium iron phosphate battery, the energy density can only reach 180Wh/kg, which is more than 200Wh/kg from ternary lithium battery, and there is still a gap.
There is another point that everyone can easily ignore-the subsidy factor. In the past, ternary lithium batteries were able to get more subsidies because of their higher energy density, so everyone naturally took a more relaxed road. However, after the overall decline of 20 19 subsidy, the gap between the two is getting smaller and smaller, which is one of the important reasons why lithium iron phosphate batteries have returned to people's field of vision. ?
How to overcome the energy density problem?
Low temperature performance and policy reasons are well understood. Here we will focus on the energy density of iron batteries. This is the key point of contemporary Ampere Technology Co., Ltd. and BYD: BYD handed over the "blade battery" structure, while contemporary Ampere Technology Co., Ltd. handed over the "CTP technology".
Characteristics of BYD blade battery
According to the patent disclosed by BYD, the blade battery is an ultra-long battery of 430mm or even 2500mm, and both ends of the battery have tabs. Compared with the traditional square battery, it presents a "flat" and "long" shape, directly omitting the battery module.
The existing battery pack structure has more side plates, end plates, fasteners, cross beams, longitudinal beams and other components of each module under the condition that the total volume of the battery pack is the same; BYD battery pack with brand-new structure, excluding battery management system, distribution box and other components, has a space utilization rate of about 62%. Affected by different cell layouts, the space utilization rate in the package is 55% to 65% respectively, and can even reach 80% when necessary.
Due to the reduction of parts and weight, the energy density per unit mass can also be improved, and the cruising range of the whole vehicle can also be improved. With the new structure of the battery pack, the charging capacity can be increased by about 20%-30%, and the cruising range can also be increased by 20%-30%.
Characteristics of CTP in Contemporary Anpu Technology Co., Ltd.
Compared with BYD's blade battery, Contemporary Ampere Technology Co., Ltd. is not so radical in technology. It still retains the concept of modules, but the number of modules has decreased, or each module has become larger.
According to the patent of Contemporary Amperex Technology Co., Ltd., a large module is divided into small spaces by several plastic cooling plates, and the battery with square shell can be inserted into these small spaces like a computer hard disk.
A heat-conducting silica gel gasket is attached to the side of each battery cell, and a heat dissipation channel is left on the heat dissipation plate in the width direction of the battery cell, which can be directly connected with an external cooling pipeline.
According to the data of Contemporary Ampere Technology Co., Ltd., this can reduce about 40% of the parts, which come from the connecting wiring harness, side plates and bottom plates between modules. In addition, under the condition of constant battery volume, the volume utilization rate of battery pack using CTP technology is also improved by 15%-20%.
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The CTP technology of contemporary Amperex Technology Co., Ltd. and BYD's blade battery technology greatly improve the energy density of lithium iron phosphate battery. When this short board is filled, we may soon see the return of iron batteries in the post-subsidy era.
In fact, no matter which technical route Tesla and Contemporary Ampere Technology Co., Ltd. finally decide to adopt, the choice of Tesla and BYD will have a great impact on the existing ternary lithium battery market. By then, the cost of car models will be reduced, and consumers can buy the same excellent products with less money.
This article comes from car home, the author of the car manufacturer, and does not represent car home's position.