This bowl of "cold water" was spilled at the right time. Is long battery life practical? Can ultra-large capacity batteries and ultra-fast charging meet the safety requirements? These issues related to the pain points of consumers need a calm analysis in the industry.
We connected Wang Chaoyang, an academician of the National Inventors' Association and a chair professor in the Department of Mechanical Engineering, Chemical Engineering and Materials Science and Engineering of Pennsylvania State University, and asked him to talk about the development of electric vehicle batteries.
Wang Chaoyang's research work mainly focuses on transportation, material manufacturing and modeling of batteries and fuel cells, and he holds more than 90 patents (USA, China, EU and Japan). His research on all-weather battery (ACB) technology was published in Nature magazine, and was later selected by the 2022 Winter Olympic Games to provide power for the Olympic electric vehicles. He also released a fast charging technology on 20 19, saying that charging 10 minute can make the electric car full of 80%, with a battery life of 300 km to 400 km. After charging and discharging for 2500 times, the battery capacity is only 8.3% loss. Recently, Wang Chaoyang team developed a thermal control lithium iron phosphate battery (TMB), which can meet the requirements of low cost, super safety, long life and all-weather. This achievement was published in the world's top journal Nature? Energy magazine.
Talking about the hot news of batteries, he repeatedly emphasized the law of conservation of energy. He said, "All news, all releases or some stories we are hearing, if we analyze them with a simple law of conservation of energy, we can know its authenticity and reliability."
Why a duck? Recently, Academician Gao criticized the long battery life and super fast charging. Is this a dislocation between industry and laboratory research? Or does the enterprise have some exaggerated elements?
Wang Chaoyang: This is problematic both in science and in business.
The business problem is simple. If the battery life is 1000 km, it will probably take 150 kwh, so even if it takes 10 minute to charge 150 kwh, it will probably take 900 kW charging power, which is not available at present. The highest power Tesla third-generation charging pile is 250 kW, so from a commercial point of view,
From a scientific point of view, there is also a big problem. With such a long cruising range, the battery must have a high energy density. For example, the six-rate charge is not established in science at present, at least there is no such report, and it has not been reviewed by peer scientists.
In fact, there is a very simple scientific judgment that the three data must coexist and be indispensable. The first is the charging time; The second is how much energy or cruising range you get after charging; The third data is how many times the battery can be cycled, which is also very important. If you charge quickly, you will get a lot of energy, but you will only waste the battery once or twice. This is not a new technology. All freshmen can do it.
These three data are indispensable. With this rule, basically any news released by any media or enterprise can be judged by itself.
The energy industry must abide by the law of conservation of energy, that is, how much energy is the charging power multiplied by the charging time. According to the simple law of conservation of energy, we can immediately calculate what they are talking about.
Why Duck: The public has high expectations for some black technologies and hopes to have a breakthrough technology.
Wang Chaoyang: Everyone is looking forward to it, but all black technologies must be based on the law of conservation of energy. This is the basic rule. If it is found that black technology is a perpetual motion machine and does not conform to the conservation of energy, this technical problem is very big.
Why Duck: Let's take a look at the research you just published. What is the fundamental difference between this low-cost battery and the fast charging technology released in June 20 19?
Wang Chaoyang: The most fundamental difference is that our research focuses on one theme, reducing the cost of batteries.
We just hope that the cost of batteries can be reduced to the same level as that of fuel engines, so that electric vehicles in the mass market can be popularized. It is of great significance for reducing carbon emissions. It is impossible to achieve carbon neutrality just by selling thousands of high-end electric vehicles.
To put it more simply, we can reduce the overall cost of the battery by miniaturizing the battery pack and then keeping the unit cost at a relatively low level.
This direction is just the opposite of the direction of many domestic car companies, and they all have long battery life. To develop a battery with a battery life of 1000 km, what is the concept of a battery with a battery life of 150 degrees? Take the current ternary lithium battery as an example. One watt is one yuan, and this 150 degree battery is150,000 RMB. This car is not a mass-market electric car, and the battery cost is too high.
Besides, you carry such a big battery around. It's dangerous, right? That's a big energy pack.
Therefore, we have applied some previous technologies to new batteries, including the traditional lithium ferrous phosphate, which does not perform well in winter, so our batteries are not affected by the ambient temperature, because our batteries must be preheated to 60 degrees in advance to work, and it can always give you a good performance.
This all-weather battery has been tested. This battery is used in the 2022 Winter Olympics, and there are a large number of vehicle test results, including the test results of these teams in Heihe, Northeast China.
Why: Please know about all-weather batteries (self-heating batteries).
Wang Chaoyang: Traditional lithium-ion batteries are particularly afraid of cold. If the temperature is low, the transmission of lithium ion between the anode and cathode will be greatly hindered, so its performance will be reduced by 9 times, reaching 10 times.
The traditional method is to use external heating, but it consumes a lot of energy and is not very direct. It takes a long time and takes more than an hour, which can't meet the needs of consumers for immediate use, and it can't be recharged quickly in winter.
Our all-weather battery is to add a nickel sheet to the battery core, and only 10 micron nickel foil can generate self-heating and make the battery temperature rise rapidly. Although the temperature of the environment is below zero, we have achieved a temperature rise of 60~200 degrees per minute, while the traditional external heating is generally 0.5~ 1 degree per minute, and our speed has increased by two orders of magnitude. Generally, it takes only a few tens of seconds for the battery to heat up and then work normally.
In addition, after a lot of experimental research, we found that this self-heating method consumes very little energy.
Why: This method is essentially active control, which can quickly make the battery reach a suitable charging temperature without changing the material itself and safety, right?
Wang Chaoyang: Yes. We first propose structural innovation. The traditional battery structure is a positive electrode, a negative electrode and a separator, which is called a three-stage structure. We added a fourth component, nickel foil, which can store energy and adjust the temperature by itself.
Why Duck: Speaking of the concept of solid-state battery, I think some companies are already pushing this product, but some people say it is semi-solid battery. Please explain the essential differences among solid-state batteries, ternary batteries and lithium iron phosphate batteries. Is it the difference between liquid and solid?
Wang Chaoyang: The real significance of solid-state batteries is to replace the traditional lithium ferrous phosphate and the electrolyte in ternary batteries with solid electrolyte. However, the research and development of solid-state batteries should be far from real commercialization.
You can see from the media reports or the news released by the company that our R&D personnel and enterprises have basically not figured out what kind of solid-state battery products to make.
Why do you say that? I can give a few examples. In the first example, you may often hear in the media that the ionic conductivity of solid-state batteries is too low and the solid-solid interface resistance is too high; At the same time, you can see that solid-state batteries can be charged quickly. This is a contradiction. How to charge a battery with large internal resistance quickly? That's impossible.
Some people say that the semi-solid battery means that there is electrolyte in the anode and more than half of the dangerous electrolyte remains in the battery. Can this be safe?
Reason: Some big companies, including Toyota, said that they would manufacture solid-state batteries in the future, because solid-state batteries are safer.
Wang Chaoyang: Everyone should make solid-state batteries, which is considered as the next development direction. Every enterprise has its own considerations, not only the reasons for the development of science and technology, but also the orientation of the enterprise and the direction of investment. But are solid-state batteries necessarily safe? We sometimes take it for granted that it is safe, but if you really think about it, you will find that it has many unsafe factors.
First, if a company's solid-state battery is 150 kWh, it is a big energy package. Even if it is solid, it is not safe to run around with such a big energy pack. Once discharged, that is, all the electric energy is discharged, the temperature rise of the battery should be above 1500 degrees.
That is, if a certain part is short-circuited, the electric energy will be released instantly, and the temperature of the battery material is above 1500 degrees, and no material is safe. Even if 10% of electricity is discharged instantaneously, the temperature of the solid-state battery reaches 180 degrees, and lithium metal melts.
Why Duck: Back to the 40 kWh battery, is it easier to control the safety with a small capacity?
Wang Chaoyang: The 40 kWh battery we invented is the safest battery on the market at present. First, after all, it is only 40 kWh. Secondly, its anode is made of lithium ferrous phosphate, which is a very safe and thermally stable material. Third, although we are also graphite negative electrode, because we work at 60 degrees, we can make graphite particles bigger and the specific surface area smaller, which also improves the safety and thermal stability. Fourthly, we use low-voltage electrolyte, because the voltage in lithium ferrous phosphate is only 3.6/3.7 volts, and ternary is 4.2/4.3 volts, so the electrolyte is safer.
Why ducks: There is another concept that needs to be explained. Now, what is the relationship between graphene and graphite anode? Why is graphene a hot spot?
Wang Chaoyang: In most applications, graphene is only a conductive agent, which increases the electronic conductivity, so the dosage is very small, such as 1%, 2% and 3%, while graphite is an energy storage material. For example, this graphite is what makes you full, while graphene is just monosodium glutamate and seasoning.
Why Duck: How do you think we should choose ternary lithium batteries and lithium iron phosphate batteries in the future?
Wang Chaoyang: Ternary batteries have higher energy density, but the disadvantages are poor safety and high cost. Cobalt is also needed. Cobalt is strategic metals, so it has obvious disadvantages.
After the energy density of battery core material is high, the safety is poor, so it is necessary to make more safety devices on the battery pack to prevent the ternary battery from being unsafe. Adding another device to the battery will reduce the energy density of the whole system, so 150 kWh battery will definitely not choose heavier lithium ferrous phosphate, so there will probably be no passengers on this car. After the battery is made small, lithium ferrous phosphate is a very good choice, because it has incomparable advantages, that is, its safety is particularly good and its cost is particularly low.
So in different occasions, both batteries will be useful. Recently, I am making batteries for flying cars, that is, batteries for electric planes. In the future, we can all go to work by flying car. Flying cars can use the three-dimensional traffic network to reach their destinations without traffic jams. For flying cars, ternary batteries will be the first choice, because after all, planes are flying and are particularly sensitive to weight.
I can't use miniaturization technology to make batteries for flying cars. It can't be charged in five minutes, and it can't be charged in the air 10 minutes, so I think these two technologies are useful in different occasions.
Why Duck: I'm also curious about flying cars, including domestic companies that are doing this project. Isn't it the same if you use a fuel engine as power?
Wang Chaoyang: At present, our flying cars take off and land vertically. It is a means of transportation used in metropolis, and it is very sensitive to pollution and noise, so using fuel is not a development direction now.
In the future, airplanes will be intelligent and unmanned. Without a driver, you can save seat space and people's weight. In this way, it is necessary to equip a relatively large computer with many data processing functions. At this time, a large battery is needed. Therefore, even if a gasoline engine is used, it must be equipped with a large battery. In this case, the overall weight will exceed the pure electric mode.
There is a huge obstacle to the transition from a fuel car to a smart car, because some sensors used need to be electronically controlled. Including braking, power control will be faster and more accurate.
Why Duck: Speaking of future trends, Toyota is also pushing hydrogen battery electric vehicles. There are also pilot projects of hydrogen energy batteries in China and Beijing. In your opinion, what is the trend of hydrogen energy batteries?
Wang Chaoyang: I have been studying hydrogen fuel cells for more than ten years. Its biggest problem is that its cost is too high, and another problem is that its life span is not enough. It needs scientific breakthrough to reduce the cost by an order of magnitude before it can be commercialized. At present, it is still a long way from ordinary consumers.
In the past 20 years, there are at least 20 companies in the world, and each company has invested almost $2 billion in hydrogen fuel cells. My laboratory has invested about 300 million RMB in R&D and written some papers in this field, but I dare not have the idea of commercialization.
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