Talking about fast charging power L822 battery technology: Who is reliable and who is fooling around?

In recent years, there have been a lot of big news about battery fast charging, but most of them are gimmicks, and the truly reliable technology has always been in a low-key state. Especially with the increase in news related to the safety of automobiles and mobile phones recently, people are paying more and more attention to the safety of fast charging technology. Previously, the author has done a popular science of fast charging in the previous article, introducing the requirements of fast charging technology related to materials and battery structure, and more inclined to material technology analysis; in this article, the important thing is to introduce to you the difference between reliable and unreliable fast charging battery technology, and in the field of electric buses, analyze the technical route and applicability of power lithium-ion batteries of representative manufacturers (Microvast, CATL, Yinlong), so that those battery companies that have been working hard behind the scenes can unveil their veils and let consumers better understand them.

Those unreliable fast charging technologies?

It is not difficult to imagine the convenience that battery fast charging can bring to us, and recently all kinds of "full charge in a few minutes and seconds" news have been flying all over the sky, some of which are true and some are really the result of technical accumulation, and some may be more used to attract attention and cheat money. The author believes that the unreliable fast charging technology (reports) have the following important characteristics:

1) Infinitely magnifying the results in the laboratory and linearly extrapolating them to the practical fields of kWh and MWh. Many news in this regard really have little to do with scientific researchers. Many of them are big news fabricated by journalists for unknown purposes. In fact, anyone with a little experience in scientific research and engineering knows that there is a huge difference between them. It takes a lot of energy to achieve engineering. The author is too lazy to talk to some people who talk about the feelings of technological advancement: many people advocate that "new technologies seem unreliable at the beginning", but they don't know that more unreliable technologies have already died, and many people have no concept of survivorship bias.

A typical big news fabricated by the media, the researchers said they were innocent

Typical sentimental party: Long live sentiment, spiritual victory, conspiracy theory logic is rich in imagination, but as a professional keyboard warrior, he didn't even type the key word "ene" correctly...

2) Confusing important contradictions, talking about power when it should be energy density, in fact, power, cost, and life are more important contradictions in many cases. Confusing capacitors (Supercapacitors are more used for fast charging) and batteries (Battery) is a typical manifestation.

3) Using various media propaganda tricks, using emotional words to fool people: such as "shocked", a bunch of exclamation marks, and even using inexplicable names such as "congratulations motherland" to kidnap everyone's cognition, as if you don't agree with it, you are unpatriotic, but there is no substantive content in the article. For example, the author searched for graphenano's US and European patents and found that the number is 0. Many of the new battery technologies that are boasted about do not have any specific information at all: no energy density, no power density, no electrochemical reaction mechanism, no charge and discharge typical lines, no lifespan, in short, almost nothing, only a self-assessed international leading - let's just say: empty words without evidence.

On the other hand, reliable fast-charging battery technologies all have real products that have gone through a long process from the laboratory to stable mass production, and most of them are produced by large companies with good product quality control. They have undergone good inspections in specific applications, and the company's patent layout and specific product introduction information can be seen. It's just a pity that most battery companies themselves are relatively low-key, far less than the automotive and consumer electronics companies that can directly connect with consumers. They are good at influencing consumers, or deliberately reduce the promotion of their own products due to the need to cooperate with mobile phone companies in the industrial chain.

The author believes that in this era, sometimes the wine is afraid of being hidden in the alley. Reliable battery technology should promote itself more, so that it can seize the position of publicity, and will not always let some gimmick news grab the limelight that should belong to it.

Comparison of reliable typical fast-charging power lithium-ion battery technology

The author has collected some information related to power lithium-ion batteries through the Internet and other channels, which are listed in the following table. Here, the information mainly points to the application field of (fast-charging) electric buses, which are similar to ordinary passenger car applications, but there are also some differences. The important ones are:

1) Higher safety requirements. After all, electric buses use more batteries and carry more passengers. Once an accident occurs, the potential loss may be greater than that of electric cars.

2) The mass-to-energy density requirements are reduced. After all, the battery usage is large but the available space is larger. It is appropriate to use more batteries to solve the endurance problem, and buses are often fixed routes. Therefore, lithium iron phosphate, which has more obvious mileage anxiety in ordinary passenger cars, has some new advantages here.

3) In terms of cost, the author believes that it is basically at the same level as ordinary passenger cars, and there is a certain floating space depending on the technical route.

Due to limited conditions, the information collected on the fast-charging power lithium-ion battery products of various companies is not complete, but a preliminary analysis of the technical routes of each company can be made to help readers better understand the fast-charging technology and related manufacturers of power lithium-ion batteries (for buses). Several companies are representative companies in the industry that the author respects very much. They have been working hard in their own fields for many years, have their own core competitiveness, and are leaders in the field of fast-charging batteries.

Microvast

Microvast Power, located in Huzhou, Zhejiang, was established in 2006. Microvast Power Systems (Huzhou) Co., Ltd. is a modern high-tech company integrating the research, development, production and sales of new energy and power storage technologies, combined chemistry and new chemical processes. In 2011, it took the lead in putting fast-charging technology into commercial operation.

The basic situation of several generations of Microvast products is as follows:

1) The first generation of fast-charging battery products: that is, lithium titanate technology used in LρTO batteries, which is promoted in the market. However, the negative electrode potential of lithium titanate itself is about 1.5V, which leads to its low energy density, limiting its greater use. Therefore, this product is more suitable for short-distance and fixed-route buses with frequent stops and charging. Another problem is that the cost of lithium titanate materials is significantly higher than that of graphite, and the cost of batteries has also risen. Although the cost of batteries must take into account factors such as life, cost, performance, and safety, the relatively high cost of lithium titanate-ion batteries themselves is also a concern for the one-time investment in electric vehicles and energy storage industries.

2) The second generation of multi-component composite lithium-ion batteries: The positive electrode is a ternary material + lithium manganese oxide mixed system, but the negative electrode is changed from lithium titanate to porous composite carbon as the negative electrode material. Porous composite carbon is a hard carbon material. The biggest feature is that its specific surface area is increased to more than 20 times that of traditional graphite. The newly added specific surface area and pores also greatly increase the number of lithium ion migration and embedding channels, allowing lithium ions to be quickly and stably embedded and removed, thereby solving the technical bottleneck that has long hindered the rapid charging of high-energy density graphite negative electrode lithium-ion battery products, while greatly improving the ability of fast charging, and the cost has also decreased compared to the first generation. However, the disadvantage of this system battery is that the cycle life is not long enough, the compaction density, gram capacity and first charge efficiency of hard carbon are not ideal, and the high potential of hard carbon material also leads to low energy density of the whole battery (so the energy density of ternary-hard carbon system battery is definitely lower than that of ternary-graphite system, so it is not a particularly strange result that it is lower than that of lithium iron phosphate-graphite system), and the safety of ternary material system batteries for passenger cars still needs to be focused on and constantly tested in practice (I dare not say there is no problem, whether the use of ternary materials on passenger cars is safe enough is also an old topic). But one thing is certain: if you want to use it on a bus, the safety risk is still an underlying problem that cannot be ignored.

Why is it not recommended to use ternary material batteries for buses? It's very simple: a passenger car has 4 doors, and the escape time in the event of an accident is a few seconds; while the battery loading capacity of a bus is nearly 10 times that of an ordinary passenger car. The risk factor is higher when calculated by multiplying the probability of battery failure, and the number of passengers on board is more, and the need for escape is more urgent. Therefore, using battery technology with a higher safety factor on buses is a very reliable and rational choice. The country's previous policy of restricting subsidies for ternary material batteries is actually based on such considerations to a large extent.

Excerpted from the PPT of the Microvast Power "Non-burning Battery" Press Conference

About "Non-burning Battery": Microvast launched its "Non-burning Battery" at the beginning of this year, which was very eye-catching at the time and caused widespread discussion among people in the technology circle. The author specifically asked about this information among friends at the time and learned that Microvast used a series of special optimization technologies such as a special electrolyte system and Kevlar fiber diaphragm to improve the safety of the battery. These technologies are naturally more reference and guiding for the development of batteries. However, it is a pity that Microvast did not introduce key information such as the energy density and cost of the battery, and from the perspective of its performance and material system, I am afraid that these data are not optimistic. Some people in the industry also believe that this is also sacrificing cost and energy density to ensure safety, but in any case, the technological progress is still worthy of recognition. Therefore, the author is more inclined to believe that the technology in non-combustion batteries will be very meaningful for future technological development, but in the near-term engineering application, it will be limited by comprehensive factors such as cost and technology. It may take a long time for it to become a real product and go to the market.

Industry insiders' evaluation of Microvast's "non-combustion battery"

To sum up:

Microvast's power lithium-ion battery has good rate performance, is relatively safe, has good adaptability to various environmental conditions, has a long cycle life, and is new in technology.

The important problem is that the safety of the ternary material positive electrode in its technical route is still a big problem, and the promotion of new technologies faces a series of problems in terms of cost, etc., and there is a long way to go.

CATL

CATL is Contemporary Amperex Technology Co., Ltd., founded in 2011 and located in Ningde City, Fujian Province. CATL is committed to providing efficient energy storage solutions for global green energy applications through advanced battery technology. The company has established complete R&D and manufacturing capabilities in the field of power and energy storage batteries, and has core technologies in the entire industry chain of materials, battery cells, battery systems, and battery recycling.

CATL has many years of research and application experience in fast-charging batteries. Its technology is in line with ATL's mobile phone fast-charging battery technology, but its technical advantages in this area have not been well known to consumers. Insufficient publicity may be a problem. In fact, in the battery industry, CATL's technical level has always been recognized by the majority of technical personnel, and it is well-known in the circle, but it is not so well-known among ordinary people. Recently, with the outbreak of some news about mobile phone battery safety, CATL's product quality has gradually begun to receive more attention in the news, which further proves the company's technical strength and product quality level.

CATL's bus fast-charging battery technology is mainly about optimizing and tapping the potential of traditional classic materials, ensuring safety, cost and comprehensive performance, and attaching importance to quality control. CATL has developed several generations of fast-charging negative electrode graphite since the development of mobile phone fast-charging batteries. The main thing is to carry out comprehensive surface optimization treatment (CATL claims to be "fast ion ring" technology) to improve its ability to accept lithium ions in all directions, accelerate the rate of lithium ion embedding, and reduce the tendency of dendrites during charging. Moreover, such modified graphite takes into account the advantages of fast charging and high energy density.

As for the positive electrode, CATL uses the well-known high-safety lithium iron phosphate system. Considering the poor intrinsic conductivity of lithium iron phosphate, CATL uses carbon layer coating and doping treatment, and the conductivity can be improved from the intrinsic (10-9S/cm) to (10-3S/cm), which is better than the ternary material (10-4~10-5S/cm), and the impact on capacity is not significant.

Another factor to consider is the issue of voltage and safety. People who have studied electrochemistry know that the higher the battery voltage, the stronger the positive electrode oxidation, and the more intense the reaction with the electrolyte. At high temperatures, various reactions will intensify, and the battery is very afraid of working at high temperatures, and the coefficient of danger will be very high. Therefore: high temperature + high voltage is the worst. At this point, the voltage of lithium iron phosphate itself is relatively low (3.45V), and CATL has equipped it with a temperature control system that cooperates with the fast-charging battery. The charging system is optimized according to the charge and discharge degree (SOC) and temperature of lithium iron phosphate, thereby further ensuring safety. In the old topic of lithium iron phosphate vs. ternary materials, safety has always been a fundamental advantage of lithium iron phosphate, and this feature is even more important in the field of buses.

The battery charging system should be adjusted according to the ambient temperature

To sum up:

The advantages of CATL technology are: good performance, high safety, and low cost. Safety and cost can be said to be important considerations in the actual engineering promotion of power lithium-ion batteries, and they have certain comprehensive advantages in promotion at the current stage.

The important shortcomings of CATL technology are: 1) The energy density of lithium iron phosphate fast-charging batteries is not as high as that of ordinary energy-type batteries of ternary-graphite, so it is not suitable for use in passenger cars, but only for fast charging on buses. 2) The performance of lithium iron phosphate is not as good as that of ternary at low temperatures, so CATL has designed a related circulating water temperature control system to alleviate this problem.

Yinlong

Yinlong New Energy, founded in 2009, is located in Zhuhai. It acquired the American Aoti Company in 2010 and began to engage in the battery business with lithium titanate materials. In 2012, it began to acquire automobile companies to produce electric vehicles. Yinlong has established an industrial chain from materials to automobiles. The batteries it produces are mainly self-produced and self-sold. In order to occupy the market in the public transportation system, the company has specially developed a financial leasing business model for public transportation, which provides 10-year insurance for vehicle replacement and zero-yuan vehicle purchase. Zhuhai Yinlong raised two rounds of financing in 2015 and 2016, with 20 brand companies including CITIC Securities, Huarong Asset, Sunshine Insurance, and Beijing Public Transportation jointly investing billions of RMB. Beijing Public Transportation, one of its investors, is also its largest customer.

Yinlong's various business platforms

As a new energy vehicle company, pure electric vehicles are an important sales product of Yinlong, and the end users are public transportation companies in various places. Among them, Beijing Public Transportation Group Co., Ltd. is its largest customer, accounting for 37.11% of sales. What is particularly noteworthy is that Yinlong accounts for almost 80% of Beijing Public Transportation orders. Beijing Public Transportation is also one of Yinlong's investors, which may have played an important role in Yinlong's entry into the Beijing market.

Recently, with the news of Gree's acquisition of Yinlong, Yinlong's popularity has been further improved, and the concept of lithium titanate has also been hot. In fact, lithium titanate is not a new technology, and a lot of research has been done before: an introduction to lithium titanate written by the author on Zhihu two years ago was recently re-opened and sent to the editor's recommendation, which is very interesting. Next, the author will analyze Yinlong's lithium titanate ion battery technology route.

Yinlong's battery technology route is lithium titanate fast charging battery, with lithium titanate as the negative electrode. Similar to lithium iron phosphate, lithium titanate also has poor conductivity.Problem. The problems are similar, and the solutions are the same. Yinlong's core technology is the production process of nano-sizing and doping (other lithium titanate companies can only achieve micron level), solving a series of problems in material ion conductivity and other aspects. According to actual measurements, Yinlong's battery cell is 2.3V, so the positive electrode material it uses is not lithium iron phosphate (if lithium titanate is paired with lithium iron phosphate, the voltage is less than 2V), nor should it be lithium manganate (if lithium titanate is paired with lithium manganate, the energy density is too low), so its positive electrode uses ternary materials. The ternary-lithium titanate ion battery has better rate performance and better low-temperature performance, which gives it certain advantages in the extremely cold northern regions, and its safety and life are also stronger than the ternary-graphite system.

However, this technical route also has problems:

1) The outstanding problem of lithium titanate ion batteries is still that the voltage is too low, and when paired with ternary materials, it can only reach 2.3V (4.2-1.5) at most. As a result, the energy density of mature mass-produced batteries is very low, not as good as the typical lithium iron phosphate and ternary batteries (3~4V) with carbon-based materials as negative electrodes. The energy density of the lithium titanate battery currently used by Yinlong is 70-80Wh/Kg, and the system energy is close to 60Wh/Kg. Its fourth-generation new lithium titanate battery is expected to be close to the lithium iron phosphate battery in energy. It may be in the laboratory stage at present, and may be enlarged later.

The low battery energy density caused by the inherent low voltage of lithium titanate batteries makes it impossible to load too much lithium titanate batteries on cars. Therefore, if the balance of power-energy (fast charging-endurance) is considered more, lithium titanate batteries will be very troublesome. At this time, the technology of lithium iron phosphate and ternary graphite is much better. If the mileage is not considered at all, only a small number of batteries are installed and charged at any time, lithium titanate can be used.

2) The gas production of ternary and the flatulence of lithium titanate are both prominent. By adjusting the electrolyte, the inherent flatulence problem of lithium titanate can be basically controlled. In addition, it is disadvantageous in energy density and production cost. After adopting ternary materials, Yinlong's latest energy density of battery cells has been increased to 80Wh/kg, which is about half of that of ternary-graphite battery cells. In terms of battery types, Yinlong has two types: cylindrical batteries and soft-pack batteries: cylindrical batteries use lithium titanate, and soft-pack batteries use lithium iron phosphate + graphite. The energy density of cylindrical batteries is not high. Even if the battery cells are densely stacked, more space is wasted after forming a battery pack. Therefore, energy density and battery life may be a core issue. If lithium titanate is used to prepare soft-pack batteries with higher energy density, it is very sensitive to flatulence and the battery cannot be made larger. In other words, the material system may limit the development of its battery technology route to a certain extent.

3) Cost, the cost that is often mentioned:

The cost of lithium titanate ion batteries is significantly higher than that of other system batteries, mainly due to the following factors: A) The lower energy density itself; B) The high cost of titanium; C) The problems that need to be solved in the performance of lithium titanate technology, etc. At present, the cost of ternary-lithium titanate ion batteries is about twice that of ternary-graphite batteries. In the field of batteries that are very sensitive to cost, this is a factor that must be seriously considered. The high cost actually limits the amount of lithium titanate batteries used when installed on vehicles, as well as their endurance, which are objective shortcomings of this technology route.

To summarize:

The advantages of Yinlong lithium titanate batteries are good rate performance, relatively safe, good adaptability to various extreme environmental conditions, and long cycle life.

The important problem is that the cost is high and it is unlikely to drop significantly. In addition, the low energy density of the battery also limits its use and promotion in many fields, and its application significance in most ordinary environmental areas is not so obvious.

Postscript:

In this article (Part 1 and Part 2), the author introduces the requirements of fast-charging lithium-ion batteries for materials, the significance of fast charging, the popularization of reliable and unreliable fast charging news, and the introduction of typical domestic advanced battery companies and the analysis of their fast charging technology routes. Fast charging is a very important technology with high technical content. It is a comprehensive technology that runs from science to engineering. It requires the joint efforts of many people to do it well. I hope that more people will be willing to devote themselves to the research and development of truly reliable fast charging technology, do a good job of publicity, and let more people understand and pay attention to the real fast charging technology, rather than letting unreliable technology promote itself every day, and let those exclamation marks and "shocked" news in the circle of friends attract too much attention.

The recent big news about the safety of a certain mobile phone battery actually shows one point: my country's batteries are not necessarily worse than those of any other country, and their products are not invincible. Here, the author also hopes that my country's battery industry can take off further and make more world-class products.

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